Sunday, February 20, 2005

Why are there 5 Redtails at the Azalea Pond? Isn't that Pale Male's Territory?

Marie,

You forwarded a nice note from Sally and Peter Johnson where they noted five red-tails apparently associating together, or at least tolerating each other. None of these were Pale Male and Lola. The Johnson's noted that all of these birds were "juveniles," (exactly the same term for "immatures," birds in their first year).

This is unusual, of course. (But that’s true for so much of the rest of the Central Park red-tail saga.) Here’s my take on this.

Although the 927 nest is under daily construction, it’s still deep winter. Sex hormones are starting to flow, prompting the copulation and nest building being observed. But so far, there is no impending food shortage for any of the Central Park hawks. As I so often point out, food is everything for a hawk. If food is abundant and available, territorial imperatives recede. If resident hawks perceive that ample food is close at hand, they will be rather accommodating of intruders in the fall and winter. Prime red-tail habitats, areas with lots of prey, often have large fall and winter groups of hawks. In the winter, in prime areas, red-tails can be almost social, just as the Johnson's described in their email forwarded to me.

Presently, Pale Male and Lola have access to essentially unlimited prey animals. From this, they are expressing virtually no territorial defenses. Don't for a second think that our resident pair is inadvertently unaware of each of the other red-tails in Central Park. They see every wing flap of these youngsters and keep track of where they fly, perch, and hunt. Our experienced adults know and keep track of the entire red-tail scoreboard.

For now, the young hawks are hunting and eating in CP just like our celebrity pair. But let’s see how long this continues. All is well just now. Presently, there is a general raptorial rapprochement regarding hunting and perching venues. There is plenty to go around.

But things are likely to change significantly when Lola becomes gravid, when her first egg begins to form. Egg formation requires a large amount of calcium, proteins and lipids, which are all absorbed from the mother’s body tissues. Very quickly, the female’s outlook on life changes. I've watched this in the female red-tail in my captive breeding trials. When eggs begin to form, the female takes on a serious, even morbid attitude. Life instantly gets very, very serious.

Food becomes very important, and competition from interloping youngsters is likely to met with stern behavioral warnings to leave. Pale Male will perceive the new hunting and territorial regime, one that precludes un-needed competition from other nearby hawks.

The inordinate winter abundance of red-tails in Central Park is not likely to persist. For now, food is abundant. But when our resident adults begin to perceive that things could start to get tough, first to produce a pair or trio of eggs, then to help feed Lola during incubation, and finally, when eyasses have to be fed for 16 hours each day, our birds are likely to become downright intolerant.

Once again, the entire CP red-tail phenomenon revolves around the abundance of prey animals. If there is lots of food, there will be lots of hawks. When food begins to become harder to procure because of competition, the adults will either drive off the interlopers, or have a reduced brood size. If five or so immature red-tails remain and compete with Pale Male and Lola, only one or two eyasses may be produced this year. At worst, none would be. It could be an empty nest year.

It’s possible that the following could occur. What happens if the five immature winter hawks simply disregard the behavioral admonishments of the adults to scram, to leave the area? Would that be possible? Could be. Booting out one or two incursive intruders is a reasonable task for an experienced resident pair. But perhaps the five youngsters perceive that the pair of old fogey adults simply can't cover enough space to keep them out. As an adult chases after one youngster, another simply flies over to the abandoned space that the adult just left. If the immatures are impudently unresponsive (unlike your kids and mine, who perfectly responded to our adult admonitions), the entire process could devolve into something of an unproductive flying circus. Do we have now a gang of juvenile delinquents that might disrupt the normal conventions of red-tale domesticity? Let’s see what happens.

Again, I've never seen anything like this in the rural wild. This is all new. Nothing is decidedly settled. And should, perchance, this year’s brood size be reduced or altogether absent, don't fret. Let’s honestly prepare ourselves for what might become a biological reality, that the annual production of three-eyass broods is unsustainable and atypical.

As long as Pale Male and Lola had no hunting and prey competition, when they were the only game in town (or the Park), everything went their way. But that may no longer be the case. The rats and pigeon prey base may now have to be divided with, or shared among, some other Central Park hawks. At some point, a CP red-tail saturation point must be reached. Originally, I would have projected that a single pair exploiting the entire Park was saturation. I was wrong. There have been as many as three Central Park resident pairs in recent years, and now there are the added winter immature population. (After all, this is New York City. Residents of every species live closely packed together in high density.)

Let’s watch what develops. I'm betting that the intruding youngsters will be driven out and few or none will be seen in March and April. But a quite alternate scenario might develop, with unexpected, even untoward results for our pair.

And most of us just thought we were merely watching the uneventful lives of a single pair of red-tailed hawks. Nature is seldom so neat and tidy. Things in the wild are usually a continuing interplay of multiple forces and factors, just as are being seen with Pale Male and Lola. Isn't this as good as the plot of a great novel, the thematic development of a great symphony, or a walk through a great art exhibition?

Sincerely,

John A. Blakeman