Determining the impact of intrinsic and extrinsic factors throughout the annual cycle on the reproductive behaviour of a migratory songbird, Purple Martin Progne subis
The causes of steep rates of population decline in migratory songbirds remain largely unknown. In a trans-hemispheric migratory swallow (purple martin, Progne subis), I examined carry-over effects from spring migration on an individual’s subsequent reproductive success as well as latitudinal variation in clutch size and timing of provisioning. I show that martins that spent more days at spring migratory stopovers initiated their clutches earlier after arrival at breeding colonies, and lost fewer offspring. I found that martins at more northern latitudes provisioned their young for more hours per day but I did not find a predicted positive correlation between clutch size and latitude. Overall, I show for the first time how spatio-temporal factors during migration carry over to affect the reproductive success of individual songbirds and my results suggest that the increased risk associated with longer migration is not compensated for by higher productivity at more northern latitudes.
Biological Sciences, Carry-over effects, Latitudinal variation, Reproduction