Breeding of White-tailed Tropicbirds (Phaethon lepturus) in the western South Atlantic

Abstract

Basic information on natural history is crucial for assessing the viability of populations, but is often lacking for many species of conservation concern. One such species is the White-tailed Tropicbird, Phaethon lepturus (Mathews, 1915). Here, we address this shortfall by providing detailed information on reproductive biology, distribution and threats on the Fernando de Noronha archipelago, Brazil -the largest colony of P. lepturus in the South Atlantic. We assessed reproduction from August 2011 to January 2012 by monitoring tropicbird nests and their contents. A population estimate was obtained through a combination of active searches for nests and by census at sea between 2010 and 2012. Breeding success was calculated by traditional methods. The growth curve of chicks and life table were also calculated. Additional information on nest and mate fidelity and on age of breeding birds was obtained from the banded birds. Our results indicate that the unusual nest form (limestone pinnacles) and predation by crabs may be responsible for the observed patterns of hatching and fledging success. Although the Fernando de Noronha population appears to be stable (at between 100-300 birds), a long term monitoring program would be desirable to assess fluctuations in this globally important population. Conservation strategies should focus on controlling predation by land crabs and tegu lizards.Keywords: Phaethon lepturus, seabird, breeding biology, Fernando de Noronha, Brazil. Biologia reprodutiva, tamanho populacional e conservação do rabo-de-palha-de-bico-laranja no Atlântico Sul ResumoInformações básicas sobre história natural são cruciais para acessar a viabilidade de populações, mas são ausentes para muitas espécies que necessitam de conservação. Uma destas espécies é o rabo-de-palha-de-bico-laranja, Phaethon lepturus Daudin, 1802. Aqui, vamos abordar o déficit de dados para esta espécie, fornecendo informações detalhadas sobre a biologia reprodutiva, tamanho da população, distribuição e ameaças em Fernando de Noronha, Brasil -a maior colônia de P. lepturus no Atlântico Sul. Acompanhamos a reprodução do rabo-de-palha-de-bico-laranja de Agosto de 2010 a Janeiro de 2011 monitorando ninhos e seus conteúdos. A estimativa da população foi obtida através de uma combinação de busca ativa de ninhos e censo no mar entre 2010 e 2012. O sucesso reprodutivo foi avaliado por métodos tradicionais. A curva de crescimento da coorte e a tabela de vida também foram obtidas. Além disso, informações sobre fidelidade ao ninho e parceiro e, a idade de reprodutores foi obtida a partir das aves anilhadas anteriormente. Nossos resultados indicam que a forma incomum de ninho (pináculos de calcário) e a predação por caranguejos podem ser responsáveis pelo sucesso observado de eclosão e recrutamento. A população de Fernando de Noronha parece estar estável entre 100-300 aves. No entanto, um programa de monitoramento a longo prazo seria desejável para avaliar as flutuações desta população globalmente importante. As estratégias de conservação ...

Foraging behavior and at-sea distribution of White-Tailed Tropicbirds in tropical ocean

“…In fact, if one of the parents did not return to the nest by dusk, the chick remained alone throughout the evening. This lack of attendance might facilitate chick's' predation and egg consumption by Land Crab Johngartia lagostroma and Goniopsis cruentata, since both species are more active at night, as documented in this study and in Leal et al (2016). Evidence suggests that chicks might also disappear from intra-specific competition, since fights between adults, adults and chicks > 30 days and injuries were observed.…”

Foraging habitat choice of White-tailed Tropicbirds revealed by fine-scale GPS tracking and remote sensing

“…26 km 2 , and has been protected by Brazilian legislation as a marine national park since 1988. The islands hold large concentration of tropical seabirds, including a breeding population of 100 to 300 of White-tailed Tropicbirds (Leal et al, 2016). The climate is tropical with two marked seasons, the rainy season from January to August and the dry season from September to December.…”

“…The climate is tropical with two marked seasons, the rainy season from January to August and the dry season from September to December. The average annual temperature is 27 °C and the rainfall is 1,400 mm (Leal et al, 2016). The region is influenced by two main oceanic currents, the near surface westward central branch of the South Equatorial Current and the deeper eastward South Equatorial Undercurrent (Tchamabi et al, 2017).…”

“…The seawater is considered oligotrophic, where phytoplankton productivity is limited by low nutrient concentrations (de Souza et al, 2013). Surface salinity ranges between 35.0 and 37.0‰ (Leal et al, 2016).…”

“…Tracked White-tailed Tropicbirds were captured during chick-rearing (chicks of 1 to 3 weeks old) in Morro do Chapéu islet (Fig. 1), which holds the largest breeding colony of this species in the whole archipelago (Leal et al, 2016). The 15 tagged White-tailed Tropicbirds were captured by hand in the nest at dawn (4 to 4:30 am), before they leave for the sea, between August 28th to October 16th 2015.…”