Intra-seasonal changes in distribution and habitat associations of a multi-brooded bird species: implications for conservation planning

Intra-seasonal changes of the ecological needs and the distribution patterns of multi-brooded bird species are a poorly studied but potentially important topic in avian conservation planning. In this study of a passerine species of conservation concern, the woodlark Lullula arborea, we highlight the conservation implications of spatial shifts of breeding territories and changes of habitat requirements during the course of the breeding season. We described the factors affecting the distribution and habitat selection of this species in the Trebbia river valley (northern Apennines, Italy), where we mapped woodlark territories during the average time of first and second clutches. A strong shift of territories towards higher altitudes with the progression of the season was observed. The habitat models predicting woodlark occurrence varied between the early and the late period. Specifically, fodder cover positively predicted occurrence early in the season, whereas late in the season occurrence was positively influenced by shrub cover, length of woodland edge, alfalfa cover and rocky areas. Accordingly, territories that were occupied throughout the entire season had greater fodder, shrub and rocky cover compared with those that were occupied only early in the season, suggesting that these variables were important in determining territory quality for woodlarks. Therefore, changing ecological needs of multi-brooded bird species during the breeding season have to be taken into account for defining appropriate conservation strategies. This was demonstrated by showing that the habitat variables predicting woodlark occurrence early in the season poorly predicted occurrence late in the season and vice versa. In conclusion, this study provides the first detailed assessment of habitat factors affecting the occurrence of breeding woodlarks in an important portion of the species' range, and represents the first explicit attempt to model seasonally changing ecological requirements of bird species for conservation purposes. Our findings suggest that complex data and flexible habitat management strategies are required to account for temporal changes in habitat suitability in multi-brooded bird species.