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Vol. 48 No. 6, 2009
Prey Selection by Breeding Brown Dippers Cinclus pallasii in a Taiwanese
Mountain Stream
Ming-Chih
Chiu1, Mei-Hwa Kuo1,
Chyng-Shyan Tzeng2,
Cheng-Hsiung Yang2,
Chao-Chieh Chen3,
and Yuan-Hsun Sun4,*
1Department
of Entomology, National Chung Hsing University, Taichung 402, Taiwan
2Institute of Bioinformatics and Structural Biology,
and Department of Life Science, National Tsing Hua University, Hsinchu
300, Taiwan
3Department of Biomedical Science and Environmental
Biology, Kaohsiung Medical University, Kaohsiung 807, Taiwan
4Institute of Wildlife Conservation, National Pingtung
University of Science and Technology, Pingtung 912, Taiwan
Ming-Chih Chiu,
Mei-Hwa Kuo, Chyng-Shyan Tzeng, Cheng-Hsiung Yang, Chao-Chieh Chen, and
Yuan-Hsun Sun (2009) Optimal foraging theory predicts that
prey selection by breeding birds is governed by tradeoffs among diverse
prey types with different energy gains per unit energy expended.
This is particularly so in central-place foragers such as dippers
(Cinclidae), which must provision nest-bound young using prey gathered
along a linear habitat. In this study, we examined changes in the
dietary composition of nestling Brown Dippers Cinclus pallasii over the course of
the nestling period in the mountainous Dajia River of central
Taiwan. Prey preference was associated with prey morphological
traits: fish and trichopterans, with relatively large body sizes, were
the preferred prey items, while smaller prey such as ephemeropterans,
plecopterans, and dipterans were least preferred. However, the
nestling dietary composition significantly shifted over the 1st 1/2 of
the nestling period, with the proportion of large prey and daily
maximum prey size increasing as the nestlings grew. Our data
suggest that the increasing energy demands of the nestlings are
responsible for the increase in prey size, while nestling gape-size
possibly limited the maximum prey size early in the nestling
period. These results bear a striking similarity to data reported
for other dipper species, implying identical constraints and strategies
in nest provisioning.
Key words: Aquatic insects, Birds, Bottom-up,
Predation, Rivers.
*Correspondence: Tel: 886-8-7740481. Fax:
886-8-7740417. Email:ysun@mail.npust.edu.tw
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