Foraging Ecology of Red-Billed Tropicbirds on Saba, Caribbean Netherlands, during Early Chick-Rearing

Madden, Hannah; Boehm, Helena; Mielke, Lara

doi:10.5253/arde.2022.a14

Cited by 7 publications

(1 citation statement)

References 52 publications

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“…The maximum distance travelled by red-tailed tropicbirds from Aldabra is comparable to that of similar-sized red-billed tropicbirds P. aethereus tracked in the eastern Atlantic Ocean (Diop et al 2018 ) and the Caribbean (Madden et al 2023 ). Chick-rearing white-tailed tropicbirds travelled on average 15 km from Aldabra, similar to the shorter trips recorded in the species near Brazil (Campos et al 2018 ), but unlike that study, we did not record any multi-day trips.…”

Section: Discussionmentioning

confidence: 59%

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: 59%

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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A framework and review of evidence of the importance of coral reefs for marine birds in tropical ecosystems

Cumming,

James,

Chua

et al. 2024

Ecology and Evolution

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As global heating and other anthropogenic influences alter tropical marine environments, it is unclear how marine bird populations will be impacted and whether their current roles in tropical marine ecosystems will change. Although marine birds roost and breed on tropical islands in large numbers, the direct trophic interactions between these birds and their prey across the tropics are poorly documented. We present a first framework for evaluating the dependence on and contributions of marine birds to tropical coral reef ecosystems and use it to examine the evidence for different kinds of interaction, focusing primarily on avian diets. We found 34 publications between 1967 and 2023 that presented a total of 111 data sets with enough detail for quantitative dietary analysis of tropical marine birds. Only two bird species out of 37 (5.4%) had diets of >50% coral reef fishes and only one, the Pacific Reef Egret, appeared to depend almost entirely on reef‐based production. Marine birds are also prey for other marine organisms, but insufficient data are available for quantitative analysis. Evidence for indirect effects of birds in tropical marine environments is stronger than for direct dependence on coral reefs, particularly in relation to nutrient concentration and the fertilisation impacts of guano on corals. Dispersal of propagules (e.g. seeds, spores, invertebrate eggs) by bathing, drinking, resting or foraging birds is under‐studied and poorly documented. Although the degradation of coral reefs appears unlikely to have a significant direct impact on food availability for most marine bird populations, indirect effects involving marine birds may be disrupted by global environmental change.

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Parental duties and foraging strategies of a tropical pelagic seabird (Phaethon aethereus, Aves: Phaethontidae) during the breeding season

Piña-Ortiz,

González-Zamora,

Paz

et al. 2024

Mar Biol

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Breeding seabirds must balance the energetic demands of feeding themselves and their offspring while coping with the constraints imposed by central-place foraging. As such, foraging strategies and parental care patterns are usually linked. Here, the foraging behavior of the Red-billed Tropicbird (Phaethon aethereus; n = 161) of Peña Blanca Islet, Mexico (19° 06ʹ 11ʺ N, 104° 29ʹ 12ʺ W) during the incubation and chick-rearing (≤ 4 weeks of age) stages was characterized with the aid of GPS loggers. Blood samples from adults and chicks were collected to determine δ15N and δ13C, and parental presence at the nest, meal size, and parent-chick feeding events were recorded. During incubation, parents made long trips offshore to areas far from the colony; however, immediately after their chicks hatched, the parents switched to a bimodal foraging strategy by undertaking both short and long foraging trips. The δ15N values indicated that trophic differences were present between parents and their offspring, with chicks being fed prey enriched in 15N. Parental presence at the nest was greater during early chick-rearing, which was associated with a higher provisioning rate. Parents adopted a strategy in which the parent on nest duty only made short foraging trips to provide for its offspring without leaving it unattended for long periods, while its mate undertook long trips to feed itself. After the early chick-rearing period, the parents gradually reduced the time spent at the nest and increased the time spent foraging, compensating with larger meal sizes for their offspring. Graphical abstract

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Foraging Ecology of Red-Billed Tropicbirds on Saba, Caribbean Netherlands, during Early Chick-Rearing

Abstract: Tropical marine environments are typically characterised by low productivity and prey that is patchily distributed over large areas. Seabird species that forage in oligotrophic environments have developed strategies that enable them to forage successfully (Longhurst &

Cited by 7 publications

References 52 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

A framework and review of evidence of the importance of coral reefs for marine birds in tropical ecosystems

Parental duties and foraging strategies of a tropical pelagic seabird (Phaethon aethereus, Aves: Phaethontidae) during the breeding season

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