Page:The peregrine falcon at the eyrie (IA cu31924084757206).pdf/27

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S on April 7th there was one egg in the eyrie and on the 11th there were four, it may be assumed that an egg is laid daily till the clutch is complete. On May r4th the eggs were photographed, and showed no signs of chipping. Rough weather prevented our landing till May 18th, when we found four chicks. This gives roughly an incubation period of five weeks, which is in accordance with our notes of the two previous years. I may remark that I find works on ornithology singularly reticent over the period of incubation of many birds. The Falcon flew off as we approached the eyrie, and immediately started calling the alarm as she circled overhead. Her harsh cry seemed to me to be more like "aitch, aitch, aitch" than the "kek, kek, kek" of the books. I never could tell them apart when flying, but when together it is plain that the Tiercel is smaller and his alarm note different and rather higher in pitch. Their flight consisted of a series of rather laboured beats followed by glides on outspread wings. The young formed a round heap like a pancake raised in the middle. Before we disturbed them there was only one head visible. They lay with their heads towards the middle and their eyes closed. When separated they opened their weak-looking eyes languidly; but one of them snapped and bit at our fingers. Already it was possible to distinguish two males by their smaller size; these were in the centre of the heap, and underneath. It would be interesting to know if, in a clutch of four eggs, there is any difference in size. From the early appearance of this sexual difference in the chicks I should think it quite possible. The down on the chicks was thin, so that they looked a pinkish white. The general appearance of the young gives a curious suggestion of extreme old age. We found a dried turtle-dove's head in the eyrie and a corncrake's as well as the remains