Heavy migration traffic and bad weather are a dangerous combination: Bird collisions in New York City

Bird-building collisions account for 365-988 million bird fatalities every
year in the United States alone. Understanding conditions that heighten
collision risk is critical to developing effective strategies for reducing
this source of anthropogenic bird mortality. Meteorological factors and
regional migration traffic may influence collision rates but also may be
difficult to disentangle from other effects. We used 5 years of
bird collision counts in New York City to examine the influence of
nocturnal weather conditions and bird migration traffic rates on
collisions with buildings during spring and fall. We found that
seasonally unfavorable winds and conditions that impede visibility are
important factors that influence rates of bird-building collisions during
both seasons. Specifically, northerly and westerly winds and low
visibility in the spring, and southerly and westerly winds and low cloud
ceiling height in the fall are associated with higher collision
risks. Generally, these weather variables associated most
strongly with increased collisions when nocturnal bird migration traffic
was high, with the exception of low visibility in spring, which was
predicted to triple collision rates compared to high visibility,
independent of bird migration traffic. Although legislation to
turn off unnecessary nocturnal lighting for the entirety of the migration
seasons may be an ultimate goal, a proximate goal invaluable for reducing
collisions will be predicting which nights will be of highest risk and
using this information to determine when mitigation efforts could be most
effective.