Seasonal carry-over effects and connectivity inmigratory songbirds

点击翻译按钮获取中文摘要

Each fall billions of songbirds migrate between the temperate zone and tropics but little is known about how breeding or wintering events affect the timing and pace of migration, and vice versa, or the fitness consequences of individual differences in migration strategy. I have pioneered the use of light level geolocators on migratory songbirds. Geolocators are archival tags (< 1.5g) that when retrieved after migration can be used to infer migration routes and timing. I have used geolocators on Wood Thrush and Purple Martins since 2007 and have documented extensive variation in migration route, timing, and speed for individuals breeding in the same population. I will use this innovative technology to test (1) how reproductive effort and timing affects fall migration, moult-migration overlap and subsequent survival, (2) how arrival date affects winter territory quality, survival, winter body condition and subsequent spring migration, and (3) how connectivity patterns between breeding and wintering sites are linked to population declines. To look at carry-over effects, clutch size and timing of breeding will be manipulated to test the prediction that high parental effort delays migration. I will also manipulate parasite loads to test the prediction that infection by Haemoproteus blood parasites slows fall migration. I will deploy geolocators on wintering songbirds to test how fall migration strategy affects subsequent territory quality, ownership, and over-winter survival. Experimental manipulation of winter territory quality ("upgrading" to a better territory, food supplementation) will test the prediction that poor quality territory delays spring migration and thus arrival on the breeding territory. Connectivity patterns are predicted to affect population decline on the breeding grounds because diffuse connectivity spreads the impact of low winter survival in a region over a large number of breeding populations. Geolocators will be deployed on multiple breeding and wintering populations of Wood Thrushes and Purple Martins to map connectivity patterns and test if the strength of connectivity predicts regional breeding population trends.