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San Francisco Nest Diary 2012:

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May 8: First Fledge! The tierce known as “Perry” was first to leave the nest ledge. He made his flight in low light at the end of the day and settled on the roof of 123 Mission Street. During the course of fledging, all four eyasses were picked up in a variety of locations: inside heating and cooling apparatus cover on top of 123 Mission; at the bottom of the space between 123 Mission and 135 Main; a sidewalk on Main Street; and from a little ledge close to the ground on Mission Street where it is unlikely that the bird would have been able to regain a safe perch. All four were replaced to the nest ledge on the 33rd floor of the PG&E building. One made a fatal flight error (Amelia)—she was probably caught in a wind sheer—and died upon her second attempt at fledging when she crashed into an adjacent building. The other three were seen regularly and put on a nice show 30 to 50 stories above the Embarcadero during the June 3rd fledge watch party at Cupid’s Span.

April 23: We banded two males and two females in the San Francisco PG&E nest today.

April 17: The chicks have achieved a second coat of down which protects them from the cold while both parents are hunting birds to satisfy their voracious appetites. Please do not be alarmed when the youngsters are not brooded for what seem to be long periods of time. They can take it—Peregrine Falcons live and raise young in the Arctic. One other cautionary note: It is typical for one or two young to receive more food than one or two of the others at any given feeding. Knowing that, when we see one youngster who does not seem to be eating much, it is probably because he or she ate heartily just a few hours ago and is not yet hungry. To our eyes, it seems like it is the “one in the back” who is not being fed. But in fact, it is the “one who ate most at the last meal” that is now in the back dozing.

FeedingApril 2: Three chicks hatched on the 30th and the fourth, on the 31st. Dan is providing food enthusiastically with many deliveries per day.

March 30: Hatching is underway today. At first light, one chick could be seen and a second was in the final stages of cutting its way from the eggshell. Hatching is a long process that begins with a small, star-shaped “pip” that provides air for the chick, and then continues as it uses its egg-tooth to cut around the equator of the shell.First Hatch

March 5: Lil continues to incubate four eggs meditatively.

February 24: The third egg has arrived and this generally coincides with the beginning of what we call “hard incubation.” For the next thirty-three (33) days, mom and dad will rarely leave the eggs unattended (though they can withstand significant exposure) until hatching occurs.

SF NestFebruary 19: The first egg was laid overnight and is visible this morning in the PG&E headquarters, downtown San Francisco Peregrine Falcon nest. Egg-laying will continue at intervals of about 56 hours until three are in the nest and “hard incubation” begins. A fourth egg is usually laid approximately two days after the third and consequently hatches a little later than the others.