Cooperative Fish and Wildlife Research Units Program: Texas
Education, Research and Technical Assistance for Managing Our Natural Resources

There is a paucity of data evaluating water use by raptors. Although raptors are believed to satisfy their water requirements through metabolic processes, they are known to experience reduced reproductive success during periods of drought, and there is evidence of water being important for site occupancy in arid landscapes. Several raptor species have a seasonal or year-round presence in west Texas, a drought-prone, semi-arid region of the southern Great Plains. We used cameras at man-made water sources to examine species-specific timing of free water use by common raptors in this region, and to explore environmental conditions associated with water use over a 48-month period. We collected 4,549 camera trap-days of data across 4 years at man-made water sources placed for cattle. We recorded 1,182 detections of 14 species of raptors visiting these water sources. Of the 1,177 detections of raptors identified to species, 1,084 (92.1%) were of individuals perching at tanks, and 93 (7.1%) flying by tanks. Of the raptors that perched at tanks, 63.5% were drinking and 20.8% both bathed and drank. Barn Owls (Tyto alba; 35.6%), Swainson’s Hawks (Buteo swainsoni; 32.0%), and Northern Harriers (Circus hudsonius; 21.0%) were the predominate species detected. Barn Owls were detected year-round, Northern Harriers were detected from August to April, and Swainson’s Hawks were detected from March to October. We found visits by Northern Harriers and Swainson's Hawks were best predicted by temperature and precipitation. Visits by Barn Owls were best predicted by drought severity. Further, we found that detections per 100 trap-days increased substantively across our 4-year study period during which the region experienced one of the worst droughts on record. Although our data does not demonstrate these raptors require free water, it does reveal an increasing use in relation to hotter and drier conditions. How this influences survival and reproduction remains unknown, but may become a pressing question, as current climate models predict the study area will experience increases in heat and decreases in precipitation.