Individual study: Supplementary feeding increases immunocompetence but not growth in black-billed magpies Pica pica in arid but not irrigated habitats in southern Spain
De Neve L., Soler J.J., Soler M., PÃ©rez-Contreras T., MartÄ±n-Vivaldi M. & MartÄ±nez J.G. (2004) Effects of a food supplementation experiment on reproductive investment and a post-mating sexually selected trait in magpies Pica pica. Journal of Avian Biology, 35, 246-251
This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.
Provide supplementary food for songbirds to increase reproductive success
A replicated, controlled trial in mixed agricultural habitats in southern Spain (De Neve et al. 2004) found that, when provided with supplementary food, male black-billed magpies Pica pica built significantly larger nests than controls (average of 5.1 units for 39 nests in fed territories vs. 4.6 units for 123 nests in controls) and females laid significantly larger eggs (average egg volume of 10.0 cm3 for 36 fed clutches vs. 9.5 cm3 for 119 controls). However there were no significant differences between groups in terms of laying date or clutch size (average of 25th April for 46 fed clutches vs. 12th April for 162 controls; 6.9 eggs/clutch for 38 fed clutches vs. 6.8 for 128 controls). Supplementary food consisted of 150 g dog food mixed with bread and water supplied every two days from before nest-building began until after the end of the breeding season.