Wednesday, August 10, 2005

Rats, why fledglings fly low, and other subjects: Q&A

Another question and answer exchange with John Blakeman:

Q. from Mai Stewart

Dear John,
I've been reading with interest your correspondence w/ Marie re rats and redtails -- I don't think our RTs will ever lack prey. The greater danger, it seems, is of a hawk eating a poisoned rat, but hopefully, thanks to Marie and others, the rat-baiting, at least in specific areas, will be discontinued (or at least paused). And it will also be interesting to see if the fledglings will begin catching pigeons (or trying to).
I've noticed on the website a couple references to the eyasses doing "a lot of low flying" among the trees, but not going about the treeline. I wondered about this, esp. since from birth, they've had experience high above the treeline. And these particular fledglings seem to have an affinity for the grass! (And twigs!) (Well, maybe something they recognize from their nesting days.)
I was wondering whether this is normal, and whether after awhile the young hawks will become more adventurous and begin to fly higher and higher, eventually soaring in the sky, the way we've seen PM, PMJ and their mates do. Is this a kind of learning curve, as hunting is? Or a matter of "growing up," of maturing? Will they do it on their own, or will their parents "teach" them? Or at this moment are they so intent on being fed, and they know the food arrives down about where they are, that they don't want to go too far away from it?
Thank you,
Mai Stewart

A: from John Blakeman

Most rats that die from poisoning end up dead in a "rat hole," back under cover where no red-tail can discover the dead carcass. I'm not overly concerned about this, although rat poisoning in environments like Central Park has little real effect. When one local rat population is wiped out by some poison, it merely opens things for adjacent populations from down the street. Unless the entire park and all adjacent buidlings can be simultaneously poisoned, the rats will persist. I'd much prefer that poisoning not occur, but I think it's a minor threat.

About the hawks' low perches, you nailed it exactly in the last sentence. Once again, food is everything to a red-tail, much more than having a good perch to sit on, more than having a good view of the landscape, or even of being able to fly high in the sky. The bird's entire existence depends on procuring fresh flesh to eat each day, and from experience the birds know that's not always easy.
Consequently, they go to where food is, and for first-summer Central Park red-tails, it's not up in the sky, nor even high in trees. It's primarily running around on the ground. The young hawks have learned that if they want to capture a wholesome (to them) rat, they better be perched low in a tree to be able quickly pounce on an exposed rat. By the time a young red-tail drops down from a hunting perch high on a building or tree, a rat is likely to escape back into cover.
Out here in rural northern Ohio, I see this from time to time even with experienced adult red-tails. A few weeks ago, I discovered an Ohio Pale Male sitting on an isolated fence post along a major highway. This red-tail was sitting just four feet above the ground. But it knew that the vole family in the grass below couldn't be preyed upon from any height. From the low perch, the hawk could grab a running vole before it got back into its hidden runway. So even adults will sometimes hunt from very low perches.
For the Trump Parc youngsters, they will continue to stay low in their hunting. But as they continue to gain experience, they will attempt to pursue other, more difficult prey such as pigeons. Eventually, they will take high tree and building perches, after they've learned to consistently take prey each day. But for now, they've got to play the hunting game only as they know it, and it's close the ground, where the rats are.
Many have surely noticed that the young birds incongruously pounce onto sticks and leaves, "killing" them. The hawks will even just grab a clump of turf, prompted perhaps by grass's similarity to the fur of prey animals. Don't confuse any of this with the playful activities of young children. This is not play in any human sense. The birds simply aren't able to much distinguish authentic prey (live small animals) from objects sitting on the ground. The instinctive behaviors to pounce and kill are profound, and after a period of seeing no moving prey, the young birds will be compelled to "kill" something. They drop onto a stick and squeeze it to "death." From our intellectual perspective, this seems to be either play, or misdirected and ineffective hunting. From the hawks' perspective, it is perfectly normal and effective. They birds are continuing to hone timing and muscle/nerve reflexes used in their daily killing. It's not play. It's serious perfection of motor neuron reflexes and hunting techniques. Don't discount or misrepresent it.
But in time, the birds will have to start getting up in the air. As days begins to shorten,
the reduced period of light prompts instinctive motivations to start migration. Hawks don't migrate down Park Avenue. They will instinctively soar several thousand feet into the sky, where they can then start to drift southward, well above everything below, even New York City. When Big and Little are seen soaring above the tops of nearby buildings, they may be learning to feel the air up there, preparing to drift off to the south for winter.
That, of course is normal for typical rural red-tails. But the Central Park red-tails have violated normal red-tail behaviors time and again. After first learning of this wonderful population last December, I won't be surprised at all if the two immatures decide to stay in Central Park for the winter. It's another six to eight weeks before the migration begins, before the birds would likely depart. If food gets short, they could fly off to some marsh or wild area in New Jersey in a day. I'm not trying to be alarmist in any way. But immature red-tails are almost always driven from their summer haunts by either a) their parents, b) by unmitigated hunger from a lack of local prey, c) by instinctive migration behaviors, or d) by a combination of these. Don't be surprised (or alarmed) if the Trump Parc immatures just "disappear" in the next few weeks.

John A. Blakeman