The nest of this bird found in Jamaica by Mr. March was constructed on a lofty tree, screened by thick foliage, and was a mere platform of sticks and grass, matted with soft materials, such as leaves and grasses. It contained four eggs, described as “round-oval or spherical” in shape, measuring “1.38 by 1.13 inches, of a dull clayish-white, marked with sepia and burnt umber, confluent dashes and splashes, irregularly distributed, principally about the middle and the larger end.” Four others, taken from a nest in the St. Johns Mountains, were oblong-oval, about the same size and nearly covered with chocolate and umber blotches. Mr. March thinks they belong to different species.
Mr. Hutchins, in his notes on the birds of Hudson’s Bay, states that this species nests on rocks or in hollow trees; that the nest consists of sticks and grass, lined with feathers; and describes the eggs as white, thinly marked with red spots. In the oviduct of a Hawk which Dr. Richardson gives as Falco æsalon, were found “several full-sized white eggs, clouded at one end by a few bronze-colored spots.” A nest was found by Mr. Cheney at Grand Menan, from which he shot what he presumed to be the parent bird of this species. Its four eggs agreed with the descriptions given by Hutchins and Richardson much more nearly than with the eggs of this species. The eggs found by Mr. Cheney may have been very small eggs of A. cooperi, in which case the presence of the columbarius on the nest cannot be so easily explained.
Three eggs, two from Anderson River and one from Great Slave Lake, range from 1.53 to 1.60 inches in length, and from 1.20 to 1.22 in breadth, their average measurements being 1.56 by 1.21. They have a ground-color of a rich reddish-cream, very generally covered with blotches and finer markings of reddish-brown, deepening in places almost into blackness, and varying greatly in the depth of its shading, with a few lines of black. In one the red-brown is largely replaced by very fine markings of a yellowish sepia-brown, so generally diffused as to conceal the ground and give to it the appearance of a light buff. Mr. Ridgway, after a careful analysis of the varying markings and sizes of twenty-one eggs, has kindly given the following:—
“Extremes of twenty-one eggs (mainly from Forts Yukon, Anderson, Resolution, and MacKenzie rivers): largest (10,687, Yukon, June), 1.75 × 1.28; smallest (8,808, Anderson River, June), 1.55 × 1.20. The ground-color varies from creamy-white to deep purplish-rufous, there being one egg (4,090, Great Slave Lake, June 6, 1860) entirely and uniformly of the latter color; the lightest egg (normally marked, 2,663, Saskatchewan) is creamy-white, thickly sprinkled with dilute and deep shades of sepia-brown, thickly on large end, and sparsely, as well as more finely, on the smaller end. The markings vary in color from dilute indian-red to blackish-chestnut.
“H. richardsoni is larger than columbarius, and probably has a larger egg. There are no eggs such as Richardson describes in the series of columbarius in the Smithsonian Collection.”
The var. richardsoni was recognized by Richardson as distinct from the more common columbarius; and a single specimen, killed at Carlton House, and submitted to Swainson, was pronounced by him, beyond doubt, identical with the common Merlin of Europe. Other specimens have since been procured, and are now in the Smithsonian Collection. They are recognized by Mr. Ridgway as identical with Richardson’s bird, but quite distinct from the Æsalon of authors. He has named the species in honor of its first discoverer. Of its history and habits little is known. A single pair were seen by Richardson in the neighborhood of Carlton House, in May, 1827, and the female was shot. In the oviduct there were several full-sized white eggs, clouded at one end with a few bronze-colored spots. Another specimen, probably also a female, was shot at the Sault St. Marie, between Lakes Huron and Superior, but this was not preserved.
Mr. Hutchins, in his notes on the Hudson’s Bay birds, states that the Pigeon Hawk “makes its nest on the rocks and in hollow trees, of sticks and grass, lined with feathers, laying from two to four white eggs, thinly marked with red spots.” As Hutchins has been found to be generally quite accurate in his statements, and as this description does not at all apply either to the nest or the eggs of the columbarius, it is quite possible that he may have mistaken this species for the Pigeon Hawk, and that this description of eggs and nests belongs not to columbarius, but to richardsoni.