Breeding of White-tailed Tropicbirds (Phaethon lepturus) in the western South Atlantic / Biologia reprodutiva, tamanho populacional e conservação do rabo-de-palha-de-bico-laranja no Atlântico Sul

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.

Resumo Informações 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 devem se concentrar em controlar a predação por caranguejos e lagartos teiú.

Estuarization increases functional diversity of demersal fish assemblages in tropical coastal ecosystems.

This study assessed the influence of the seasonal fluctuation of abiotic conditions (wet v. dry season) on the functional diversity (FD) of tropical coastal fish assemblages. Sampling was carried out in three regions of north-east Brazil with contrasting coastlines (influenced by reef, lagoon and estuary). In each region, fishes were sampled from three depth strata (10, 20 and 30 m) and FD was estimated using an index based on key phenotypic and behavioural characteristics. All three regions had higher FD in the wet season at shallower depths, indicating the coexistence of species with low functional redundancy in sites subject to seasonal flushing of fresh water. Deeper sites had lower FD than shallower sites, although this difference was less pronounced for region 3, which is strongly affected by its proximity to the São Francisco estuary. The results broadly support the hypothesis that alterations in abiotic conditions in the wet season allow estuarine-adapted fishes with a different suite of functional traits to invade shallow coastal regions.

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

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.

Parasites and sex: Catching the red queen.

One version of the Red Queen hypothesis suggests that sexual reproduction may be an advantage in a coevolutionary arms race. Antagonistic biotic interactions, especially those between parasite and host, are thought to represent a sufficient evolutionary force to counterbalance the supposed inefficiency of sexual reproduction. Recent experimental studies demonstrate negative frequency-dependent selection, increased parasite load in parthenogenetic races relative to sympatric sexual conspecifics and correlations between recombination rate and frequency of parasitic chromosomes. These studies provide strong empirical evidence that there is an important role for parasites in maintaining sex.