Speaking of Nature

Speaking of Nature: The cooper’s hawk

When I heard that we were getting a large snowstorm last weekend, I was actually pleased. We’ve had a dearth of snow the past couple winters and I thought it would be nice to see the landscape covered in white again. But in addition to my purely aesthetic reaction to snow, I was also hoping it would generate some extra business at my feeders. I was quite anxious to see one customer in particular.

Many of you have contacted me this winter with concerns that the birds seem to be missing. Others have mentioned that is not so much a lack of birds, but rather a diminished number of birds. Well, I want you to know that you are not alone. I have noticed the same thing.

The flock of redpolls that arrived many weeks ago has persisted. I only get the chance to see them on weekends, which means I am only able to provide the bountiful, never-ending buffet of seed for a couple days in a row, but the redpolls are always there. First there are a few, then there are a couple dozen and then the horde arrives. You could do far worse than having to endure a horde of repolls.

The other species that normally inhabit my yard can still be seen, but in numbers far lower than seems normal. I’ll see one white-breasted nuthatch every once in a while, a handful of goldfinches and house finches, and a half-dozen juncos. Then there will be the occasional woodpecker, or jay and, every once in a while, a dozen mourning doves will arrive. But one species is conspicuous in its absence.

The white-throated sparrow is a chunky lithe brown “body bird” that I have featured in several columns. This species tends to nest at higher altitudes and latitudes than we have here in these parts so it tends to disappear during the summer. Yet it faithfully returns every autumn to set up shop and is a reliable visitor to feeders throughout the winter. Except for this year.

This year, I haven’t seen a single white-throated sparrow and that’s a little odd. Other people have them, but when I asked my mother about her yard, she said that the white-throated sparrows had been there, but that she hadn’t seen any in a while. I have been watching birds for over 20 years and this is the first time I haven’t seen a white-throated sparrow. It feels like something is afoot.

But the scientist in me has to wonder if there isn’t something less ominous that explains the low numbers. When I moved into the area, there were virtually no birds at all. After a couple years of faithful feeding, I generated a reliable clientele and the numbers were quite large. Then, we had a couple or three rather mild winters and now numbers are low.

Could the combination of open country around my house and the large number of songbirds at my feeders have created an attractive hunting ground for accipiters? Could I ultimately be the cause of the low numbers? Is it possible that … What’s that? What’s an accipiter? Well, that’s easy to explain.

In the world of raptors (birds of prey) the method of hunting and the target hunted will shape the body of the hunter. Owls tend to be nighttime raptors that eat small mammals. Their eyes are extremely large and their feathers are extremely soft. This combination of traits allows them to fly almost silently and pounce on animals that never see them coming.

Hawks are daytime predators, which opens up a wider variety of targets. The buteos are the big, soaring hawks like red-tails. They have fantastic vision and can loiter above a summer field for hours just waiting for a mouse, a rabbit or a vole to make a mistake. Buteos have broad, rounded wings and broad, fan-shaped tails.

The falcons are another group of daytime raptors that tend to target birds in open country. This means that falcon wings are long, tapered and swept back and they have long, straight tails. Falcons tend to hunt like cheetahs; they see you from a great distance away and then simply overtake you with sheer speed.

And then there are the accipiters. These raptors also hunt birds, but instead of hunting in open country, they hunt in brushy thickets and forest edges. These birds tend to sit and wait for an opportunity, then catch their prey by surprise in an ambush. Sometimes, they will also go on patrol and see if they can’t catch another bird off guard while flying fast and low. Accipiters have to be highly maneuverable, which means they have rather short, rounded wings and long tails that can open up like a paper fan.

The most interesting thing about the accipiters is the fact that they come in three different sizes. The sub-compact model is the sharp-shinned hawk, which is not much larger than a blue jay. The mid-size model is the Cooper’s hawk, which is about the size of a crow. The luxury model is the northern goshawk. Slightly larger than the Cooper’s hawk, this bird is one that I have only seen once.

So, as I pondered the general lack of birds at my feeder on Sunday, I happened to look to the trees to the west of my house and I suddenly saw the issue. There, in a tree that was recently killed by gallery beetles, I saw a Cooper’s hawk. When I got the binoculars out I could tell, even from 80 yards, that this was an immature bird.

When sitting in a tree, the accipiters have a very upright posture. The adults of these species tend to have slate-blue feathers on the back and brilliant red eyes. This bird had chocolate brown feathers and pale yellow eyes. But as it sat and preened, I could see the horizontal stripes of brick-red feathers that identify an adult bird starting to show on the breast. Our little Cooper’s hawk was growing up.

The hawk sat in the tree for over three hours and actually allowed me to walk out onto my porch and take photos on a number of occasions. This is an uncommon occurrence, but the winter does present certain challenges to any predator. Energy is precious and hunting opportunities are rare. The bird may have decided to avoid wasting energy with frivolous flying until I presented more of a threat. As luck would have it, I was there just in time to see the hawk fly from its perch. I wonder if it was any coincidence that a flock of mourning doves had recently flown overhead?

I’m not convinced that one Cooper’s hawk can explain the lack of white-throated sparrows at my feeders. But the only time I have ever seen an accipiter make a kill was right underneath my porch. The victim was a white-throated sparrow.

Bill Danielson has worked as a naturalist for 16 years. In that time, he has been a national park ranger, a wildlife biologist and a field researcher. He currently works as a high school chemistry and biology teacher. To contact Bill, or to learn more about his writing, visit
www.speakingofnature.com

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