two eggs less than the first. Usually incubation does not begin until the full complement of eggs is deposited, 
but some species habitually begin sitting as soon as the first egg is laid. The Yellow-billed Cuckoo, and 
perhaps, also, the Black-billed Cuckoo, sometimes sits upon one egg until it is nearly hatched, then a 
second one is dropped, and, when the embryo is quite well developed in this, a third egg is laid, and 
later, perhaps, even a fourth or fifth. In this way it so happens that the young bird from the first egg 
attains such size that the warmth of its body is sufficient to incubate numbers two and three, and when 
the first-born leaves the nest the second-born assumes its duties. Tame Pigeons often resort to this same 
means of escaping the task of incubating, as also does the Turtle Dove. The period of incubation for 
each species is difficult to determine, and but little accurate knowledge is in print upon the subject. 
The relative time required for the development of the ovum of each species could readily be ascertained 
by placing the eggs in an artificial incubator, and it is probable that this would not vary much from the 
actual time when hatched naturally. But such observations seem not yet to have been made. Personally, 
but few birds have been carefully timed during the period of their sitting, and these were watched to 
discover variations due to outside circumstances. In the species observed, temperature and moisture play 
an important part. A few cold rainy days always retarded the growth of the embryo from twelve to 
forty-eight hours. Cold and rain also often retard oviposition, some birds being able to withhold laying a day 
or two. A Chestnut-sided Warbler was ten days laying three eggs during the cold, wet summer of 1878, 
and at this time many other birds were similarly influenced. Some birds are by nature fond of such 
weather as referred to; these are, of course, exempt from the influence mentioned. Thus the water-birds, 
the birds of prey, and some land birds that build in very protected spots, disregard inclement weather. 
The earliest birds to nest are the Owls and Hawks. These begin often in February to hunt a 
suitable site for a home, and by the first of March egg-laying is usually completed. The Cedar Waxwing 
and the American Goldfinch go to the other extreme, and defer building till August or September. May 
and June are, however, the chief nesting months with most of the birds of Ohio. The earliness or 
lateness of the season has much to do with the time of nklification. In 188 2, the season was so rainy 
and cold that vegetation was delayed in Southern Ohio about two weeks, and birds which commonly 
build the last of May delayed until late in June, and even seemed to be less abundant. The May of 
1886 was so cold that the Summer lledbirds abandoned partly finished nests and betook themselves to a 
warmer climate, nor did they return that year. And in the fall of ’82, after the leaves had fallen from 
the branches, the nests seemed fewer in number than ever before, suggesting that many birds sought 
breeding grounds elsewhere during the continued cold of May and June. But the Owls and Hawks are 
hardy, and defy all inclemencies of weather. The nest of the Horned Owl often contains young when 
the ground is covered with snow, and the Red-tailed Hawk sometimes sits upon her eggs when an hour’s 
absence would freeze them. To the young and eggs of many birds such temperatures would be fatal. 
Even wet weather, without extreme cold, kills many young birds, such as Quail, Ruffed Grouse, and 
others which early follow their parents in search of food. Running through the grass and over damp 
ground, their downy plumage becomes soaked, their tender muscles become fatigued and benumbed, and 
they fall, unable to farther follow their parents. Thus, one by one, a flock of Quail will soon be decimated. 
Birds that do not leave the nest till able to fly are also affected by wet. Beating rains soak the spongy 
fabric of their home by striking it directly or dripping from overhanging foliage, and the feeble nestlings, 
if not cared for by an experienced parent, are soon soaked and chilled to death. Continued rains also 
soften many nests that are largely composed of mud, and, melting away under this constant action, they 
fall from their position by the weight of themselves and their precious contents. Cold, wet summers are 
indeed hard times for young birds and their anxious parents. The days pass slowly to the watching- 
parent and hungry brood, the mother-bird being unable to leave the nest for food, lest upon her return 
her little ones be dripping and cold. The night is worse than the day, for the chilliness has increased, 
XXXI 
