Deadly windows

A white-throated sparrow caught during the experiment. You can see the band on it’s leg, used to make sure they did not record the same bird more than once.

The activities are as follows:

Glass makes for a great windowpane because you can see right through it! However, the fact that windows are see-through makes them very dangerous for birds. Have you ever accidentally run into a glass door, or been confused by a tall mirror in a restaurant? Just like people, birds can mistake a see-through window or a mirrored pane for an opening to fly through or a place to get food, and will accidentally fly into them. These window collisions can hurt the bird, or even kill it. Window collisions kill nearly 1 billion birds every year!

Urban areas, with lots of houses and stores, have a lot of windows. Resident birds that live in the area may get to know these buildings well, and may learn to avoid the windows. However, not all the birds in an area live there year-round. There are also migrant birds that fly through urban areas during their fall migrations. They will use gardens and parks in urban areas to rest along their journeys to their winter southern homes. During the fall migration, people have noticed that it seems like more birds fly into windows. This may be because migrant birds are not familiar with the local buildings. While looking for food and places to sleep, migrant birds might have more trouble identifying windows and fly into them more often. However, it could also be that there are simply more window collisions in the fall because there are more birds in the area when migrant and resident birds co-occur in urban areas.

Researchers identify the species of each bird caught in one of the nets used in the study. They then place a metal bracelet on one leg so they will know if they catch the same bird again.

Natasha was visiting a friend who worked at a zoo when he told her about a problem they were having. For a few weeks in the fall, they would find dead birds under the windows, more than they would during the rest of the year. He wanted to figure out a way to prevent birds from hitting the exhibit windows. Natasha became interested in learning whether migrant birds were more likely to fly into windows than resident birds, or if the number of window collisions only increase in the fall because there are lots of birds around. To do this she would have to count the total number of birds in the area, and also the total number of birds that were killed in window collisions. To count the total number of birds in the area, Natasha hung nets that were about the same height as windows. When the birds got caught in the nets, Natasha could count and identify them. This data could then be used to calculate the proportion of migrants and residents flying at window-height. She put ten nets up once a week for four hours, over the course of 3 months, and checked them every 15 minutes for any birds who got caught.

Researcher identifying a yellow-rumped warbler, one of the birds captured in the net as part of the study.

Then, she also checked under the windows in the same area to see what birds were killed from window collisions. She checked the windows every morning and evening for the three months of the study. Different species of bird are migratory or resident in the area where Natasha did her study. Each bird caught in nets was examined to identify it to species using its feathers, which would tell us whether the bird was a migrant or a resident. The same was done for birds found dead below windows.

If window collisions are really more dangerous for migrants, she expected to see a higher proportion of migrants would fly into windows than were caught in the nets. But, if window collisions were in the same proportion as the birds caught in the nets, she would know that windows were just as dangerous for resident birds as for migrants.

Featured scientist: Natasha Hagemeyer from Old Dominion University

Flesch–Kincaid Reading Grade Level = 8.7

There is one scientific paper associated with the data in this Data Nugget. The citation and PDF of the paper is below:

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