Temporal Dynamics of Mangrove Bird Communities in Venezuela with Special Reference to Migrant Warblers

Abstract

ABsmAcr.-We studied bird phenology and abundance patterns relative to rainfall, ground inundation, and food abundance in three mangrove sites of northeastern Venezuela over two complete annual cycles. Bird abundance, breeding and molting activities were assessed through mist-netting sessions scheduled twice monthly. At the same frequency, food abundance was evaluated through the percentage of trees bearing flowers, and by sweep-netting arthropods. The birds' breeding season occurred from the mid-dry to the mid-wet seasons and was linked to the abundance of some arthropod taxa including caterpillars. The higher abundance of arthropods and the presence of breeding activities during the dry season suggest that environmental factors are less limiting in mangroves than in adjacent arid habitats. The abundance of most birds, grouped according to their diet and frequency of mangrove use, varied significantly over time. Many species from other habitats exploited the mangroves in the late-wet and dry seasons to take advantage of a higher food abundance and to join mixedspecies flocks. Abundance of Nearctic migrants was correlated with the abundance of several arthropod taxa, and diet analyses suggest that these birds feed opportunistically on seasonal abundant arthropods during their stay in mangroves. Received 3 March 1993, accepted 17 November 1993. ALTHOUGH MANGROVES are widely distributed along the littoral in tropical and subtropical