Habitat switching by Bewick's swans: Maximization of average long-term energy gain?

Nolet, B.A., Bevan, R.M., Klaassen, M., Langevoord, O. and Van Der Heijden, Y.G.J.T. 2002, Habitat switching by Bewick's swans: Maximization of average long-term energy gain?, Journal of animal ecology, vol. 71, no. 6, pp. 979-993, doi: 10.1046/j.1365-2656.2002.00662.x.

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Title Habitat switching by Bewick's swans: Maximization of average long-term energy gain?
Author(s) Nolet, B.A.
Bevan, R.M.
Klaassen, M.ORCID iD for Klaassen, M. orcid.org/0000-0003-3907-9599
Langevoord, O.
Van Der Heijden, Y.G.J.T.
Journal name Journal of animal ecology
Volume number 71
Issue number 6
Start page 979
End page 993
Total pages 15
Publisher Wiley
Place of publication London, Eng.
Publication date 2002-11
ISSN 0021-8790
Keyword(s) Cygnus columbianus bewickii
Depletion
Habitat shift
Potamogeton pectinatus
Time-energy budget
Science & Technology
Life Sciences & Biomedicine
Ecology
Zoology
Environmental Sciences & Ecology
BRANTA-BERNICLA-BERNICLA
WHITE-FRONTED GEESE
BELLIED BRENT GEESE
GREATER SNOW GEESE
PREDATION RISK
HUMAN DISTURBANCE
MIGRATING BIRDS
EXPENDITURE
TIME
SELECTION
Summary 1. In a system where depletion drives a habitat shift, the hypothesis was tested that animals switch habitat as soon as the average daily net energy intake (or gain) drops below that attainable in the alternative habitat.

2. The study was performed in the Lauwersmeer area. Upon arrival during the autumn migration, Bewick's swans first feed on below-ground tubers of fennel pondweed on the lake, but subsequently switched to feeding on harvest remains in sugar beet fields.

3. The daily energy intake was estimated by multiplying the average time spent foraging per day with the instantaneous energy intake rate while foraging. In the case of pondweed feeding, the latter was estimated from the functional response and the depletion of tuber biomass. In the case of beet feeding, it was estimated from dropping production rate. Gross energy intake was converted to metabolizable energy intake using the assimilation as determined in digestion trials. The daily energy expenditure was estimated by the time-energy budget method. Energetic costs were determined using heart rate.

4. The daily gain of pondweed feeding at the median date of the habitat switch (i.e. when 50% of the swans had switched) was compared with that of beet feeding. The daily gain of beet feeding was calculated for two strategies depending on the night activity on the lake: additional pondweed feeding (mixed feeding) or sleeping (pure beet feeding).

5. The majority of the swans switched when the daily gain they could achieve by staying on the pondweed bed fell just below the average daily gain of pure beet feeders. However, mixed feeders would attain an average daily gain considerably above that of pondweed feeders. A sensitivity analysis showed that this result was robust.

6. We therefore reject the hypothesis that the habitat switch by swans can be explained by simple long-term energy rate maximization. State-dependency, predation risk, and protein requirements are put forward as explanations for the delay in habitat switch.
Language eng
DOI 10.1046/j.1365-2656.2002.00662.x
Field of Research 060801 Animal Behaviour
Socio Economic Objective 970106 Expanding Knowledge in the Biological Sciences
HERDC Research category C1.1 Refereed article in a scholarly journal
ERA Research output type C Journal article
Copyright notice ©2002, British Ecological Society
Persistent URL http://hdl.handle.net/10536/DRO/DU:30076018

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