Live at Sea, Nest on Land Breeding Success of Red-billed Tropicbirds (Phaethon aethereus) St. Eustatius Sustainability Conference, 2013 Hannah 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 landtheir 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 +/ 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 StatusTENT 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)

Results Eggs laid: 99 Eggs hatched: 59 Not yet hatched: 4 Eggs lost: 36 Birds banded: 146 Primary and secondary nests: 197 Primary nests: 85 n=11n=4n=14n=45 n=25n=99 Percent Hatching Success RBTR Colonies (percentage of hatched eggs per number of eggs)

Results (cont.) Chicks apparently fledged: 46 Dead chicks: 2 (not predation) Fate unknown: 11 n=11n=4n=14n=45n=25 n=99 Percent Fledging Success RBTR Colonies (% fledged chicks per number of hatched eggs)

Results (cont.) n=11n=4n=14n=45n=25n=99 Percent Breeding Success 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