NESTING SUCCESS OF NEOTROPICAL THRUSHES IN COFFEE AND PASTURE

摘要

We monitored nesting attempts of White-throated (Turdus assimilis) and Clay-colored thrushes (T. grayi) over 4 years in southern Costa Rica to compare nest success in recently abandoned coffee (Coffea spp.) plantations, pasture, and along roads. Daily mortality rates of Clay-colored Thrush nests were lower in pasture (0.054 ± 0.014) than abandoned coffee plantations (0.096 ± 0.012). Daily mortality rates of White-throated Thrush nests were not influenced by land-cover type but were lower at highly concealed nests (0.058 ± 0.005) compared to less concealed nests (0.090 ± 0.017), and at nests that were on the ground (0.0580 ± 0.005) versus in vegetation (0.076 ± 0.007). Daily mortality rates for nests of both species were very low at an active coffee plantation where nests were monitored in 1 year (0.006 ± 0.004 and 0.015 ± 0.015, for White-throated and Clay-colored thrushes, respectively). Nests at the active plantation were heavily concealed which, along with results for White-throated Thrushes in abandoned coffee, indicates concealment has a strong influence on tropical thrush nest success. Nest success appears to be heavily dependent on factors that may influence both concealment and or habitat for predators. Nest success also appears to be strongly site-specific, making it difficult to provide general statements about the conservation value of different land-cover types.