Counting Colonial Nesters in a Rookery

The ground beneath my feet crunched with dried droppings, broken tan and blue-green eggshells, and layers of leaves as I walked slowly up and down under the trees trying to count nests, adult birds, nestlings and fledglings. Every so often I had to step over a dead chick.

I was participating in a colonial water bird survey for the U.S. Fish and Wildlife Service’s Migratory Bird Program, coordinated by Bill Howe. It seemed like a daunting task, given the multiple nests in many trees, and the constant comings and goings as birds left the nest to feed, while others returned.

The owner of the property had invited me in to get a better look. The trees were so dense that it would have been difficult to get an accurate count from the road.

“We feel so fortunate they have chosen to nest here,” she told me. “However, my neighbors are not as enchanted. They do what they can to disturb the birds and try to get them to move elsewhere, including throwing firecrackers into the approximately two-acre yard.”

She explained that the egrets and herons previously had nested near the river; however, moved to this spot after a fire in the bosque a few years ago.

While a few were interspersed throughout the rookery, most of the Black-crowned Night Heron nests seemed clustered on the western edge of the property. There were adults still sitting on their flimsy stick nests, while others had nestlings and fledglings. Participating in these types of activities always provides opportunities for learning opportunities. From my Birder’s Handbook (Ehrlich, Dobkin and Wheye), I discovered that both males and females incubate the light bluish-green eggs for 24-26 days, and that the birds are not ready to fledge for 42 – 49 days.

Cattle Egret

Next was clustered several rows primarily of Cattle Egret nests, although they too were found throughout the grove of elms. They also were in all stages from incubation or brooding, to nestlings and fledglings. There seemed to be more comings and goings of the Cattle Egrets. When one of the pair returned to the rookery, it settled on the top branches of the tree containing the nest – as if it were reluctant to take its turn at the nest. Interestingly, they fledge at least 10 days sooner than their neighbors the Black-crowned Night Herons.

Snowy Egret pair and nestlings

The Snowy Egret nests tended to be mostly on the eastern edge of the grove, although a few built nests in other parts of the grove. I did not find any nests of this species with fledglings.

Some trees had more than one nest, often with more than one species occupying a tree. Perhaps some of the raucous bird conversations I heard were such things, as “you’re in MY part of the tree,” “stop making the branches bounce,” or “have you seen my partner?”

In addition to the herons and egrets, Great-tailed Grackles also nested and roosted in the grove and were busy flying in and out.

After I finished my counting, I visited again with one of the owners. “We just love to set up our lawn chairs after dinner and watch the birds,” she explained, “especially as they all fly in just before dusk to roost.”

Their philosophy is to let nature take its course. If a nestling or fledgling falls out of a nest, “we don’t try and rescue it. If has enough flight feathers, it might make it back up to the nest – and often parents will bring food down to it.”

When the fledglings begin leaving the nest, they often fly down to the ground and start exploring the yard. This sometimes leads them to peek in the sliding glass doors.

“People think we are crazy putting up with all of this, but we love it,” she concluded. I promised to send them a copy of my count.

It had been an awesome experience to walk through the rookery – and with all of the birds above me, I considered myself fortunate to have come out splatter-free.

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6 thoughts on “Counting Colonial Nesters in a Rookery

  1. Pingback: Gray Catbird – Bird of the Day at Los Lunas River Park « It’s a bird thing…

  2. This is a great location for birders to visit. You captured the feeling of it very well in your writing and photos.

  3. Thanks, Judy.
    That’s a great account of an amazing phenomenon.
    Glad the owners are so receptive and protective.
    The neighbors we encountered were far from an appreciation of the rookery and its inhabitants.
    Thanks for the good work!

  4. Pingback: Isleta Marsh, Los Lunas River Park and Bosque Farms Rookery « It’s a bird thing…

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