Factors of Non-Breeding Habitat in Shorebird Social Systems

• Main Authors: Bodega Marine Reserve, University Of California Natural Reserve System, Pitelka, Frank A.
• Format: Dataset
• Language: English
• Published: KNB Data Repository 2007
• Subjects: shorebird; aquaculture; sanderling; Calidris alba; Sanderling
• Online Access: https://dx.doi.org/10.5063/aa/nrs.763.1; https://knb.ecoinformatics.org/view/doi:10.5063/AA/nrs.763.1

This research, now in its 6th year, deals with the population ecology of a wintering shorebird, the sanderling Calidris alba and its invertebrate prey. We are concerned with three major research areas: (i) the influence of resource abundance and predation risk on sanderling spacing behavior: (ii) the effects of shorebird predation on their invertebrate prey: and (iii) temporal and spatial definition of shorebird populations along coastal California. Our work on sanderling spacing dissects ecological factors governing the wide variability observed in their behavior, from tight flocking to strong territorial defense. This is a field study, and it involves long-term, intensive monitoring of prey abundances, of sanderling predators (chiefly raptors), and of sanderling behavior. A major part of the work is describing time-space distributions of invertebrates exploited by sanderlings on outer beaches. Chief among these are the sand crabs Emerita analoga and isopods Excirolana spp. This field sampling has been complemented by extensive analyses of caloric values of invertebrate prey, as well as laboratory experiments on the factors governing prey availability to sanderlings. The study on shorebird effects on their invertebrate prey centered around a series of bird exclosures set out in Bodega Harbor from October 1980 - March 1981. These cages kept out birds but allowed in fish. An intricate sampling method allowed us to combine measurements of prey density with information on caloric values of prey and on factors controlling prey availability, thereby permitting the effect of shorebird predation in to be calculated terms of a reduction in caloric intake rates of birds feeding in control plots vs. exclosures. Birds had strong and significant prey to removed effects: they enough decrease their caloric intake rate by 41%. Our research on the temporal and spatial definition of shorebird populations focuses on movements by sanderlings among different estuary-beach systems in central coastal California. We have discovered a strong seasonal pattern in the degree of vagility of sanderlings wintering examine monitor this Bodega Bay. To at we turnover rates of individuals within the local population, and also make periodic expeditions to surrounding areas in search of color-marked individual birds. This research has important practical implications because it reveals that environmental disturbances may a far affect local greater set of shorebirds than indicated by simple static censuses of an area. This research is supported by the National Science Foundation. In addition to the staff listed above, periodically through the winter we employ 5-lO students for invertebrate sampling. One member of the staff, G. Ruiz, has now become a UCB graduate student and will center his dissertation around aspects of this work. As of July a UC Santa Cruz senior, Richard Culver, has begun his senior thesis under our direction. Through the past year, Dr. J.R. Walters associated with our program as an NSF Post-doctoral Fellow.