Thursday, June 15, 2017

Eastern Phoebe

Phoebe Nest Parasitized by Cowbirds

Eastern Phoebe
 We are lucky to have a nest of Eastern Phoebes (Sayornis phoebe) over our patio this year.  The female phoebe has been a diligent mother, faithfully sitting on her eggs and now working hard to catch insects around the yard to feed her brood.  But we did not know until two days ago that she was feeding an interloper.

The Eastern Phoebe is a flycatcher that is common here in New Brunswick.  It frequently nests under eaves, bridges and  other man-made overhangs.  It is a medium-sized flycatcher that characteristically wags or dips its tail.  It is grayish above with the gray being darker on the head.  Its underparts are white with a pale yellow wash on its sides and breast.  It has a friendly call note, saying its own name, 'Phoebe phoebe'.  In our yard it receives a warm welcome as it returns in the spring from its wintering area in southeastern US and Mexico.

Eastern Phoebe
Phoebe nests are made of mud and moss and are lined with fine grasses.  The incubation period is 16 days and both the male and female incubate the eggs.

The first fledgling that left the nest was the bird pictured below, a young Brown-headed Cowbird (Molothrus ater).

Brown-headed Cowbird Fledgling
Fortunately, in the next day or two the phoebes fledged.  Their nest was parasitized by the cowbirds!  The female cowbirds watch and somehow find out where there are suitable nests in which they can deposit their eggs.  Each female lays as many as 35 eggs!  That is a lot of normal bird 'families' to be burdened by her young.  The cowbird egg incubation time is 10-13 days.  So, what usually happens is that the cowbirds hatch first and the host adults have to feed this interloper, thinking it is one of their own.  Often the cowbird nestling out-competes the host young resulting in their starvation, abandonment or death.  Yesterday we saw the adult phoebes catching insects around our yard and hopefully feeding their own fledglings as well as the cowbird.  The adult cowbirds are nowhere to be seen.  They leave the rearing of their young to someone else - true parasites!

Brown-headed Cowbirds - 2 Males, Female
The adult male Brown-headed Cowbird is iridescent black and green on its back and sides and brown on the head.  The female is a uniform medium gray-brown all over.

Brown-headed Cowbird Male
The Eastern Phoebe was the first species to be banded in North America.  It was done by John James Audubon in 1804 who placed a silver thread around the leg of a phoebe to see if it would come back to the same place the next year.    We are pleased they come back by the hundreds of thousands every year for a good place to raise their young and for our enjoyment.

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