The lack of information on the protection status of birds in the winter period is a serious concern, as the survival of many populations depends on this period. Here, we consider the seasonal changes in distribution patterns of bird species in central Spain to assess the value of protected areas (PA) for simultaneously conserving breeding and wintering avifauna. We used a stepwise algorithm of complementarity to select the minimum set of Universal Transverse Mercator 10 × 10-km squares containing all species at each period and then contrasted selected areas in order to test the degree to which breeding and wintering birds overlap. Using Gap analysis, we identified areas that are still unprotected. Our results show both a weak correlation and a scant overlap between areas that are important for bird conservation during breeding and wintering periods. Thus, we conclude that valuable areas for bird diversity differ between seasons, implying that breeding hot spots are not good surrogates for overwintering hot spots. This paper addresses the need of identifying not only important areas for breeding birds, but also wintering birds, revealing potential gaps in current PA networks. Future conservation policies should take these results into account in order to optimize bird conservation, especially considering that the appropriate protection of the bird species overwintering in Spain will, overall, benefit European breeding populations.