Individual study: Supplementary feeding increases nest size and egg size in black-billed magpies Pica pica in mixed agricultural habitats in southern Spain
De Neve L., Soler J.J., Ruiz-Rodriguez M., Martin-Galvez D., Perez-Contreras T.A.S. & Soler M. (2007) Habitat-specific effects of a food supplementation experiment on immunocompetence in Eurasian Magpie Pica pica nestlings. Ibis, 149, 763-773
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Provide supplementary food for songbirds to increase reproductive success
A replicated, controlled trial in habitats in southern Spain in 2001 (De Neve et al. 2007), found that black-billed magpie Pica pica nestlings provided with supplementary food had significantly higher cell-mediated immune responses (CMI, the change in swelling around insect bites, a measure of immunocompetence) in arid scrub, but not in irrigated farmland and woodland (arid scrub: average CMI of approximately 1.18 mm for fed nestlings vs. 0.85 m for controls; irrigated farmland/woodland: average CMI of 1.20 mm for fed nestlings vs. 1.18 mm for controls; 58 nests studied). In addition, fed nestlings showed significantly lower levels of the ectoparasite Carnus haemapterus (Diptera: Carnidae), but only in arid habitats (arid scrub: average infestation intensity of 0.40 arbitrary units for fed nestlings vs. 0.90 arbitrary units for controls; irrigated farmland/woodland: average 1.60 arbitrary units for fed nestlings vs. 1.65 arbitrary units for controls; 28 nests). Feeding had no effect on chick growth, weight or on the prevalence of blood parasites. Supplementary feeding consisted of 0.1 ml of high-calorie, nutrient-rich paste provided every other day for a total of 14 days.