Effect of prior nesting success on future nest occupation in raven Corvus corax

Based on the fate of 48 nests of Raven Corvus corax we tested the hypothesis that low return rates of Raven were caused by unsuccessful nesting attempts in previous seasons. Ravens nested on electrical power pylons in 1996-1998 in an intensively managed farmland (W Poland). The studied nesting sites were divided into two groups: (1) sites with a reduced breeding success at a late nestling stage caused by the cleaning of power pylons; (2) sites that were not disturbed by human interference. Nesting sites with a ‘experimentally’ reduced breeding success were significantly used less in the following years. Because Ravens have a long life, we suggest that they use a decision rule based on prior experience to select nesting sites. Sites characterised by low reproductive success are more likely to be subsequently unused in favour of an alternate breeding site, whereas sites where birds nested successfully were more likely to be re-occupied in the next year

Piotr Tryjanowski, Adrian Surmacki & Jan Bednorz, Ardea 92(2): 251-254