Monday, January 03, 2005

A CHALLENGE TO CENTRAL PARK HAWKWATCHERS

A CHALLENGE TO CENTRAL PARK HAWKWATCHERS
FROM JOHN BLAKEMAN: YOU TOO CAN BE FIELD SCIENTISTS!

I SENT JOHN BLAKEMAN THE LATEST OF LINCOLN'S PICTURES SHOWING THE NEST WITH A GROWING NUMBER OF TWIGS.[SEE BELOW] HE SENT THE FOLLOWING REPLY, FULL OF FASCINATING INFORMATION ABOUT REDTAIL NEST-BUILDING HABITS. HE ALSO INVITED CENTRAL PARK HAWKWATCHERS TO SEND IN SOME OF THEIR OBSERVATIONS. AN EXCITING CHALLENGE.


Marie,

Yes, I just checked out the new nest site image, with both birds on it, and I smiled again. These birds are doing just what most experienced, red-tailed pairs should be doing right now, on schedule. As you know, I've never much doubted the fidelity of this pair to this refurbished nest sub-structure, and now that extends to the emerging nest itself. All is well.

Let's watch and see what happens. The pair isn't going to waste any time or energy with any tentative alternate nests. That happens sometimes in the wild. This pair is now totally re-committed to 927 Fifth Ave.

But here's something to watch for. Nest construction is likely to proceed in one of two modes. Rural birds usually start selecting a nest site in earnest about now. That's what's happening with this pair. But many other pairs dawdle around with a meager pile of sticks for a week or so, then all of a sudden, in a day or two, they bring hundreds of sticks to the nest, causing it to pop up to full size rather instantly. I've been in the field on a late January day, discovered a new low nest like the 927 on one today, then came back a day or so later, and little more had transpired. Upon resumption of nest observations in February, still not much more.

But when I've skipped two days and come back, a full-sized nest is in place. Instant nest. Let's watch to see if Pale Male and Lola get into one of these "let's build the house in a day" modes. It's very likely they will.

Someone should be measuring (estimating) the height of the nest at the end of each day and creating a graph on this. If someone can email daily images, I can easily do this on my CAD program with an accuracy of an inch or less. If someone can measure a brick the same size as the one behind the bird, we can easily figure out the dimensions. From just looking at the bird itself, I can estimate dimensions. Such nest-building data would be really fine field observations. And if a day or so is missed, we can interpolate. I'd be glad to post the readings every four or five days.

The alternate, less exciting mode is the go-it-slow one, where the nest just gets put together at a leisurely, incremental pace. That can happen, also. Let's see which method the pair chooses (And they might do something I'm not familiar with, too. We can all learn.)

The other observation of the immature bird eating suet is plainly weird. If I offered a piece of suet to my red-tail, she'd give me that "How dumb do you think I am?" look, sneering in absolute repugnance. I can understand how the Park hawk might have taken its first bite of the suet. The suet was obviously placed in the Park for other birds, and as I always contend, red-tails sit around and see and contemplate everything. It saw a woodpecker on the suet, and noticed that it looked like the winter fat it consumes on the squirrels and rats it eats. So yes, it could have taken a single evaluative taste. But to pull up the entire chunk and go off and eat from it is unheard of. Red-tails just don't consume much fat. And they aren't particularly enamored of beef products, especially those with lots of fat. (Don't try to feed a red-tail ground beef or hamburger. Too much fat.)

Another Central Park red-tail mystery.

One last point. Apparently another RT pair had an active nest in CP last year. For authentic ecological understandings of red-tails in CP, I think it would equally valuable to monitor the activities of all other CP red-tails this year. I'm impressed that Pale Male and Lola allowed another pair to reside and nest in CP. How these two pairs interact will be very interesting. Are they communally hunting throughout CP (unlikely, as RTs are very territorial)? If not, which pairs are hunting where, and with what success? How have the two pairs partitioned the small hunting territories of CP? That's important, because if a second tree-nesting (or other) pair becomes as experienced and stable as the 927 pair, the new pair might begin to claim more territory, perhaps some that Pale Male and Lola now claim. That could reduce the availability of food to feed the offspring, which could, in turn, reduce the brood size to a more normal one or two.

As I mentioned in a previous note, this is rather equivalent to the noteworthy predator/prey relationships of the great cats on the savannas and grasslands of east Africa. You NYC people get a better chance of studying this than I do out here in rural Ohio. My RT territories are 2-4 sq mi. I've got to be traveling all over the countryside to see adjacent pair interactions, if any are to be seen at all. You fortunate folks need merely to rotate your spotting scopes, or to walk a block or so to another part of the park.

Look, the CP red-tails are no longer just a wonderful urban curiosity. They are legitimate wild denizens of a major human ecosystem, the Park. It's time their behaviors be documented and quantified. I no longer question the persistence of CP red-tails. They are with us for the present, and I think for the future, too.

Let's see how this year progresses. It's February. Let's see when the first copulation is noted. (And it's not "mating." They did that several years ago by forming the pair bond, the social relationship.) All of us, including hawks, are noting the increased day length. The testosterone and estrogen (well, mostly just the testosterone) are starting to ooze. Copulation will start soon. Somebody, keep track of copulation events by time of day and site. Do they have preferred times and locations for red-tail sex, or are these things just rather random? For red-tails, how is "Sex in the City?" I'm betting that the raptorial thing is every bit as engaging as that of the show. And now, there may be two CP pairs to observe.

See why we observational field biologists have so much fun? We can all get into the red-tail's mind when we see and understand what they do in their daily lives.

I've run on a bit here again. Got to get back to work.

Keep us all posted.

Sincerely,

John A. Blakeman