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, www.fotoportmann.com

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--

Donna,

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?

AND NOW--CAT BEHAVIORAL TACTICS


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.


Hmmm.

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.

Sigh.

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

2 comments:

Roe said...

One thing to consider is that a diet of primarily pigeon would not be a sufficient source of calcium for a raptor that I was housing.

If the hawk is catching mice or rats on at least a weekly basis then it should be ok but if it is only sticking with pigeons that could lead to a calcium deficiency and then the beak may weaken and make it easier to break up higher in the new weaker growth part of the beak.

This is all just hypothesis on my part, it's a sad and interesting case.

Donegal Browne said...

Roe,

Great point. Thanks for throwing that into the mix. I'm going to put your comment on today's post to make sure everyone sees it.

Do you know if there is a chart or other info that would quote how much calcium your average squirrel, pigeon, or rat might bring to a predator's diet? I haven't found one yet, but I'll keep looking.