Inclement weather and American woodcock building collisions during spring migration

Abstract

Weather appears to influence collisions of migratory birds with human‐built structures including buildings, but formal analyses are lacking. In 2018, as part of a two‐year study at 21 buildings in Minneapolis, Minnesota, USA, we observed a large number of American woodcock Scolopax minor collisions during two early spring snowstorms. We describe these events, analyze associations between weather and woodcock collisions during spring 2018, and compare observations to past studies across the woodcock's range. Most spring 2018 woodcock collisions (11 of 15; 73.3%) occurred in association with the two snowstorms. Analyses indicated collisions were positively associated with maximum and average wind speeds the night before collision surveys, and most collisions occurred with north winds. Collisions also increased with lower cloud base height two nights before surveys. These results support that woodcock collisions were greatly influenced by inclement weather, specifically the coincidence of strong north wind and low clouds. Comparing results to past studies illustrates that building collisions could be a major range‐wide source of woodcock mortality, especially in spring migration when mortality is likely additive. Although more research is needed to understand range‐wide, population‐level effects of woodcock collisions, management to reduce building collisions during migration may benefit woodcock populations. Additional research is needed to clarify effects of weather on bird collisions because management efforts could be refined if collisions of woodcocks and other bird species were forecastable like the weather.

The invisible enemy: Understanding bird‐window strikes through citizen science in a focal city

“…Although the two bird species that collided most with windows in our study area are migrants, we recorded significantly more collisions during the month of April, congruent with the beginning of the breeding season and the last part of the spring migration. This result agrees with previous studies that have reported more collisions during this season (Gelb & Delacretaz, 2006; Kahle et al, 2016; Loss et al, 2020; Schneider, Barton, Zirkle, Greene, & Newman, 2018). It has been proposed that this pattern could be related to birds having more active behavior, with increased speed of flight, differing dispersal patterns, and behavior related to nest construction and defense (Hager & Craig, 2014; Klem, 1989).…”

Multi-scale temporal variation in bird-window collisions in the central United States

“…Weather also was likely to contribute to the temporal variation we observed, especially for week-to-week variation in collisions. Weather conditions have been shown to influence building collisions for one species, the American Woodcock ( Scolopax minor ) 56 . Although formal analyses of weather effects on total bird collisions are lacking, weather appears to have contributed to several major bird collision events, including at buildings 45 , 57 , 58 and other types of structures 59 .…”

“…Weather conditions such as precipitation, cloud cover, and the presence and/or strength of headwinds or tailwinds—as well as extreme weather events like intense storms—are known to influence the timing and magnitude of bird migration 35 , and are thus likely to influence collision risk. Some of these factors (e.g., low cloud ceilings) may have especially strong effects on nocturnal migrants by exacerbating effects of nocturnal lighting and driving birds into areas of greater collision risk 32 , 56 . When considering the week-to-week variation we observed within seasons, the fine-scale peaks and lulls in collisions may respectively reflect weather conditions that favor or disfavor bird migration (e.g., strong tailwinds or headwinds, respectively) and/or elevate or reduce collision risk for migrating birds (e.g., low cloud ceilings or clear skies, respectively).…”

“…Although we documented the expected pattern that more migrant birds than resident birds collided in fall, we documented other unexpected patterns, including the highest monthly total of collisions occurring in the spring migration month of May, roughly equivalent high numbers of resident and migrant bird collisions in spring, and a similar amount of migrant mortality in spring and fall migration. At seasonal, monthly, and weekly temporal scales, weather, reproductive phenology, and other seasonal changes likely drive collision variation, thus predictions of collision risk based on weather and date may allow better focusing of collision deterrence efforts 56 . Our results can also inform sampling protocols for future studies of bird-window collision.…”

Predicting bird‐window collisions with weather radar

“…Further, ALAN ‘sky glow’ is exacerbated by low clouds and precipitation (Kyba et al., 2015). Studies have linked building collisions with both ALAN (Lao et al., 2020; Winger et al., 2019) and the above types of inclement weather (Loss et al., 2020), suggesting that low average flight altitude, as driven by factors like weather and lighting, may also increase collisions.…”