Some male Pied Flycatchers Ficedula hypoleuca in Iberia become collared with age

The development of a collar in Pied Flycatchers Ficedula hypoleuca in Spain is described and its ontogenetic and genetic variation and phenotypical correlates are analysed. Collared males were older than males having traces of collar or lacking one. Also, males showing a collar or trace of a collar had larger white forehead patches than those lacking a collar. Intrapopulation variation in both collar expression and white patch size, which might be genetically determined but phenotypically decoupled in temporal expression, resembles between-species variation among the black and white European flycatchers.