Bay Nature magazineOctober-December 2008

Ask the Naturalist

The Paranoid Jay

October 1, 2008

Q: A blue jay has been flying against the windows of our house and poking at them. I thought it might be territorial, but I put out rice that the jay ate peacefully with another jay! Why is the jay doing this? What can I do to deter it? [Venkat, Union City]

A: I get a variation on this question every year. First, the jay that you are referring to, while its dominant color may be blue, is not a “blue jay.” Blue jays are common to the eastern United States but do not normally cross the Rockies, though they are expanding their range into Washington and Idaho. In the Bay Area, we have two widespread species of jays. Look for scrub jays (mostly blue and gray) in suburban yards, chaparral, and scrubland. Steller’s jays (bluer with a large crest) live in forests and wooded yards.

The behavior you witnessed is clearly related to breeding. These jays are defending their territory. The jay sees an image of itself in your window and assumes that it is a stranger invading his turf. In defense, he attacks. It is usually the male doing this, though in a monogamous pair of birds, the female can also get aggressive. The communal feeding behavior you saw was likely the happy couple sharing resources and reinforcing their pair bond. Mating could follow. The same thing happens in humans. A nice dinner out followed by . . . .

The only way to prevent the bird’s attacks is to do away with the reflections. That’s more easily said than done. Putting a paper covering or perhaps a silhouette of a falcon or accipiter hawk on the window may work. Eventually the testosterone will wear off and the bird will cease that behavior at the end of the breeding season. And hopefully both the bird and your window will still be intact.

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About the Author

Send your questions to Rosa-based naturalist Michael Ellis leads nature trips throughout the world with Footloose Forays (

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