Growth and Development of Peregrine Falcon Chicks
Female peregrine falcons typically lay two to four eggs, which they incubate for 31 days with help from the male. Hatching begins when the eyas hammers a hole in the egg with a special "egg tooth" on the end of its beak. The bird makes a neat cut all the way around the egg, essentially cutting off the large end of the egg. This process may take up to 48 hours and requires a great deal of energy.
A newly hatched falcon chick weighs about one and a half ounces (60 grams) and is virtually blind. Covered only with a light coat of fluffy white down, it requires constant brooding by the female in order to stay warm. Obtaining energy from the small remnant of the egg yolk, now neatly tucked away inside its body, the newly hatched eyas isn't usually fed by the parents for about 24 hours. Feeding commences on day two, when the young falcon gapes and bobs its head around in search of small pieces of meat delicately provided by the female. She elicits their food-begging and feeding behavior by evoking a sharp "eeechup" call as she approaches the brood with food.
In its first weeks, the peregrine chick develops at an astonishing rate.
SOME HIGHLIGHTS . . .
Ten Days: The eyas has grown a second coat of down, much heavier and fluffier than the first. It requires little or no brooding, but an ever-increasing amount of food.
Two Weeks: The eyases are four times their hatch size. They have gained their keen eyesight and a recognition of their self-image by seeing their parents, an important development process referred to as imprinting. They have acquired strength in their legs and are now moving about the nest.
Three Weeks: Flight feathers and body contour feathers are poking through the down. Very active, the young birds are moving out of the nest scrape and exploring the area around the nest. They have a marked interest in anything that moves.
Five Weeks: Most of the down, save for a few tufts on top of the head, has given way to regular plumage. Having discovered their wings can grasp the air, they engage in bouts of wing-flapping and eventually, often accidentally in a strong wind, discover that they can actually separate themselves from the ground.
Six Weeks: The eyases take their first flights away from the nest. Not always choosing to or being capable of returning to the nest site, they will be found on adjacent buildings or sometimes on the ground.
Six to Seven Weeks: Exploratory, tentative flight attempts give way to ever increasingly complex sorties involving soaring, chasing, dog-fighting with siblings, and general aerobatics. Prey still tends to elude them, however, so they remain dependent upon the parents for food.
Eight to Nine Weeks: The young falcons start to show a keen interest in pursuing other birds, and soon experience their first successful capture of prey.
Ten to Twelve Weeks: The young peregrines become more adept at acquiring their own food. As July gives way to August, they disperse from the nest site. The aerial extravaganza that has provided enjoyment for many people, and a serious learning program for the falcon eyases, dissipates with the summer's heat, not to be repeated for another year.Originally printed in The Falcon Flyer, University of Minnesota, Volume 1, Number 2 and used with permission.