Saturday, March 05, 2005

Lining the Nest

Lining the Nest

Yesterday afternoon at about 4:45 pm Pale Male, who had been perched on the Oreo building at Fifth Ave and 81st St street, flew to a terrace on a high floor of Woody's building, broke off a small branch from an ornamental shrub someone had paid big bucks to have planted there [a shrub that already looked pretty scraggly from previous depredations] and brought it to the nest. He circled around it first, flying almost to 72nd street to the south, and then past the nest again to the north, as if trying to avoid giving away its location. He doesn't seem to know or care that through the various telescopes set up at the model-boat pond, and on the giant video screen of Lincoln's telescope hundreds of people were watching every move he made .

The hawk patriarch worked the stick into the center of the nest,, and then broke off a part of a twig sticking up to the right, and wove it in somewhere out of our sight. A little before 5 p.m he flew off towards the boathouse. No deceptive circling on the way out as he does on the way in.

Lola, a few minutes later, flew from her perch on the Oreo Building and landed on a different terrace garden a few buildings to the north of Woody's. She hopped onto the terrace floor. Through the slats of a railing, [and on Lincoln's video screen, since he had focused his telescope on her as she landed] she could be seen digging around in a planting bed. Soon she hopped onto the railing with something brownish in her beak-- leaves, or moss or something else soft and mushy -- and flew directly to the nest. Lola never does any circling and feinting when she arrives at the nest.

At the Hawk Bench we could see her deposit the brownish stuff into the nest and seem to be tamping it down. It was clearly lining material. For a few days now both hawks had been bringing in strips of bark -- also lining material.

Nest-lining is the last stage of the nest-building process. Its purpose is to plug up any holes that might allow cold air into the nest and interfere with the incubation of the eggs. A nest, after all, is not a hawk's home. It is a place to lay eggs and keep the young alive until they are ready to fledge. The lining materials will help to keep the eggs warm during incubation. The finer lining materials will also serve to shed water, to cushion the eggs, to insulate them. In a nest made on top of sharp anti-pigeon spikes such as Pale Male's and Lola's the lining stage is especially important, it seems to me.

Since we have been watching the hawks bringiing in twigs, hundreds upon hundreds of them, for the last month, how, in fact, do they know when they have enough twigs and can begin the nest-lining process?

According to Christopher Leahy in the Birdwatcher's Companion, , birds have an innate mental program showing them what the nest is supposed to look like at various stages of construction. "When one stage has been adequately completed, the bird gets a 'sense of satisfaction' and has the urge to proceed, so to speak, to the next illustration in the mental plan."

Presumably, then, the "urge to proceed" denotes a new hormone kicking in, one which induces the birds to stop breaking off twigs for the nest. Instead, they begin to collect the finer materials that go into the lining and deliver those to the twig structure they have previously formed.

Egg laying and incubation should follow within the next week or two. When you think of where we were last December 7th, with a bare ledge where once the nest had stood, and today, with Pale Male and Lola's nest approaching completion, it is enough to make one stop feeling glum about the state of the world, and begin to hope that somehow there is hope for our diminished planet.


David Gray, a new hawkwatcher, sent me this picture of Pale Male and prey, taken on 2/27/05 at Cedar Hill. He thought it was a pigeon. I'm wondering if it isn't a starling. Isn't that a sharp yellow beak sticking up there?

John Blakeman writes:

" The current posts on hunting observations are really filling in holes of comprehension. I'll have more next week."