Buildings and Migrating Birds | Ecology Action Centre

Buildings and Migrating Birds

hermit thrush
This hermit thrush (shown shortly after release) was found on the sidewalk after colliding with a downtown Halifax window one early morning in April. 

In the spring of 2014, after consulting with the FLAP and a municipal official in Toronto, our bird team set out to document the extent of bird strikes during migration season in Halifax. At six on a crisp spring morning, a team of volunteers set off on a survey of downtown buildings. We had a kit, carefully prepared by Noel Taussig, our Bird Intern, containing a net, gloves, paper bags, and labels. At the very first building we came across a hermit thrush sitting on the pavement, alive, but clearly dazed and confused. We took the thrush to the Needham Hill Park and released him (or her). Interestingly, for the rest of the spring, despite thrice weekly surveys we found no other birds.

We did another survey of the same buildings in the fall and found 10 birds. The difference between fall and spring can be explained by the experience of the birds. By the time spring migrants reach Halifax, they will have already travelled thousands of miles from Canadian breeding grounds to the Southern US and Central and South America and back again, passing over hundreds of cities, many larger than Halifax. In the fall, Halifax is the first city many migrants would encounter on their way south.

The problem is different in Halifax

In comparison with the hundreds to thousands found in Toronto, the number we found in Halifax is low.  It also seems that in Halifax, many of the strikes occur during daylight hours, not at night as is the case in Toronto.  Nonetheless, if you were to extrapolate our results to include the days and buildings we didn’t survey and the buildings we missed, the number of bird casualties caused by downtown office buildings would, we can assume, be higher.

The difference between the findings in Toronto and Halifax could be explained by the height and number of buildings. When nocturnal migrants hit downtown Toronto they could easily become “trapped” between buildings, get confused, and fly into a window. In Halifax, we don’t have the number and density of buildings for this to happen.  What does appear to be happening, based on the time of day we are finding some birds, is that migrants, resting and feeding in vegetation around downtown buildings, are getting tricked by reflective glass. We have found birds (alive and dead) several hours after daybreak.

Two of the birds that collided with Halifax office buildings this fall
A black and white warbler (left) and an ovenbird (right), found after colliding with Halifax office buildings this fall.

Office vs Residential Buildings

This past year we focused on office buildings, but residential buildings—our homes—may be bigger killers in Nova Scotia, simply because there are many more of them.  Birds do not see glass, they only see habitat on the other side.  They are particularly confused by reflective glass. Dan Klem, an American researcher, has estimated that over 100 million birds are killed in each year in the U.S. alone from hitting windows.  The mortality is heightened by stunned birds, which might otherwise survive, getting picked off by domestic cats, crows and other predators. 

What about turbines?

Recently, I have heard opponents of wind power raising concerns about turbines and birds. Turbines do kill birds, particularly raptors, but after investigating birds and windows we are more concerned about the picture window than about a turbine that can help offset GHG emissions.

What can you do?

  • If you find an injured bird, please contact Hope for Wildlife or your local veterinarian.  FLAP’s Bird First Aid tips can be found here.
  • Avert a strike before it happens! FLAP has suggestions on how to make windows friendly for birds.

Learn More:

This project was conducted by our Bird Conservation Committee. The committee works to educate the public about preventable causes of bird death and advocates for legislative change that will help protect local bird populations. Learn more about our Bird Conservation Committee and current projects here (link to main page).

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