Tuesday, April 25, 2006

A question and an answer from Blakeman

Pale Male bringing twig to nest - April 23, 2006
Photo by Lincoln Karim

Dear John and Marie,
As I was reading all the comments on today's website, the thought occurred to me that, after the first nest was destroyed and rebuilt by the RTs, it took 2 years before there were viable eggs and babies in the nest -- am I remembering correctly? Perhaps it's just the same this time around -- it'll take 2 years for the nest to become well-enough constructed and protected for the eggs to hatch again -- what do you both think?

Although we all are greatly disappointed with this year's non-hatching (for whatever reason's, including perhaps penetration by pigeon spikes), might it be that it's all part of the process of getting the nest to the size and density it needs to be in order for next year's eggs to be successful. This may be a gloomy thought, but perhaps w/ a silver lining --??
I've noted John's comments re the RTs looking down into the nest, as though an egg had hatched -- I certainly hope, whatever the outcome this year, that it will be somehow possible (even if a crane has to be hired!) (well, yes, expensive) to be able to look into the nest and retrieve whatever is left behind, to try to determine exactly why the eggs have not failed to survive again this year.
Any thoughts you have would be appreciated --
Mai Stewart
Yes, with each passing year more material should be building up at the base of the nest, elevating the useful, working central bowl that holds the eggs. But this base is composed only of nest lining material, not sticks, so it may never get elevated enough to rise above whatever metallic parts might be at the bottom. Lining materials are typically fine grass, moss, thin bark strands, and other similar things that don't weather so well during the year.

In wild nests, which are typically parked in the crotch of a tree, or in some regions in the West on a bare rock ledge, the sticks used to construct the nest are continually tucked inwardly to create a firm, un-wiggling nest. Then, nest lining materials are brought in and tucked into the bottom of the nest. The lining has to be replaced and refurbished each year as summer, fall and winter rains degrade the linings. The majority of the sticks usually don't have to be replaced. New ones are just tucked into the stick pile, making up for the older ones that soften and rot.

Remember, red-tails seldom use the same nest site year after year. Unlike Pale Male at 927, rural red-tails typically use a nest for just one or two years, then abandon it and build a new one a few hundred yards to a half-mile away, somewhere within the territory. This brings up the question of why Pale Male would elect to use the same nest site for over a decade. That seldom occurs in the wild. My only explanation for this lengthy continuity is that the 927 pair prefers to be high above the prolific activities of the ground. The parades of cars, people, dogs, and who knows what other ambulatory disruptions have probably driven both resident Central Park red-tail pairs inordinately high into the sky. In typical tree nests in the East and Midwest, red-tails build their nests usually between 40 and 60 ft off the ground, beneath the tops of the trees. The two CP nests are way above this normal nest zone -- far higher than I would ever have predicted. But they clearly like it way up there.

So, in reference to your good questions, what might be the probabilities of nesting success next year? I'd like to suggest that I know all about what's happened and have an informed, reliable outlook. But I've dealt with wild species long enough to know that they don't just act linearly or arithmetically. Yes, Pale Male should be successful next year, and so should Pale Male, Jr. But these things can never be assured. These are wild animals, subject to a plethora of known and unknown life history and survival factors. It's a crap shoot, and for reasons we may never know, the dies may not roll the ways we'd like next year. They sure didn't this year.

Now let me make a statement that might cause some to question both my expertise and my concern. Like everyone else, I'm distraught that things haven't turned out well at either nest this year. Thoroughly disappointing. But am I really concerned? Do I see any of this as portending the loss of Central Park red-tails? No, not so. As a wildlife biologist I've learned in over three decades of field observations that "failures" happen, more often than not for no good reason. The birds, as I previously claimed, did everything right. There should have been eyasses this year. But they didn't appear. That's the way nature is arranged -- not much concerned with the successes or failures of either individuals or entire populations within short time frames. The mere occupation of Central Park by two mated pairs of red-tailed hawks is sufficient enough. In decadal (or longer) time frames, red-tails have been very, very successful in Manhattan. I'm not going to get too concerned until two years pass without any resident Central Park red-tails.

I don't think that's going to happen. The remarkable thing is not that red-tails have reproduced in CP. That's an end result of the greater marvel, their ability to come into the park and so successfully adapt their hunting and occupancy behaviors to that unique environment. For me, that's the real, continuing story. The fledging of eyasses is an almost peripheral byproduct of the greater occupancy miracle.

So, let's not be overly depressed with how things turned out this year. Four regal red-tailed hawks will still be seen and marveled at by those with the opportunity to lift their eyes into the Manhattan skies. For me, the mere residential presence of these great birds in Central Park is enough. Nature has its vicissitudes, and hawk reproduction in the last two years has been nil. The adults are still with us, however, and that's adequate. Be thrilled once again when you see a perched or passing Central Park red-tail. Even without offspring this year, their nobility is sufficient. Let's learn from nature. Life can be hard and the lives of no one, human or animal, can always be assured. The lessons of former years, happily, were ones of rebirth and renewal. The lessons of the recent two seasons are a bit more weighty. Survival and reproduction for any organism is never assured.

John A. Blakeman

P.S. -- A cheap digital web camera could be extended temporarily on a pole over the edge of the 927 roof to get images of what's in the nest. No need for a crane or any other mechanical device. A laptop connected to a camera would work.