PARENT SESSION
Poster Session 24: Agro-Ecology
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Species richness and abundance of birds in field margins of central Mexico: Local and landscape-scale effects.

Zuria, Iriana^{*,1, 2}, Gates, J. Edward², Castellanos, Ignacio¹, ¹ Centro de Investigaciones Biologicas, Pachuca, Hidalgo, Mexico² Appalachian Laboratory, Frostburg, Maryland, USA

ABSTRACT- In many agricultural landscapes of central Mexico, vegetated field margins are important elements that represent a valuable habitat for many bird species. Despite their abundance and importance for the conservation of birds and other wildlife, these structures have not been studied in much detail. Therefore, we analyzed data concerning resident and Nearctic-Neotropical migratory birds found in field margins of El Bajio, central Mexico. Resident and migratory birds were surveyed during the spring and winter 1999 and 2000 in 40 field margins located in this agricultural landscape. The structural and botanical characteristics of the field margins, as well as the characteristics of the surrounding landscape, were related to species richness and abundance of birds. We found a significant relationship between bird species in field margins and the environmental variables measured at both the local and the landscape scale. At the local scale, the size of the field margin, its vertical complexity, and the abundance of trees and tree species had a positive influence on bird species richness and abundance. Native trees, especially mesquites, were particularly important for many bird species. The most important landscape-scale variable was the density of hedgerows around field margins. Bird species richness and abundance of birds was positively influenced by the length of the hedgerows measured within 100-m, 200-m, and 500-m radius circles centered on each field margin. Also important was the distance to the closest area covered by native scrub forest. In general, field margins closer to the scrub forest had more bird species and more individuals. Different bird species responded differently to local and landscape-scale variables, therefore management of field margins for the benefit of birds must be directed toward specific goals. Our observations would have management implications for the conservation of birds in the region.

Key words: hedgerows, birds, spatial scale, mesquite