Zeitschriftenartikel

Clustered nesting and vegetation thresholds reduce egg predation in sooty terns

Colchero, F., Bass, O. P., Zambrano, R., Gore, J.
Waterbirds, 33:2, 169–178 (2010)

Abstract

Nesting seabirds reduce the risk of egg predation by aggregating near conspecifics or by selecting habitat features that reduce the nest's exposure to predators. In particular, ground-nesting seabirds aggregate in open areas, avoiding vegetation or other structures that could limit visibility and accessibility to the nest. Yet, a few populations of ground-nesting species are known to select sites with structures that provide cover above the nest possibly in response to an increase in the risk of egg predation. The Dry Tortugas (DRTO) Sooty Terns (Onychoprion fuscata) are known to nest on sandy substrate. However, a steep change in the onset of their breeding season has increased their exposure to aerial predators, which could have in turn trigger a change in their nesting behavior. During eight years, data on number of nests and egg predation and percent vegetation cover were collected from 132 survey plots at the DRTO. These data were analyzed using a hierarchical Bayesian model to test for the relationship between nest numbers and vegetation cover and if this nesting behavior reduced the incidence of egg predation. A clear non-linear relationship between vegetation cover and nesting numbers was found, where thresholds of 65% cover of woody vegetation such as shrubs, and less than 13% of forbs, maximized the number of nests and significantly reduced egg predation. These results have important implications for nesting habitat management and outline that Sooty Terns are capable of changing dramatically their breeding behavior in response to an increase in the risk of egg predation.
Schlagwörter: Vereinigte Staaten, life histories
Das Max-Planck-Institut für demografische Forschung (MPIDR) in Rostock ist eines der international führenden Zentren für Bevölkerungswissenschaft. Es gehört zur Max-Planck-Gesellschaft, einer der weltweit renommiertesten Forschungsgemeinschaften.