Carry-over effects from passage regions influence breeding phenology and performance of three avian migrants

Fig 1 Finch et al 2014

Fig 1 Finch et al 2014 Breeding (green), spring passage (orange), the Sahel zone (yellow) and winter distributions (blue) of British breeding a redstart, b spotted flycatcher and c wood warbler used in this analysis.

Carry-over effects from passage regions are more important than breeding climate in determining the breeding phenology and performance of three avian migrants of conservation concern

“We find that carry-over effects from passage regions consistently had stronger impacts on breeding phenology than breeding climate. Warm Mediterranean passage conditions promoted earlier breeding in all species, and redstarts also bred earlier following higher Sahel rainfall. Warmer springs on the breeding grounds promoted slightly earlier breeding in redstart and wood warbler, but not spotted flycatcher. Carry-over effects also typically influenced breeding performance to a greater extent than weather on the breeding grounds. Greater rainfall in the Sahel increased redstart brood size, warmer Mediterranean passage conditions increased spotted flycatcher brood size and, to a lesser extent, the number of wood warbler fledglings. In contrast to the concern regarding climate change impacts on migrants’ breeding grounds we found no evidence that warmer temperatures on the breeding grounds were associated with reduced reproductive performance.”

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