eWestern Birds

Long-billed Curlew Distributions in Intertidal Habitats: Scale-Dependent Patterns

Ryan L. Mathis, Mark A. Colwell, Linda W. Leeman, and Thomas S. Leeman

ABSTRACT: Key ecological insights come from understanding a species’ distribution, especially across several spatial scales. We studied the distribution (uniform, random, or aggregated) at low tide of nonbreeding Long-billed Curlew (Numenius americanus) at three spatial scales: within individual territories (1–8 ha), in the Elk River estuary (~50 ha), and across tidal habitats of Humboldt Bay (62 km2), California. During six baywide surveys, 200–300 Long-billed Curlews were aggregated consistently in certain areas and were absent from others, suggesting that foraging habitats varied in quality. In the Elk River estuary, distributions were often (73%) uniform as curlews foraged at low tide, although patterns tended toward random (27%) when more curlews were present during late summer and autumn. Patterns of predominantly uniform distribution across the estuary were a consequence of territoriality. Within territories, eight Long-billed Curlews most often (75%) foraged in a manner that produced a uniform distribution; patterns tended toward random (16%) and aggregated (8%) when individuals moved over larger areas. At each spatial scale, food probably had the strongest influence on distributions, whereas predation played a relatively minor role in determining patterns.

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