Effect of Passerine Size on Number of Lethal Building Collisions

• Hanna Hauck

  Juniata College

  Author

Nighttime migrators such as passerines utilize magnetic and visual orientation cues. These cues could be the sunset, stars and even a full moon (Åkesson and Sandberg, 1994). In buildings with lights being left on in the night can make these nocturnal passerine migrants more susceptible to collisions due to a phototactic response (Winger et al., 2019). Does passerine size impact the amount of collisions? If so, larger passerines would have less building collisions than small passerines. The data were collected in Cleveland, OH and Chicago, IL by Winger et al. and was later published on DataWorld. Data were collected in several areas of both towns, by different groups and organizations. I downloaded this dataset and combined the numbers from each city. After the data were totaled, I researched all species and recorded their average length (in), wingspan (in) and mass (oz). I multiplied these numbers together to make categories that I could group the scores into (Table 1). This aided me in making size scores from 1-10. The results from regression analyses (Figure 1 and 2) showed no significant correlation between the number of collisions and size scores with a weak negative correlation, r-squared value of 0.0438 and a p-value of 0.562. After realizing that the smaller birds may have higher collisions due to being more abundant, I divided the totals of each size scores’ collisions by the number of species within that size score. This result was also insignificant with a weak positive correlation, r-squared value of 0.004 and a p-value of 0.863. The outlying size score is seven, with seven species total and four that were especially abundant: the hermit thrush, song sparrow, white-crowned sparrow and white-throated sparrow. These species are highly abundant, which could be the cause of them having over 20,000 collisions between the four species. There are many initiatives to decrease passerine mortality, such as the practice of turning off lights at night and the use of tinted windows, which appear to be reducing mortality (Erickson et al., 2005). For further studies, the species could be divided into their IUCN statuses so that species of least concerned are not directly being compared to species less abundant than them.

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