Tuesday, March 01, 2005

BLAKEMAN ON URBAN HUNTING STYLES


Photo by KELLIE QUINONES
Pale Male With pigeon in Ramble
2/27/05

BLAKEMAN ON URBAN HUNTING STYLES

Jeanine Chanes is a lawyer in the downtown Manhattan area. About a week ago she sent me a note about her redtail observations from her office near Battery Park. a [For non-New Yorkers, that's right next door to where the World Trade Center stood before 9/11] She also sent a note to John Blakeman, who responded with the letter below.


Jeannine,

I appreciate your astute observations of the downtown red-tail. It’s not just 927 Fifth Avenue, nor even just Central Park any more. RTs are popping up in a number of very core urban sites in NYC. As you've noted, the bird you saw was perching on buildings. That is completely expected for peregrine falcons, as they are natural cliff nesters. But red-tails nest on cliffs only in the West, where trees are not so available.

The new behaviors being seen by astute urban hawk watchers like yourself are dramatically adding to our knowledge of the diverse capabilities of this otherwise common species. We raptor experts thought we knew just about everything red-tails do in the wild.And I think we were correct on that. But Manhattan is quintessentially the least wild of all urban cores, the very last place any of us would have envisioned new breeding populations of the red-tailed hawk.

Now, for your observations:

The bird you saw was an immature, as you noted. Therefore, it’s almost surely not going to attempt a nest this year. There are a few, scattered cases of immatures building nests, [NOTE FROM MARIE: PALE MALE WAS SUCH A ONE, A BROWNTAIL IN 1991!] and a very few where a mate (always an adult) has been attracted to the territory [ MARIE: THAT WAS FIRST LOVE, BACK IN 1991.] I even recall a aberrant case or two where an immature was thought to be an actual parent. [ NO, PALE MALE and FIRST LOVE FAILED THAT FIRST YEAR] There are enough of these to be “case law” in raptor biology, but they are rare and almost surely not applicable to the Manhattan jurisdiction of raptor biology. In short, don't expect your bird to attempt any nesting this year. Next season, things could get quite interesting, however. See if you come across a molting red-tail in your area this summer.

As with red-tails everywhere, everything balances on the fulcrum of prey availability. Your red-tail isn't residing in lower Manhattan because of the nice views and perches on the buildings there. She’s there because she can hunt and eat with moderate ease. Like the CP red-tails, your bird has discovered a food resource that other red-tails don't know about. There are surely a multitude of red-tails in the greater NYC area in the landfills, air port edges, and other open sites with both perching sites and green swards filled with mice and voles. But the Manhattan red-tails have learned to successfully exploit new food sources, and at least in Central Park, those surely aren't the common meadow vole, the sustenance of virtually all rural red-tails.

What are the New York City red-tails eating? I still want to know. It’s not mice or voles, and it surely is a lot of pigeons, rats, and squirrels – but in what proportion? A red-tail can easily capture any rat that, against it’s instinctive nature, ventures forth into an open sky area in the daylight. I'm sure that a few do this, to their own peril. But I really want to learn how the red-tails are capturing pigeons. They have clearly learned of some new, unexploited vulnerability of this species in the urban environment.

The pigeons themselves haven't even learned much about the risks of red-tails. If a peregrine falcon flies over a pigeon feeding ground, the birds will all dart beneath a bush, or take off vertically and quickly attempt to get above the falcon before she can make a plunging stoop. Pigeons are never oblivious to the presence of a falcon. But they apparently are to the red-tails. When Pale Male soars over a portion of Central Park where pigeons are feeding, do they instantly duck under benches or bushes, or take off in opposite directions? I think not. Pigeons (rock doves) have no native fear of large, buteonine raptors such as our red-tails, as they can easily out fly them. Somehow, Big Apple red-tails have learned to capture rock doves at just some vulnerable instant. I'm guessing that they learned to swoop in low on a flock of feeding pigeons and strike the slowest bird as it raises into the air. For the first three or four feet of ascent, the pigeon isn't any faster than our big red-tail.

What we really have is a brand new bit of ecology. The rock dove is a native of the Old World, where peregrine and dessert falcons have been preying upon the species for millennia. Any ancient rock dove that didn't take evasive measures when the distinctive silhouette of a large falcon appeared overhead, it had markedly reduced chances of ever passing on its genes for inattention to such lethal matters It got captured and eaten. Today, there’s not a pigeon alive, whether wild or domestic, that doesn't instantly and instinctively respond to the sight of a falcon.

Not so with the sighting of a red-tailed hawk. To the pigeon eating the bread crumbs some lady just scattered in Central Park, a red-tailed hawk drifting overhead looks to be no different from any other large bird utterly incapable of pursuing and overtaking it. Pigeons are fast, and they know it. They know that they can simply disregard our large hawks – until recently, anyway. Our clever hunters have learned some new way of catching the rock doves off guard, exploiting an unknown vulnerability. What specifically that is, I'd like to know.

I've yet to see a single posting describing the specific details of a red-tail capturing either a pigeon or a rat. The entirety of the New York City red-tailed hawk story rests upon these events. Any one, please help. How do NYC red-tails capture their food? It surely isn't anything like watching my rural birds drop 65 ft off a field-edge oak to capture a gerbil-sized vole in the grass below? [ NOTE FROM MARIE: JOHN, I'M GATHERNG SOME OBSERVATIONS ON THIS FOR YOU. WE'VE SEEN THESE CAPTURES MANY, MANY TIMES.]

The successes of the Central Park red-tails are now manifold. What you are seeing in the Battery Park are is almost surely more of the same phenomenon, albeit at an earlier stage. There are rats, pigeons, and squirrels there, too.

And dare I raise the now-apparent question of the local ancestry of the Downtown red-tail you've been watching? Could it be the progeny of Pale Male? Sure could. Perhaps it’s even likely, as the bird could have learned the new pigeon-hunting techniques from its Central Park parents last summer. Now, it may be staying out of mom and pop’s hair (well, territory) and taking up residence in a new, previously-unexploited habitat using hunting techniques Pale Male and Lola demonstrated to it.

Smart birds, these, when it comes to finding and capturing food. Again, let’s not forget that they are predatory hunters and killers. They hunt and kill to survive, once again in a new NYC habitat.

Thank you so much for your cogent observations. As with some others, they've caused us to “think outside the Park.”

Sincerely,

John A. Blakeman