“Live at Sea, Nest on Land”

Breeding Success of Red-billed Tropicbirds (Phaethon aethereus)

St. Eustatius Sustainability Conference, 2013Hannah Madden

St. Eustatius National Parks (STENAPA)

Importance of Seabirds

Global seabird populations are declining at a faster rate than any other group of birds.

In the Caribbean region, seabird populations are a mere remnant of their historic numbers and face numerous threats, including loss of breeding habitat, introduced predators, and mortality from oil spills and offshore development.

Most seabird species that nest in the Caribbean were impacted by the 2010 Deepwater Horizon Oil Spill.

Red-billed Tropicbirds

Tropicbirds live poised between the sea and the land—their breeding sites and foraging areas can be hundreds or even thousands of miles apart.

Despite spending most of their lives at sea, tropicbirds must come on land to breed and nest.

Tropicbirds are long-lived top predators. Therefore, egg size and growth rate are indicators of the health of the ocean.

Statia:- 11 sq miles- 4,000 people- Estimate +/- 300-500 pairs of RBTR- Together with Saba, 33-40% of global RBTR population

Saba

Important Bird Areas (IBAs) on Statia

Primary Nesting and Study Sites

Zeelandia

Pilot Hill

Pilot Ridge

Signal Hill

Crooks Castle

Background and Rationale

A similar study conducted on Saba (2011) resulted in the discovery of high levels (100%) of predation at one nesting site

Status TENT Colony

Eggs laid 39

Eggs (probably) hatched 34

Chicks fledged 0

% Breeding Success 0.00%

Predation of Tropicbirds

Methodology

Record timing of egg laying Individually marked nests and adult birds Status of nests regularly followed Chick growth and development recorded Fieldwork supported by 24-hour infra-red

cameras Preliminary predator control (rat traps)

ResultsEggs laid: 99Eggs hatched: 59Not yet hatched: 4Eggs lost: 36

Signal Hill Crooks Castle Zeelandia Pilot Hill Pilot Ridge Total0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%

Hatching Success

Birds banded: 146Primary and secondary nests: 197Primary nests: 85

n=11 n=4 n=14 n=45 n=25 n=99

Perc

ent H

atch

ing

Succ

ess

RBTR Colonies

(percentage of hatched eggs per number of eggs)

Results (cont.)Chicks apparently fledged: 46Dead chicks: 2 (not predation)Fate unknown: 11

Signal Hill Crooks Castle Zeelandia Pilot Hill Pilot Ridge Total0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%

Apparent Fledging Success

n=11 n=4 n=14 n=45 n=25 n=99

Perc

ent F

ledg

ing

Succ

ess

RBTR Colonies

(% fledged chicks per number of hatched eggs)

Results (cont.)

Signal Hill Crooks Castle Zeelandia Pilot Hill Pilot Ridge Total0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%

Apparent Breeding Success

n=11 n=4 n=14 n=45 n=25 n=99

Perc

ent B

reed

ing

Succ

ess

RBTR Colonies

(% fledged chicks per number of laid eggs)

Egg Loss/Chick Mortality

Evidence of Predators

Future Plans

Investigate egg loss at one site (Pilot Hill) in 2014

Possible diet study in collaboration with IMARES (NL) and Science Centre (Statia)

Long-term monitoring of nest fidelity / inter-island movements (Saba/Statia)

RBTR movements - geolocators (Dr. Pat Jodice, Clemson University)

Continued population and productivity monitoring

Acknowledgements

- SCSCB - STENAPA interns and volunteers- NuStar- Dutch Caribbean Nature Alliance (DCNA)- Dr. Adrian Delnevo- Dr. Pat Jodice & Dr. Will Mackin- Jose-Luis Garcia and Giovanni Balensuela

Questions