klaassen-whydogull-2008.pdf (262.28 kB)
Download file

Why do Gull-billed Terns Gelochelidon nilotica feed on fiddler crabs Uca tangeri in Guinea-Bissau?

Download (262.28 kB)
journal contribution
posted on 01.01.2008, 00:00 authored by E Stienen, A Brenninkmeijer, Marcel KlaassenMarcel Klaassen
Gull-billed Terns Gelochelidon nilotica wintering in Guinea Bissau mainly fed on fiddler crabs Uca tangeri and were occasionally seen feeding on fish and locusts. As fiddler crabs have a low energy content, terns need a large gross intake to meet daily energy demands. Fiddler crabs also have a low ratio of digestible flesh to exoskeleton, and therefore tern food intake may be limited by gut capacity. Activity budgets of Gullbilled Terns feeding on fiddler crabs showed that a considerable part of the time was spent resting. The duration of resting intervals increased with energy intake and was positively correlated with the metabolisable energy content of the crab eaten, suggesting that resting periods were required for a proper digestion. The poor quality of fiddler crabs was offset by high capture rates. So daily energy expenditure of the terns could easily be met by feeding on fiddler crabs. Even when resting pauses were included in foraging time, foraging for only 1.5 hours on fiddler crabs satisfied the terns’ daily energy demands. Instead, feeding on energy-rich fish would require about 2.5 hours to satisfy daily energy demands. Compared to the more specialised piscivorous Little Tern Sternula albifrons and Sandwich Tern Sterna sandvicensis, capture rate of fish was poor in Gull-billed Terns. From an energetic point of view, wintering Gull-billed Terns feeding on fiddler crabs seem to have an easy living in Guinea Bissau.

History

Journal

Ardea

Volume

96

Issue

2

Pagination

243 - 250

Publisher

Nederlandse Ornithlogische Unie

Location

Amsterdam, The Netherlands

ISSN

0373-2266

Language

eng

Notes

Reproduced with the kind permission of the copyright owner.

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

2008, Nederlandse Ornithlogische Unie