Friday, March 11, 2005

JOHN BLAKEMAN on INCUBATION

On Thursday, March 10, Lola began to spend many hours sitting on the nest. She also didn't leave it at the end of the day, as she has been doing previously, but spent the night on the nest. This led many hawkwatchers to conclude that incubation has begun. In years past we assumed that the day the female began to spend nights on the nest marked the onset of incubation [Don't forget we cannot see into the nest to set an exact date by the presence of eggs.]

However, I have come to the conclusion that we have been jumping the gun, in previous years. If you check Lincoln's chart of previous years' important events, you'll see that there are often 38, 39, or 40 days between the day we have assumed that incubation has begun and the day the eggs hatch [We figure hatch day from changed behavior too. When the female no longer sits all day, but now frequently stands at the end of the nest and does little up-and-down motions with her head, as if she were feeding something tiny in the nesty. Also when Pale Male begins to bring food to the nest.]

But there cannot be a 40 day incubation period. That's too long. Scientists tell us that the incubation period of RT Hawks is 28-32 days. A few stretch that to 28-34 days. But no longer. And here is John Blakeman's response to Donna Browne's question to him about our observations of changed behavior at the nest, with Lola sitting long hours and spending the night:

3/11/05 -- Blakeman's Reply

I think this is likely all to be egg laying preliminaries. Females will spend long periods of time
sitting on the nest before laying. This can happen frequently during the week or so before eggs are laid. I doubt that an egg was laid, because if it was, you
probably would have seen egg-turning behaviors (although these can occur a bit after all eggs are
laid, depending, I think, on the particular
female).

No doubt, however, things are entering a new
stage. Egg laying and incubation are at hand.