Saturday, December 13, 2008


2006- Cathedral Nest Fledgling looks coy; good beak view too.

First a mini-recap, yesterday Roe, who is a falconer, suggested that perhaps urban hawk beaks might be more fragile than their rural counterparts due to a lack of calcium in a diet weighted toward pigeons.

2006-The same hawk if a slightly different view of her beak.

I forwarded Roe's comment onto John Blakeman for his take and here it is.


Doubtless, dietary calcium is crucial for raptor health. Captive-bred eyasses, as with wild-bred young hawks, can easily have soft bones and deformed bones when raised on a diet of pure, bone-deficient flesh, whether that of pigeons or any other animal. Hawks, both in the eyass (baby) and adult stages of life need ample calcium.

But NYC Red-tailed Hawks are not calcium deficient by eating pigeons. First, there is a moderate amount of bioavailable calcium in the blood and flesh of such prey. More significantly, the hawk will ingest a good number of small pigeon bones, including ribs and other bones of the torso. The head is often cleanly plucked off and eaten in a single gulp, thereby ingesting all of the cranial bones.

Lastly, there is little calcium in the hawk's beak. It is not bony. It is composed of keratin, the same material as the bird's talons. It is horny protein, not a calcium salt; very much like our fingernails, but harder and denser.

Like our fingernails, the beak continues to grow out and downward. It naturally wears down, or is even deliberately worn down by the bird. The beaks of hawks in captivity often over-grow, with the hook or vertical portion growing too long. This never happens in wild raptors, but is common with those in captivity, whether in a falconer's mews, a rehabilitator's cage, or in a zoo, for the following reasons.

Those who closely watch Red-tailed Hawks feed in the wild will almost always observe that immediately after consuming a meal, the birds leans over and quickly strokes their beaks back and forth on their perch. This curious behavior, in falconry parlance called "feaking," does two things. It helps wipe off blood and flesh from the beak after the sometimes gory meal. It also microscopically helps shape the beak. In captivity, where birds often don't sit on hard woody surfaces, feaking takes place on soft perches. With these, insufficient microscopic keratin layers are feaked off, and after a few months, the bill get too long and thick.

There is a third factor in keeping the bill properly shaped, at the right length. Same for the talons.

For a long time falconers wondered why their birds, even when they feaked on hard, rough surfaces such as rock, still tended to get beaks too long. They also noticed that talons tended to get too thick and dull. As part of the required falconry apprenticeship, new falconers have to learn how to "cope," trim, overgrown talons and beaks. It's not a difficult skill, but one that should be observed before attempting it on a captive hawk -- a mistake I made in college, where I clipped off a millimeter too much of a Red-tail's beak. It bled for a few minutes. Lesson learned (falconry was not legal or practiced in Ohio then, so I was unfortunately on my own on this, with my captive research hawks).

So, for centuries falconers have been coping the beaks and talons of their birds, with good effect. It's little different from the work farriers do in trimming and applying shoes to captive horses.

But in recent years, American falconers have noticed that Red-tails kept in open cages, properly called "weathering areas," where the birds get exposed to rain in the manner of free-flying hawks, tend to retain sharp talons and properly-sized beaks. It is now very clear that incidental wetting, from rains or baths, is a crucial factor in the maintenance of properly sharp talons and properly sized beaks. The rainwater loosens and softens the appropriate outer keratin layers of the beak and talons. These layers are laid down in such a manner that the hawk's exposure to rain, and it's postprandial feaking, perfectly shape these structures as microscopic layers are worn or sloughed off by these processes.

All of this is why I'm contending that the hawks that have lost their beak hooks will eventually have them grow back. But it could take many months, or a year or longer.

Actually, it would be scientifically useful for NYC hawkwatchers to monitor and record this. I don't know that anyone has any beak growth-rate data. Like so much else with NYC Red-tails, the recording of how long it takes for the truncated beak to grow back would be an interesting, and even helpful piece of information. If beak-damaged birds have been seen in NYC, raptor rehabilitators are likely to receive similar birds. How long should they be kept before the bill is long enough to be returned to the wild? I don't know. Let's see.

--John Blakeman

Thanks John, we have a reasonably good chance of monitoring the beak growth of the Riverside Formel with photographs and binoculars if she remains in her current territory. It sounds like a terrific project.

I'm quite taken with the fact that Red-tails need to be wetted periodically for their beaks and talons to be in top shape. Particularly when one realizes that no doubt many human partnered hawks were kept dry out of compassion and therefore had to be coped. Fascinating.


This is where I came in. Squirrel One is keeping Blossom the Snowbear's seed bowl from Squirrel Two. ???

Squirrel One drops the bowl and attempts to chase Two up the tree.

They circle the trunk several times.

Then it's up the tree with Two in an obscured crotch and One looking for him.

One is being wary as Two might come his way if he goes round to the other side.

Once making it to higher ground One scolds Two and then races down the tree again. It isn't as if the bowl has anything in it. Does it perhaps still smell of sunflower seeds? Whatever the case One is protecting as if it were the last nut on earth.

One contemplates the bowl.

He digs.

Oops, disarrayed belly fur.

One then tussles with the bowl. Grabbing it by the edge and walking a few steps.

It falls open side up and One digs in the snow with gusto.

More picking the bowl up by the rim and sliding it a few inches. It wobbles back and forth.

Mighty digging.

Squirrel One brings the bowl onto it's edge and slides it toward tree a few inches.

Herculean digging ensues.

Ah ha! One is attempting to put the bowl in the hole he's dug in the snow. It does not fit.

Perhaps laid this way?

NO! One takes rim in teeth, moves bowl a foot or so to the south.
Another bout of digging in the new spot.

Squirrel Two heads down the tree and Squirrel One intercepts him. Scolding.

The Mourning Doves pause pecking and watch the interaction.

Squirrel One having thwarted Squirrel Two, has the bowl in his teeth again, moving it slightly further south. Squirrel Three on the picnic table watches with a slightly baffled expression

One sits up, pauses, looks at the bowl, the ground, and then me.

One attempts digging directly beneath the bowl.

More tussling. Tries to press the too large bowl into the too small hole.

Not a good spot?

Body rigid, teeth on rim, he shoves the bowl hoping for a fit.

Begins digging beside and west of the bowl.

Then drags the bowl back toward the tree while running backwards. I don't know how often I've seen a squirrel running backwards dragging a red plastic bowl.

One begins intense frantic digging, slides in the snow, and vibrates physically. (Severe frustration?)

Attempts a body press, and still the bowl will not fit in a large walnut sized hole. Is it possible that squirrels are wired to dig nut sized holes and they haven't the mental acuity to figure out that a bigger object needs a bigger hole? Or is it just this particular frustrated individual squirrel who can't do it. Besides he's burying a BOWL, which is a bit strange in the first place. Put then squirrel Two seems to want the bowl as well. Or Squirrel Two might just want to come down the tree, or always makes it his business to give Squirrel One a hard time.

Squirrel One is on guard once again. There is Squirrel Two attempting to come down the tree, possibly to nab the bowl. Plus if you look carefully, you'll see the tail of yet another squirrel at the top of the frame.
Then I can wait no longer, I have to leave for an appointment.

Much later when I return, the squirrels are gone and the bowl, with a rather sizable hole and a gnawed bottom, is abandoned in the snow at the foot of the tree. Where it has stayed.
Donegal Browne

Friday, December 12, 2008

John Blakeman On the Brown-tail's Broken Beak, and Pye Tries to Get a Rise Out of a Squirrel

Photograph by Francois Portmann,

The question? If Midwestern John Blakeman, who has seen many, many, Red-tailed Hawks in his time, has never seen a broken beak on a Red-tail, might it be something about the urban environment that causes these injuries more often in the city than the country ?

I wrote John with the questions:

1. Do hawks ever crush bone in order to eat the marrow as my African Grey parrot does? If so could they damage their beaks doing it?

I'd never seen a hawk do that, but then again larger animals like rabbits aren't part of a Manhattan hawk's diet but there are some pretty hefty rats in town.

The only broken beak I've run across here in Wisconsin was that of a juvenile Bald Eagle who was suffering from lead poisoning. As she wasn't lucid she had flown smack into a sign. So I tried the following question. Cities do have a lot of very tall things to fly into after all.

2. Could a hawk break her beak by being blown into a building by a freak gust of wind?

3. How about misjudging in a swoop for prey on a sidewalk? (I just thought of this one tonight so no response from Mr. Blakeman on it yet.)

Here's what John had to say in response--


This is getting weird. (Well, it is NYC.)

Again, I've never, ever encountered a broken-off beak in any Red-tail, or other raptor, for that matter.

Can the bird break off the beak hook by tearing too hard, or at the wrong angle, of something it's trying to eat. No. First, it would hurt before it broke, causing the bird to stop pulling on the food. The beak, like a fingernail (same biomaterial) is slightly flexible, not as ceramically rigid as a tooth.

And no, hawks don't crack the thick bones of their prey. With the hook on their beaks they can pierce thin bones, such as those in the skulls of the animals they capture. But unlike dogs, they do not crush leg or am bones to get to the marrow. They use the hook to gouge into the flesh, allowing it to be physically torn away. Hawks tear their prey. They do not crush in any mammalian (or parrot) sense.

I think the loss of the hook by way of a collision is problematic, inasmuch as any impact strong enough to break off the beak tip could really give the bird a terminal concussion.

For this immature hawk, I think the most probable explanation is a bite by a squirrel. With this bird, there appears to be a slight nub remaining, right where a frantic squirrel in the piercing death grip of six sharp talons could have bitten the hawk.

--John Blakeman

For a juvenile hawk without much experience in dispatching tough skinned, very sharp toothed, and strong jawed squirrels immediately upon grabbing them, that could certainly explain the missing beak tip.

And from my experience, the country hawks I've seen hunting are going for prey in the small rodent category, like voles or mice. I believe urban hawks, particularly females, hunt squirrels far more frequently than their rural counterparts and as not every grab for prey is perfect even a mature hawk might be injured that way.

Though I still wonder about the collision theory, even though Mr. Blakeman is no doubt correct that a straight on smack of the beak could well cause concussion. The beak of the Eagle I mentioned, was so damaged from the impact that it was unrepairable to the point it would never grow back. I'll check to see if she had a concussion. Though Eagles do have a larger and more sturdy beak who's point might compare more to the broadsword category as opposed to the point defined rapier of of Red-tails. And to continue the metaphor would a Peregrine's beak be a tiny stiletto?


Pye has just made a mad run from one end of the house to the other coming to a sliding halt on the throw rug trying to get a reaction from the squirrel. The squirrel on the other hand doesn't even twitch. This is Stubby, by the way. Stubby the squirrel knows that Pye can't come through the glass and continues eating sunflower seeds like there is no tomorrow and Pye finds this really boring of him.


Any chance of getting a rise out of the other squirrel?

It turns out that Friend is up in the Maple tree watching the whole thing. He no doubt is waiting for Pye to find something else to do. The birds are much too wary to subject themselves to the mini-heart attacks a cat can cause a bird even if it is behind glass.

I'm beginning to believe that Stubby is tormenting Pye on purpose.

Here's Pye patting the glass and what does Stubby do? He looks at me taking the picture.
Doesn't Stubby look like he's even got his arms folded while he's doing it?

Pye stares.

Then a quick move to her side and pat, pat. Aha! At least Stubby quit chewing for a moment.

Pye jumps at the door. No good!

What's that?

Pye crams her nose into the teeny crack between the door and the wall.
No good. It won't open.
Pye meows.

Stubby stares.

Stubby postures and growls. Stubby is tough. He even takes on the Crows.

Could there be a hole under the rug?

Scratch. Scratch.

Pat, pat!

Tic, tic, screeeeek go the claws on the window.


Maybe, just a check underneath the rug here.

Stubby, having exhausted the sunflower seeds on the step, turns to head for richer foraging grounds. Pye's ears slowly begin to lie flat. She stays that way for a few seconds, then gets up and heads for the basement. There might be a mouse down there, you never know.
Donegal Browne