Thursday, March 03, 2005

A HAWKWATCHER PROVIDES DATA and JOHN BLAKEMAN RESPONDS

Hello John,

As per your past request I'd been keeping a prey tally
for Central Park Redtails. Currently the sample is still very small,
covering only some days within the last two months, it breaks down to roughly:
65% pigeon, 20% Squirrel, 10% rat, 5% unidentified.


Pale Male's pigeon hunting technique that I have most
often observed consists of nabbing pigeons out of
trees. Though there are many Hawkwatchers who have
observed the hawks for far longer than I and in all
seasons, who will have observed many other strategies
I'm sure.
. . .
As this is Central Park there is a good bit of
wildlife feeding, some of which goes on in the
environs of the Hawk Bench. I think that the feeding,
the birds vying with each other for that moments food,
may be a distraction that makes the pigeons more
vulnerable to attack. One of the ways we know that a
raptor is about to be sighted in our area, usually
from the west, is that the pigeons take off in a
flash, banking and wheeling over the model boat pond
sometimes just making the circuit a few times and
sometimes completely disappearing east of Fifth
Avenue. The smaller birds take to the bushes in the
area behind the bench for cover. (We also have a
Cooper's that sits in the area about five feet from
the ground in a small tree trolling for snacks.)

Pale Male will fly through the branches of trees, lots
of space between branches in some of the park trees,
particularly the London Planes, and seize pigeons that
have remained in the branches, I assume thinking
themselves hidden or hungry enough to chance it in
order to be closer, and therefore, get more of the
people supplied food sitting on the ground, before the
competition gets back.

And, on at least one occasion, I saw Pale Male glide
into the London Plane above the bench and seize a
pigeon before any of the other birds had seen him.
Needless to say the rest left in a hurry. John has a
great sequence of photographs that show Pale Male
grabbing a pigeon out of the top of a conifer.

Lincoln Karim who has watched Pale Male and his
progeny closely has observed Pale Male displaying
pigeon hunting technique to his fledged young in the
area where the Central Park carriage horses wait to be
hired. Not only is it a high tourist area where pigeon
snacks are often obtained but more importantly pigeons
congregate in the area to cadge the highly prized oats
meant for the horses.

Once again there is a food competition distraction for
the pigeons.

Early this year I saw a Red-tail come in low and grab
a pigeon that was standing on the curb with his head
leaning down in the gutter to get spilled oats from a
carriage that had just exited the spot.

As you have pointed out, Red-tails have many learned
hunting strategies to remember and I would say these
are examples as recently I've observed a Red-tail
repeatedly hunting pigeons on the wing to no avail.


The hiding youngsters brought to my mind that I've not
seen one juvenile pigeon in the park in three months.
In my Westside neighborhood, at 43rd and 9th, I always
see at least some newly fledged pigeons in the winter.
Pigeons being year round breeders, though of course
more prolific in warmer seasons due to weather, plus
more people are outside eating raising the pigeon food
options.
. . .

Sincerely,
Donna Browne

John Blakeman answers:

Donna,

WOW! This is the info I was searching for -- and not
all of it was expected.

I'll have to go back and carefully re-read your two
emails. The information is astounding. Here are a few thoughts off the top of my head, in no particular order.

The fact that Pale Male (and surely others) have
frequently plucked pigeons sitting in trees is a really new and astounding observation. I would have
never thought this possible, because it's difficult
for the big red-tail to maneuver among tree limbs, and because I would have presumed the pigeons would
have simply flown away at the sight of the hawk.
Apparently the pigeons erroneously believe that they are safe in the tree limbs. That's true for a pursuing falcon, which will never enter woody vegetation in a hunt.

It's becoming clear, as I mentioned in yesterday's
posting, that the pigeons of New Your City haven't experienced red-tail predation and don't have any
innate, instinctive cautions about the hawks, which
they do for the peregrine.

And I appreciate your observation about the
vulnerability of juvenal pigeons. That seems very reasonable to me. Young birds with little experience and
reduced flight powers could be vulnerable in a
number of settings. Our discerning red-tails, as they carefully peruse the local prey from a hunting perch,
must be able to determine which of those pigeons
down there aren't paying attention, or don't move very quickly.

I have no questions regarding the hunting of
squirrels. A squirrel on the ground is highly vulnerable to a plunging stoop by a red-tail. No questions there. The moderate hunting of squirrels is expected. RTs don't particularly savor squirrels, as they have extremely dense hides and can be hard to dispatch. They can also offer severe bites. Wild red-tails will take squirrels, but
only infrequently and judiciously.

From your observations, it appears (as I initially
presumed) that the pigeon is the primary prey species for NYC red-tails. Your information on how this
resource is accessed is crucial. Keep me posted.

Thanks much.
Sincerely,

John A. Blakeman

Wednesday, March 02, 2005

BLAKEMAN ON PIGEON HUNTING etc.

I forwarded JB the following letter from Kellie Quinones:

Hi Marie,

This is what I saw:

Pale Male was perching on a balcony two buildings away from his nest
site when Jay and I saw him swooping down towards the nw side of the
pond. He dropped his legs as he got closer to the ground,
but unfortunately, because he flew so low and there were so many people
around, we were unable to see him grab the pigeon. We went to the area
where we last saw him drop and found him perched with a pigeon in his
talons on a tree that was only about 8 - 10 feet above the ground.

After about 5 minutes he flew to one tree and then another, where he
proceeded to pull out the pigeon's feathers. Pale Male took a couple of
gulps of meat and started calling. He then flew way up overhead and
started circling over the boat pond with the pigeon in his talons.

I hope this helps.

Kellie Q.

Here is John Blakeman's response:

This description of Pale Male nailing a pigeon, at least in this one case, appears to be exactly what I envisioned. The fact that the bird folded its wings and dropped close to the ground is just the strategy I'd use to get a NYC pigeon as it fed on the ground, were I a red-tailed hawk.

As I pointed out before, pigeons are very fast fliers and can completely out fly any big red-tail in open sky. But while the pigeon is on the ground, it's completely vulnerable. When it sees an approaching hawk it will instantly jump into the sky and accelerate. In just 5 - 8 ft it will be nearly at full speed and pulling away from a pursuing red-tail.

But the pigeon's escape depends upon its ability to first see the approaching hawk. I think Pale Male and all of his urban cohorts have slyly learned to shoot at good speed low across the landscape, swinging around bushes, benches, and other visually obscuring landscape features in such a way that the target pigeons aren't able to discern the approaching killer hawk.

You know that I somewhat castigated the native intelligence of the red-tail. A crow or raven they are not. But I also pointed out that their intelligence in hunting was supreme. This account was an indication of this. The hapless pigeon was grabbed at 45 mph before it could get three feet into the air, perhaps while it was still on the ground looking for some last proffered grain morsel -- its very last.

The role of humans feeding pigeons may be crucial to the entire phenomenon. If the pigeons weren't lured to the ground by such food, they would probably never be at risk.

This was a single hunting incident. I want to learn the details of many others. Do our hawks use this single hunting technique, what I'll call here the ground-skimming ambush, or are there others?

This is now starting to make some sense to me. (But how do they capture rats?)

By the way, lest anyone begin to question any sense of morbid thought here, what we are observing and reacting to is a very normal, albeit sometimes gruesome, natural activity of these avian predators. I want to assure everyone that I personally, and raptor biologists and falconers in general, take absolutely no pleasure in observing the death of even so much as a pigeon or rat. Is the pursuing flight thrilling and exciting? It surely is. Is the death of the captured prey exciting in any way? Surely not. The greatest hope of all is that each prey animal might die as quickly and painlessly as possible. None of us delights in the death of any animal, predator or prey. But to deny the essential presence of this primal natural event is to deny the natural reality we are observing. For the hawk, the capturing of a pigeon means another meal. It means that life continues. For the plundered pigeon, its life has been sacrificed to that of the hawk. It's raw nature of the most elemental kind. Consider it all thoughtfully and seriously.

Sincerely,

John A. Blakeman

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