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 A IIISTOR )F CERTAIN GREAT II{)RNED OWI.S 1.5 Jan.,1911 began to visit the nest as often as possible to ascertain as nearly as I could when the chicks appeared and how long the hatching process lasted. It was not until March 6, at 2 p.m., that I.found one of the eggs pipped, a small round area no larger than a pea being broken. On March 7 at the same hour the broken area was the size of a dime. I could distinctly hear, however, several times repeated, the low twittered note of the still imprisoned chick. The other eggs still showed no sign. Bad weather and pressure of other work now prevented a further visit until March 11, at two-thirty o'clock. Two very callow owlets were now in the nest and one slightly pipped egg. The young birds were not'completely protected by their white down as yet, the bare skin being visible between the tracts. On March 16 three young owls of different sizes were found in the nest, oue being quite markedly smaller than the other two. Tile query remains: how long does it Fig. 11. APRIL 22, 1907; DORSAL AND LATERAL VIEV,'S; AGE FORTV-ONE TO FORTV-FIVE I)AVS take a Great Horned Owl's egg to hatch? The above are the data kept and any- one can make estimates on them. It seems certaiu that these birds did not lay an egg oftcrier than once in two days and that the period of incubation could not have bee n less than thirty days, with the probabilities on the side of a rather longer period. For our second year's work we had the experience of the first to go on, we were more confident of the owlets' ability to bear exposure, and so decided to photograph them at least once a week, let the weather offer vhat it vould. And the offerings were of sufficient variety! On March 16, with the young from four to eight days old approximately, the temperature was well above freezing and conffortable, but we were unable to expose a plate until 4 p. m., the sun became covered with black clouds, and we were on the shady side of the tree. We were not hopeful, but a long exposure accomplished our purpose. In addition to the parts of three adult cotton-tails and one Bob-white vhich the camera shows, a