Sul Ross State University

Metapopulation Dynamics of Plain Chachalaca in Fragmented Landscapes

by Adan Gandaria (Texas A&M University), Roel Lopez (Texas A&M University), Marcus Peterson (Texas A&M University) and Louis A. Harveson

The Lower Rio Grande Valley (LRGV) of Texas is an ecologically diverse region in the United States and marks the northernmost extension for many tropical species of plants and animals.

Since the early 1900’s, nearly 95% of native Tamaulipan brushlands have been cleared due to agricultural practices and urban development. The plain chachalaca (Ortalis vetula) is a medium-sized bird endemic to the brushlands of the LRGV.

In 2003, we trapped and radio-tagged 32 birds to evaluate the effects of fragmentation on the population dynamics (i.e., survival, mortality, movements) of this brushland bird. We found annual mortality for chachalacas was high (45%), with the greatest mortality attributed to mammalian predation (e.g., bobcat, Felis rufus).

Average bird dispersal was 0.5 km with recorded maximum distances up to 1.5 km. Bird movements across natural barriers were common (e.g., flying across the river into Mexico); however, no movements across fragmented landscapes (e.g., agricultural lands) have been observed, suggesting the importance of Tamaulipan brushlands to chachalacas.

Future restoration efforts should consider corridor design in the management of brush-dependent species such as the plain chachalaca.

Cooperative funding provided by Texas A&M University, United States Fish and Wildlife Service, and the United States Department of Agriculture.