Blakeman answers questions
Pale Male and mate on Fifth Ave on January 6, 2012
photo courtesy of PaleMale.com
On 1/13, at my prompting, a NYC hawkwatcher named Jessica Schein wrote a note to John Blakeman with some interesting questions. As he always does the Ohio raptor expert promptly answered her. Below is the illuminating correspondence.
Hello,I am new to the NY birding community as a result of the NYU hawks, although I read Red-tails in Love when it was published and kept up with the news of Pale Male & family.
I am more taken by raptors than by small (song) birds. I have been trying to finish off your Q&A's from 2005 on Marie's website. There is a lot to read. But I wonder if it needs an updating. Much has happened in NYC since 2005.You have been very good at responding to questions first on the NYU chat room and then on Roger_Paw, but it would be nice to be able to ask some questions in a forum (older use of the word) other than a chat room or blog or Facebook to find out what you think.
My questions mostly relate to what will happen now that the city is just about filled with RTHs, other hawks are arriving, the Peregrines are expanding their territory (perhaps to be the battle of Bobst), and Bald Eagles have been seen in Manhattan, Brooklyn and beyond.The blog The Origin of Species http://yojimbot.blogspot.com/ just posted some photos and videos of Peregrines (a long-time resident) a Cooper's and a juvi RT "battling" over the area around Morningside Park in Harlem.
Is it possible that any of these raptors will learn to live within the same territory? That two nesting pairs of RTs can live close to each other? Most of the larger park areas (say, over 5 acres) have lots of food. Rats and mice are around, but we humans don't always see them. Pigeons are everywhere in droves, and squirrels are way over their normal density.What happens when the niches in the city are also filled up? Do the birds start seriously fighting, does the birthrate decline, or do more birds just die from starvation?
Why do I want to know? I'm just one of those people who likes to ask questions and learn.
Jessica ScheinNY, NY
Here is John Blakeman's reply:
You have the mind of a raptor biologist, much above the pedestrian perspectives of most NY hawkwatchers.
First, in regard to my postings at Marie Winn's site (which she so graciously still provides), it may be time for me to put up a dedicated urban raptors blogsite, where I'd elaborate on cogent issues; including the ones you raise.
Your prime question concerns the saturation density of red-tails and other raptors in greater NYC. It's a question I've been pondering since I learned of Pale Male in Central Park. How many RT pairs can Manhattan and the other boroughs sustainably support. I have a pretty comprehensive understanding of this out here in the Ohio countryside. Our RTs require about 2 sq miles around each nest.
But clearly urban RTs tolerate a much greater territorial density than rural pairs. We know that territory size is primarily determined or controlled by prey density. That's exceptionally high in NYC, with the rats and squirrels (mostly rats, I think), so RT territories are much smaller.
So, is Manhattan now saturated with RTs? Hard to tell. Obviously, Washington Square Park was occupied last year, a new pair and territory. Will there be any more elsewhere in Manhattan? I don't know (actually, I've never been to NYC, so I have no idea where new nests and territories might occur).
But it sure looks like there must be some open turf or park space for the hawks to hunt in. I think that's the case with the St.. John the Divine Cathedral, the Riverside nest, clearly with Pale Male in Central Park, and now the NYU pair at Washington Sq Park.
I don't think a red-tail can survive by hunting in pure streetscapes, in concrete canyons without ground vegetation where rats can be hunted and killed.
Then you ask the question about survival of new birds seeking territories, with all the available ones occupied. Same phenomenon out here in the countryside, where all available RT habitats are (and have been) fully occupied. The multitude of young red-tails looking for unoccupied territories (and mates) each spring simply are out of luck. Only a fraction (small) of eyasses fledged each spring ever attain a mate and territory and pass on their genes to a new generation. Simply, the vast majority of young red-tails die before the end of their first year, mostly of starvation induced by trying to survive in prey-poor bad habitats. The good habitats are occupied by experienced haggards who don't much tolerate competition from youngsters. Out here, the young are forced to try to survive by eating voles caught in roadside ditches, where the adjacent fields are vast deserts of corn and soybeans.
Interspecific (between species) competition for prey and territory is a well-studied matter. Yes, there is lots of apparent confrontation. But most of this is ritualized, inasmuch as each species requires different territories. Peregrines kill birds out over open water. Cooper's Hawks kill small birds in woody or brushy areas. Red-tails hunt ground prey (rats) in area with low vegetation. The birds of these species will confront each other, often with great display. But there is seldom any physical contact.
Just how close an adjacent pair of red-tails will occupy territories in urban areas needs to be studied (as does all of urban red-tail biology -- no one is doing this, sadly; even though the birds live in urban areas very differently from their lives out in the more natural countryside).
Hope this information helps. Feel free to shoot me any other questions.