The Passage of North American Migratory Land Birds Through Xerophytic Habitats on the Western Coast of Venezuela

Abstract

We recorded 11 species of North American migratory land birds during fall migration in arid scrub habitats on the Paraguana Peninsula in northwestern Venezuela. Passage of migrants was greatest during October and gradually declined through December. By the latter month virtually all migrants were gone from ParaguanA and no species permanently winters in the xerophytic environments of the peninsula. The total period of transience of fall migrants was approximately 17 weeks. During spring migration birds avoided the northernmost arid coastal sites and with few exceptions did not enter the peninsula proper. Sampling in similar habitats on the nearby showed a shorter period of passage of spring migrants (5 weeks) and a smaller number of species (seven) than during the fall sampling. A comparison with xerophytic habitats of the Netherlands Antilles and northern Colombia shows a similar temporal pattern of habitat use by migrants, that is, a conspicuous fall migration, little or no permanent overwintering, and a very inconspicuous spring migration. By contrast, migrants overwinter closer to the North American mainland in xerophytic habitats. We suggest that the need to deposit larger fat reserves under unfavorable spring conditions make xerophytic habitats farther from North America more stressful for premigratory birds.