402 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 
month J began to visit the nest.as often as possible to ascertain as 
nearly as I could when the chicks appeared and how long the hatch- 
ing 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 2.30 o’clock. Two very 
callow owlets were now in the nest and one slightly pipped ege. 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, one being 
quite markedly smaller than the other two. The query remains: 
How long does it take a great horned owl’s egg to hatch? The above 
are the data kept and anyone can make estimates on them. It 
seems certain that these birds did not lay an egg oftener than once 
in two days and that the period of incubation could not have been 
less than 30 days, with the probabilities on the side of a rather longer 
period. 
Yor 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 what 1t would. And the offerings were of sufficient 
variety. On March 16, with the young 4, 6, and 8 days old, approxi- 
mately, the temperature was well above freezing and comfortable, 
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 cottontails and one bobwhite, 
which the camera shows, a fourth rabbit and a second bobwhite, also 
a plump field mouse, do not appear in the picture, being tucked away 
under the overhanging roof to the left or buried under other remains. 
It was chilly on March 30 and a high wind was blowing in from the 
northwest. On April 13 we had a regular northwest gale to contend 
with and freezing temperature added. We varied our work with the 
camera, by runs across the frozen timber pasture. Why it was that 
our negatives taken on these last two dates did not show motion we 
have never satisfactorily explained to ourselves, for only time expo- 
sures could be used. Certain it is that both the big elm and our 
nearly 30-foot stretch of ladder were swaying back and forth under 
the lash of that roaring wind. The gentle rain that was falling when, 
on April 18, Mr. Benedict helped me bring the now lively owlets to 
the base of the old nest tree, proved to be really no obstacle at all. 
it splashed water against the lens of the camera but the negatives 
