Combining monitoring data from multiple sites to assess population status and trends of White-tailed Tropicbirds (Phaethon lepturus) in the Seychelles

Burt, April J.; Cagua, E. Fernando; Sanchez, Cheryl; Calabrese, Licia; Crommenacker, Janske van de; McClelland, James L.; Shah, Nirmal; Richards, H. C.; Bunbury, Nancy

doi:10.5751/ace-01858-160228

Cited by 2 publications

(2 citation statements)

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“…This is supported by an experimental study in Chile, which found evidence of avian predators only visiting more exposed red-tailed tropicbird nests (Luna et al 2018 ). Such high predation pressure, added to other failures caused by bad weather, egg breakage or abandonment, led to substantially lower breeding success than previously recorded in both species (Prys-Jones and Peet 1980 ; Burt et al 2021 ). This could explain the decline in red-tailed tropicbird breeding activity observed on Aldabra since the 2010s, through lack of recruitment.…”

Section: Discussionmentioning

confidence: 75%

“…Population monitoring at Aldabra has revealed that the number of red-tailed tropicbird nests has strongly declined since 2010 (2010–2019: − 75.9%, Seychelles Islands Foundation (SIF), unpublished data). In contrast, the number of white-tailed tropicbird nests appears more stable (2010–2019: + 1.8%), but their breeding success is poor (Burt et al 2021 ), so their population might be affected in the future. Understanding the foraging ecology of both species may help to understand why.…”

Section: Introductionmentioning

confidence: 99%

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Marked differences in foraging area use and susceptibility to predation between two closely-related tropical seabirds

Fayet,

Sanchez,

Appoo

et al. 2023

Oecologia

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Ecological theory predicts that closely-related species must occupy different niches to coexist. How marine top predators achieve this during breeding, when they often gather in large multi-species colonies and are constrained to central-place foraging, has been mostly studied in productive temperate and polar oceans with abundant resources, but less so in poorer, tropical waters. Here, we track the foraging movements of two closely-related sympatric seabirds—the white-tailed and red-tailed tropicbirds Phaethon lepturus and P. rubricauda—breeding on Aldabra Atoll, Seychelles, to investigate potential mechanisms of niche segregation and shed light on their contrasting population trends. Combining data from GPS, immersion, depth and accelerometry loggers, we show that the two species have similar behaviour at sea, but are completely segregated spatially, with red-tailed tropicbirds flying further to feed and using different feeding areas than white-tailed tropicbirds. Using nest-based camera traps, we show that low breeding success of both species—which likely drives observed population declines—is caused by high nest predation. However, the two species are targeted by different predators, with native avian predators mainly targeting red-tailed tropicbird nests, and invasive rats raiding white-tailed tropicbird nests when they leave their eggs unattended. Our findings provide new insight into the foraging ecology of tropicbirds and have important conservation implications. The extensive range and spatial segregation highlight the importance of considering large-scale protection of waters around tropical seabird colonies, while the high level of nest predation provides evidence in support of rat eradication and investigating potential nest protection from native avian predators.

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Section: Discussionmentioning

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Marked differences in foraging area use and susceptibility to predation between two closely-related tropical seabirds

Fayet,

Sanchez,

Appoo

et al. 2023

Oecologia

Self Cite

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Differences in foraging range between white-tailed tropicbirds breeding on inner and outer Seychelles islands

Ensanyar-Volle,

Appoo,

Bunbury

et al. 2023

Mar. Ecol. Prog. Ser.

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The foraging ecology and distribution of Phaethontiformes, an order of tropical seabirds, remains generally poorly understood, despite being essential to inform their conservation. Here, we tracked, for the first time, the foraging movements of breeding white-tailed tropicbirds Phaethon lepturus, a common but poorly studied seabird, in the Indian Ocean. We compared the foraging movements and habitat preferences of 2 populations, one from Aride Island in the inner Seychelles and the other from Aldabra Atoll in the outer Seychelles, ca. 1200 km to the southwest. We found considerable differences in foraging trip metrics between populations, with birds from Aride having an average foraging range 2 times greater (231 km on Aride vs. 105 km on Aldabra), and both populations feeding far beyond the protected areas around their respective colony. We also found differences in foraging range between incubation and chick-rearing stages and sexes. Using habitat models, we highlight the birds’ preference for deep waters, which may explain the greater foraging range of Aride birds, although human activities may also play a role. Our study provides unprecedented insight into the foraging ecology of white-tailed tropicbirds in the Western Indian Ocean.

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Combining monitoring data from multiple sites to assess population status and trends of White-tailed Tropicbirds (Phaethon lepturus) in the Seychelles

Abstract: Combining monitoring data from multiple sites to assess population status and trends of White-tailed Tropicbirds (Phaethon lepturus) in the Seychelles. Avian Conservation and Ecology 16(2):28.

Cited by 2 publications

References 25 publications

Marked differences in foraging area use and susceptibility to predation between two closely-related tropical seabirds

Marked differences in foraging area use and susceptibility to predation between two closely-related tropical seabirds

Differences in foraging range between white-tailed tropicbirds breeding on inner and outer Seychelles islands

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