Preventing Window Strikes

Millions of wild birds are killed each year flying into windows. Birds may be injured (fractured bones or bills, head trauma, internal bleeding, broken beak), killed, or eaten by a predator while stunned. According to David Malakoff (Audubon magazine, March 2004), window strikes kill between 100 million and 1 billion birds in North America each year, particularly migrating birds. 25% of North American and Canadian bird species have been documented striking windows. Window strikes are reportedly the most common cause of death associated with bird feeders.

Birds collide with glass for four reasons: either they

  • cannot see the glass at all because it is transparent (especially a problem with two windows or a window and mirror opposite each other, creating a”corridor effect”)
  • see a reflection of the outdoors, and try to fly through what looks like unobstructed open space (the “mirror effect”)
  • are attempting to defend their territory from a perceived intruder – their own reflection (“territorial strikes”).
    Bluebirds, cardinals, and robins typically do this. Territorial window strikes are more common in springtime, but may occur year round. During the fall, male birds often get a second flush of testosterone (called “gonadal recrudescence”).
  • some bluebirds are just “nosey,” and will cling to a window screen or will come to the window to beg for mealworms, but do not crash headlong into it. (See bluebirds apparently alerting hosts to problems.)

Move attractants: feeders, bird baths, nestboxes and perches

  • Do not place feeders directly in front of windows.
  • Move bird feeders or bird baths farther away (25-30 feet from the window).
  • Put feeders or bird baths closer (within 1-3 feet of the window) so birds aren’t moving fast enough to get hurt. They are also more likely to see the windows.
  • Move nestboxes 100 feet or so from the building (to prevent territorial strikes).
  • If the bird is using a favorite perch or two while watching the window, try removing those perches, or temporarily blocking access to them (territorial strikes).
  • Don’t hang houseplants inside windows where strikes are common.