AMES, Iowa ― Spring is in the air, which also brings nesting time for Iowa’s songbirds. While many homeowners enjoy seeing and feeding the birds, it can be disconcerting for homeowners who have birds fly into glass doors or windows again and again. So are Iowa’s songbirds crazy, or is something else going on?
"I’ve received multiple questions from homeowners asking about this behavior, what is causing it and what can be done about it," said Rebecca Christoffel, Iowa State University Extension and Outreach wildlife specialist. "Most incidences of birds flying repeatedly at a glass door or window are simply issues of territory."
Christoffel said male songbirds who see their own reflection mistake it for an “interloper” invading their territory. Very few, if any, species are able to differentiate their own image in glass from that of another of their species ― the bird flies at the glass, often colliding with it, in an effort to drive off the “interloper” they see. Birds that commonly exhibit this behavior during the breeding season include American robins, cardinals, American goldfinches and some sparrow species.
“This seemingly erratic behavior will eventually subside once the bird is no longer in breeding mode,” Christoffel said. “However, with birds that raise multiple broods of young over the course of the spring and summer, it could be months before the animal stops.”
Christoffel said there are options available to homeowners to help alleviate this behavior by birds:
- One option is to cover the outside of the window or glass door with an opaque substance such as brown paper bags. The idea is to prevent the bird from seeing its own reflection. Windows and doors also can be soaped up on the outside to produce the same effect.
- A less obtrusive option is to purchase a set of raptor silhouettes from a local bird feed supplier or home shop. When the bird sees the raptor’s silhouette in a window, it will be seeing a potential predator and avoid the window. However, the homeowner’s view will be obstructed by the opaque raptor silhouettes.
- Even less obtrusive is to purchase a set of raptor silhouettes that are only visible in the UV light spectrum ― these are clear or nearly invisible to human eyes but clearly visible to birds. These decals also can be found at a local bird feeding supplier or home shop.
- An alternative to raptor silhouettes is to place pieces of colored tape or flagging in irregular patterns on the window.
- Finally, placing non-reflective screen outside the window 2 to 3 inches from the glass also will deter the bird and prevent it from reaching the glass.