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Rationale Red-billed tropicbirds (Phaethon aethereus) (fig. 1) occur across tropical waters of the Atlantic and Pacific Oceans, and in the north Indian Ocean (Orta,1992). It holds approximately 2,000 pairs in the western north Atlantic and less than 8,000 pairs globally (Lee & Walsh-McGehee, 2000). In western Africa, It breeds only in Cape Verde and Senegal, but none of these two populations have been well studied so far. In Senegal, the species holds only one breeding site in the Madeleine Island, a small uninhabited volcanic island just 4km off Dakar (fig. 2).

Results Abundance and Breeding periodicity Red-billed tropicbird was present all year round in Madeleine Island (fig. 3). The number of active nests (nest with an egg or a chick) increased from October to January, reaching 41 nests and 40 adults on the island (fig. 3). Females laid a single egg once a year. Laying peak was in January (19 eggs) and first hatching occurred in November (fig. 4). Discussion The breeding cycle of red-billed tropicbirds in Madeleine Island is similar to that described in Ascension (Stonehouse, 1962) but differs from the cycle described for the same species in the Gulf of California, where seasonality is more marked (from November to June, Castillo-Guerrero et al. 2011). Breeding success in Madeleine Island (58%) is similar to that reported in Ascension Island (51%, Stonehouse1962) and greater than that reported from St Helena (11%, Beard et al. 2013). In summary, red-billed tropicbird in Madeleine Island hold a small and vulnerable population, breeding meanly in winter, although some breeders can be found throughout the year. Currently, breeding success is relatively high.

With the financial support of MAVA Foundation

Methods We monitored nests content every 15 days from June 2014 to July 2015.

Hatching success= eggs hatched / eggs laid Fledging success= chicks fledged / eggs hatched Breeding success= chicks fledged / eggs laids

Breeding success and nest mortality Hatching and fledging success was estimated 77,96 and 73,91 respectively (fig. 5). Overall breeding success was 57.6% (n=59 nests).

REFERENCES •  Beard A., Clingham E., Henry L. 2013. St helena seabirds report. •  Castillo-Guerrero J.A.,Guevara-Medina M.A. &Mellink E. 2011. Breding ecology of the red-billed tropicbird Phaethon aethereus under

contrasting environmental conditions in the Gulf of California.Ardea99:61-71. •  Lee D.S & Walsh-McGehee M. 2000. Population estimates, conservation concerns , and management of tropicbirds in the western

Atlantic.Carribb.J. Sci. 36: 267-279. •  Orta J. 1992. Castillo-Guerrero J.A.,Guevara-Medina M.A. & Mellink E. 2011. Breding ecology of the red-billed tropicbird Phaethon aethereus

under contrasting environmental conditions in the Gulf of California.Ardea99:61-71. •  Stonehouse B. 1962. The tropicbirds (Genus Phaethon) of Ascension Island. Ibis 103: 124-161

Fig. 3: Abundance of adults and nests

Fig. 4: Breeding phenology

2nd World Seabird Conference “Seabirds: Global Ocean Sentinels” 26-30 October 2015 Cape Town, South Africa

Fig. 5: Reproductive success

Acknowledgements This work was conducted as part of Alcyon project funded by MAVA and implemented by FIBA and thereafter by BirdLife International. We thank the staff of the national park of Madeleine Island and Paul Robinson for their support.

ABUNDANCE, BREEDING PHENOLOGY AND SUCCESS OF THE RED-BILLED TROPICBIRD (Phaethon aethereus) IN MADELEINE ISLAND (DAKAR, SENEGAL)

Ngoné Diop1 2 Cheikh Tidiane Ba1 Papa Ibnou Ndiaye1 Jacob González-Solís2

1. Department of Animal Biology, Cheikh Anta Diop University, Av Cheikh Anta Diop, Dakar, Senegal 2. Institut de Recerca de la Biodiversitat (IRBio) and Department de Biologia Animal, Universitat de Barcelona, Av Diagonal 643, Barcelona 08028, Spain

Fig. 1: Red-billed tropicbird bird on nest

Fig. 2: Location of Madeleine Island

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