Species Dossier: Brown-headed Cowbird

by Carl Strang

Cowbirds haven’t arrived in our area yet this spring, but it won’t be too long. The following represents my limited knowledge of this, our main local nest parasite.

Cowbird, Brown-headed

Male brown-headed cowbird

This blackbird has been common essentially everywhere in the eastern U.S. I’ve gone. They feed in and around open areas and fields. Females lay eggs in other birds’ nests, early examples observed in warbler nests of a few species. They sometimes stayed around Culver, Indiana, in winter, taking seeds from feeders.

31MR99. First of season noted at Willowbrook.

29MR00. Willowbrook. Cowbird males displaying in high, bare tree tops: a group of 5, and a group of 3 (one of the latter had left the first group). No females were present with the group, but a female was present elsewhere on the preserve. The display consisted of fanning the wings out to the side, fanning the tail and lifting it above back level, then bowing or leaning forward to the point of sometimes losing balance. While performing the display, the bird at least sometimes gave its high‑pitched call. (I call this the falling-down-drunk display.)

Falling-down-drunk display, closely watched by a female.

1JL00. A female yellow warbler fed a cowbird fledgling near the south end of Silver Lake at Blackwell. Earlier this week a pair of scarlet tanagers fed a cowbird at Willowbrook, and half a dozen times this spring I have seen male cardinals feeding them (some were the same pair, but at least 3 different broods were involved), also at Willowbrook.

12OC02. After not seeing many in recent weeks, a couple individual cowbirds appeared earlier in the week at Willowbrook, and today, a number of them, especially young ones, were at Fermilab.

19JE08. A pair of gnatcatchers fed a cowbird fledgling at Fullersburg.

20JE09. Last year I also saw song sparrows feeding a cowbird at Fullersburg. This year at Mayslake I have seen cowbirds fledged by phoebes and Baltimore orioles.

Fledgling cowbird being fed by a female Baltimore oriole.

15JL09. Mayslake. Yesterday in the south savanna a cowbird fledgling was being attended by a song sparrow. Today another fledgling was in the north savanna being fed by a phoebe, clearly a different brood or pair than the earlier one (last observed 3 July).

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2 Comments

  1. Beth said,

    May 27, 2012 at 8:11 am

    I have not seen any cowbirds this year in eastern Pennsylvania. It is very strange indeed! I did see a catbird knock a robins egg from the nest, but don’t know yet if she donated one of her own.

  2. November 2, 2012 at 6:07 am

    […] have mentioned cowbird displays before, for instance in my species dossier on them. The display consisted of fanning the wings out to the side, fanning the tail and lifting it above […]


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