Common Kingfishers Alcedo atthis along the coast of northern Iberia during the autumn migration period

Abstract

Iberia receives many dispersing, migrating and wintering Common Kingfishers Alcedo atthis. The majority of these individuals occur in coastal marshes. Between August and mid-October 2007 and 2008, Kingfishers were mist-netted at a tidal marsh in Txingudi, northern Iberia. They were especially abundant from August to September, indicating that Txingudi receives an influx of migrants from northern Europe or local birds dispersing from nearby natal areas. The population mainly consisted of juveniles (only 5.8% adults), the sex ratio was 1:1 and the timing of passage was similar between the sexes. Body mass controlled for body size was constant with time. The stopover duration was affected by sex, date (month of first capture) and a body mass/size ratio, here used as a proxy of fuel load. Females with a lower body mass/size ratio were more likely to remain for longer than those with higher ratios, but the opposite was found in males. Kingfishers captured in August were more likely to be already settled in the area than those first captured in September. Moreover, birds with short stopovers systematically lost mass, while birds that remained in the area for longer did not. These findings are discussed in the light of possible competition between newly arriving and already settled birds.