Retrodicting patch use by foraging swans in a heterogeneous environment using a set of functional responses

Nolet, Bart A. and Klaassen, Marcel 2009, Retrodicting patch use by foraging swans in a heterogeneous environment using a set of functional responses, Oikos, vol. 118, no. 3, pp. 431-439, doi: 10.1111/j.1600-0706.2008.16857.x.

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Title Retrodicting patch use by foraging swans in a heterogeneous environment using a set of functional responses
Author(s) Nolet, Bart A.
Klaassen, MarcelORCID iD for Klaassen, Marcel
Journal name Oikos
Volume number 118
Issue number 3
Start page 431
End page 439
Total pages 9
Publisher Wiley - Blackwell Publishing
Place of publication Malden, Mass.
Publication date 2009-03
ISSN 0030-1299
Summary Effective conservation of important bird areas requires insight in the number of birds an area can support, and how this carrying capacity changes with habitat modifications. When food depletion is the dominant mechanism of competition, it should in principle be possible to calculate the total time foragers can spend per patch from their functional response (intake rate as a function of food density). However, in the field there are likely to be factors modulating the functional response. In this study previously published results of experiments on captive Bewick's swans were used to obtain functional responses of swans digging for tubers of Fennel pondweed on different foraging substrates: sandy and clayey sediment, and in shallow and deep water. In a field study, four 250×250 m sections belonging to different types (sandy–shallow, clayey–shallow, sandy–deep and clayey–deep) were delineated. Here tubers were sampled with sediment corers in three years, both before and after swan exploitation in autumn, and swans were observed and mapped from a hide in two of these years. Giving-up tuber biomass densities varied among sections. Substitution of these giving-up densities in the derived patch-type-specific functional responses yielded the quitting net energy intake rates in the four sections. As expected from the marginal value theorem, the quitting net energy intake rates did not vary among sections. Moreover, the observed foraging pressure (total foraging time per area) per patch type was in quantitative agreement with the integrated functional responses. These results suggest that in spatially heterogeneous environments, patch exploitation by foragers can be predicted from their functional responses after accounting for foraging substrate.
Language eng
DOI 10.1111/j.1600-0706.2008.16857.x
Field of Research 060201 Behavioural Ecology
Socio Economic Objective 970106 Expanding Knowledge in the Biological Sciences
HERDC Research category C1.1 Refereed article in a scholarly journal
Copyright notice ©2009, The Authors
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