The affects of an access road on the winter bird community in the Rio Bravo Conservation and Management Area, Belize

McFarland, Kent P.
Tom Wessels, MA,
Department of Environmental Studies
1994
I compared point count data from an access road, forest edge to interior forest sites in a Belizean forest to assess the affects upon the winter, forest landbird community. Point counts were conducted once in 1993 and twice in 1994 during February and March in thirty 50 meter radius plots abutting the road edge and thirty plots 250 meters into the interior forest. 70% of the interior forest census sites were found to contain at least one tree fall gap indicating a high internal patchiness. Total species richness and avian frequency was not significantly different. Migrant frequency was significantly higher in the road edge. 30 species were only found in the road edge and 20 species were only present in the forest interior. The Rufous-tailed Jacamar, Spot-breasted Wren, Gray Catbird, Hooded Warbler, Black-headed Saltator and the Blue-black Grosbeak were found to be edge specialists. Forest interior specialists included the Keel-billed Toucan, Olivaceus Woodcreeper, Red-capped Manakin, tropical Gnatcatcher, Golden-crowned Warblar, and the Black-faced Grosbeak. Species were placed in 36 guilds based on strata, food preference and feeding location. The forest interior contained significantly more birds in four guilds: (understory ; small insect ; branches + trunk); (canopy ; small insects ; foliage); (understory ; large insects ; foliage); (canopy ; large insects + fruit + small vertebrates ; foliage). Likewise, the edge also contained significantly more birds in four guilds: (shrub ; grass seeds - foliage); (canopy ; omnivore ; foliage); (canopy ; small insects + fruit ; branches and trunk); (canopy ; small insects ; foliage). For four habitat strata (ground, shrub, understory, and canopy) species richness was not significantly different. Avian frequency in the ground strata was significantly higher in the edge and lower in the understory. The results suggest that the human generated successional areas along the access road form an important habitat for many species. The presence of a substantial number of bird species in the road edge and the forest interior habitats indicates that the distribution and evolutionary history of these birds has been strongly effected by the continued alteration and regeneration of the forest on a small and patchy scale.

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