Date: 5/1/25 2:23 pm From: ChicoBill via groups.io <w.e.haas2...> Subject: Re: [slocobirding] Cassin's Kingbird - unusual breeding season behavior??
Did someone recently mention "agonistic behaviors"?
These observations are almost certainly the result of raging breeding season hormones (although this can occur out of the breeding season with strongly territorial birds, including, for example, desert-dwelling Say's Phoebes).
These bird are likely responding to the (virtual) presence - i.e., the mirror image - of a perceived competitor. Bluebirds, phoebes (E, B, & S), mockingbirds, and orioles are probably the most often reported species displaying these behaviors but any reflective surface within a breeding territory could stimulate such behaviors in virtually any territorial species.
And why at some windows/reflective surfaces and not others? Angle if incidence, what's behind the mirror (aka glass pane), what's on the mirror (e.g., presence or absence of visual disruptors), proximity to territory center, etc.
And on the matter of interesting behaviors, over the past two weeks (until two days ago), we've had an adult male Nuttall's Woodpecker drumming on all things aluminum on the back side of our house, especially aluminum door and window frames. Why?
1. Raging hormones.
2. To make noise.
3. Specifically, to make noise to attract a mate (i.e., "advertising") - this resident bird had recently lost its mate to our also resident (adult female) Cooper's Hawk.
. . . and two days ago, a lovely female Nuttall's Woodpecker came to our suet feeders (I'm now feeling a bit like a matchmaker). Aside from a few brief incidents, the drumming has ceased and the two have been spotted alternately feeding on our suet cakes.
What is most amazing to me, especially given aluminum's high degree of malleability, is that one would be hard-pressed to find evidence of the drumming. Apparently, this fellow was able to adjust the reach of his drumming sufficient to broadcast an annoying racket (annoying, at least to some humans, but apparently more like a Mendelssohn symphony to kindred spirits) but insufficient to rattle its brain. Impressive!
