Naturespeak A naturalist's view of the world

April 14, 2010

Homemaking: Cooper’s Style

Filed under: Uncategorized — wykes @ 8:53 pm

‘Tis the heart of the season for nesting birds. Big ones, little ones, and more than a few middle sized ones are now engaged in home-building and clutch rearing. Robins, Starlings, and House finches go about their nest chores within easy eye-shot. It is, in fact, near impossible not to see these familiar fowl flitting back and forth with a mouthfuls of grass, mud, or twigs. Most birds are secretive about such proceedings or make it a point to conduct their business in fairly secluded locations. Cooper’s Hawks stick to the latter plan, but not the former. They are not commonly seen as nesting pairs because they are forest hawks who build up in the top branch layer, but because of their talkative nature they make a habit of announcing their plans to the world. In other words, when these raptors are in a domestic mood they let everyone know.

A pair of vociferous Cooper’s Hawks have taken up nesting atop a Hawthorn tree at Lake Erie Metropark. The location is fairly low as hawk nests go – about 25 feet or so – but well concealed in maze of thorny branches. Soon the location will be completely hidden by emerging leaves. I found the nest only because the female caught my attention and then led me right to it.  As you can see (below) the nest is very hard to see even when you do “see” it. A crow-sized platform of pencil-sized sticks and small branches, the tangled structure blends in perfectly when placed in a tangle.

Normally quiet birds, these large accipiters do a lot of squawking around breeding time. The best way to describe the “keeping in contact call” is that it sounds like a big rubber dog toy. I say “big” because the tone is more guttural and loud than squeaky – a Great Dane toy, perhaps. “Eee-n  Eee-n” is the best I can do to describe the mewing pattern. Listen to this call (here) and you’ll hear what I heard on the first day. You’ll also get a brief glimpse of her leaving the nest in this video/sound track.

She’s been performing this call consistently over the past week. A visitor stopped by the museum and attempted to describe a bird call he was hearing the other day. “It sounded like someone was pulling on a Toro snowblower that wasn’t starting,” he said.  Unfortunately, his visual sent me off in another direction and it wasn’t until he told me where the sound was coming from that I finally was able to key him in on the Cooper’s hawk. I played my recorded call and he said “that’s it!”  A Toro???

The second call is a much more familiar Cooper’s vocal. It consists of a rapid fire “cak cak cak cak” (you know, like rapidly beating on a rubber toy or a toy toro snowblower).Listen to this call (here) and it’s likely you won’t forget it.

Though I heard the male a few times, I’ve yet to spot him. All my eye time has been on the busy female. It is likely that she is already mated (Cooper’s apparently mate hundreds of times!) and was in the mid-stage of nest construction when I first came upon her. The slightly unusual thing about this gal is that she was a subadult bird still garbed in her 2nd year brown outfit (see below and here). Cooper’s Hawks don’t attain their full plumage until their third year. At that point they will have slatey gray backs, ruby red eyes, and rusty brown breasts. Our female retains her yellowish eye and brown back. Her white breast was still covered with vertical brown paint drips.

Although it’s not unheard of for 2nd year Coopers to breed, it is fairly rare. Oddly enough, it is usually the female that is the young chick of the pair when it does happen. It is very rare for a subadult male to engage in breeding and even rarer for both members of a pair to be subadults. I’m assuming our female’s mate is an adult bird, but I can’t tell from his call alone. His voice wasn’t cracking, so that might be a sign of maturity! You can actually hear his distant call 38 seconds into the first call video track if you want to give it another listen. She responds at 43 seconds and quickly leaves the nest as if to say “yes, I’m still working dear. I could use a little help.”

The female has been working diligently on her task. I watched her repeatedly bounce through the tree-tops and grab small twigs with her powerful beak. She’d try a few before finding one that snapped off. Her beak is made for ripping apart little birds – not for playing pick up sticks. Once a twig was secured, she’d immediately fly to the nest and position it before repeating the whole procedure.

I suspect, if everything goes well, she’ll be laying her eggs within the week.  Subadult females tend to lay their eggs later than adult females and they pop out fewer eggs when they do lay, but they certainly don’t lack the energy when it comes to nest-building and gabbing.

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