This image was shot on June 13 in the wetlands near Sacramento, California. At first, I thought it might have been a female Blackbird, but the beak is all wrong. Could this be a female Brown-headed Cowbird?
ID Help, Please!
This image was shot on June 13 in the wetlands near Sacramento, California. At first, I thought it might have been a female Blackbird, but the beak is all wrong. Could this be a female Brown-headed Cowbird?
Got it in one Peter, it is indeed a female Brown-headed Cowbird, or possibly a young male or female- the scaly nature of the feathers suggests an immature bird. And they are indeed blackbirds so you were right on both counts.
For those non-North Americans in the audience who may be unfamiliar with this species, it's just about the closest bird we have to the European Cuckoo, although unrelated. Cowbirds don't build their own nest but lay a single egg in the nest of other species. They are not as sophisticated as Cuckoos however, For example, the newly hatched cowbird chick does not eject the eggs or chicks of the parasitised species, like the Cuckoo does. Many ducks in the stiff-tail group (e.g., the North American Ruddy Duck) are also nest parasites.
Last edited by John Chardine; 06-23-2009 at 06:33 PM.
John, who kicks out the eggs, cowbirds or cuckoos?
The Cuckoo Axel. I see I should have used a comma to make the sentence in the OP a bit clearer.
Cowbirds don't do this? If so, the sentence just needs a negation for the cowbirds.Originally Posted by John Chardine
Edited. Many thanks!
The cowbird will usually throw a host nest egg out of the nest when she lays hers.
http://www.birds.cornell.edu/Publica...d_cowbird.html
Jim
Last edited by James Prudente; 06-24-2009 at 01:43 PM.
Apparently, yes Jim. However, the "motivation" of cowbird nest destruction is unclear and may not be related to parasitism, and it occurs in by no means all parasitism attempts. According to studies I've been reading, female cowbirds will often depredate eggs or chicks of other species but not then lay an egg themselves. This seems to be simple predation, also seen in other Icterids such as grackles, which are notorious nest predators. The interesting twist here is that some host species will grab hold of a cowbird egg and remove it from their nest; others simply build a floor over the existing eggs and lay again. Still others do not reject a cowbird egg and happily incubate the egg and rear the parasite chick to independence. This is done at a huge cost to the host's breeding success and lifetime fitness.
Very interesting, John! I remember reading that cowbirds also destroy nests of birds who kick out the cowbird's egg. Is this true?
I've not heard of that Axel but it could be true. I don't think cowbirds are particularly discriminatory but some of their hosts tend to be. The cowbird or buffalobird as it was called, was a species of the American plains and parasitised the grassland species of the region. Many of these species such as meadowlarks have been in contact with the cowbird for a very long time and have evolved rejection behaviours as mentioned above. Cowbirds have expanded their range hugely as forest habitat was opened up and suddenly species were being parasitised for the first time. Some of these do not reject cowbird eggs and happily incubate the egg and rear the chick, to their detriment.
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