Friday, August 05, 2005

How do they learn to hunt? Q&A

Mai Stewart asks John Blakeman:
Do the parents teach the fledglings how to hunt? I can see that they've been very diligent in their daily feeding of their offspring, but, as you've mentioned, this will cease after awhile. So I was wondering whether the parents give the kids any lessons -- it's clear they do communicate -- and, if not, how do the offspring learn how to hunt for themselves? It's been amusing to read about the fledglings chasing pigeons, but unless they learn how to actually capture one, they'll get pretty hungry --
Also, I've noticed a number of references to the RTs, particularly the fledglings, being harassed by robins, bluejays, etc. -- there was even a picture of PM being yelled at by a mockingbird -- mocked by a mockingbird, seemed too ironic -- I just wondered whether the RTs ever realize that they're BIGGER than these other birds, and could chase THEM away, if they wished -- seems to me it'd be no contest!

Blakeman replies:
How do the adults teach the young to hunt? It's almost by accident. At first, the adults merely drop dead food (or rendered pieces) essentially at the feet of the fledglings. The young birds first have to learn to "foot" the food, to successfully grab and grip the food in their feet. That doesn't happen so instinctively. Just watch an 18-month old child try to eat. You'll then understand how important it is for the young hawks to learn how to manipulate their feet.
Next, the adults will begin to drop prey that aren't completely slain -- just disabled. This may be just about to happen with the Trump Parc fledglings. With flinching prey, the youngsters have to learn how to grip and dispatch the prey.
Then, essentially live food is dropped at ever greater distances from the young. They have to learn to chase the fleeing prey. Finally, the parents will offer unhindered prey, much of which just escapes. The key here is that the parents will markedly reduce their food offerings, allowing the young hawks to get hungry.
Falconers for millennia have known that hawks (except when feeding offspring) never hunt or kill unless they are motivated by hunger. Falconers never overfeed (nor underfeed) their charges, as the hawks or falcons would then just sit on the fist or perch without hunting. The adult red-tails use exactly the same technique with their offspring. Although the fledglings will sit for hours in a tree crying out with their morbid begging calls, the parents will not be dissuaded from withholding food. At best, Jr. or Charlotte will fly near the weeping young, dangling a food item in the parent's talons. This will entice the young to begin to chase the food-carrying adult.
The adult can use this technique to lure the youngster to an area that has available prey. When in a good hunting area, the parent may drop the prey animal, enticing the pursuing offspring to dive to the ground after the dropped animal.
Sooner of later, the hungry young hawk learns that it had better take a hunting perch and start to look around for something to kill. Finally, the adult hawks stop providing any food whatsoever, usually some time in August. The young are now on their own. No food will be provided. It's now hunt and kill, or starve and die.
. . .

In summary, after the adults stop providing food in August, the young hawks learn simply by trial and error. They attack time and again, and begin to remember what worked and what didn't.

* * *
About songbird harassing of the young hawks. This was one of the most interesting things I noticed with one my first research red-tails, an immature female. When I parked her out tethered in my backyard on a perch, she was mobbed with blue jays, robins, starlings, and other incensed songbirds. The hawk just sat there and ducked.
But when I parked my trained adult red-tail in the same place, it never got a single bird flying at it. Falconers have noted this. Finally, an ornithologist observed this (elsewhere) and noted that only hungry immatures are mobbed. In a very descriptive paper, the ornithologist noted that the songbirds are able to detect the hunger and hunting state of the hawk by its perched posture. An adult sits in a posture that seldom attracts mobbing songbirds. Immatures, especially when hungry (which is most of the time in their first summer), sit rather erect. This posture is instinctively recognized by the songbirds, and they mob the hawk, trying to drive it away from their nearby offspring.
I noted that the mobbing birds disappeared after I fed my young red-tail a full crop of food. After her meal, she propped up a foot and assumed a more adult posture.
One of the reasons that the songbirds seldom mob adults is that in the air, an adult can turn over and snatch a bird that gets too close.

John A. Blakeman