Surveys for dead birds under windows have raised public awareness of bird-window collisions recently.
There are still significant gaps in our knowledge of how and why birds fly into windows and what happens to the birds afterward because collision events are challenging to directly observe.
Opening the black box of bird-window collisions
JOHN MACDOUGALL/AFP via Getty Images
By examining audio and motion-triggered video recordings taken at a residential setting with bird feeders, new research recently published in the Open Access, peer-reviewed journal PeerJ offers the first glimpse of what transpires just before a bird collides or avoids impact with a window, as per ScienceDaily.
The article offers a fresh perspective on a crucial conservation issue and offers empirical data that are currently lacking but essential for informing estimates of the effects of bird mortality at the population level and for developing successful collision prevention technologies.
The characteristics of bird flights leading up to collisions and near misses were compared by Western University and Purdue University researchers.
They logged and examined nine near-misses as well as 29 collisions.
The results of collisions were predicted by the birds' flight speed and angle of approach, with faster flights and closer-to-perpendicular angles of approach being more hazardous for the birds.
The pre-collision behavior of birds exhibits previously unrecognized variation, according to these data.
Only a small percentage of the 29 collisions that were observed during the study caused immediate death and were noticed by building occupants.
In the majority of collisions, the bird flew off into the distance.
Some of these birds may reportedly sustain wounds before passing away far from the window site.
This finding suggests that the extent of collisions may be greatly underestimated by conventional survey methods and has implications for estimating the population-level impacts of bird-window collisions.
The majority of the research on bird-window collisions has concentrated on measuring the frequency of fatal window collisions at larger structures, but since residential buildings have the most window-containing structures overall, they pose the greatest overall threat to birds.
Many regions of the world are prioritizing the construction of new housing as demand for large glass windows and glass railings increases.
Over the pandemic, backyard bird feeding has grown in popularity, luring more birds into risky environments.
Daytime and nighttime window collisions are the two main categories.
Birds often fly into windows during the day because they can see vegetation reflected in the glass, or they can see through the glass potted plants or vegetation on the other side, as per All About Birds.
Most songbirds and other nocturnal migrants crash at night when they fly into lit windows.
Lights cause nocturnal migrants to deviate from their intended course for unknown reasons, especially in low-ceiling or foggy conditions.
They move around the illuminated area, occasionally bumping into one another or the illuminated building.
Migrants may roost safely nearby after being thrown off course by urban lighting as a secondary risk, but the following day they may become vulnerable to daytime reflections in windows.
Start by identifying potentially hazardous windows, such as big picture windows, windows that are paired at an angle, or windows that have feeders outside. Step outside and observe your windows from the perspective of a bird.
The birds will also see any branches or sky that are reflected in or visible through the glass.
According to Christine Sheppard, the director of the American Bird Conservancy's Bird Collisions Program, previous guidelines regarding safe distances for feeders outside windows are no longer considered to be applicable.
"Don't worry about how far away they are if you have windows near a bird feeder; make them bird-friendly."
