Saturday, May 13, 2006

Blakeman response to questions about redtail nests

Before we get to Red-tailed Hawks, here's a photo of a migrant seen in big numbers throughout Central Park these days-- a Black-and-White Warbler.
Photo by Lloyd Spitalnik

A few days ago Christopher Lyons, a New York City birdwatcher who follows bird activity in Van Cortland Park, Prospect Park and other city parks, sent me some questions to forward to John Blakeman. JB sent back his answers, with Chris's questions in blue.

A pile of really good questions. Let me try to answer as many as I can.

I actually have a two-part question, both parts
relating to the Red-Tail pair currently nesting at
Fordham University in The Bronx. Last year, this pair
nested in an oak tree across from the Walsh Library,
and successfully fledged two chicks. This year, they
went about things very differently, and chose to build
a new nest on the horizontal cornice of a closed
triangular pediment, on top of Collins Hall. The
cornice, as you might guess, is liberally adorned with
pigeon spikes, which hold the sticks in place.

Incubation seemed to proceed on a similar schedule to
last year (maybe a little earlier), and Rose (the
female) began sitting regularly on the nest around
March 25th, with Hawkeye (the male) relieving her for
a few hours each day.

A live chick was sighted on May 4th, though feeding
behavior was observed several days before that. On
May 1st, however, a dead chick was found around the
corner of the building. It couldn't possibly have
fallen to that spot from the nest, nor does it seem
likely, given its state of development, that it would
have been able to get out of the nest at all.

...I'm obviously wondering what this
means to the speculations regarding the Fifth Ave.
hawk nests. Hawkeye and Rose have successfully
hatched out one chick, still apparently healthy (knock
wood), in a first-year nest built on pigeon wire.
There are significant differences between the Collins
Hall nest and the 927 Fifth Ave. nest, but the
similarities are equally striking.

I, too, saw the photo of the small dead eyass.

It is very clear that this little bird just barely made it out of the egg before it died. In fact, it may have fallen out of the egg after being punctured by a pigeon prong. It doesn't look entirely developed. The down appears too thin. I think this bird got dropped out its shell after at was broken, either while being rolled, or in normal incubating activities. This little eyass just doesn't look entirely developed. I don't think it ever was able to lift its head for single tidbit of food.

You also intelligently asked if red-tails are known to carry away dead hatchlings. You searched the ornithological literature and couldn't find any references on the subject. That's reasonable because a nest observer would have to be extremely fortunate to be able to document this singular event. It would be hard to clearly distinguish the carrying away of a little parcel like this. It would look like all the other trash the adults carry off.

I'm rather certain red-tails will carry away a dead eyass. A dead hatchling, as in the photo, just sits still and motionless on the bottom of the nest. Because it doesn't open its mouth or beg for food or try to scoot under the brooding mother, the adults would not be able to keep from thinking that the dead hawk is nothing more than another piece of dead food debris that should be carried off. I'm certain that's what happened to the photographed dead eyass.

I strongly suspect this very same pair [the adults of the dead hawkling] built a nest on an apartment building fire escape on nearby Creston Avenue in The Bronx, back in 2004. This site was directly across from St. James Park, adjacent to the Grand Concourse and Fordham Road. Two chicks were hatched out, but had to be removed by the DEP, along with the nest, due to unwholesome interest taken by some local youths. The adults did not try to renest in that area. The 2004 nest site is extremely close to the 2005 and 2006 nest sites at Fordham, and Rose has a band on her right leg. I've yet to directly confirm that the Creston Ave. female was banded in the course of that operation, but she was definitely handled, and the photos I've seen resemble Rose greatly. So this may be Hawkeye and Rose's second nest on a human structure, but it's almost certainly the first one they built on pigeon wire.

Anyway, curious to hear your thoughts.

Red-tails commonly abandon last season's nest and build a new one somewhere within a quarter or half mile. So the multiple nests you've observed of this pair is typical. In fact, the continued use of the 927 Fifth Ave nest in Central Park is the exception. Rural red-tails only infrequently continue to use the same nest year after year. They more commonly move around each year, just as you've seen in your area.

And of course, the question of pigeon prongs arises once again. It appears to me that the prongs in your referenced photoare rather short and thin. They might easily have been bent over in the center of the nest during construction. But without photos into the nest bottom, we'll never know. Just one of these little demons could have poked a premature hole in the egg just before pipping. Recall that I described previously how hawk egg shells are thinnest just before pipping. Chunks of metal, of any shape or length just have no positive benefit in red-tailed hawk nests. Just as with the 927 nest, the pigeon prongs artificially keep the nest together with a reduced depth. Not good.

Hope these thoughts are helpful.

--John A. Blakeman