SHORT COMMUNICATION Bird predation on insects reduces damage to the foliage of cocoa trees (Theobroma cacao) in western Panama

In the Neotropics, crops that are grown in agroforestry systems with shade trees support high levels of bird diversity compared with crops grown without shade (Estrada & Coates-Estrada 2005, Faria et al. 2006). Several experiments in shaded coffee farms have explored how insectivorous birds reduce herbivore numbers and their damage to plants and have simultaneously approached ecological questions that are applied (e.g. biological control) and basic (e.g. tri-trophic interactions) (Borkhataria et al. 2006, Greenberg et al. 2000, Perfecto et al. 2004). Here we used exclosures to test whether birds lower the densities of herbivorous insects and reduce insect damage to cocoa (Theobroma cacao L., Sterculiaceae) foliage in shaded farms of western Panama. Although bird predation has been shown to reduce insect damage to crops in other systems (Mols & Visser 2002), we provide the first test for shade-grown cocoa. We maintained bird exclosures on cocoa trees at two focal farms, in the communities of La Gloria (9◦20′N, 82◦28′W, altitude 45 m) and Charagre (9◦23′N, 82◦33′W, altitude 25 m). The study farms were within 2 km of 10–20-ha primary forest fragments. Both study farms were in the flood plains of large creeks, in locations which were chosen for their accessibility and flat ground. No chemical inputs (i.e. insecticides, fungicides) were applied to foliage in these farms. The mean canopy cover from shade trees was 54% (measured with a concave densiometer for 20 plots per farm, Van Bael, unpubl. data) and the farms shared the same predominant shade-tree species, Cordia alliodora (Ruiz & Pavón) Cham. (Boraginaceae). Throughout western Panama, 102 shade-tree morphospecies were counted in