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Posts Tagged ‘altricial’

oriole

One of the nice things about the trees losing their leaves in the winter is the way that the activity of the bird community is revealed.
Nests hidden in the summer suddenly become conspicuous. There are quite a few nests to be seen in the trees around here, including the Baltimore Oriole’s nest (Icterus galbula) pictured above. There are also some nests in unexpected places, such as this nest I noticed in the hoophouse. Can you see it?

nest1

The hoophouse was once one of three that were used by a former owner as part of a nursery operation. The last owners of the property had 2 of the houses removed and allowed the third to deteriorate, its equipment unmaintained, and it was full of junk and garbage when we first viewed it. The wood for the garden monster is stored in here now. I noticed that high up on an old bit of machinery, there was a nest.

nest2

I climbed up to take a closer look at the nest. It was clearly that of an American Robin (Turdus migratorius), readily identifiable by the mud cementing the structure. Robins and swallows are the main employers of mud in nest construction, and the cup-like shape points to the former as the builder of this nest. When I reached my fingers over the edge of the nest, I could feel that there were still eggs in the nest. I removed it from its perch for closer inspection.

mudnest

Obviously, something disrupted the robin parents after their eggs were laid. It could have been simply that someone closed the door to the hoophouse, cutting off their access. Four lovely eggs remain, sadly, never to hatch.

Normally, the female robin would incubate the eggs for 12 to 14 days. Like the young of most songbirds, robin hatchlings have closed eyes, are naked, and require feeding by their parents. Such hatchlings are termed altricial. These babies are very different from the hatchlings of birds like ducks and geese, who have open eyes and down when they hatch and are able to leave the nest within 24 hours of hatching. Those hatchlings are termed precocial.

The baby robins would have grown quickly. In just over 2 weeks, they would have been close to the size of their parents, would be fully-feathered, and ready to leave the nest and fly. The fledglings would continue to be fed and cared for by the male until they could manage on their own. Meanwhile, Mom would begin to incubate a second clutch of eggs. Robins raise 2 or 3 broods, or families, each summer.

4eggs

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