Are nest sites actively chosen? Testing a common assumptionfor three non-resource limited birds

摘要

Many widely-accepted ecological concepts are simplified assumptions about complex situations thatremain largely untested. One example is the assumption that nest-building species choose nest sitesactively when they are not resource limited. This assumption has seen little direct empirical testing: moststudies on nest-site selection simply assume that sites are chosen actively (and seek explanations forsuch behaviour) without considering that sites may be selected randomly. We used 15 years of data froma nestbox scheme in the UK to test the assumption of active nest-site choice in three cavity-nesting birdspecies that differ in breeding and migratory strategy: blue tit (Cyanistes caeruleus), great tit (Parus major)and pied flycatcher (Ficedula hypoleuca). Nest-site selection was non-random (implying active nest-sitechoice) for blue and great tits, but not for pied flycatchers. We also considered the relative importance ofyear-specific and site-specific factors in determining occupation of nest sites. Site-specific factors weremore important than year-specific factors for the tit species, while the reverse was true for piedflycatchers. Our results show that nest-site selection, in birds at least, is not always the result of activechoice, such that choice should not be assumed automatically in studies of nesting behaviour. We usethis example to highlight the need to test key ecological assumptions empirically, and the importance ofdoing so across taxa rather than for single "model" species.