Day 194: While they aren't exactly the brightest crayons in the box, Brown-Headed Cowbirds have a nesting strategy which ensures their survival at the expense of other bird species. Molothrus ater does not construct a nest of its own. Rather, this native species (N.B.!) is known to parasitize the nests of at least 140 hosts with a wide range of sizes from Kinglet to Meadowlark, and has been shown to contribute to the decline of such species as Kirtland's Warbler. A female Cowbird may lay as many as 30 eggs in a year, and takes no part in feeding the young, leaving that task to the host. Young Cowbirds generally develop more rapidly than the chicks of the host species and often displace them from the nest. Cowbirds frequently share roosts with blackbirds (here, Red-Winged and Brewer's), and communal roosting sites may hold populations of 100,000 or more. In the last two weeks, several dozen Brown-Headed Cowbirds have joined forces with the Red-Wingeds in my yard, much to my annoyance. While I would never wittingly hurt a bird, my slingshot sits at the ready beside a bowl of rocks at the back door. I aim low, hoping to hit a branch. The ensuing "THUNK!" sets them in flight, but seldom for long. By the time I've walked back around to the living room, one or two of the bravest will have re-settled, inspiring me to run at the window, arms flailing as I scream, "Get outta here, you (censored)!" I won't win, but at least the method has deterred a few.
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