Seasonal changes in feeding success, activity patterns, and weights of nonbreeding Sanderlings (Calidris alba)

摘要: -Seasonal changes in Sanderling (Calidris alba) feeding success, time budgets, and weights were followed throughout the nonbreeding season at Bodega Bay, California. Sanderlings spent more roosting fall than winter, adults juveniles. prey capture rates high spring declined through winter. paralleled seasonal success activity patterns: birds heaviest lightest These results reflect lowered food availability winter imply that may have difficulty balancing their energy budgets during part of season. Received 6 July 1984, accepted 31 December 1984. RESOURCE conditions faced by northern Temperate Zone shorebirds often deteriorate considerably Prey decline due to reductions density (Evans 1976, Evans et al. 1979, Goss-Custard 1980, Myers 1981, Quammen 1980), physical foraging environment (Dobinson Richards 1964, Pienkowski 1982), or alterations behavior (Smith 1975, Reading McGrorty 1978, 1983). The question is whether these material effects on shorebird behavior. This need not be case if fluctuations occur over a range values where caloric intake are affected-for example, asymptotic curve relating rate density. Fluctuations within this will negligible impact shorebirds. If fact, many do alter basis relation availability. They spend as progresses (Goss-Custard 1969, 1977; Puttick 1979) switch new sites Smith 1982). wintering Bay central coastal California experience regular annual cycle abundance (Myers unpubl. data; Connors 1981). Upon arrival until midautumn, resources abundant both outer sandy beaches tidal sand flats. During storms beset drastically reduce numbers. Cumulative predation flats also reduces MS). In recruitment cohorts, particularly Emerita analoga, increases once again (Connors paper we consider affect local rates, patterns, weights. STUDY AREA AND METHODS study was conducted from August 1982 April 1983 which along coast Reference photographs archived VIREO (Academy Natural Sciences). arrive depart May 1985). Birds feed two exposed tide then fly nearby flat recedes (Con-