Migratory birds adjust their refuelling rates at stopover sites based on habitat characteristics and physiological state. For Least (Calidris minutilla) and Western (C. mauri) Sandpipers on southward migration in British Columbia, I investigated species differences in foraging habitat, diet, and fattening rate, and long-term trends in body mass related to species, age, and site during a period of changing predation danger (1980s-2000’s). Least Sandpipers disproportionately used more vegetated habitat, and foraged at a lower trophic level than Western sandpipers. Least Sandpiper fattening rate was higher than in Western Sandpipers, but did not differ with respect to covariates in either species. Western Sandpipers of both age classes were heavier at a safer site. At a more dangerous site, adult Least Sandpiper mass decreased over three decades, while juvenile mass remained consistently low. I interpret patterns of variation in stopover ecology as species-specific prioritization of danger management, feeding conditions, and migratory route.
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Thesis advisor: Ydenberg, Ronald
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