Abundance of non-breeding horned larks and chestnut-collared longspurs on grazed and rested semiarid grassland

Abstract

We counted birds monthly from October through April of 1999-2000 and 2000-2001 on regularly grazed and rested (since 1973) semiarid grassland of central New Mexico. Horned larks (Eremophila alpestris) and chestnut-collared longspurs (Calcarius ornatus) accounted for 66% and 10% of all birds detected, respectively. We examined variation in counts of these species relative to grazing history, site, and vegetation characteristics. We used an information-theoretic approach to evaluate a set of 11 candidate models to determine which best described the variation in abundance of horned larks and chestnut-collared longspurs. There was little agreement between models for the 2 species or the 2 years. While grazing was a factor in the most likely models of abundance in the 1999-2000 sampling season for both bird species, this factor was not an important variable in explaining abundance in 2000-2001. These results suggest that abundance of horned larks and chestnut-collared longspurs are not as closely tied to grazing use during the non-breeding season in the semiarid grasslands of the northern Chihuahuan Desert, which contrasts with literature from breeding sites in the shortgrass prairie.

Citation

Kelly, Jeffrey F.; Hawksworth, David L.; Meyer, Raymond A. 2006. Abundance of non-breeding horned larks and chestnut-collared longspurs on grazed and rested semiarid grassland. The Southwestern Naturalist. 51(2): 172-180.