Nesting Height and Nest-Cup Volume Variation in Rufous Bush Chats ( Cercotrichas Galactotes ) Inhabiting Algerian Oases: Consequences for breeding success

Abstract

The placement and size of birds’ nests may have direct consequences for their breeding success. Here, we examined if the location and design of Rufous Bush Chat (Cercotrichas galactotes) nests influenced their breeding success in the Al Amri Oasis, at the base of Saharan Atlas, north Algeria, in 2008–2009 and 2011–2013. The mean height of nests above ground level was 2.26 ± 0.09 (SE) m, ranging from 0.5 to 4.9 m and the mean nest-cup volume was 246.60 ± 11.82 (SE) cm³, ranging from 102.95 to 471.24 cm³. Nest-cup volumes were positively associated with the height of nests and breeding success was strongly positively associated with the height of nests above ground level. We conclude that pairs of Rufous Bush Chats that bred in higher nests had higher levels of breeding success because they suffered lower predation rates from ground-based predators than lower nests. Lower nests, which are more vulnerable to ground-based predators are likely to be smaller in order to make them less visible to visually searching predators and may also fit more snugly into the smaller leaf stems of smaller palms. These findings agree with the hypothetical predictions based on the properties of palm physical structure as a support for nests, the tree size structure of plantations and the risk of predation.