Nest-site selection and breeding success of the semi-desert bird, Grey Hypocolius Hypocolius ampelinus, in relation to plant structure of Ziziphus nummularia

Nest-site selection and breeding success of the Grey Hypocolius (Hypocolius ampelinus) were surveyed in relation to plant structure in 2010 and 2011 in southwestern Iran. Microhabitat parameters such as Ziziphus nummularia as the main shrubs used for nesting, were measured in 20 x 20 m plots around the nest and compared with random plots. There were no best clear model for predicting the nest-site selection, however, plant variables especially the canopy cover and diameter of the Z. nummularia, were the most important determinant for nest-site selection (w(i) = 0.5). Grey Hypocolius preferred areas with a higher density of Z. nummularia than other available habitats (28.21 vs 1.2 of cover). There was no strong predictor for breeding success, the best models incorporated either Z. nummularia density or diameter (with model weights of 0.25 and 0.17, respectively). Nests of Grey Hypocolius had a higher chance of success at higher densities of Z. nummularia in nesting plots. We found that a higher density of Z. nummularia improved both the probability of nest-site selection and the breeding success of Grey Hypocolius. Shrubs with greater diameters were more likely to be selected for nesting, but had lower breeding success. To identify the key reasons of nests being successful, more habitat parameters should be monitored. The majority of failure in breeding occurred during the incubation stage (52%).