Along with their food they swallow particles of gravel, frequently of considerable size. I have found some a quarter of an inch in diameter." [Illustration: THE PIED OYSTER-CATCHER, OR SEA PIE (_Hæmatopus ostralegus_).] Bivalve shells, when closed, are usually opened by these birds by striking them at the hinge, while cockles are obtained by holding the shell with the foot and wrenching with the bill as with a crowbar. When the shores are flat and the surface thus remains covered with a shallow stratum of water, after the tide has ebbed, the Oyster-catchers find their prey more readily, as the shells are then partially opened, and they can easily insert their wedge-shaped bill and force them asunder; but where the sand soon dries and there are no rocks from which the limpet can be obtained, they follow the line of the advancing and retreating waves. Such of these birds as are stationary during all seasons commence the business of incubation as early as the middle of April, while such as migrate do not lay until somewhat later in the spring; at this season, after the usual rivalry between the males, the pairs keep apart from each other, but frequently remain in the immediate vicinity of some of their weaker feathered associates, with whom they live in the utmost harmony. The nest of the Sea Pie is a mere hollow in the shore, and is usually situated amongst the tangled weed thrown above high water mark, or on grassy spots in the immediate vicinity of the sea. The eggs, two or three in number, are large and of an oval form with a pale brownish shell, spotted, streaked, and very variously marked with light violet, deep greyish brown and greyish black. The female, who alone broods, does not sit during the noonday hours, and hatches her little family in about three weeks. The young at first conceal themselves if alarmed, but even at a very early period can run, swim, and dive with considerable facility. Whilst in charge of their offspring, the parents exhibit unusual courage and foresight, and should the mother perish, the father at once undertakes all her duties. The flesh of the Sea Pie is unpalatable, but by many the eggs are much esteemed. Gadamer states that a pair of Oyster-catchers reared by him from the nest became so tame that they knew his voice and greeted his appearance with loud cries. These birds were allowed to run freely about the poultry-yard, and rendered excellent service to its more timid occupants by warning the Fowls of the approach of a Hawk, or any other feathered marauder. * * * * *