Meeting Abstract

P2.14  Sunday, Jan. 5 15:30  Breeding in an urbanizing world: Reproductive adjustments of seasonally breeding birds to urban areas DAVIES, S*; DEVICHE, P; Arizona State University; Arizona State University Scott.Davies@asu.edu

Urbanization is altering the environment at an unprecedented rate. Urban animals inhabit an environment vastly different from that of their non-urban conspecifics and to survive they must adjust to these modified environmental conditions. For seasonally breeding birds, the timing of breeding has a considerable effect on fitness and reflects adjustments to local environmental conditions. We used a meta-analytical approach to compare the timing of seasonal breeding of birds inhabiting urban vs. corresponding non-urban areas. Our analysis included 17 published studies that encompassed a paired comparison of the same species in both urban and non-urban areas during the same breeding season. Studies of lay, clutch initiation, and hatch dates indicate that, on average, urban birds breed 3.1 days earlier than their non-urban conspecifics. Furthermore, effect size is positively related to the latitude of the city. To identify the driving force behind this advancement, we also used meta-analysis to examine whether the change in timing of breeding is mirrored in the timing of gonadal development and the seasonal increase in plasma levels of reproductive hormones. Vernal gonadal development in both male and female birds occurs earlier in urban birds compared to their non-urban counterparts. However, this habitat-related difference is not associated with a difference in reproductive hormone levels between urban and non-urban birds. Thus, the observed difference in timing of breeding and gonadal development appears to be controlled by factors other than reproductive hormone levels.