Ageing nestling Barn SwallowsHirundo rustica: an illustrated guide and cautionary comments

Ageing is a crucial requisite for any analysis of growth and development. However, ageing by regular nest visits around hatching is time-consuming. Thus, species-specific developmental patterns are used to estimate nestling age at infrequent nest visits during the nestling period. Unfortunately, comprehensive species-specific data on the timing of other developmental traits than body mass and feather growth are rarely published. Here, we present...