Latitudinal Clines in Food Distribution Correlate with Differential Migration in the Western Sandpiper
From Pubwiki
[edit] Author(s)
- Mathot, K. J.
- Smith, B. D.
- Elner, R. W.
[edit] Journal
Ecology 88.3 (2007): 781-91.
[edit] Keywords
biofilm calidris mauri differential migration intertidal invertebrates latitudinal gradients in resource distribution nonbreeding distribution shorebird western sandpiper calidris-mauri sex-ratio migrant shorebirds size dimorphism bill length predation ecology invertebrates segregation morphology
[edit] Abstract
We report that a latitudinal cline in intertidal food distribution is associated with the nonbreeding distribution of the Western Sandpiper ( Calidris mauri). This novel result is the first to demonstrate a clear relationship between patterns of differential nonbreeding distribution and food availability for any shorebird species. Within each age class and sex, longer- billed Western Sandpipers winter further south. Moreover, females, the longer- billed sex, tend to winter south of males. Thus, both inter- and intra- sexual clines in bill morphology result in an overall gradient of increasing bill length from north to south. Longer- billed birds are able to extract prey that are buried more deeply in the sediment; therefore, we predicted shifts in the vertical distribution of food resources to coincide with the clines in bill morphology across the nonbreeding range. We tested our prediction by measuring bio. lm density and the vertical distribution of macrofaunal invertebrates at six nonbreeding sites. Although no latitudinal trend was observed for bio. lm, the vertical distribution of invertebrates was consistent with our prediction and revealed that the greatest relative abundance of surface prey occurred at northern nonbreeding sites and declined with decreasing latitude. We discuss the potential implications of these. ndings in the context of competing evolutionary hypotheses of differential migration and bill dimorphism in shorebirds.
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