EARLY EXPERIENCE AND TEE DEVELOPMENT OF FOLLOWLNG

BEHAWOUR IN TRUMPETER SWAN (CYGNUS BUCCINATOR) CYGNETS

A Thesis

Presented to

The Faculty of Graduate S tudies

of

The University of Guelph

by

WAYNE BEZNER KERR

In partial fuIfi1ment of requirements

for the degree of

Master of Science

January, 200 1

O Wayne Bezner Kerr, 2001

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ABSTRACT

EAEUY EXPERIJENCE AND DEVELOPMENT OF FOLLOWING BEHAVIOUR IN TRUMPETER SWAN (CYGNUS BUCCWA TOR) CYGNETS

Wayne Bezner Kerr University of Guelph, 2000

Advisor: Professor T. Nudds

Induced migration behind aircrafl has been proposed as a technique to conserve

and restore some bird species, but success has been variable. To investigate whether and

how early experience aEected the development of ability to follow akcraft, 4 groups of

tmmp eter Swan (Cygms buccinutor) cygnets were raised under 4 dif5erent combinations

of hatching and rea.ring conditions, ranghg fiom minimal human contact to a fully

maniputated regÏmen in which cygnets were incubator-hatched and reared by human

handlers. One group of hand-reared and one group of initiaily parent-reared cygnets were

trained to follow an ultralight aircraft d e r 10 d post-hatch. One group of hand-reared and

one group of initially parent-reared cygnets were isolated fiom human contact after 10 d

post-hatch. AU cygnet groups were subsequently tested for ability to foilow aircraf't.

Cygnet association with human handlers and the research aûcraft, time-activity budget

data and the tendency for cygnets to takeoff with the aircraft were recorded. Between 10

d and 80 d post-hatch, initidy parent-reared cygnets demonstrated signincantly lower

preference for human handlers and the aircraft compared to initialiy hand-reared cygnets,

but eventually followed the aircraft better in fiight than initially hand-reared cygnets after

90 d post-hatch. The group of initidly parent-reared cygnets was the only group in which

foilowing behavior was sufficiently developed that they could be led by aircraft on a 1250

km migration.

ACKNOWLEDGMENTS

The field of swan conservation and migration is a smaii one, and many times 1

found myselfat a loss for curent data. Despite a lack of published data, people involved in

ongoing conservation and restoration work were able to supply important information. 1

could not have completed my thesis without their help. Ruth Shea, executive director of

The Trumpeter Swan Society provided helpfkl information and comments on several

occasions. Michelle Hudolin was Swan Keeper at Wye Marsh for much of their restoration

work, and provided information about their restored flock's winter habits. Madeleine

Linck, The Trumpeter Swan Society's coordinator keeps an incredible amount of swan

count data close at hand and was able to pass on Minnesota flock and Interior Population

numbers at short notice. Sumner Matteson of the Wisconsin Department of Natural

Resources amwered many questions about his own state's innovative restoration program,

and sent reprints of previous reports and papers.

The United States Fish and Wddlife SeMce's Whooping Crane Conservation

Coordinator is Richard Urbanek, who has worked tirelessly for dozens of years on crane

research conservation. 1 am t h a d h l for his fia& and candid assessrnent of crane

conservation efforts over the last 10 years. Rod Dnewen led the U.S.F.&W.S.'s Roclq

Mountain whooping crane migration experiments, and shared information about that

project's successes and failures. .

1 am gratefùl to Bob Michelutti and Joe Fife of FaIconbridge Limited's

EnWonmental Services division in Sudbury, Ontario. Falconbridge Limited provided the

core fiinding that made three years of work economicaliy possible.

1 owe a debt of gratitude to Wiam Carrick, whose creative enthusiasm for

aviculture in generai, Swan restoration in particular and beautifùl cinematography about

both helped to first direct me down this path. If Bili had not invited me to see his swans fly

f?om Lake Scugog on a windy day in 1995, it is unlikely 1 would have developed the keen

interest in waterfowl migration that 1 have today. Bill's original thinking is ofien

misunderstood and almost universally undervalued. f i s support and fnendship over the

last 5 years was essential, and I can't imagine this work succeeding without him or his

many quiet contributions. Bill has probably forgotten more than most experts have ever

learned about living and working with animals. 1 am gratefùl for the opportunity to Ieam

some of what he hows. Hany Lumsden provided some cygnets for use in the project.

A-J. Fedonik joined the project as a summer research assistant and became a

tnisted and vaiued member of our team. She spent hundreds of hours in f?eeUng water

and chose to stay with us even after the money ran out. Every graduate research project

should be so lucky.

Jamie Emslie was the behind the scenes infiuence that helped us obtain Our own

private refuge to begin our 1997 season. As the days passed, we came to rely on his

mechanical skills, energy, generosity and willingness to try almost anything at least once.

In 1998 he joined the project fbii time as an unpaid but enthusiastic volunteer who never

lost faith, even when there was Little or no reason to believe. It is a privilege to have him

as a fiend-

Mac Nussey welcomed us to Sudbury one snowy night in 1997 with keys to his

house, hot food and cool dry wit. No situation is so dire, nor any temperature so cold that

Mac won't happily grab his coat and tackle your problems head on. In 1998 he became the

adoptive father of our team, and kept our spirits high, bodies nounshed and airplanes

fiying. 1 will always be grateful for the memory of Mac flying beside us on the migration

route's first t e m g leg over northem bush and swamp.

Bryan Quickmire kept his enthusiasrn and good humour for two years in the face

of seeming failure, and was as good a chase pilot as can be imagined when he was called

upon. Ken K e ~ e d y left house and home to corne to Sudbury, and first drove then flew

with us ail the way to Muscatatuck. John Goddard agreed to help a total stranger with

airplane repairs and became another good fiiend.

Car1 Hiebert became a personal inspiration, constant source of good humour,

favourite traveling cornpanion and ali around aviation and safety mentor. His motor home

was our house on wheels for two years in a row at no charge. His incredible photographs

became the best record of what we were able to achieve. We are grateful for ail his help.

The greater Sudbury cormnunity and our £iiends and neighbours on South Bay

made the stones of northern warmth and generosity ail corne tme. It is a rare town that

doesn't complain when aircraft start their engines at 7:00 on Saturday morning and

proceed to buzz the rooftops for severaI hours. A steady strearn of visitors, dimer

invitations and helping hands kept Our spirits up though two long, coId seasons.

I am gratefUl to my supervisor, Professor Tom Nudds. Tom accepted me into the

MSc. program despite my unusual background and interests, and then immediately

allowed me tremendous fkeedom to disappear for as much as eight months at a t h e . He

fought for my nght to do this work the way we felt it needed to be done, and was a

powerful ally on a few crucial occasions. 1 am certain the project could not have

succeeded $Tom wasn't willing to fight messy battles. He stayed supportive over three

years, fourteen months in the field, the wonder and confiision of our first child, two

airplane wrecks, six moves and two long trips to southem f i c a for unrelated work. His

dedication to looking for answers in new and creative ways sets a high standards for

scientists and students alike.

Much of what is d e n ais0 applies to my long suffering conmittee members,

Dave Noakes, Sandy Middleton and Ed Bailey. They have been willing to provide

comrnents on short notice after months of foreign silence. Their experience and

perspective is greatly appreciated. Patrick Bateson dso took time from his busy schedule

at Cambridge to provide wise comments and helpfùl encouragement.

1 am fortunate to be a member of two wonderfùl families. My parents, Hart and

Marilyn Berner as well as my parents-in-law, Hugh and Elizabeth Kerr, stayed steadfastly

loyal over the years of long hours and neglect of family duties. Their faith and helping

hands were reflected in countiess facets of the project. My brothers and sisters from both

families also accepted our strange life with good grace and humour.

Lastly but clearly most importantly, I thank my wonderful and understanding wife,

Rachel Berner Kerr. Rachel wiihgly agreed to pour our Me's savings into this work, and

when the money ran out, she went with me to the bank for more. Her love and support

were the foundation 1 needed when tùst considering graduate school, and her tireless

dedication to helping me achieve my goals made it possible. She suffered alone and in

silence on the opposite side of the world during three separate years, so 1 could retum to

work with birds, once being abandoned in the middle of a low scale war. She worked

beside me during long, cold days, and endured the eeezing nights. She soothed my fears,

consoled me after my losses, bolstered my courage when 1 was fkightened and then

joyously celebrated our victories. After the anival of our wonderfid daughter Carmen, she

worked even harder while 1 pursued my work outside the home. This is for her.

TABLE OF CONTENTS

ACKNOWLEDGMENTS

TABLE OF CONTENTS

LIST OF TAE3LES

LIST OF FIGURES

INTRODUCTION

METHODS

STATISTICAL ANALYSIS

RESULTS

DISCUSSION

FUTURE DIRECTIONS

LITERATURE CITED

vii

. -. wu

List of Tables

Table 1. Origins and training regimens of experimental groups.

Table 2. Research phases and activities of experirnental groups.

List of Figures

Figure I

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Research aircraft and cygnets engaged in training exercise.

The-activity budgets of initially hand-reared (a) and initially parent-reared @) cygnets under bo th "observed" and

"unobserved" conditions.

Chi square and values of p f?om comparisons of initially hand- reared and initiaiiy parent-reared cygnets' "observed" (a) and "unobserved" (b) time-activity budgets.

Chi square and values of p derived fiom comparisons of initially hand-reared and initiaily parent-reared cygnets' observed (a) and unobserved @) time budgets.

Tirne-activity budgets of initidy hand-reared and initially parent- reared cygnets under both "observed (a) and "unobserved" (b) conditions.

Tolerance (a) and affinity @) of initially hand-reared and initially p arent-reared cygnet s for human handlers over t h e .

EIapsed times before following (s) for initiaily hand-reared and Uiitiaily parent-reared cygnets.

AircraR launch fidelity of initidy hand-reared and initially parent- reared cygnets.

Launch success rates of initially hand-reared and initialiy parent- reared cvmets.

Introduction

Human settlement and land use have profoundly altered the distribution of biota

across North Arnerica. Aithough the landscape is never in stasis, human immigration

associated with European colonization accelerated processes of change (Samson and

Knopf 1 996). European colonizers were industrious and their impact was nearly

immediate. As forests feil and land was tiiled, however, few likely noticed the decline of

bird and animal populations in the remaining vestiges of wilderness. In some cases,

subsistence or commercial hunting pressures accelerated the disap pearance of a species

(Banka 1960). Two well known examples of North American species extirpated fkom the

majority of their range are the whooping crane (Grus americnmts) and the trumpeter Swan

(Cygmrs buccinutor).

Historical context

Whooping cranes were probably never nunierous; popdations are estimated to

have totaled between 500 and 700 individuais in the mid 1800s (U.S.F.&W-S. 1994). In

the late l8OOs, completion of raiiroads, expansion of agriculture and commercial market

hunting increased. Human development came at the cost of crane habitat; in 19 18 one

farmer was credited with kiUing 12 whooping cranes at his thresher @oughty 1 989).

Despite protection under the Migratory Bird Treaty in 19 17, the predicament of the

whooping crane worsened (USF&WS 1994). By 1941 the last migratory flock of

whooping cranes had declined to only 16 birds, and a non-migratory flock of 12 birds in

Louisiana was reduced to 6 after a non-seasonal humcane (Edwards et al. 1994). During

the 1950s captive propagation programs were started at several facilities and extensive

public education campaigns were directed at reducing human caused mortality during

migration. In 1998 the single migratory flock increased to 205 birds, a twelve fold increase

in less than 60 years. Almost the same number of birds is held in captive propagation

programs throughout North Amenca (Pratt 1999).

Unlike whooping cranes, trumpeter swans were both numerous and widely

distributed in the last 200 years (Lumsden 1984, Compton 1996). The historical breeding

range included most of temperate North America Erom Central Alaska as far east as

Nedoundland (Compton 1996). Estimates suggest that flocks east of the Rocky

mountains contained as many as 130 000 birds (Lumsden 1984). The European millinery

trade and a growing urban market finded large scde commercial hunting of swans for

their skins and plumage (Mïtchell 1994). During the same penod, distribution of firearms

and settlers increased subsistence hunting pressure fiom both abonginal and colonial

communities. By the late 1800s, population densities were very low throughout the

species' range. By 1890, tnimpeter swans were completely extirpated east of the Rocky

mountains (Gillette 1996). In the lower United States, the species only sumived in the

rugged and sparsely occupied Yeliowstone region (Shea et al. 1994). The total known

population consisted of 69 individuals in 193 5 . However, much larger breeding

populations remained in remote areas of Alaska and northwestern Canada, and were

discovered in 1954 (Mitchell 1994). Extensive captive propagation and release efforts,

habitat protection rwd advocacy have resuited in an apparent conservation success story;

the continental population is nearing 20 000 birds, the R o c b Mountain population has

grown to nearly 3 000 birds and restored interior flocks number over 1500 (Ruth S hea,

pers comm).

The problem of migration

Despite the growth of both whooping Crane and tnimpeter swan populations,

serious difficulties rernain (U.S.F.&W.S. 1994, Shea et al 1994))- In the case of

whooping cranes, the entire wild population migrates in one flock between a breeding area

in Wood Buffalo National Park in north central Canada and Aransas National Wiidlife

Rehge on the gulf coast of Texas (Doughty 1989). Because whooping cranes are not

widely dispersed in either their breeding or wintering range, there is concern that a disease

outbreak, industrial accident or natural emergency could seriously darnage the species'

prospects for recovery (U.S.F.&W.S. 1994). To spread the Bsk across a wider genetic and

geographic base, the Whooping Crane Recovery Plan caiis for the establishment of two

additional breeding populations by the year 2020 (Edwards et al. 1994). The viability of a

reintroduced population wiii likely be dependant on the development of reliable migration

between secure breeding and wintering areas @chard Urbanek, WCRT, pers comm).

Under natural conditions, young whooping cranes appear to learn their migration routes

by accompanying older cranes (U. S.F.&W.S. 1994). Therefore, in the absence of adult

tutors a way to teach a migration route to released birds must be found before a new flock

c m be established.

One c m distinguish between effective annual migrations, as observed in extant

populations with unintempted histones, and non-migratory seasonal behaviour observed

in reintroduced populations lacking traditional migration routes. The former case is

characterized b y large numbers of birds successfilly moving between breeding and wint er

habitats with a high degree of route and destination fideIity. The latter case is

characterized by nomadic behaviour as birds wander individuaily or in small flocks across

potentially unsuitable Iandscapes without either clear direction or physiological scheduie.

Despite high population growth in the Rocky Mountain population of trumpeter

swans, migration routes Ieading to useable winter habitat at lower elevations and latitudes

have not been re-established. High swan densities on high altitude winter habitat increase

vulnerabiiity to severe winter conditions and disease due to crowding; in 1988/89 for

example, over 100 swans died when low water levels ailowed ice to form at a heavily used

feeding site (S hea e t al. 1 994). Accordingly, supplemental feeding was discontinued in

1992 to encourage swans to move fiuther south in winter (Gomez 1996).

Restored flocks in North Dakota, Minnesota, Michigan and Ontario face sirnilar

problems. High population growth in the absence of migratory behaviour has resulted in

high population densities at marginal winter sites where supplemental feeding is required.

Southerly pioneering by tmmpeter swans in the mid-west has resulted in high mortality in

the absence of appropriate migration routes (Compton 1996). In 1995, approximately

80% of 270 fiee flying trumpeter swans in Minnesota relied on warm water outnow and

supplementary feeding during winter months (Gillette 1996)- The 1 999 counts located 740

trumpeter swans in Minnesota (U. S -F.&.W. S. 2000). Of these, an estimated 90 - 95%

remaked in the state throughout the winter (Madeleine Linck, pers cornm). Between 50 -

90 % of the approximately 60 reintroduced tmmpeter swans released at Wye Marsh,

Ontario (N 44"3 8' W 79" 52') fail to leave the area during winter, and rely on

supplemental feeding and mechanical bubblers that prevent ice formation (Michelle

Hudolin, pers comm).

EventuaUy, the achievement of restoration gods for trumpeter swans and

whooping cranes may hinge on managers' ability to induce appropriate migration in

restored populations. 'We, as a profession, restored these magnificent birds to their

former breeding range without adequate regard for their winter survival. It is now

incumbent on us to h d suitable winterhg habitat and cnrsist the species foflnd it" (Kraft

1996: 100, my italics).

Restoration:

Restoration has been defined as, "the introduction of a species in a previously

occupied area in order to improve the conservation of the species" (Sarrazin and Barbault

1996: 474). In addition to conservation, restoratiunists may also be motivated by

aesthetic, moral or economic concerns. Perhaps due to the complexity of competing

motivations, many reintroductions are based on an incomplete understanding of the

original extirpation and the potentiai viability of reintroduced populations in changed

environments. In some cases managers attempt to restore populations with poor

knowledge of a species' basic biology and behaviour (Kraft 1996). Such reintroductions,

especially when based on fadlty understanding or incomplete data, are Iikely to end in

fadure. In some cases, misguided or uninformed restoration efforts worsen a species'

prospects for long term persistence. At the same t h e , managers may lament the urgency

for restoration that precludes coiiecting more complete information on a species' biology

and behaviour. Under these circumstances, it may be prudent to " l em while doing", and

conduct restoration experiments as integral component s of reintroduction efforts.

Management efforts

Birds that hatch at a relatively advanced state of development are known as

precocial species. Filial imprinting is a process in which the social preference of young

precocial birds becomes limited to a particular object or class of objects as a result of

exposure to them (Bolhuis 199 1). This form of learning occurs in a short penod of time

near hatching (Bateson and Horn 1994). In contrast to precocial species, altricial species

of birds hatch relatively early in development and are usualiy confined to the nest for

several weeks. Altricial species are not sensitive to imprinting stimuli to the same degree

as precocial species. Lorenz (1989) observed that imprinted precocial hatchlings wi11

follow ''unnaturai" objects such as bicycles ifthey are exposed to the objects shortly afler

hatching. Sexual irnprinting may be dehed as a similar developmental process in which

sexual preferences are acquired through leaming the characteristics of the parents (ten

Cate 1999). Although there is an extensive body of Iiterature dealing with sexual and filial

imprinting, the majority of work has focused on a very smail number of species (for review

see Bolhuis 1991). As a result, little is known about the effect of early experience on the

development of "normai"aduit behaviour in wiid populations (Eadie et a' 1995). Several

recent projects have attempted to induce migration in restored populations of threatened

species such as whooping cranes, m p e t e r swans and lesser white fronted geese (Amer

albzji-om) (Sladen and Rinnlliger 2001, Ellis et ai 1999, Mouliec 1999). Each of these

projects have in some ways altered what might be considered the "naturai" early

experience of hatchlings. AU of these projects have fallen short of producing migratory

populations of reintroduced birds with adequate potential for success in the wild

(Operation Migration 1998, Sladen and Rinninger 200 1).

Between 1975 and 1988, managers attempted to create a migratory population of

whooping cranes in the Rocky Mountain area (U.S.F.&W. S. 1994). Like tnimpeter

swans, whooping cranes appear to l e m a migration route as well as foraging and defense

behaviour fiom parents (Doughty 1989). Over 13 years, 289 whooping crane eggs were

placed in nests of incubating wild sandhill cranes on the Grays Lake National Widlife

Reserve in Idaho (USF&WS 1994). The hope was that surrogate parents would raise the

whooping cranes and lead them on their first migration, after which the whooping cranes

would become independent and seek out associations with their own species c i n e 1995).

The sandhill surrogate parents successfùliy reared the cross-fostered young, and several

whooping cranes fledged and migrated with the sandhill crane flock to Bosque del Apache

National Widlife Reserve in New Mexico (LJSF&WS 1994).

After the initial "successy7, serious problems arose. Whooping Crane mortality in

the Rocky Mountain population was high, due in part to coyote predation and collision

with power h e s (Lhe 1995). Most S ~ ~ O U S of ail was the subsequent failure of cross-

fostered whooping cranes, especiaiiy fernales, to show reproductive interest in members of

their own species. By the fall of 1992, cross-fostered adult female whooping cranes had

survived a totai of 34 individual nesting seasons without pairing (USF&WS 1994). The

project was canceled and 3 birds suvive today (Rod Driewen, pers comm).

The Wisconsin Department of Wildlife has conducted an experimentai trumpeter

swan captive rearing and release pro- since 1989 (Matteson et al. 1996). Swans were

incubated, hatched and reared under one of three sets of conditions: by costumed human

caretakers; by a remotely controlled decoy adult Swan; and by captive adult tnimpeter

swan pairs. Costumes were used in the first case to avoid cygnets irnprinting on human

caretakers. Swans fiom all three groups were reared successfùliy and released into the

wild. However, a number of swans reared by costumed human caretakers either failed to

leave release sites by fieeze up, died after attacking automobiles, were killed by humans

defending themselves after being attacked by swans or were recaptured after directing

inordinately aggressive behavior towards humans (Sumner Matteson, pers cown). A

large percentage of the released birds reared by decoy or captive pairs flew to better

quality winter habitat with the advent of fieezïng weather. However, few swans have

subsequentiy developed reliable annual migration to the same sites, and mortaiity due to

shootings and lead poisoning remain hi& (Matteson et al 1996).

Because the process of i m p ~ t i n g results in young birds directing their attention

towards a partidar object or class of objects, and is often manifested by hatchlings

following the object ifit is moved, several projects have relied on the tendency of yourg

geese, swans and cranes to follow the object of their imprinting experience as a means of

inducing migration. Ultralight Induced Migration 0, in which young birds are trained

to follow a smali aircraft, is thought to offer a possible mechanism for establishg

migration patterns in reintroduced populations ( L w d e n et al. 2 990). Strong imprinting

of young birds on their human handlers during the initial stages of UlM projects is

reported to increase the success rates of fiight training (Sladen and Lishman 1994).

However, results fiom other reintroduction programs have suggested that some captive

reared birds may not develop s u ~ v a l and reproduction behaviors appropriate for success

in the wild, possibly due to interspecific imprinting (Mahan and Simmers 1992).

Specifically, sexual imprinting of birds on human handlers or interspecific foster parents

contributed to breeding failure in the Rocky Mountain whooping Crane experiment and the

development of inordinately aggressive adult tnunpeter swans in Wisconsin ( U S .F.&W.S.

1994; Mattseon et ai. 1996). Canada geese (Branta canadensis) released after being led

on an ultralight-induced migration fkom Ontario to South Carolina were so tame that they

were easily approached by soldiers at a busy military base and may have been killed there

(Kuk Goolsby, pers comm).

The use of costumes that disguise the characteristic fonn and outline of human

handlers has been proposed as a means to avoid hatchlings identwng with, and sexually

imprinting on, hurnans during captive rearing projects where the final goal is release into

wild populations of conspecifics (Urbanek and Bookhout 1 992). To train cranes to follow

aircraft, sandhiil cranes (Grus canadensis) were hatched in incubators and then imprinted

on costumed hancilers (Lishman et al 1996). Despite being raised by costumed caretakers,

the cranes showed little fear of uncostumed hurnans, and exhibited identical preferences

among staff rnembers both with and without costumes after project termination (B ezner

Kerr, unpublished data). In a subsequent project, sandhill cranes were incubator hatched,

costume-reared and led by ultralight fiom southem Ontario to Virginia. The cranes

returned to Ontario the following spring, but were extremely tame. They landed in

schoolyards, busy Street intersections and even inside a prison yard (Operation Migration

1998). The use of costumes by caretakers clearly failed to avoid the taming of birds

during captive rearing.

Ifimprinting of hatchlings on humans was a prerequisite to successfbl application

of UlM, but it reduced the prospects of successful reproduction and suMval of induced

migrants, it would appear to be a tool of limited use to managers seeking to improve the

long term viability of s m d or threatened populations. It has been suggested, however,

that waterfowl foilow mechanical surrogates for reasons ünrelated to imprinting

experiences (Carrick and Lumsden 1995). SpecEcaiiy, Carrick suggested that an innate

"following response" emerges as a young bird approaches fledgling age (Carrick, pers

comm). Such a response may have adaptive value if it serves to improve brood cohesion

while young birds acquire the ability to fly. If foIlowing behaviour as employed by UIM is

not iinked to imprinting expenences, then potential problems related to improper

imprinting might be avoided altogether, thus improving W ' s prospects of becoming a

viable option for Swan managers.

My study was designed to test the effect of early experience on trumpeter swan

cygnets' ability to leam to foilow an airplane. As such, it fit within the goals of the

ongoing Ontario Trumpeter Swan Restoration Project (Lumsden 1999). In 1 997, 1

demonstrated that cygnets could be trained to fiy with an aircraft without resorting to

hand rearing during the first 10 d post-hatch (Berner Kerr, unpublished data). In 1998, I

developed a refined and enlarged expenment to test more reliably the hypothesis that

exposure of tnimpeter swan cygnets to humans or aircraft during the immediate post-

hatch penod is not required to elicit foliowing behaviour as employed in UIM. Ifnot, then

ability of swans to l e m to foiiow an airplane should not M e r between initially hand-

reared and iaitially parent-reared cygnets.

Methods

Twenty fertile trumpeter nvan eggs were obtained from avicultunsts participating

in the Ontario Tmpe te r Swan Restoration Project. Al1 procedures were carried out

under the authority of an Animal Utiiization Permit provided by the Ontario Ministry of

Natural Resources. Eggs were assigned to 4 treatment groups (Table 1). Two groups

were hatched by captive pairs of tnimpeter swans while the others groups were artificially

incubated and hatched. A total of 17 cygnets was produced. Due to constraints imposed

Table 1. Origins, training regimens and sarnple size of experimental groups.

Group 1 1 Initiaiiy hand-reared AND Aircraft-trained 1 n = 4

Group

Group 2 1 Xnitiaiiy hand-reared NOT Aircraft-trained 1 n = 3

Treatment

Group 4 1 Inïtialiv parent-reared NOT Arcraft-trained 1 n = 5

Sample Size

Group 3 Initially parent-reared AND Aircraft-trained 1 n = 5

by clutch timing, eggs could not be randody assigned to treatment groups, but were

maintained in sibling groups as laid. Potential implications of this constrained design are

discussed Iater-

The project consisted of three distinct phases (Table 2). Phase 1, early rearing,

lasted from O - 10 d post-hatch, during which groups 1 and 2 were hatched in incubators

and hand-reared by humans, while group 3 and 4 cygnets were hatched in nests and reared

by their parents. Phase 2 lasted fiom 1 1 - 75 d post-hatch, during which aircraft trainin%

took place for two treatment groups (groups 1, 3), wMe group 2 was isolated Corn

humans and group 4 was reared by its parents without human interference. Phase 3

consisted of flight testing for alI 4 groups and lasted fiom 90 - 150 d post-hatch.

Phase 1: early reanirg

The early rearing period was considered to last 10 d, a penod intended in the

absence of specifïc data to extend beyond the "sensitive period" for imprinting described in

other species as lasthng between 15 h and several days (Bolhuis 199 1). Ten eggs were

incubated in a G.O.F. Manufacturingo mode1 1202 forced air electric incubator.

Incubation was supervised by W. Carrick. The incubator temperature was maintained at

99" and 87% relative humidity. Mechanical turners rotated the eggs through 180 degrees

every 2 h. Seven of the 10 eggs hatched and were separated into sibling groups (1 and 2)

(Table 1). Researchers associated closely with cygnets to increase the likelitio O d of

imprinting on humans. Exposure sessions included t h e spent at rest, swimming, feeding

Table 2. Research phases, durations and activities of experimental groups.

Phase: Duration: Group:

I 2 3 4

Activity:

hand-rearing hand-rearing p arent-rearing parent-rearing

aircraft-training isoIation aircraft-training paren-rearing

flight testing flight testing Eght testing fIight testing

and wallcing and involved extensive handling and use of speech. Exposure sessions lasted

2 h. Each group received a minimum of 8 h of exposure per day. The cygnets were

introduced to the ultralight aircrafl beginning at approximately 24 h post-hatch, and began

to foliow the aircraft the same day. By the end of the 10 d period, both groups of

innibator-hatched cygnets followed the aircraft with the motor running. A fùrther 10

cygnets were produced by 2 captive pairs of tnimpeter swans. The two nest-hatched

groups (three and four) were not manipdated by humans in any way during the 10 day

period (Table 1). Cygnets in alI 4 treatment groups had 24 h access to feeders filled with

20% protein Raiston Purina commercial duck starter mixture.

Phase 2: aire@ training

At 1 1 d post-hatch, cygnets from group 2 were relocated to a 15 x 7-m isolation

pen with shade, swimming area and feeder at W. Carrïck's facility near Toroiito, Ontario

(N 43 O 26' W 79O 159, while group 1 remained at the hatchery site near Waterdowq

Ontario (N 43 O 15' W 79"563 for training to foiiow the aircraft. Cygnets fiom group 3

were taken fiom their parents at 10 d post-hatch and relocated to the hatchery site to

begin aircraft training. Group 4 remained with its parents at Midhurst provincial park,

Ontario (N 4S035' W8O080').

Cygnets at the hatchery site were kept in 4 x 6-m pens with shade, swimming areas

and feeders during daylight. Cygnets were placed in 0.75 x 1.2 m wooden brooder boxes

heated by 75 watt electric heat lamps overnight- The brooder boxes were equipped with

water and feeder. When the youngest cygnets were old enough to spend evenings outside

without the artincial heat provided in the brooder boxes (group 1; 20 d post-hatch),

groups 1 and 3 were relocated to the training site at Guelph Lake Conservation Area, near

Guelph, Ontario (N 43 "35' W80° 11'). Cygnets were transported by covered pickup

truck. Two 5 x 10 m pens were built on the lakeshore for each group with shade, feeding

and swirnming areas in each. The training area consisted of a 15-ha artincial lake

surrounded by agricultural land and conservation easements, A restriction on motorized

use of the area and lack of road access permitted my training activities to take place

without interaction with humans not affiliated with the research. The aircraft was tied

down on the shoreline within sight of both groups of cygnets. Staff kept a 24-h watch and

slept in tents at the site. M e r 3 5 d post hatch, cygnets were fed Ralston Purina 17%

protein commercial waterfowl layer ration.

Aircruff h-aining

Groups 1 and 3 were exercised daily by swimming on the lake and a variety of

observations were made. As development pennitted (see below), cygnets were exercised

daily with a modified I&J Tukan 8 ultralight aircrafl. mounted on straight floats. In order

to reinforce foilowing behaviour, a mass of plant food (Potarnogeton pecfinafzrs) from the

cygnets' preferred feeding areas was harvested and placed on the floats of the aircraft

(Fi-we 1). Ifcygnets followed the aircraft, the operator would stop and allow the cygnets

to eat the food. As cygnets increased their endurance, the akcraft was used to lead them

across the lake to other feeding areas. Training sessions lasted approximately 1 h. On

Figure 1. Research aircraft and cygnets engaged in training exercise.

some occasions, a kayak was used to herd reluctant birds closer to the aircraft. Ifhigh

winds made use of the ultralight aircraft difEcult, training exercises were conducted with a

kayak.

Time-activity budgets

Behaviour was observed daily and Erom these observations, time-activity budgets

were calculated to determine whether early rearing conditions had an effect on cygnet

behaviour. A modified instantaneous scan sampling procedure was employed (Martin and

Bateson 1986). The observer s c a ~ e d aii members of an experimental group at precise 5

min intervals measured with a wrist stopwatch, and noted the number of cygnets engaged

in each of 5 behaviours. Time-activity observations were conducted with cygnets located

inside their pens. Observations were recorded on a paper template and transcribed to a

notebook. Behaviours were identified as foiiows:

Feeding: Foraging, eating and pecking directed at prepared food or natural

vegetation.

Preening: Down or feather cleaning and maintenance, or bill manipulation of the oil

gland.

Locomotion: Walking, nvimming, ciirnbing, flapping and fiight attempts.

Resting : Stretching, yawning, sleeping and time spent motionless with the cygnet ' s

body in contact with the water or earth and the head placed in contact with

the body.

Erect postures with at l e s t the upper 50% of the neck held verticaily on

either land or water where the cygnet is not erîgaged in locomotion.

To determine whether the presence of humans afEected cygnet behaviour, time-activity

budgets were conducted with human observers visible to the cygnets ('obsenred' time-

activity budgets) as weU as with the observer concealed behind natural blinds of tail

vegetation surroundhg the pens ('unobserved' time-activity budgets).

ToZerance and a$?nity

To measure cygnets' tolerance of and affinity for humans, an observer entered a

group's pen and chose a location near the cygnets (position one). A circle centered on the

observer with a diameter of 5 m was visualized, and the number of cygnets inside the

circle was recorded at precise 5-min intervals for 15 min measured with a wrist stopwatch

as a reference. The observer then changed locations by a minimum of 5 m and conducted a

second set of observations. Each cygnet inside the circle during each observation received

a score of 1, while a cygnet outside the circle received a score of O. Scores were summed

for the group after each observation. High group scores at the first position indicated that

the group of cygnets tolerated the approach and presence of the human. High group

scores at the second position indicated that cygnets rnoved with the observer to the new

location, and was interpreted as preference or affinity for the human. Tests were

conducted daily.

The-to-foZZow

The tendencies of cygnets to follow were measured as the time interval (s)

between when a human left a cygnet group's area and at least 50% of the group foliowed.

Each test score was equal to the number of seconds that elapsed between the human

leaving the area and the majority of the group foiiowing. A low score indicated a very

quick following response, while a high score indicated a slow or weak response. Tests

were terminated after 3 0 s if no foiiowing behaviour was observed. Between 10 and 3 5 d

post-hatch, tirne-to-follow tests were conducted by humans moving on foot. M e r 36 d

post-hatch, time-to-follow tests were conducted on water with the aircraft.

Phase 3: friglt t te&-ng

By 75 d (group l), 80 d (group 2) and 90 d (groups 3 and 4) post-hatch, aii

groups had been relocated to the tiight testing area at South Bay, located on Ramsey Lake

in Sudbury, Ontario (N 46'28' W 80 46O58') by covered pick-up truck. The spread of ages

at time of relocation was due to variation in hatch dates for the dif3erent treatment groups.

Relocations were made on two occasions. Groups 1 and 3 were relocated simultaneously;

and groups 2 and 4 were relocated in a subsequent trip. Four contiguous 3 x 7 m pens

were built on the Iakeshore such that the majority of the pen enclosed water, but included

sufficient dry land that cygnets could stand on a dry area ifpreferred. Feeders were

located on dry land. Each pen had a door in the water that opened directly onto the lake.

Groups 2 and 4 were sexed, banded and tagged through the patagium after

20

relocation to South Bay. Patagiai tags were not avaïlable for groups 1 and 3, so they were

left untagged until120 d (group 1) and 135 d (group 3) post-hatch. The implications of

tagging at dafferent ages are discussed below.

Ftighr Tesring

During each flight test, the aircraft was taxied to the &ont of the pens while an

assistant waited at the door. A gearbox clutch allowed the aircraft engine to operate

without rotating the propellor, pennitting the pilot to adjust the aircraft's position. When

the pilot signaied his readiness, the pen doors were opened and the a i m a accelerated

towards open water away fiom the pens. A 5-point scale was used to evaluate the swans'

tendency to takeoff with the aircraft, referred to as "launch fidelity". Video tape records

were used to resolve any f l c u l t y in s c o ~ g launch fidelity. Scores reflected the

behaviour of the rnajorïty of birds in a group; and groups were scored once per flight

attempt. The scores were:

Score Flight Behaviour

O Group does not take off

1 Group flees aircraft

2 Group nies between 90' and 45" of aircraft course (neither flee nor follow)

3 Group tlies between 45 " and 10" of aircraft course (same generai

direction, but not directly foliowing)

Group follows aircraft on the same course

When swam matured to the extent that flight durations lasted longer than a few

seconds, total time aloft was recorded. A Bail 0 mode1 19 electronic variorneter and

aitirneter was used to measure altitude above the lake surface as well as rate of cIimb. An

aircraft radio was used to report the number of swans aloft to a recorder on the ground, as

well as the altitude and speed as the flight progressed. Takeoff attempts were initiated

with the same group until the swans would no longer follow the aircraft. At the end of

each flight testing session the group of swans was herded with kayaks back to the pens,

but would occasionally swim back unassisted. As fight durations increased, swans often

landed back at the pen area.

Statistical Analyses

The-activity budgets

Time-activity budget data were analyzed in 10-d blocks. Chi square goodness of

fit tests were carried out between data sets fiom "observed" and 'hnobserved" time-

activity budgets for each group to test the statistical nuil hypothesis of no observer effect

(Zar 1996:458). Chi square goodness of fit tests were also used to compare initially hand-

reared and initially parent-reared cygnets, to test the statistical null hypothesis of no

difference between groups. Where group-level analysis indicated that a difEerence existed,

2x2 Yates' corrected contingency tables were used to explore pair-wise daerences in

individuai behaviours (Fowler and Cohen 1986). Where expected values feIl below

thresholds required for the Yates corrected chi square test, the Fisher exact test was

employed (Dean et al. 2996). As data £rom the same subjects were used in 7 comparisons,

the p value required to reject the null hypothesis was adjusted to 0.007 using the

Bonferroni correction for multiple comparisons which adjusts the value downwards by

dividing by the total number of comparisons (0.05 / 7 = 0.007).

Tolerance and affina

Two tailed t-tests were used to evaluate the statistical null hypothesis of no

Merence between groups. P values required to reject the null hypothesis were adjusted to

0.007 using the Bonferroni correction for multiple comparisons.

The-tu-follow

Time-to-follow scores for both groups were highly skewed. The data were

normalized by log transformation (Fowler and Cohen 1984). As there were many zeros, a

score of 1 was added to all scores before transforming. Skewness of transformed data was

tested in SPSS (SPSS Inc. 1999). Data in 10-day blocks were compared by 2-tailed t-tests

to test the statistical null hypothesis that no difference existed between treatment groups.

Bonferroni's correction for multiple comparisons was used to adjust the p-value required

to reject the null hypothesis to 0.007. Derived means were calculated by finding the

antilog of analyzed data and subtracting 1.

Long distance induced migrations are only feasible ifsubject birds foUow the

aircraft within narrowly defhed margins. To sirnpw anaiysis, launch fidelity data were re-

coded £tom the original 5-point nominal scale reflecting a broad range of flight outcornes

to a binary scale indicating £iïght success (birds foliow aircraft within IO degrees of aircraft

course) or failure (birds do not follow aircraft within ten degrees of aircrafl course). Two

by two contingency tables were used to test the statistical nuli hypothesis of no difference

between groups. Chi square statistics were calculated using Yates' correction where

expected ce11 values were greater than 5 (Fowler and Cohen 1986). The Fisher exact test

was used in ali other cases (Dean et al 1996). The p-value required to reject the null

hypothesis was adjusted to 0.007 using the Bonferroni correction for multiple

comparisons. Launch success was converted to percent for purposes of plotting (number

of successfül launches / total number of flight attempts).

Results:

Aircraft Training Period

Time-activity budgets: Observer efJects

When able to see human observers, a greater percent of initially hand-reared

cygnets were resting and feeding, and fewer preening and aiert, than when they could not

see humans. lnitiaily parent-reared cygnets that could see human obsenrers spent

significantly more time resting and less time preening than when they could not see human

observers (5 comparisons; p < 0.01) (Figure 2). When the complete data were

Percent of cygnets engaged in actlvlty Percent of cygnets engaged in activity

examined over the 60-d observation penod, both initially parent-reared (x' = 26; df = 4; p

c 0.005) and initially hand-reared cygnets' (x2 = 5 1; df = 4; p < 0.005) time-activity

budgets difEered overail between the observed and unobserved conditions. Thus, the

statistical null hypothesis of no observer effect was rejected.

The observer effect was strongest in initially parent-reared swans. When examined

in 10-d blocks of observations, signincant @ < 0.007) dserences between "observed" and

'I.mobserved" time-activity budget data were found in 4 of 7 sets of observations of

initially parent-reared cygnets, and in 3 of 7 sets of initially hand-reared cygnets (Figure

3 -

Time-acrivity budgets: EfSecfs of rearing

The effect of rearing was strongest in ccobserved" time-activity budgets (that is,

those data coilected when cygnets could see humans). Signifïcant differences were

detected between initiaily parent-reared and initially hand-reared cygnets in 5 of 7

complete 1 O-d time-activity budgets, compared to only 2 of 7 "unobserved" 10-d tirne-

activity budgets (Figure 4). Overail, initially hand-reared cygnets rested more and preened

less than initiaiiy parent-reared birds, regardiess of whether humans observers were visible-

InitiaUy hand-reared birds spent more time eating and less time alert than initiaüy parent-

reared birds when they could see their human observers. However, no significant

dEerence was detected in eating or alert behaviour when observers were concealed

behind blinds (Figure 5). When the complete tirne-activity budget data were examined

lmpact of observer on behaviour P vs age: initially parent-reared

0.3 -

e> * * * 3

7ü 0.15 -. > a

10-19 30-39 50-59 70-79

Impact of observer on behaviour P vs age: initially hand-reared 0.3 -r

Age post-hatch (d) Age post-hatch (d)

Figure 3. Chi square and values of p derived from comparisons of "observed"and "unobserveci" time-activity budgets fiom initidy hand-reared (a) and initiaily parent- reared cygnets (b). With 7 comparisons, a p value of 0.007 is required to reject the nul1 hypothesis. Asterisks (*) indicate significant ciifferences.

Chi square vs. age Chi square vs age lnitially parent-reared Initially hand-reared

60 -

50

-a 5 3 0 m -

0- 20 -

I O -

O 1 0 - 1 9 30-39 5 0 - 5 9 70-79 10-19 3 0 - 3 9 5 0 - 5 9 7 0 - 7 9

Age post-hatch (d) Age post-hatch (d)

50

2 4 0 : j $ h 2 u 20 - r

O -

-r

f!:b : I

P vs. age Observed time budgets

Age post-hatch (d)

Chi square vs. age Observed time budgets

O J : 10-19 30-39 50-59 70-79

Age post-hatch (d)

P vs. age Unobserved time budgets

0.7 7

Age post-hatch (d)

Chi square vs. age Unobserved time budgets

2' : Y

10-19 30-39 50-59 70-79 Age poçt-hatch (d)

Figure 4. Chi square and values of p derived from comparisons of initiaüy hand-reared and initiaily parent-reared cygnets' observed (a) and unobserved @) time budgets. With 7 comparisons, a p value of 0.007 is required to reject the nuli hypothesis of no rearing effect. Asterisks (*) indicate signifïcant ciifferences.

Effect of rearing on behaviour "Obsewed" time - activity budgets

Reçting Preening Feeding Alert Locomotion Activity

pq &y, Initially Parent Reared . -C-.

Initially Hand Reared

"Unobserved" time - activity budgets

Resting Preening Feeding Alert Locomotion Act ivity

Figure 5. Percent o f total group engaged in 5 behaviors and standard errors calculated from time - activity budgets of initially hand reared and initially parent reared cygnets under both "observed" (a) and "unobserved" (b) conditions.

over the 70-d obsenration period, there were signi6cant differences between initially

parent-reared and initially hand-reared cygnets under both observed (x2= 85; df = 4; p <

0.005) and unobserved (x2= 45; df= 4; p c 0.005) conditions. Thus, the statistical nul1

hypothesis of no effect of rearing was rejected .

Rearing and observation effects interacted with each other. For example, initially

parent-reared and initially hand-reared cygnets' time-activity budgets differed ~i~gpificantly

in 13 of 35 pair wise cornparisons of individual behaviours analyzed in 10-d bIocks when

cygnets coutd see the human observer. When humans were hidden fkom the cygnets'

sight, pair wise comparisons of tirne-activity budgets differed in only 2 of 3 5 possible

cases (35 comparisons; p < 0.001).

Tulerance ami afin*

Figure 6a shows that initially hand-reared cygnets were significantly more tolerant

of human observers than initially parent-reared cygnets overall (t = 5.47; df = 244; p <

0.005). Initially parent-reared cygnets were intolerant of human presence during the f i s t

15 d of the aIrcraft training period ( j? = 48 %; n = 180). Dunng the same period, initially

hand-reared cygnets were highiy tolerant (R = 100%; n = 150). After 30 d post-hatch, the

dserence between initidy parent-reared and initiaiiy hand-reared cygnets largely

disapp eared, and dserences remained smaU throughout the remainder of the aircrafl

training period.

Tolerance

age post-hatch (d)

-lnitially hand reared - lnitially parent reared

Affinity

age post-hatch (d) - lnitially hand reared - Initially parent rear

Figure 6. Tolerance (a) and affinity (b) of initiaily hand reared and initially parent reared cygnets for human handlers over time. Bars indicate standard error.

Similarly, initialiy hand-reared cygnets exhibited significantly greater RfFinity for

human handlers compared to initialiy parent-reared cygnets (t = 8 -4 1 ; df =228; p <.0.005)

(Figure 6b). As was the case when tested for tolerance, initialLy parent-reared cygnets

showed Little or no affin* for human observers during the fkst 25 d of the aircraft training

penod (Z = 7 %; n = 218). During the same period, initiaiiy hand-reared cygnets exhibited

high a E t y for observers (R = 99 %; n = 284). The dserence between the 2 groups

disappeared by approlcimately 40 d post-hatch.

Time tu fo2Zo-w

Figure 7 shows that initially hand-reared cygnets followed humans and the aircrafl

sooner (derived n = 2 s) than initially parent-reared cygnets (derived n = 8 s) over the

course of the 70 day aircraf? training period (t = -7.53; p <0.005; df = 182), though the

difference between the two groups changed over tirne. From 11-29 d post-hatch, initially

parent-reared cygnets tended to crowd against the far side of the pen when humans

approached, and failed to foilow humans even once during 1 7 tests. During the same

period, initiaily hand-reared cygnets followed humans after a mean delay of 5.7s.

Between 30 and 39 d post-hatch, dflerences in following behaviour became less

obvious. As was the case in 1997 (Berner Kerr, unpubiished data), initiaily parent-reared

cygnets suddenly responded to humans and changed following behaviour. At 29 d post-

hatch, initially parent-reared cygnets showed no inchation to follow humans; at 3 1 d,

cygnets followed on 3 occasions after delays of 16, 22 and 5 s respectively. InitialIy

Age post hatch (d) - lnitially hand reared - Initially parent reared

Figure 7. Elapsed times before following (s) with standard error bars for initially hand reared and initially parent reared cygnets. Tests were terminated after 30 s if no following occurred.

parent-reared cygnets then continued to follow humans and the aircraft promptiy

whenever tested during the remainder of the aircraR training period.

Between 40 and 59 d post-hatch there was no significaut difference between

initially hand-reared and initially parent-reared cygnets' scores (t = -042; p >O -007; df =

27). A significant difference re-emerged in the final 20 d of the aircraft training period (t =

-6.42; p < 0.007; df= 44). Notwithstanding the overd merences between time-to-

foUow scores, 1 observed that initiaily parent-reared cygnets appeared to become more

adept at following by the late stages of the aircraft training period, as initialIy hand-reared

cygnets occasionaUy refused to leave their pen if the aircraft was in sight and, on several

occasions, even refiised to exercise.

Flight Testing Period

As descnbed above, patagial wïng tags were fitted to cygnets in groups 2 and 4 at

the beDoinning of the fight testing period. Patagial tags were applied to members of groups

1 and 3 when the tags became available, 30 d after flight testing began. Significant

reductions in fiight performance were observed. Maximum altitudes dropped £tom

approximately 100 m to 3 m following application of the tags, and flight durations

dropped fiom over 10 min to approximately 30 S. The tags were removed after 30 d and

immediate improvements in fiight performance were O bserved. At this point, in light of the

large performance fluctuations apparently associated with tagging, 1 decided that flight

testing data collected fiom groups 2 and 4 were too seriously compromised by the

differences in development that had arisen between tagged and untagged birds during

extra 30 d of tagging, and they were not considered fùrther in the experiment.

Figure 8 shows that fiom the first days of flight testing, initiaily parent-reared

cygnets demonstrated a greater wiiiingness to takeoff with the aircrafl compared to

initially hand-reared cygnets. Figure 9 compares the percent launch niccess of the two

groups. The reluctance to follow humans or the aircraft occasionaily exhibited by initialiy

hand-reared cygnets during training became more pronounced during flight testing,

aEecting the results in a few important ways. Most importantly, the initidy parent-reared

cygnets' greater ;iffini@ for the aircraft during this penod resulted in a greater number of

takeoffs per testing session compared to iaitially hand-reared cygnets, which biased the

total number of flight attempts in favor of the former. In 126 launch attempts, initially

parent-reared cygnets were three times more likely to successfully takeoff with the aircraft

compared to initiaily hand-reared cygnets (Fisher Exact test, p < 0.001), similar to what 1

observed the previous year (Berner Kerr, unpublished report).

The performance gap increased between the groups of cygnets throughout the

flight testing penod. Initidy parent-reared cygnets improved launch fidelity with

expenence, and flîghts tended to increase in duration. By contrast, when following the

aircraft, initidy hand-reared cygnets became increasingly unpredictable in £iight

behaviour, and night durations never increased to the level where cross country flights

could be attempted. Initially parent-reared cygnets consistentiy landed near the pen area at

Launch fidelity

. . . . . . . . . . . . . . . . . . . . . . 80-84 95-99 110-114 125-129 140-144 155-159 170-174

Age posthatch (d) - lnitially hand reared ,- Initially parent reared

Figure 8. Aircraft Iaunch fidelity of initidly hand-reared and initiaiiy parent-reared cygnets.

Launch success

Age posthatch (d)

lnitially hand reared - lnitially parent reared

Figure 9: Launch success rates of initidy hand-reared and initiaiiy parent-reared cygnets.

the end of praaice flights but initidy hand-reared birds landed in a variety of locations,

including neighboring fields and ponds, which cost valuable hours while staff searched for,

captured and retumed them to the pen area. As winter was approachg quickly and

initially hand-reared cygnets were not showing improvements in following, 1 decided that 1

had monitored the experiment proper about the effects of early experience on the

development of following behaviour for as long as possible without compromising the

success of the planned UIM. 1 fùrther decided that it would not be possible to monitor the

experiment throughout the UIM as origindy planned, because the initially hand-reared

group 3 wodd not be ready in time in any case. 1 decided instead to concentrate on

preparing the initiaiiy parent-reared cygnets for the planned induced migration flight to

Mascatatuck National Wildlife Refuge near Seymour, Indiana (N 3 8 O 5 5' W 8 5 O 49'). What

follows is included to complete the description of the overail project of which the

experiment was a part, but also serves to contrat with the results of UIMs using hand-

reared birds only (see introduction).

A volunteer team consisting of four pilots, 2 aircraft and ground support

equipment left Sudbury, Ontario on 8 December, 1998 with 5 initially parent-reared

cygnets. The training aircraft was used to lead the swans using the same procedures as

during training, while the second aircraft flew alongside 10 - 200 m away in case of

emergency, or to round up straying birds. On the first leg of the trip, one cygnet turned

away over dangerous terrain, while the aircraft continued on with the rest of the group.

After the loss of the bird, the remaining 4 cygnets fiew steadily on the next 7 legs to

Mascatatuck National Wildlife Refiige near Seymour, Lndiana (N 3 8 O 5 5' W 8 5 O 49'),

where the flight ended on December 23, 1998. The total migration distance was 1200 km.

Maximum altitude en route was 950 m and airspeeds averaged 70 km/h with bnef periods

in excess of 100 M. The longest distance flown on any leg was 210 km- Temperatures

measured at flying altitude ranged between 10 OC and - 1 5 OC .

At Mascatatuck NWR the cygnets were colour marked with idiosyncratic patterns

of black and yellow dye and then released on the refuge. Unlike hand-reared birds in other

projects, the cygnets did not associate with stafï or visitors on the refùge, and were rarely

sighted aRer release. The cygnets were last sighted on the refuge in late Januaq 1999. ,

Flooded conditions made it difiïcult for rehge staff to search for swans in large areas of

the refuge. Thus, the lack of sightings codd not be interpreted to mean that the swans

were not in the refùge area after late January 1999. Numerous sightings of immature

trurnpeter Swan cygnets between Indiana and Ontario were received fiom the public in

March and April 1999, but none could be con£irmed as an experimental cygnet. On 5 May

1999,4 swans were reported in Sudbury. Two were confirrned as members of the

experiment al group by independent readings of leg band numbers.

DISCUSSION

Although shy of human contact, cygnets initidy reared by their parents eventudly

foIiowed the aircraft better, and flew more reliably, than hand-reared cygnets. The results

indicate that imprinting on h a n s during the early stages of training is not necessary, and

possibly even detrimental, to the efFicacy of ultralight training as a method to induce

migration in tnimpeter swans.

Captive rearing of animals intended for eventual release to the wild can have long

t e m deleterious consequences (ten Cate 1995). In the case of migratory birds, captive

rearing has led to improper sexual imprinting in severd species and has hindered

restoration efforts (Mahan and Simmers 1992, U.S.F.&W.S. 1994). Despite the use of the

UIM procedure for over 10 y, it is noteworthy that rigorous experimental investigations of

UItralight Induced Migration and its ramifications have not been made. As far as 1 know,

this study was the fkst application of hypothesis testing to an Wtralight Induced Migration

project. If a controlled experimental design had not been adhered to, and the experiment

run to its conclusion, merences in flight success between hand-reared and UiitialIy parent-

reared cygnets wodd not have been detected. Initialiy parent-reared cygnets would likely

have been culled i?om the project before following abilities emerged, due to the

preconceived notion that aircraf? foilowing results fiom imprinting on humans or aircraft,

and that the birds were "too wiid". Previous work confùsed the 'pattern' of following

behaviour with the 'process' of imprinting as originaiiy described by Lorenz (Lishman et

al 1996). Because of this mistaken and simplistic understanding of imprinting, the

observed phenornenon was attributed to imprinting, and the misunderstanding was

maiatained and even reinforced. However, by segregating the effects of imprinting and

hter training, my experiment shows that other processes (such as training) can result in the

same pattern with even greater likelihood of success.

However, because initiaily parent-reared cygnets were cooperative, they were

fligbt tested 3 times as often as initidy hand-reared cygnets. Therefore, it is fair to

question if initialiy parent-reared cygnets did not benefit in some way during the

experiment from hcreased testing f?equency, possibly at the expense of the initially hand-

reared cygnets. The question, however, is a 'red herrhg'. My research was concemed

with whether close contact between humans and hatchlings in the early post-hatch penod

is a prerequisite to the subsequent development ofa foilowing response as employed in

Wtralight Induced Migration. Based on my results, the answer is "no".

My research may be vulnerable to the criticism that the observed dserences in

foilowing and flying behaviour were due to varying expressions of heritable traits. In other

words, the observed behaviour of initially parent-reared and inîtidly hand-reared cygnets

may have dEered for genetic reasons, rather than manipulation of the experimental

variable. Future work on this question would benefit &om a randomized assignment of

eggs into treatment groups. Total randomization, however, wiil require a much Larger pool

of breeding pairs with synchronized laying and incubation schedules to guarantee sufficient

sarnple sizes in sirnultaneous experiments. As captive rearing programs in the east appear

incapable of meeting this criterion, the role played by heritable traits in the development of

following behavior will not likely be tested in the near future. In my experiment, however,

treatment groups were randomized at a second level. Clutches were assigned to treatment

groups by hatch order rather than by pair quality or previous rearing success. In two

consecu tive years, 1 observed that iaitially parent-reared clut ches from two unrelated pairs

followed and flew with greater endurance, at higher altitudes and with greater

predictability than initialiy hand-reared cygnets of the same age.

A preliminary review of these results suggests that the following behaviour at the

core of Ultraiight Induced Migration is a simple product of associative leaming. In fact,

following success as measured by time-to-foliow tests, tolerance and affinity tests, launch

success and flight duration improved steadily over time. When cygnets began to folIow

handlers and then the aircr&, they were rewarded by both food and reductions in anxiety

caused by the handler moving away. How then do we explain dzerences in following

success between hand-reared and initiaily parent-reared cygnets? 1 believe that initially

parent-reared and hand-reared cygnets underwent quite different learning processes and

experiences. 1 suggest that the Merences that became apparent late in the experiment

stemmed fiom the very early experience of the cygnets in the period between O - 1 0 d post

hatch.

Incubator hatched cygnets imprint on their human handlers, a process that is

inevitable whenever humans incubator-hatch and hand rear precocial waterfowl (ten Cate

1999). In my experiment, an outcome of this close contact between cygnet and human

handler, was that the social behaviour and attention of young cygnets was directed at their

human handlers. It may be that the early experience of hand-reared cygnets and

subsequent direction of attention towards human handlers Iimits their ability to l e m about

future associative relationships. In contrast, cygnets uiitially reared by their parents in a

"naturai" context appeared to leam to associate foUowing behaviour and a rewarded state.

Hand-reared cygnets were not successfd at leamhg to foUow beyond the very simple

context of walkïng behind a handler at low speed. Initially parent-reared cygnets

eventually leamed to foUow the aircraft reiiably enough to fly over 1200 km.

Althougti most of the foUowing behaviour observed in this experiment can be

adequately explained as outcomes of associative leaming, there is one exception. When

parent-reared cygnets first foliowed a human handler, they responded to a previously

experienced stimulus (the handler leaving the area) in a novel way (by leaving the pen and

following the handler outside). It should be noted that the following response had not been

directed at humans previously, and the outcome was a high level of stress for the cygnets,

as demonstrated by loud distress calling, ninning and hiding in undergrowth immediately

outside the pen door (Lorenz 1989). In other words, the response (following) resulted in a

highly stressfül state. Despite the stressfùl result of their response, following was relatively

easy to eIicit on aU subsequent occasions. Based on this observation as well as similar

observations in 2 previous experiments (Berner Kerr, unpublished data), 1 suggest that a

latent following tendency does exïst in cygnets. It is only when the fear of handlers andor

novel situations is habituated that this latent foIlowing response can emerge. Associative

leaming strengthens the association steadily until the fùliy developed following response

emerges.

Future directions

We have seen that ultralight aircraft may be used to successfully instil at least the

b eginnings of migratory behaviour in cap tive-reared birds. Having develo p ed a mechanism

by which the first step may be taken, it is incumbent upon managers to deveiop methods

capable of producing appropriate or "wild" behaviour in released birds. That initidy

parent-reared cygnets with 10 days of parental exposure learned to fouow an airplane

suggests that significantly longer contact with parents may be desirable in a release

program. It is reasonable to assume that greater parental contact is likely to result in

greater persistence of "Wild" behaviour. However, in the case of IlIM work there is likely

a length of parental contact beyond which diminished aircraft following success will be

obtained, as completely parent-reared birds are not known to follow aircratt, despite

innumerable opportunitties to do so. Determining the maximum length of parental contact

d e r which reliable folfowing c m stiU be elicited in trumpeter cygnets is recommended.

Regardless of the initial experîence of anbals, many species may eventually be

tamed by repeated exposure to humans (ten Cate 1995). Experience shows that the fear

response of swans can also be habituated if repeated contact with humans occurs without

negative outcornes. Ifthe goal of reintroductions is to produce a population of birds which

avoids human contact, then future work should minimize the number of contact hours with

humans. To minimize or prevent generalization of foliowïng behaviour, trainers should

rernain with the aircraft at ail times during training sessions. Speech should be avoided in

the training area, and cygnets should be isolated fiom humans. To fûrther prevent contact

between cygnets and the public, training areas and release sites should be selected not only

according to habitat quality, but aiso for Low probability of human contact.

IfUIM is to be used to restore migratory populations of waterfowl, these results

suggest that imprinting of hatchling on humans should not be a part of the protocol.

Nonetheless, a rigorous long term evaluation must st3.l be undertaken. Before UItralight

Induced Migration can be considered a useful tool We cycle success of induced migrants

must be documented and compared to individuals released through other means. Lf the

numerous questions about the efficacy of Ultralight Induced Migration as a management

tool are to be answered, then adequate resources for a thorough investigation should be

committed.

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