Aspects of municipalities associated with occupancy of Chimney Swifts and Common Nighthawks in Illinois

Occupancy;Chimney Swift

Hurd, Maureen L. ; Stodola, Kirk ; Benson ; T.J. ; Ward ; Mike

关键词: Occupancy;    Chimney Swift;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/107869/HURD-THESIS-2020.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Aerial insectivorous birds like the Chimney Swift (Chaetura pelagica) and Common Nighthawk (Chordeiles minor) are experiencing population declines across North America.While causes of declines are unknown, habitat availability is likely a contributing factor.Both species breed in urban areas.Chimney Swifts historically nested in tree cavities but now primarily nest in masonry chimneys, while nighthawks nest on both gravel rooftops and bare ground in grasslands and woodlands.Suitable chimneys and gravel rooftops are becoming less common as building practices change, and the loss of available nest sites may be driving declines.To understand factors of decline, I conducted surveys in municipalities of varying size throughout Illinois and examined the influence of various habitat and landscape factors (e.g., land cover surrounding points, areal extent of cities, and age distribution of buildings) on Chimney Swift and Common Nighthawk occupancy.Chimney Swifts occupied 97% of municipalities (n = 126), 20% of natural areas (n = 10), and 72.5% of all sampled points (n = 476), but abundance varied considerably.Swift abundance was greatest at the center of small, isolated municipalities where uncapped chimneys tended to be most prevalent.I detected swifts at all points with at least five uncapped chimneys (n = 60), but only 21% of points with no uncapped chimneys (n = 270).Common Nighthawks occupied 16.0% of municipalities, none of the natural areas, and 5.5% of sampled points.Nighthawk occupancy was most dependent on high-intensity development and proportion of older buildings, possibly related to gravel rooftop availability.My results suggest that although Chimney Swifts and Common Nighthawks are still widespread, contemporary building practices may continue to drive population declines and management should focus on approaches for providing and maintaining suitable nesting sites.