Monday, January 31, 2022


Rough-legged hawk (Buteo lagopus), an Arctic buteo wintering on the high plains of eastern Colorado. 


My ever-observant Jessa asked, "Is it just me, or are the feet really small?" It's not just her; the roughie's wingspan averages longer than a redtail's, but the feet and talons are significantly smaller. The only other North American buteo with a comparable body plan—large body, disproportionately small feet—is the ferruginous hawk (B. regalis), which also happens to be the only other North American buteo with legs feathered down to the feet. 

I'll try to post something soon on Allen's Rule, but suffice it to say for now that both the rough-legged hawk's namesake feathered legs and its small feet are cold-climate adaptations. The small feet also correspond with the roughie's diet, which is about 90% comprised of lemmings, voles, and mice. Did the roughie's small-mammal specialisation drive the evolution of small feet in conjunction with Allen's Rule, or is it the result of having smaller feet pursuant to Allen's Rule? I suspect...both. Natural selection is full of feedback loops.

Photos © Jessa and Mark Farrell-Churchill. 

Saturday, January 29, 2022

Big T / Muley

Scenes from the Big Thompson River, Estes Park, Colorado.

Some of the creekside trees are wrapped in chicken wire.

Here's why.

Wednesday, January 26, 2022

Mountain retreat

Jessa and I like a nice roadside chapel every now and again, and found this one while cruising through the Rocky Mountains in Colorado on a snowy day: the St. Catherine of Siena Chapel on the Rock, built in the 1930s.

You know who else likes a nice roadside chapel? Apparently, Pope John Paul II, who visited here in 1993.

St. Catherine of Siena.

The rock.

Sunday, January 23, 2022

Age classes in bald eagles

We hadn't necessarily intended this, but in our forty-five minute shoot at Hershey we got enough pictures for a brief primer on ageing bald eagles. It's not an exact science—there's quite a bit of variation, especially in sub-adults, and some individuals achieve full adult plumage more quickly than others, but we can at least outline the typical progression. 

Juvenile (first-year) birds are dark overall, especially when they fledge, but the juvenal plumage seems especially prone to fading and by this point in the year some birds will be quite tawny. The eyes are brown and the beak anywhere from black to grey.

Subjectively, first-year birds sometimes present a somewhat disheveled, loose-feathered appearance—Jessa compared this one to a Muppet. That impression probably isn't helped by their often undignified behaviour. Juvenile baldies, naturally enough I suppose, seem far less...together than their older counterparts. 

The juvie is obvious in this shot, yes?

Second-year birds (sub-adult I plumage) are known to hawk-watchers as "white-bellies", though the white is often heavily mottled, as on the bird in the center here. Some third-year birds (sub-adult II) retain the white belly, while others go dark; this is where identification becomes most uncertain, although in flight SA IIs tend to have trimmer-looking wings than SA Is, who typically have more raggedy trailing edges due to moulted feathers. Beaks are still dark but the eyes gradually lighten.

SA II in flight: belly light brown but giving a whitish impression (again, this characteristic can vary), trailing edges of wings clean and even.

By their fourth year (sub-adult III), most baldies start getting some white feathers on their heads, but with a vaguely osprey-like mask crossing the eyes. This bird is a classic SA III, and as you can see its tail feathers also show some white.

This photo is of a mixed-age group; the bird in the foreground (with neck extended, looking like the Seattle Seahawks logo) and the bird following behind it are both SA IIIs. At the far right, and almost hidden behind the two younger birds at the left, are two sub-adult IVs. In their fifth year, these birds have yellow eyes, yellow bills, and almost adult plumage—recognisable even to non-birders as bald eagles—but their heads retain a few dark feathers, mostly behind the eyes, and though it's not visible here, their white tails probably have a few dark smudges. As if to balance things out, they retain just a few white feathers amidst their otherwise dark brown body plumage.

These two eagles (I love this shot) are adult birds—but the faint smudges on their white heads and tails mark them as young adults, probably in their sixth year. While some adults attain their definitive plumage at this age, others may not be picture-perfect until they are seven or eight years old.

Now this bird has arrived.

Okay, quiz time. Can you identify these eagles? My answer will be in the comments section below.

Thanks to my wife, travel partner, and photographer, Jessica Farrell-Churchill. You were right, Jessa, it was worth driving back around.

Saturday, January 22, 2022

Duck: It's what's for dinner

Along Interstate 80 in the central Platte River Valley of Nebraska are numerous ponds that originated as borrow pits during the highway's construction. Jessa and I stopped to take pictures at one such near the town of Hershey last weekend. Most of the pit ponds were frozen over, but this one had been kept partially open by bird activity. At one end of the pond were the engineers of the opening, a flock of mallards with a few gadwall, widgeon, and cackling geese (mini-Canadas) mixed in.

And in the other corner...

Actually, the pond was nigh infested (from the ducks' point of view) with bald eagles of all ages; there was a fair bit of coming and going that made an exact count problematic, but we estimated a total of fifteen eagles present at any given moment: on the ice, in the air, or perched in the trees that ringed the pond.

Most of the activity centered on the ice near the eastern extent of the open water, where a duck carcass was squabbled over and changed hands several times. 

We didn't see the kill—it had happened well before our arrival—but I'm pretty sure I can describe how it happened. Any time one of the eagles gathered on the ice took off, flying low over the pond to take a perch in the cottonwoods—or anytime the reverse happened, with an eagle gliding down to take part in the melée—pandemonium ensued amongst the ducks. Not all of the ducks—most of the flock remained alert but calm—but those in the immediate vicinity of the low-flying eagle scrambled all over each other trying to get out of the way, lest the raptor reach down with a taloned foot and snatch one of their number into another plane of existence. But in my mind's eye, that's not how it went down.

While the eagles on the pond casually, perhaps even innocently, kept the ducks wary of daylight kidnap/murder, another eagle making a long, flat stoop from a half-mile away was suddenly in their midst, with a mallard dead on the ice almost before its compatriots realised they were under attack. My guess is that this happens a couple of times a day, and how are the ducks to plan a defense?

But perhaps they get plucked from the pond by casual, low-flying eagles as well.

In truth, none of the eagles, even the young birds, seemed desperately hungry, and at times the carcass was in no one's actual possession—further evidence that the pond was in a state of equilibrium: the eagles (the adult eagles, at any rate) catching ducks basically at will, and the ducks numerous enough to sustain these losses without feeling pressured enough to depart.

Eventually, one of the young eagles carried what was left of the duck to a tree, prompting more brief squabbling but soon thereafter putting an end to the eagle show, or at least bringing it to an intermission.

We had a concert ahead of us and many miles left to go, so Jessa and I reluctantly left the pond...but the eagles seemed to have things well under control.

Friday, January 21, 2022

Another day afield

A few photos by Jessa while out hawking on a very pleasant January day:

Hawk and moon.

Cottonwoods are the dominant tree in this riparian forest, but I love the sycamores.

End of the hunt: down on a rabbit; standing by; up to the fist.

As we got back to the car, this passage female redtail landed nearby. Stekoa calmly finished his meal on the fist and then leapt eagerly into his box as usual, our visitor watching the proceedings with interest. Jessa started calling her "Stekoa's girlfriend", but I don't think so: Stekoa and I were back here for a morning hunt a few days later, and I had to call the whole thing off because Stekoa was too intent on chasing a passager off his field—this same bird, I suspect—to get down to the business of hunting.

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