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Energy density and variability in abundance of pigeon guillemot prey: support for the quality–variability trade-off hypothesis
Article first published online: 29 OCT 2004
DOI: 10.1111/j.0021-8790.2004.00890.x
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How to Cite
LITZOW, M. A., PIATT, J. F., ABOOKIRE, A. A. and ROBARDS, M. D. (2004), Energy density and variability in abundance of pigeon guillemot prey: support for the quality–variability trade-off hypothesis. Journal of Animal Ecology, 73: 1149–1156. doi: 10.1111/j.0021-8790.2004.00890.x
Publication History
- Issue published online: 29 OCT 2004
- Article first published online: 29 OCT 2004
- Received 20 November 2003; accepted 22 April 2004
- Abstract
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Keywords:
- foraging;
- patchiness;
- resource heterogeneity;
- resource quality;
- risk sensitivity
Summary
- 1The quality–variability trade-off hypothesis predicts that (i) energy density (kJ g−1) and spatial–temporal variability in abundance are positively correlated in nearshore marine fishes; and (ii) prey selection by a nearshore piscivore, the pigeon guillemot (Cepphus columba Pallas), is negatively affected by variability in abundance.
- 2We tested these predictions with data from a 4-year study that measured fish abundance with beach seines and pigeon guillemot prey utilization with visual identification of chick meals.
- 3The first prediction was supported. Pearson's correlation showed that fishes with higher energy density were more variable on seasonal (r = 0·71) and annual (r = 0·66) time scales. Higher energy density fishes were also more abundant overall (r = 0·85) and more patchy at a scale of 10s of km (r = 0·77).
- 4Prey utilization by pigeon guillemots was strongly non-random. Relative preference, defined as the difference between log-ratio transformed proportions of individual prey taxa in chick diets and beach seine catches, was significantly different from zero for seven of the eight main prey categories.
- 5The second prediction was also supported. We used principal component analysis (PCA) to summarize variability in correlated prey characteristics (energy density, availability and variability in abundance). Two PCA scores explained 32% of observed variability in pigeon guillemot prey utilization. Seasonal variability in abundance was negatively weighted by these PCA scores, providing evidence of risk-averse selection. Prey availability, energy density and km-scale variability in abundance were positively weighted.
- 6Trophic interactions are known to create variability in resource distribution in other systems. We propose that links between resource quality and the strength of trophic interactions may produce resource quality–variability trade-offs.