Alleviation of nest thermal extremes by incubating snowy plovers in the Southern high plains of Texas

Nesting within thermally stressful environments poses many challenges for avian species, including alleviation of heat stress of both adults and eggs and synchronization of hatching. In the Southern High Plains (SHP) of Texas, Snowy Plovers Charadrius nivosus nest within a semi-arid, thermally stressful saline lake environment, where incubation temperatures and mechanisms by which Snowy Plovers alleviate thermal stress are unknown. We recorded incubation temperatures of 104 Snowy Plover nests located on saline lakes within the SHP of Texas in relation to ambient substrate (control) temperatures, month, nest success, and time during incubation. Nest temperatures mirrored control temperatures, ranging from 12.2-47.2°C, but did not exhibit the same extreme amplitude between high (day) and low (night) temperatures as controls. Wide ranging temperatures between day and night forces Snowy Plovers to be relatively plastic in incubation techniques, from heat application during night to egg cooling during day. Nest temperatures increased as the season progressed, suggesting survival and physiological benefits for Snowy Plovers to arrive and initiate egg-laying early in the season. Snowy Plovers appear to change incubation routines as nests approach hatching, potentially facilitating hatching synchronization during early morning hours (i.e., before noon). Thermal extremes experienced by nesting Snowy Plovers in the SHP of Texas necessitate adaptive behaviors to alleviate heat stress. However, habitat features (i.e., water from freshwater springs) necessary for mitigating heat stress and thermoregulation are declining within regional saline lakes that support nesting Snowy Plovers. Therefore, conservation within this region should focus on conserving freshwater springs discharging into saline lakes, the Ogallala aquifer, and the entire complex of wetlands within the SHP of Texas.