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Individual study: Supplementary feeding leads to earlier laying in blue tits Parus caeruleus but only in one of four sites investigated on Corsica, France

Published source details

Bourgault P., Perret P. & Lambrechts M.M. (2009) Food supplementation in distinct Corsican oak habitats and the timing of egg laying by blue tits. Journal of Field Ornithology, 80, 127-134

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Provide supplementary food for songbirds to increase reproductive success Bird Conservation

A replicated and controlled study in a range of oak forest habitats on Corsica, France, in the springs of 2006 and 2007 (Bourgault et al. 2009) found that blue tits Parus caeruleus (also known as Cyanistes caeruleus) provided with supplementary food began laying eggs significantly earlier in a holm oak Quercus ilex dominated site (females from 30 fed pairs began to lay approximately seven days earlier than controls), but not in two broad-leaved oak Q. humilis dominated sites or a second holm oak site. The authors suggest that this difference is due to broad-leaved oak forests having up to ten times more food for blue tits than holm oak forests. Clutch size did not differ between fed and control territories in any of the sites. Supplementary feeding comprised unlimited access to food in feeders within territories, beginning in mid-January and continuing until egg laying began.