Amphibian concentrations in desiccating mud may determine the breeding season of the white-shouldered ibis (pseudibis davisoni )

Wright, H.L., Collar, N.J., Lake, I.R. and Dolman, P.M. (2013) Amphibian concentrations in desiccating mud may determine the breeding season of the white-shouldered ibis (pseudibis davisoni ). Auk, 130 (4). pp. 774-783. ISSN 0004-8038

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Abstract.-Many waterbirds reproduce seasonally in response to fluctuations in food supply. White-shouldered Ibises (Pseudibis davisoni) breed during the dry, water-drawdown season, but, unlike other waterbirds, they do not take advantage of prey concentrated in diminishing pools. To understand how this species successfully feeds and breeds at the driest time of year, we studied its habitat use and diet, and the habitat conditions that influence intake rates and prey density at waterholes. Foraging observations, prey sampling, and landscape-scale assessment of habitat availability were undertaken (at 7, 47, and 58 waterholes, respectively) over two breeding seasons. Although they rarely foraged in water, the birds used all exposed substrates, feeding on amphibians and small invertebrates. Amphibians were the most abundant prey in waterhole substrates and accounted for 81% of overall biomass intake. Both intake rates and density of amphibian prey biomass were greater in dry than in moist or saturated substrates. Intake rates and density of prey biomass changed little through the dry season, but exposed substrate extent increased by 74%. The White-shouldered Ibis's use of dry waterhole substrates to exploit seasonally concentrated prey is unusual among large waterbirds, and we suggest that its breeding season may be timed to coincide with receding water levels and increasing substrate exposure. Estimated prey requirements of a breeding pair over the nesting period were equivalent to nearly two-thirds of amphibian biomass found at large waterholes. Each pair may therefore require multiple waterholes to overcome prey depletion and breed successfully, which is consistent with the noncolonial dispersed distribution of nesting pairs.

Item Type: Article
Uncontrolled Keywords: ecology, evolution, behavior and systematics,ecology ,/dk/atira/pure/subjectarea/asjc/1100/1105
Faculty \ School: Faculty of Science > School of Environmental Sciences

Faculty of Science
Faculty of Science > School of Biological Sciences
University of East Anglia > Faculty of Science > Research Centres > Tyndall Centre for Climate Change Research
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Depositing User: Pure Connector
Date Deposited: 13 Jan 2014 12:12
Last Modified: 30 Sep 2021 05:10
DOI: 10.1525/auk.2013.12235

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