Meeting Abstract
Reduction of grassland nesting habitat for Common Nighthawks (Chordeiles minor) has resulted in nesting on urban rooftops in the Northern Prairie region. I documented nest microclimates and hatching success at rooftop sites in southeastern South Dakota in 2014-2015 to document the potential thermal stress on incubating adults. Bird body temperature reaches lethal levels at approximately 46°C. As an index of thermal microclimates, I measured operative temperatures (a measure of heat exchange between an animal and its environment) and their influence on hatching success using copper sphere operative temperature thermometers. I used Student’s t-tests to compare mean minimum temperature, mean maximum nest temperature and mean percent of temperature readings greater than 46°C between nests where eggs hatched and those abandoned for these preliminary data (12 successful and 7 failed nests). Nest mean minimum temperature (9.4±1.1°C, 10.2±1.1°C), mean maximum temperature (50.0±0.8°C, 48.9±0. 7°C), and mean percent of temperature readings greater than 46°C (2.00±0.005%, 1.49±0.004%) did not differ significantly for successful and failed nests, respectively. Thus, thermal microclimate for incubating adults does not appear to be a major cause of nest abandonment in southeastern South Dakota. However, this result might change with increasing temperatures due to climate change, so thermal microclimates should be incorporated into future projections of population responses to land use and climate change for this declining species. Future studies should also examine the relationships of thermal biology and microclimates of eggs and nestlings and their impact on nesting success to determine if these factors might contribute to nest failures.
