But little is known of the nesting economy of the Knot. Its great breeding grounds—the nesting places of the vast flocks that pass southwards in autumn—still remain undiscovered. Where they are situated it is useless to speculate. Naturalists are ignorant of its eggs, which still remain unknown in collections, although the young in down have been obtained. The Knot breeds in the high Arctic regions, in the North Polar Basin, mostly, if not entirely above lat. 80°; and here it has been met with during summer by various travellers. The Knot is another bird remarkable for the great seasonal changes which its plumage undergoes. In winter, the plumage is ash-gray above, white below; in summer, the feathers of the upper parts become black margined with reddish-brown and mixed with white, those of the lower parts rich bay or chestnut. It has been remarked that the birds that winter on our coasts do not assume such rich tints in summer as individuals that pass along our coasts from more southern latitudes. This is probably because the birds wintering with us are younger individuals, only the oldest penetrating to the remoter winter home. The Knot has a wide distribution during winter, including the Southern States, and Mexico, Africa, and it is said Australia, and New Zealand! It is possible that in the latter countries the Eastern Knot—the _Tringa crassirostris_ of science—is confused with the present species. CURLEW SANDPIPER. This pretty little species, known to many as the “Pygmy Curlew,” and to modern naturalists by the scientific name of _Tringa subarquata_, is one of the rarest of the British Limicolæ. It very closely resembles the Knot in the colour of its plumage, and in the seasonal changes that plumage undergoes, but it is not much more than three-fourths the size, and has a curved Curlew-like bill. This little Sandpiper, like most of its order, is a migrant, breeding in some yet undiscovered part of the Arctic regions, retiring southwards to winter in Africa, various parts of southern Asia and in Australia. It is during these journeys between the Arctic regions and the tropics that it occurs on the British coasts, a few individuals even remaining upon them all the winter through. As might naturally be expected it is most frequently observed on the vast stretches of low coast on the eastern side of England; it is also a tolerably frequent visitor to the south coast, even as far westwards as Devon and Cornwall. A few Curlew Sandpipers arrive on our coasts in April, but the greater number pass along them in May, stragglers lingering until June. The return flight is noticed in August, and consists mostly of young birds, the older ones reaching us during September and October. The habits of this Sandpiper very closely resemble those of the Dunlin, in whose company the bird is very frequently found, and from which it may readily be distinguished, even at a distance, by its pure white upper tail-coverts.