A History of North American Birds; Land Birds; Vol. 2 of 3

by Spencer Fullerton Baird; T. M. Brewer; Robert Ridgway

season, and towards dusk thousands of these birds and of C. texensis and C. henryi might be seen flying in towards the river from the prairies, this one being the least common of the three. In Northern Florida it is also a common species, and I have rarely received any collection of eggs from that State without the eggs of this bird being found among them. They are known there as Bull-bats.

In many of its habits, as well as in its well-marked generic distinctions, this species exhibits so many and such well-marked differences from the Whippoorwill that there seem to be no good reasons for confounding two birds so very unlike. It is especially much less nocturnal, and has, strictly speaking, no claim to its common name, as indicating it to be a bird of the night, which it is not. It is crepuscular, rather than nocturnal, and even this habit is more due to the flight of the insects upon which it feeds at morning and at evening than to any organization of the bird rendering it necessary. It may not unfrequently be seen on the wing, even in bright sunny weather, at midday, in pursuit of its winged prey. This is especially noticeable with such birds as are wont to frequent our large cities, which may be seen throughout all hours of the day sailing high in the air. Generally, however, it is most lively early in the morning and just before nightfall, when its supply of insect food is most abundant. But it is never to be found on the wing after dark. As soon as the twilight deepens into the shades of night all retire to rest as regularly, if not at quite as early an hour, as other birds in regard to the diurnal habits of which there is no question.

This species appears to be equally abundant throughout the fur countries, where, Dr. Richardson states, few birds are better known. In the higher latitudes to which these birds resort the sun does not set during their stay, and all their pursuit of insects must be made by sunlight.

In the winter this species leaves the United States, retiring to Mexico, Central America, and the northern portions of South America. Specimens from Mexico were in the Rivoli collection. They were taken by Barruel in Nicaragua, by Salvin in Guatemala, in Jamaica by Gosse, and in Cuba by both Lembeye and Gundlach.

The movements, evolutions, and general habits of this species, in the pursuit of their prey, bear little resemblance to those of the Antrostomi, but are much more like those of the Falconidæ. They fly high in the air, often so high as to be hardly visible, and traverse the air, moving backward and forward in the manner of a Hawk. At times they remain perfectly stationary for several moments, and then suddenly and rapidly dart off, their wings causing a very peculiar vibratory sound. As they fly they utter a very loud and shrill cry which it is almost impossible to describe, but often appearing to come from close at hand when the bird is high in the air. Richardson compares this sound to the vibration of a tense cord in a violent gust of wind.

In some of the peculiarities of its breeding the Mosquito-Hawk displays several very marked variations of habit from the Whippoorwill. While the latter always deposits its eggs under the cover of shady trees and in thick woods, these birds select an open rock, a barren heath, or an exposed hillside for their breeding-place. This is not unfrequently in wild spots in the vicinity of a wood, but is always open to the sun. I have even known the eggs carelessly dropped on the bare ground in a corner of a potato-field, and have found the female sitting on her eggs in all the bright glare of a noonday sun in June, and to all appearance undisturbed by its brilliance. A more common situation for the eggs is a slight hollow of a bare rock, the dark weather-beaten shades of which, with its brown and slate-colored mosses and lichens, resembling both the parent and the egg in their coloring, are well adapted to screen them from observation or detection.

The great abundance of insect life of certain kinds in the vicinity of our large cities has of late years attracted these birds. Each summer their number in Boston has perceptibly increased, and through June and July, at almost all hours of the day, most especially in the afternoon, they may be seen or heard sailing high in the air over its crowded streets. The modern style of house-building, with flat Mansard roofs, has also added to the inducements, affording safe and convenient shelter to the birds at night, and serving also for the deposition of their eggs. In quite a number of instances in the summers of 1870 and 1871 they were known to lay their eggs and to rear their young on the flat roofs of houses in the southern and western sections of the city. I have also been informed by the late Mr. Turnbull, of Philadelphia, that the flat roofs of large warehouses near the river in that city are made similar use of.

If approached when sitting on her eggs, the female will suffer herself to be almost trodden on before she will leave them, and when she does it is only to tumble at the feet of the intruder and endeavor to draw him away from her treasures by well-feigned lameness and pretended disability. Her imitation of a wounded bird is so perfect as to deceive almost any one not aware of her cunning devices.

The eggs of this bird are always two in number, elliptical in shape, and equally obtuse at either end. They exhibit marked variations in size, in ground-color, and in the shades and number of their markings. In certain characteristics and in their general effect they are alike, and all resemble oblong-oval dark-colored pebble-stones. Their safety in the exposed positions in which they are laid is increased by this resemblance to the stones among which they lie. They vary in length from 1.30 to 1.13 inches, and in breadth from .84 to .94 of an inch. Their ground is of various shades of stone-color, in some of a dirty white, in others with a tinge of yellow or blue, and in yet others a clay-color. The markings are more or less diffused over the entire egg, and differ more or less with each specimen, the prevailing colors being varying shades of slate and of yellowish-brown.

With all these variations the eggs are readily recognizable, and bear no resemblance to any others except those of texensis and henryi. From the former they are easily distinguished by the greater size, but from the latter they can only be separated by considerations of locality.