Friday, February 22, 2008

Blakeman about the Riverside Park hawks

Boat Basin in Riverside Park around 79th Street


I found the photo of the new Riverside Park nest very interesting. This is a classic new, first nest. Like virtually all Red-tail nests in rural areas, this one's in a real tree.

Notice how you can see right up through twigs on the edge, right under the bird's right wing (on the left). That area needs to get thickened with 10 to 16 inches, or more, of sticks. Right now, the nest is very thin, and still a bit small.

For birds building their first nests, they often stop construction at this stage. It's advanced enough to allow the female sit in pre-egg episodes. It will also hold her and the eggs when the first one is laid.

But typically, the air goes right through the meager bottom of these flimsy first-effort nests. This is probably the first effort of the pair (if they stop at this stage of construction). If the adults are experienced, the nest should become thicker and wider in the coming week or two, with the real prospect of nesting success.

Nest building behaviors are instinctive with Red-tails, but being fully successful also usually involves an experience component. Going through the motions in a first nesting attempt is typical. Every sort of failure can occur with flimsy first-time nests. For some, eggs are never laid. For others, eggs are laid, but they are too cool and fail to hatch. Sometimes the eggs just role out of, or fall through the nest. At the worst (for the eyasses anyway), eyasses may hatch but die from cold or rain. They may even starve, as the young parents aren't yet adept in finding sufficient food for themselves and their offspring.

Might any of this be an outcome for the new Riverside Park nest? No way to know just yet. But if the nest remains as moderate as it is, this one looks like a typical young Red-tail nesting trial walk-through for the pair.
I'm not much concerned about the nest's location over a highway. The birds, adults and eyasses, will pay no attention.
--John Blakeman