Co-Written by Emily Giles & Pete Ewins
Life isn’t easy when you’re a songbird. Consider, for example, a creature as small and delicate as a warbler –these tiny birds weigh a mere 10 grams or so, and yet must complete an incredible journey covering thousands of kilometers – not just once – but twice every year. In the fall, songbirds migrate south to their wintering grounds as far south as South America, and in the spring they return back home to their Canadian nesting grounds.
Unfortunately, life is getting more and more difficult for songbirds – predation by cats, and collisions with building windows are two of the main human-related mortality factors these days. In Canada alone, between 16 and 42 million birds die annually from collisions with buildings (Machtans et al. 2013). Large cities pose a particular problem for migratory birds. Toronto contains over 950,000 registered buildings that have the potential to kill an estimated 1 to 9 million birds annually (FLAP 2015). Artificial city lights are an issue for migrating birds, as many bird species migrate at night and are guided by the light from the moon and the constellations. Bright city lights interfere with birds’ navigation and draws them off course, often resulting in them colliding with windows and buildings.
During the day time, birds fly into windows due to the transparent and/or reflective qualities of the glass. Birds cannot detect the glass, and instead see the reflection of vegetated habitat in the window, or a safe tunnel/passageway.
During last fall’s migration period, we studied bird window collisions at WWF’s office in Toronto. A small team of volunteers patrolled the building perimeter and inspected all visible broad ledges, once in the early morning and again in the late afternoon. Evidence of a window collision could be anything from a pile of feathers close to the building, or finding an actual live or dead bird on the ground close to the building or on a ledge. Our office windows are surrounded by a 1.2 metre ledge, so when a bird did fly into a window, they often fell stunned onto the ledge, and we could record whether or not it succumbed to its injuries, or managed to eventually fly away.
Our study found some interesting things (published this month in Ontario Birds journal). Over the 6 week study, we recorded 93 window strikes, and identified 11 different species. The location of strikes was linked closely to the presence of trees close to the building’s reflective windows. We also recorded interesting behavior from a pair of crows that took up residence, scavenging many freshly stunned birds. The crows may also be using the windows to catch small songbirds, as the crows were observed chasing a kinglet into the windows, then just eating the stunned bird!
The good news is that there is growing concern for the issue of bird window collisions, and building design and regulatory codes now must address this issue. For example, in Toronto, FLAP developed the BirdSafe™ Building Standards and Risk Assessment and provides consulting to anyone looking to make their building BirdSafe™ in a more cost-effective way, by zeroing in on the façades where the majority of collisions occur. New designs of windows are available now, which break up the vegetation’s reflection in the window so that birds don’t mistake the reflection for a tree.
If you want a list of ideas on how you can make your home or office bird friendly, please check out some ideas from FLAP here.
FLAP. 2015. Fatal Light Awareness Program Canada. https://www.flap.org/faqs.php
Machtans, C.S., C.H.R. Wedeles and E.M. Bayne. 2013. A first estimate for Canada of the number of birds killed by colliding with building windows. Avian Conservation and Ecology 8(2):6. https://www.ace-eco.org/vol8/iss2/art6/
Co-Written by Emily Giles & Pete Ewins