Time-Activity Budgets of Mottled Ducks in Louisiana in Winter 712 TIME BUDGETS OF MOTTLED DUCKS *...

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  • Time-Activity Budgets of Mottled Ducks in Louisiana in Winter Author(s): Stuart L. Paulus Source: The Journal of Wildlife Management, Vol. 52, No. 4 (Oct., 1988), pp. 711-718 Published by: Allen Press Stable URL: http://www.jstor.org/stable/3800935 Accessed: 13/12/2010 18:23

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  • TIME-ACTIVITY BUDGETS OF MOTTLED DUCKS IN LOUISIANA IN WINTER

    STUART L. PAULUS,' Department of Zoology-Entomology, Auburn University, Auburn, AL 36849

    Abstract: I related time-activity budgets of mottled ducks (Anas fulvigula) in coastal southwestern Louisiana from September-February 1981-82 to sex, pair status, and environmental factors. Mottled ducks spent 43% of their time feeding, 36% resting, 9% preening, 7% alert, 6% locomoting, and

  • 712 TIME BUDGETS OF MOTTLED DUCKS * Paulus J. Wildl. Manage. 52(4):1988

    movements. Impoundments provided perma- nent, semipermanent, and ephemeral wetlands used by mottled ducks (Gosselink et al. 1979). Water depths in these areas usually averaged

  • J. Wildl. Manage. 52(4):1988 TIME BUDGETS OF MOTTLED DUCKS * Paulus 713

    Table 1. Percent time spent in activities by paired and unpaired mottled ducks in Louisiana from September to February, 1980-82.

    Paired Unpaired

    Activity Period Male Female Male Female Overalla

    Feeding Day 39.1 39.2 40.1 39.2 39.0 Night 50.6 :b 39.1 39.2 40.1 39.2 42.5

    Locomoting Day 6.2 6.3 16.5 11.8 7.2 Night 2.4 S6.2 6.3 16.5 11.8 5.7

    Resting Day 37.5 38.4 20.8 24.0 36.4 Night 33.8 : 37.5 38.4 20.8 24.0 35.6

    Preening Day 8.5 9.0 11.4 11.2 9.0 Night 7.2 f 8.5 9.0 11.4 11.2 8.5

    Alert Day 8.1 6.6 10.6 14.7 7.9 Night 5.9 :8.1 6.6 10.6 14.7 7.3

    Agonistic Day 0.2 0.3 0.1 0.1 0.2 Night 0.2

    0.2 0.3 0.1 0.1 0.2

    Courting Day 0.4 0.2 0.6 0.2 0.3 Night 0.3

    0.4 0.2 0.6 0.2 0.2

    Total hr observed Day 356.7 361.0 56.1 45.7 827.6 Night 360.6

    a Includes 368.7 hr of data on mottled ducks whose sex or pair status were not determined. b Mean for 24-hr period.

    dence-interval procedures (Marascuilo and

    McSweeney 1977) were used to detect differ- ences among group means with each activity category as dependent variables and date, sex-

    pair status, or environmental variables as in-

    dependent variables. The Mann-Whitney U-test was used to compare time spent in activities

    during day and night, at different temperatures, or while on or off Rockefeller SWR. Spearman correlation (r) analysis was used to examine re-

    lationships between activities and environmen- tal variables.

    RESULTS

    Feeding Mottled ducks spent a mean of 43% of their

    time feeding during the study. Bottom feeding (79%), tipping (9%), feeding while standing in water or on land (9%), and surface dabbling (2%) were important modes of feeding. Diving for food was observed on 3 occasions. Time spent feeding was similar among cohorts of sex and

    pair status (P = 0.937) (Table 1). Though birds were not sexed at night, individuals of pairs

    appeared to engage in feeding activities and feed at similar rates.

    Diurnal feeding was most common during early morning and late afternoon (Fig. 1). Mot- tled ducks spent more (P < 0.001) time feeding at night (50.6%) than day (39.0%). Ducks usually fed in small groups or as pairs at night and most dabbled in shallow-water wetlands. Nocturnal

    feeding was not observed when temperatures were >20 C or

  • 714 TIME BUDGETS OF MOTTLED DUCKS * Paulus J. Wildl. Manage. 52(4):1988

    Io0 COURTING

    0 M AONISTIC

    0 ALERT

    PREENING

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    jE 30~

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    -- 10.==Z=

    S10 LOCOMOTING

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    I 2 3 4 5 6 (291) (242) (295) (145) (136) (79)

    PERIOD OF DAY Fig. 1. Percent time spent in 7 activities during 6 periods of day and night (n in hr) for mottled ducks in Louisiana from September-February, 1980-82. Period 1 was 0-4 hours after sunrise, period 2 was 4 hours after sunrise-4 hours before sunset, period 3 was 4-0 hours before sunset, period 4 was 0-4 hours after sunset, period 5 was 4 hours after sunset-4 hours before sunrise, and period 6 was 4-0 hours before sun- rise. Percentages

  • J. Wildl. Manage. 52(4):1988 TIME BUDGETS OF MOTTLED DUCKS * Paulus 715

    Table 3. Simple correlation coefficients (r) of selected environmental variables, date, and activities of mottled ducks in Louisiana from September to February, 1980-82.

    Environmental variable Feeding Locomoting Resting Preening Alert Agonistic Courting

    Date -0.071*a -0.025 0.106*** -0.074* -0.024 -0.068* 0.017 Temperature (C) -0.136*** -0.029 0.077 0.142*** 0.041 0.088** -0.038 Cloud cover -0.150*** -0.074* 0.160*** 0.027 -0.029 -0.054 -0.137 Rainfall intensity 0.004 0.020 -0.012 0.012 0.003 -0.004 -0.116 Water depth (cm) -0.019 0.064* 0.017 -0.063* 0.005 -0.019 0.052 Wind velocity (km/hr) -0.204*** 0.112*** 0.180*** -0.064* 0.017 -0.050 0.004

    a Activity and environmental variable are correlated: * P < 0.05, ** P < 0.01, *** P < 0.001.

    1). Mottled ducks spent similar amounts of time

    resting during the night (33.8%) and day (36.4%) (P = 0.359). Time spent preening occurred less often (P < 0.05) during night (7.2%) than day (9.0%). When the moon fell below the horizon, mottled ducks generally spent a short amount of time preening and then rested. The ducks

    usually rested in groups.

    Alert and Locomoting Mottled ducks averaged 7 and 6% of their

    time alert and locomoting, respectively. Most locomotor activity consisted of swimming (89%), flying (4%), or walking on land (3%). Because

    flying activity was not recorded once the bird left the observation area, time spent flying was underestimated.

    Unpaired mottled ducks spent more time lo-

    comoting than paired birds (P < 0.001 for F, < 0.01 for M) (Table 1). Unpaired males spent more time alert than pairs (P < 0.001) and un-

    paired females more time alert than paired fe- males (P < 0.01). Time spent in locomotor and alert activities remained at similar levels for most of the nonbreeding season (Table 2). Mot- tled ducks spent less time locomoting (2.4 vs. 7.2%) and alert (5.9 vs. 7.9%) at night than dur-

    ing the day. At night, mottled ducks did not

    always remain at the same pond; individuals were observed arriving at, and leaving, the pond throughout the night.

    Courting and Agonistic Courting activities comprised 20 birds were gathered.

    Of 63 copulations observed, 2 were in Sep- tember, 23 in October, 11 in November, 9 in December, 13 in January, and 5 in February. Precopulatory and copulatory displays com- prised 59.5% of courtship activities of mottled ducks.

    Agonistic activities were observed infre-

    quently and at similar rates among all mottled ducks (P = 0.705) (Table 1). Chasing was the predominant agonistic activity of pairs. Un- paired birds rarely chased other birds but mostly gave bill threats (M) or incited (F). Most ago- nistic activities lasted only a few seconds, al- though paired males were observed chasing oth- er birds >20 m. No differences were found in time spent in agonistic activities during day or

    night (P = 0.280). Agonistic activities were observed most often

    in October and November, when threat behav- iors comprised 0.5 and 0.3% of time spent by mottled ducks, respectively. During the re-

    maining months mottled ducks spent

  • 716 TIME BUDGETS OF MOTTLED DUCKS * Paulus J. Wildl. Manage. 52(4):1988

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