Availability of Supplemental Corn for Sandhill Cranes, Light Geese, and Dabbling Ducks Wintering in New Mexico

Abstract

The Middle Rio Grande Valley of central New Mexico overwinters the majority of the Rocky Mountain Population of greater sandhill cranes Antigone canadensis tabida as well as numerous Mid-continent Population lesser sandhill cranes A. c. canadensis, light geese (i.e., snow Anser caerulescens and Ross’s geese Anser rossii), and dabbling ducks (i.e, Anas spp.). Stemming from changes in agricultural practices and loss of habitat, these species have become largely dependent on public lands where corn is used to supplement natural foraging resources providing a key dietary component while also discouraging crop depredation on private lands. To evaluate if supplemental corn provides a sufficient resource base, we estimated energy available in corn resources and seasonal energy requirements of the sandhill cranes, which was comprised of Rocky Mountain Population and Mid-continent Population. Additionally, we considered energetic requirements for two other wintering guilds, light geese and dabbling ducks. Depletion rates of post-mowed corn increased throughout winter from 3,673 ± 843 kg/ha/day (mean ± SE) in December to 7,014 ± 1,884 kg/ha/day in February. Estimated seasonal energetic requirements of the Rocky Mountain Population and Mid-continent Population were 1.14 × 109 kcal (95% CI = 1.07 × 109 – 1.21 × 109 kcal). Combined, seasonal energetic demands of the Rocky Mountain Population, Mid-continent Population, light geese, and dabbling ducks was 4.23 × 109 kcal (95% CI = 3.81 × 109 – 4.53 × 109 kcal) or 911,813 kg of corn (95% CI = 820,821-1,006,894 kg). From 2014-2017, corn production on public lands in the Middle Rio Grande Valley was 1,052,006 ± 58,965 kg grown on an average of 76 ha, sufficient for winter energetic requirements of all guilds. Interagency collaboration, effective planning during the growing season and strategic schedules for mowing supplemental corn crops that integrate population abundances and their respective energy demands should further promote success of the supplemental corn program in the Middle Rio Grande Valley.