Birds do not use social learning of landmarks to locate favorable nest sites.

Experiments since the classic studies of Niko Tinbergen have provided evidence that animals use visual landmarks to navigate. We tested whether birds use visual landmarks to relocate their nest sites by presenting two species of cavity nesting birds with a dyad of nest boxes with different white markings around the entrance, a circle or a triangle. When the two boxes were erected in close proximity on the same tree, pied flycatchers Ficedula hypoleuca and blue tits Cyanistes caeruleus confused the entrance of their nest both when the boxes had different external markings and when they were unmarked. Most females added nest material to both boxes of a dyad and one third of the flycatchers laid eggs in both boxes although a female can only incubate the eggs in one nest at a time. Thus, the birds did not use external markings around cavity entrances for orientation. We also tried to replicate a previous study purporting to show that migratory birds use social learning of the external appearance of nests from other species. However, pied flycatchers did not choose boxes with the same painted markings as those applied to nests of resident great tits Parus major which were judged to be high quality "demonstrators" from their large clutch sizes. We argue that conclusions from previous studies on social learning based on external markings as landmarks on nest cavities in birds need to be reconsidered. Significance: Animals may try to hide their nest site on the landscape to avoid the attention of predators and competitors. However, this may make it difficult in the beginning of the breeding season for the parents to relocate the nest site quickly, particularly in a habitat with a complex three-dimensional structure of bushes and trees. To test whether birds might use conspicuous markings around the entrance of their nest as landmarks, we presented prospecting pied flycatchers Ficedula hypoleuca and blue tits Cyanistes caeruleus with a dyad of nest boxes painted with a white circle or a white triangle affixed to different trees or the same tree. However, we found no evidence that the birds used the external markings to identify the entrance to their nest site, or that such markings on nest cavities were learned from resident great tits Parus major. [ABSTRACT FROM AUTHOR]