Fall migration continues to be unusually slow. The nights have been warm and the owls sparse, but there are other things of interest in the dark hours from the odd deer, flying squirrel, or bear to spectacular northern lights and migrating geese.
It may come as a surprise that most migration occurs at night when it’s cooler, calmer, and safer from daylight hunters like Sharp-Shinned Hawks. Studies have shown that some species even use the stars to navigate. Unfortunately, humans have made their impact on the night sky.
At the Boreal Centre for Bird Conservation (BCBC), the night sky is bright with constellations, the Milky Way, and occasionally the northern lights. Towards the south, however, is an unmistakable glow on overcast nights. Even a small town like Slave Lake emits enough artificial light to pale the sky in a mockery of early dawn. Since birds use the stars and moon as navigational cues, this can be a problem.
Lighted structures may create “light traps”, wherein birds confuse the artificial light for the moon and try to orient themselves by these false cues. This can be especially bad during inclement weather which may prevent birds trapped circling artificial light from being able to perch. If they do not strike the structure itself, they may succumb to exhaustion instead. This is made worse by the migratory habits of some species to form flocks of nearly a million birds.
The overabundance of artificial light not only affects birds while migrating, but also while breeding. A longer period of artificial daylight means earlier singing and more time for foraging. Less benign is decreased rest due to longer days, leading to higher stress and more energy burned while on alert for predators. For nestlings, light pollution may cause a higher demand for food and energy for feather growth instead being diverted to bone growth. This trade-off is possible due to the continued care of their parents, until the young birds moult before their first migration, when they too must navigate an artificially lit landscape.
While there is little we as individuals can do to counter the global light pollution problem, we can recognize and limit unnecessary light pollutants in our own lives. Many artificial light transmissions are horizontal, made by billboards, businesses, and houses. We have the ability to reduce the time and intensity of nighttime lighting on our own properties by using motion sensors and timers, switching from bright white light (which mimics daylight) to warm amber light, and ensuring light fixtures aim light to the ground instead of the night sky.
For example, while drawing in owls with audio lures to band them, we prevent them from becoming trapped at the BCBC by simply turning off exterior and interior lights at night. While it’s a slow year for owls, we have captured two Northern Saw-whet Owls banded by other researchers! It is currently unknown where one was banded, but the other was first caught near Saskatoon late last October.
To see the impacts of light pollution in your area, you can visit lightpollutionmap.info
By Bronwyn Robinson, LSLBO Assistant Bander