Bird-window collisions: different fall and winter risk and protective factors

Area of Science:

• Ornithology
• Urban Ecology
• Conservation Biology

Background:

• Millions of birds die annually from window collisions in North America.
• Ornamental pear trees and mirrored windows are known risk factors.
• Previous studies suggested bird-friendly glass may not reduce collisions.

Purpose of the Study:

• To evaluate the efficacy of bird-friendly windows in reducing bird-window collisions.
• To assess the impact of ornamental pear trees and mirrored windows on collision risk.
• To investigate seasonal variations in collision risk, particularly for Cedar Waxwings.

Main Methods:

• Trained observers monitored eight buildings on the University of Utah campus.
• Collision data were collected during Fall (September-October 2019) and Winter (October 2019-January 2020).
• Collisions were documented using iNaturalist for the Bird Window Collision Project.

Main Results:

• Bird-friendly windows showed an 84% reduction in collision odds (OR = 0.16).
• Buildings near pear trees (OR = 3.33) and those with mirrored windows (OR = 5.92) had significantly higher collision odds.
• The combination of pear trees and winter season presented the highest risk, with 40-fold increased odds.

Conclusions:

• This study provides the first peer-reviewed evidence for the effectiveness of bird-friendly fritted and ORNILUX® UV windows.
• Mirrored windows and proximity to fruiting pear trees pose significant dangers, particularly to Cedar Waxwings.
• Findings support implementing bird-friendly glass in new constructions and mitigating risks in existing buildings.