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Combining survey and remotely sensed environmental data to estimate the habitat associations, abundance and distribution of breeding thin-billed prions Pachyptila belcheri and Wilson’s storm-petrels Oceanites oceanicus on a South Atlantic tussac island
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Advisor(s)
Abstract(s)
Small petrels are the most abundant seabirds in the Southern Ocean. However, because they breed in burrows on remote and
often densely vegetated islands, their colony sizes and conservation status remain poorly known. To estimate the abundance
of these species on Bird Island in the Falkland archipelago, we systematically surveyed their breeding burrow density and
occupancy across this near-pristine tussac (Poa flabellata)-covered island. By modelling burrow density as functions of
topography and Sentinel 2 satellite-derived Normalised Difference Vegetation Index data, we inferred habitat associations and
predicted burrow abundance of the commonest species—Thin-billed Prions (Pachyptila belcheri) and Wilson’s Storm-petrels
(Oceanites oceanicus). We estimate that there are 631,000 Thin-billed Prion burrows on the island (95% CI 496,000–904,000
burrows). Assuming that burrow occupancy lies between 12 and 97%, this equates to around 76,000–612,000 breeding pairs,
making Bird Island the second or third largest P. belcheri colony in the world, holding approximately 3–27% of the species’
breeding population. We estimate that 8200–9800 (95% CI 5,200–18,300 pairs) pairs of Wilson’s Storm-petrels also
breed on the island. Notably, the latter burrowed predominantly under and within tussac pedestals, whereas they are usually
assumed to breed in rock cavities. Thin-billed Prions are declining in the Kerguelen archipelago, but their population trends
in the Falklands are unknown. Given the wide confidence intervals around our own and other population estimates for these
cryptic species, we recommend that their populations should be monitored regularly, at multiple sites.
Description
Keywords
Burrowing petrel Habitat model Seabird Colony Falkland Population
Citation
Stokes, A. W., · Catry, P., ·Matthiopoulos, J., Boldenow, M., Clark, · T. J., · Guest, A. ,· Marengo, I., & · Wakefield, E. D. (2021). Combining survey and remotely sensed environmental data to estimate the habitat associations, abundance and distribution of breeding thin-billed prions Pachyptila belcheri and Wilson’s storm-petrels Oceanites oceanicus on a South Atlantic tussac island. Biology Biology, 44(4), 809-821 https://doi.org/10.1007/s00300-021-02842-3
Publisher
Springer Verlag