Winter ecology of Sandhill Cranes (Grus canadensis ) in northern Mexico

Sandhill Cranes (Grus canadensis) are a widespread species in North America and one of the most studied cranes in the world. However, most of the research has focused on the breeding grounds of Canada and Alaska and the staging grounds of Nebraska. Although an important proportion of the Mid-continent Population of Sandhill Cranes winters in northern Mexico, little information exists on distribution, status, and ecology of the species in Mexico. The goal of this dissertation was to provide new information on Sandhill Crane winter ecology from a regional perspective to better understand population trends. I examined the physiological state of Sandhill Cranes in wild conditions by quantifying the effects of environmental factors on stress levels. My data suggests that access to water resources is the main factor affecting corticosterone levels of cranes. I validated a method to measure glucocorticoid metabolites in fecal samples using an affordable and commercially available enzyme immunoassay. I demonstrated that the use of an enzyme immunoassay provides accurate measurements of steroid metabolite concentrations comparable to the traditional radioimmunoassay. I examined winter diet of Sandhill Cranes and investigated if the species exhibits a specialized or generalized diet in Mexico. I also explored the ecological response of the species to low food availability conditions. According to my results, cranes exhibit a specialized diet of corn during winter as patterns of consumption did not vary with corn availability. Cranes responded to low food availability by moving geographically to a location where corn was available instead of shifting diets. Finally, I included a human dimensions perspective to document the attitudes of rural inhabitants towards Sandhill Cranes. I investigated if crop consumption by cranes represented a problem for Mexican farmers in the wintering grounds. The results of my interviews indicate that Mexican farmers are not affected by the arrival of cranes and do not consider the species to be a problem.