Sunday, July 3, 2011

How the eyasses learn to hunt

This week, Kay Meng who is in her third season of photographing the Franklin Institute hawks, returned from vacation.  She met up with Carolyn Sutton and me early Friday morning, and took these great pictures of a splendid morning of hawkstalking all four hawks.
We found the haggards sitting side by side on the end of the Family Court Building.

Mom had her 1000 yard stare going....

... while Dad was busy watching Kay take his picture.

We followed the two eyasses around the neighborhood as they chased small birds and perched on various buildings and wires.

They are becoming extremely skillful fliers, landing smoothly and balancing effortlessly on the most precarious perches.

When one of them spots potential prey, it goes on full alert....

 ... and then takes off in swift pursuit of some small birds.

We have yet to see them actually catch anything, and their enthusiastic chases usually peter out with perching in a new spot - in this case, a classroom window at nearby Hallahan High School!

Hawkstalking often takes one to hidden corners of the city.  Here is a little gem of a colonial street - Carlton Street - tucked behind the office buildings in Center City. 

There is a Frick & Frack tendency with the eyasses as Carolyn Sutton documented on Saturday morning.  They find the Barnes construction site simply irresistible, and have little respect for rules...

... as they dig in its dirt piles....

 ... and dive in the dumpsters!

Finally, one of our intrepid hunters was rewarded with a long-horn beetle...."Hey, ya gotta start small and work up..."

Several hawkaholics have been wondering whether the Red-tail parents teach their fledged eyasses to hunt, so I asked John Blakeman to weigh in with his thoughts:
"Yes -- and no.

Yes, in the sense that they provide food in the weeks after fledging while the offspring are as yet incapable of hunting and killing . Without this food, the young hawks would starve in a week or so.

And this food is provided in such a way that it encourages hunting. The easiest, and least effective provision of offered dead prey by the parents is to simply drop it right at the feet of a sitting immature hawk, whereupon the young bird drops upon the dead prey and has a nourishing meal -- without effort or lesson.

Inexperienced parents often do this for more lengthy periods at the start of the learning season, in June, after fledging. But with experience (or age) the haggards (adults) soon start dropping or placing food at some distance from the immatures, who then have to get up off their perches and wing their ways to the more distant food. 

The immatures learn from this that they have to fly around to find food. Eventually the parents either drop the food a some great distance, expanding the occupied geography of the young birds, or they stop feeding altogether. 

That provokes hunger, an essential experience. Without hunger, the young birds just sit around existentially, doing little. Hunger, induced by reduced parental food provision, turns on instinctive hunting and killing behaviors -- which are yet undeveloped. This is what causes the immatures to drop to the ground and start "attacking" sticks, leaves, and other uselessly inanimate objects, just as human children learn from playing with toys.

Then, by instinct, not cogent thought, the parents will start dropping only injured prey in front of the immatures. With this, they get to experience the exalting emotion of actually killing a live animal. It squirms, squeals, twitches, and finally sits dead in the young hawks' talons, whereupon it is consumed. Nothing is more enjoyable than this for a hawk.

After a few of these episodes, the young hawks start looking for prey to capture and kill on their own. This can take weeks to learn, while the parents are still providing prey when needed.

But by mid to late summer, the fledged hawks will have learned to search for and pounce upon and kill and eat prey. Did this all happen because parents "taught" them to do so? Or did the fledged eyasses learn this by watching the parents hunt and kill? I think neither. Clearly, the young hawks are not able to watch the parents capture many prey. That happens quickly, and often remotely from the eyasses.

And the parents didn't teach any hunting or killing skills. Those evolve naturally from the developing instincts and hunger motivations of the young hawks. Parents merely provide back-up food when the immatures have failed to capture their own. Eventually, they perfect their own prey-searching instincts and experiences, resulting in honed and reliable food-gathering capabilities.

When this happens, the parents retreat, leaving their offspring on their own in August. Shortening days turn on strong migration urges in September, and the year's young are soon on their way southward in migration, now fully capable of spotting and killing field mice, voles, and other sustenance prey."

-- John Blakeman


  1. Another excellent lesson in Red Tail life. Endlessly
    interesting. (though a tad yucky to read while having
    MY breakfast. Though so compelling I kept on reading).

    You are all marvelous to share all this. Many thanks.

  2. Terrific report, Della and John B! Welcome back, Kay, great pictures. Love that one of the killer stare and upraised talon. John A and I just returned from the same kind of scene 6-8 AM (Sunday July 3) on the Parkway. We were the only hawkwatchers there, with one small pocket camera, so the images aren't great, but I'll send some in anyway, with an account. We were seriously divebombed twice!

  3. Thank you for the clarity of your description of the learning process, call it "Feeding Myself 101." The haggard are not consciously teaching, but without them the immatures would have a difficult time learning. I can see a NOVA segment here.

  4. I want to thank John Blakeman for the information on hunting and feeding. I have been watching the FI hawks in conjunction with a nest that is directly across the street from where I live in the Philly suburbs. While in the early months I was unable to see what was going on inside my "home" nest as it sits about 50-60ft above in a pine tree, I could track the development of "Alpha" and "Beta" by watching the growth of the FI eyasses. My "home" eyasses were about a week or so behind the FI hawks but the parents were not newbies. According to neighbors, this same pair has been nesting here for at least 5 years and possibly longer. Mom is a magnificent lady with an estimated wing span of 5 ft (she is gloriously huge!) and Dad's spectacular markings make him a very handsome mate for her. Now the youngsters have fledged but are staying within a small radius of the "nest" tree. Thanks to Mr. Blakeman's comments on the hunting/feeding habits, I now understand what I am seeing the haggards doing with food for the fledglings. I actually saw Alpha bring home a small kill and share it with his sister. I can only assume that Alpha is a male and Beta a female but all I have to judge from is their size (Beta being significantly larger than Alpha). Thanks to the FI and my own "home" nest, I am officially a hawkaholic!