We are grateful to Maximiliano Galmes, Marcos Reyes, Andrea
Costan and Claudina Solaro for their help with sample collection
and analysis. We appreciate the improvements in English usage
made by Christina Riehl through the Association of Field Ornithologists'
program of editorial assistance The Direccion de Recursos
Naturales and Subsecretaría de Ecología of La Pampa province
made this work possible by giving permission to carry out fieldwork
in Parque Luro Reserve. This study received financial support
from the PI Nº R018 of the Departamento de Recursos Naturales,
Unversidad Nacional de La Pampa. While doing this research J.H.S.
was founded by the Consejo Nacional de Investigaciones Científicas
y Tecnicas de Argentina (CONICET).