Wednesday, April 27, 2011

At the Rookery - Part One - Black-crowned Night-Heron

Monday evening was the last meeting of the D.F.O. (Denver Field Ornithologists)for the season. So after work I headed to Denver and got a chance to do a bit of birding in City Park before it was time to head inside.

It wasn't so much birding, as watching the activity at the rookery. Of the two rookeries in the area the one I spent my time at on Monday was the smaller and more diverse. It features nests of Black-crowned Night-Herons, Snowy Egrets and a few Double-crested Cormorants. The other, larger, rookery is almost exclusively filled with the nests of hundreds of Double-crested Cormorants. Last year my visits must have preceded any of the nesting activity of the Herons and Egrets, because I had not seen those species at the park in the past.

Getting a chance to watch so many of each was fun. A couple of Night-Herons were grabbing twigs for nest maintenance from the tree above my head. They would move precariously through the limbs and select the perfect stick before returning to their island. After a few minutes of sitting the entire colony seemed to forget my presence and were much more intent on displaying and squabbling, and keeping out of the way of the Canada Geese, and their efforts to establish pairs.

There were well over a hundred Black-crowneds in the nesting colony, but this lone bird in juvenile plumage was a bit of a wonder for me. I presumed, and it seems to be backed up by online reading, that this would be a year old bird. Dates for birds showing their "Formative Plumage" (Birds of North America Online) extend into September of the year following their hatching. I found it odd that there was just a single bird hanging out that was shoeing that plumage. Is it a 'momma's bird' afraid to break out on its own and hang with the others? An overachiever - the Doogie Howser of birds, trying to hang with the adults ahead of time? Or as I had initially thought, but now seems to be unlikely, that it was a lone bird that was late to molt into adult plumage.

Very cool to have so many nesting birds in such an approachable, urban location. If you are in the area I recommend stopping by to check out the activity.

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