Saturday, April 16, 2011

April 16, 2011-Those Bad Cowbirds

The moon through the trees last night on the 15th.

A pair of Robins looking for worms in the rain today.

A Downy woodpecker high up in the branches.

I have never seen cowbirds land like this here before. I sure hope they continue on their way. I don't want them invading the other bird's nests around here. I am adding the information about them. I looked it up online to make sure what kind of birds they were.
Brown-headed Cowbirds are smallish blackbirds, with a shorter tail and thicker head than most other blackbirds. The bill has a distinctive shape: it’s much shorter and thicker-based than other blackbirds', almost finch-like at first glance. In flight, look for the shorter tail.

Male Brown-headed Cowbirds have glossy black plumage and a rich brown head that often looks black in poor lighting or at distance. Female Brown-headed Cowbirds are plain brown birds, lightest on the head and underparts, with fine streaking on the belly and a dark eye.

Brown-headed Cowbirds feed on the ground in mixed-species groups of blackbirds and starlings. Males gather on lawns to strut and display for mates. Females prowl woodlands and edges in search of nests. Brown-headed Cowbirds are noisy, making a multitude of clicks, whistles and chatter-like calls in addition to a flowing, gurgling song.

You’ll find Brown-headed Cowbirds in many open habitats, such as fields, pastures, meadows, forest edges, and lawns. When not displaying or feeding on the ground, they often perch high on prominent tree branches.
This bird is a brood parasite: it lays its eggs in the nests of other small passerines (perching birds), particularly those that build cup-like nests. The Brown-headed Cowbird eggs have been documented in nests of at least 220 host species, including hummingbirds and raptors.[2] (Ortega 1998) The young cowbird is fed by the host parents at the expense of their own young. Brown-headed Cowbird females can lay 36 eggs in a season. More than 140 different species of birds are known to have raised young cowbirds.

Host parents may sometimes easily notice the cowbird egg, to which different host species react in different ways. Rejection manifests in three forms: nest desertion (e.g., Blue-gray Gnatcatcher), burying of the egg under nest material (e.g., Yellow Warbler) and physical ejection of the egg from the nest (e.g., Brown Thrasher). Brown-headed cowbird nestlings are sometimes expelled from the nest.

The House Finch feeds its young a vegetarian diet, which is unsuitable for young Brown-headed Cowbirds. Although the Brown-headed Cowbird eggs laid in a House Finch nest will hatch, almost none survive to fledge.

It seems that Brown-headed Cowbirds periodically check on their eggs and young after they have deposited them. Removal of the parasitic egg may trigger a retaliatory reaction termed "mafia behavior". According to a study by the Florida Museum of Natural History published in 1983, the cowbird returned to ransack the nests of a range of host species 56% of the time when their egg was removed. In addition, the cowbird also destroyed nests in a type of "farming behavior" to force the hosts to build new ones. The cowbirds then laid their eggs in the new nests 85% of the time

This squirrel was really enjoying the buds of this Lilac Bush. Guess those bushes won't be so full this year.


Ratty said...

Cowbirds can be a mean bunch. You may have noticed that the males have bright yellow eyes. I've been seeing them around here too.

I love seeing squirrels eating the buds from trees. I first observed that last year around this time.

Emma Springfield said...

You are certainly overrun by those pesky little cowbirds.

ShySongbird said...

Strangely enough I found out about your Brown-headed Cowbird just this past week having known nothing about it before. It almost exactly mirrors the behaviour of our Summer visiting Cuckoo which is a very large bird which removes eggs from much smaller birds nests and replaces them with its own! It favours the Dunnock's nest which is a really tiny bird in comparison. I have seen photos of the poor little Dunnock feeding the huge Cuckoo chicks, it is a wonder the chick doesn't swallow its 'foster' mother ;)

A fascinating post Ginny!

P.S. The last four letters of the word verification are...nest!

Out on the prairie said...

I saw the cowbirds in a flock a week ago so this flock is just arriving.Last year I saw a baby with its song sparrow parents. It had adopted their language and followed graciously.

Ginnymo said...

Thanks for taking the time to leave comments everyone. Nature is amazing. I saw one of the little sparrows feeding a young Cowbird last year. Never had seen anything like it and didn't know anything till I researched it. I just hope they don't stay around here and invade too many nests. I like my little birds way better.. and now that I recall I even saw a Cardinal feeding one of those birds. I want more Cardinals around here than Cowbirds!

Jean said...

Thankfully I have only had a couple of Cowbirds at a time visit my place. BTW...they will eat at feeders. I have pictures. I do not like these birds.:(