Bromeliad Foraging Specialization and Diet Selection of Pseudocolaptes lawrencii (Furnariidae)

Abstract

ABSTRACT.-Over 50 species of Neotropical birds have been recorded foraging for animal prey in bromeliads. Of these bird species, Pseudocolaptes lawrencii is one of the most specialized. At a montane rainforest site in Costa Rica, 74% of its documented foraging efforts were in epiphytic bromeliads. P. lawrencii selected large bromeliads and foraged for arthropods within leaf litter and organic debris trapped in the plants. Based on our analyses of the bromeliad prey base and bird stomach contents, P. lawrencii was an opportunistic predator of the litter-inhabiting arthropods. Birds consumed dermapterans, orthopterans, arachnids, and coleopterans in proportions equal to the prey's availability and did not select for prey size. However, P. lawrencii avoided isopods. P. lawrencii did not consume aquatic insect larvae, which were the largest component of the bromeliad prey base and occurred in 80% of bromeliads sampled.RESUMEN.-Mas de 50 especies de aves Neotropicales han sido estudiadas mientras forrajean por animates en bromelias. De estas especies de aves, Pseudocolaptes lawrencii es una de las mas especializadas. En un bosque tropical montanoso en Costa Rica, se encontro que el 74% de los atentos de forrajeo fueron en bromelias epifiticas. Pseudocolaptes lawrencii selecciono bromelias grandes y forrajeo en las hojas y los escombros organicos atrapados en las bromelias. Basado en nuestro analisis de los animates encontrados en las bromelias y el contenido estomacal de las aves, concluimos que P. lawrencii es un predador oportunistico de los artropodos que viven en los escombros organicos. Las aves consumieron dermapteros, orthopteros, aracnidos y coleopteros en proporciones identicas a la disponibilidad de estas presas. No se encontro seleccion de presas, sin embargo, P. lawrencii evito isopodos. No consumi6 larvas de insectos acuaticos, la presa mas abundante y se encontrd en un 80% de las bromelias estudiadas.Among the masses of epiphytes that give Neotropical montane forests their "fantastic appearance" (Slud 1964:205), bromeliads are often the most conspicuous plants. Bromeliads increase the structural complexity of forests and create additional microhabitats for birds and their animal prey. Indeed, a diverse fauna exists within the impounded water and detritus of tank bromeliads (e.g., Picado 1911, Pittendrigh 1948, Laessle 1961, Diesel 1989, Paoletti et al. 1991, consisting of two primary components: animals living within the aquatic medium (e.g. dipteran larvae, frogs) and animals typically associated with soil and organic debris (e.g., earwigs [Dermaptera], roaches [Orthoptera], isopods). Thus, bromeliads can enhance opportunities for resource subdivision and specialization by birds in Neotropical forests. Foraging specialization on unique tropical resources, such as bromeliads, is thought to be one mechanism responsible for the high bird species diversity of the Neotropics relative to the Temperate Zone (Schoener 1968;Orians 1969;Karr 1971;Terborgh 1980;Remsen 1985). At least 51 Neotropical bird species h...

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