Low Breeding Success in Mediterranean Shrubsteppe Passerines: Thekla Lark Galerida theklae, Lesser Short-Toed Lark Calandrella rufescens, and Black-Eared Wheatear Oenanthe hispanica

Abstract

Breeding success of three species of Iberian shrubsteppe bird communities (Galerida theklae, Calandrella rufescens and Oenanthe hispanica) was analyzed. Nest mortality was very high (83.2, 80.8 and 67.9%, respectively), almost double Ricklefs' (1969) mean of 43.6% for open nests in temperate regions. Adding partial losses, breeding success was 14.9, 15.7 and 26.4%. The main cause of loss was predation (around 55-75% of total losses during the incubation period and 70-100% during the nestling period). Differences in daily survival rates during the nestling stage were found between 0. hispanica and the two lark species; inter-annual differences were found in C. rufescens; in 0. hispanica there was variation between sites. We suggest that high mortality rates are a common feature in Mediterranean shrubsteppe passerines and contribute to an advancement of breeding time. Furthermore, only the existence of metapopulations, with a high degree of annual and local variation in mortality rates, explains how these populations remain stable.