Population age structure as an indicator for assessing the quality of breeding areas of Common quail (Coturnix coturnix)

Quality breeding areas are vital for the management and conservation of migratory bird species, especially those under pressure from climate warming effects. The Common quail Coturnix coturnbc is a migratory species characterized by its itinerant breeding (several breeding attempts in different places) and exposure to high mortality rates, and it is a case in point. The identification and management of high quality nesting areas is essential to conserve this and other migratory species. Here, we use a Spanish long-term quail ringing dataset (1961-2014) to correlate population age structure with temporal and geographical variables. We show that northern Mediterranean regions provide optimal breeding sites and have balanced population age structures (young:adult males). The proportion of young:adult males provides an indicator of the relative quality of various breeding areas. Records of ringed quail provide data on the overlap between young and adult males temporarily resident in different geographic areas and may provide a useful tool to evaluate habitat quality. We found that the timing of sequential breeding attempts and temporary residency of quail are associated with latitude, altitude, and geographic location of quail ringing records. In southern regions, young males arrive at the breeding area later than adults, while in northern regions young birds and adults arrive at same time. Optimal breeding areas are characterized by high quality habitat, have high quail densities, and a mixture of young and adult males, factors that favour sexual selection, heterozygosity and population viability. However, not all high quality habitat areas are suitable for reproduction, being necessary enough quail density and the adequate proportion of young:adult males.