Tuesday, 18 March 2014

The early bird ... loses its eggs

Early nests are more susceptible to predation
The nesting season is underway for bird species such as blackbird and song thrush, but their nests are poorly concealed as the leaves are not yet on the trees and hedges. Analysis of our 11-year dataset by Patrick White previously revealed that early season blackbird nests were more susceptible to predation by crows and magpies than nests later in the season, although there was no such effect when nest predators were controlled as part of a game management system (1).  That work also revealed higher fledging rates and population increases during the period of low nest predation.

In another paper just published on-line (2), Patrick White's further analysis of nest data collected over the same period by John Szczur reveals that, as well as blackbird and song thrush, nest survival of dunnock, chaffinch and yellowhammer also benefited from the removal of nest predators during the breeding season as part of systematic game management. For whitethroat, the sixth species studied, there was no such effect.  However, when less intensive control of crows and magpies only was carried out, only blackbird showed higher nest survival.

1. White, P.J., Stoate, C., Szczur, J. & Norris, K. (2008) Investigating the effects of predator removal and habitat management on nesting success and breeding population size of a farmland passerine: a case study. Ibis 150 (Suppl.1), 178-190.
2. White, P., Stoate, C., Szczur, J. & Norris, K. (2014) Predator reduction with habitat management can improve songbird nest success. Journal of Wildlife Management DOI: 10.1002/jwmg.687

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