Along the forearm of Cape Cod, from the elbow at Chatham to the wrist near Provincetown, extend about 30 miles of nearly continuous ocean beaches, to which we can add 10 more if we include that long, narrow strip of beach and marsh called Monomoy. Facing the broad Atlantic and exposed to all its furious storms, these beaches are swept clean and pounded to a hard surface by the ceaseless waves. Even in calm weather the restless ocean swells and surges up and down over these sloping sands, and the winter storms may make or wash away a mile or so of beach in a single season. Here on the ocean side of the beach, the "back side of the beach," as it is called on the cape, is the favorite resort of the little sanderlings in fair weather or in foul. They are well named "beach birds," for here they are seldom found anywhere except on the ocean beaches, and I believe that the same is true of the Pacific coast. They are particularly active and happy during stormy weather, for then a bountiful supply of food is cast up by the heavy surf. But at all times the surf line attracts them, where they nimbly follow the receding waves to snatch their morsels of food or skillfully dodge the advancing line of foam as it rolls up the beach.
Spring.—To the ends of the earth and back again extend the migrations of the sanderling, the cosmopolitan globe trotter; few species, if any, equal it in world-wide wanderings. Nesting in the Arctic regions of both hemispheres, it migrates through all of the continents, and many of the islands, to the southernmost limits of south America and Africa, and even to Australia.
The spring migration starts in March, though the last migrants may hot leave their winter resorts until late in April; they have been noted in Chile from April 11 to 29, and even in May. The earliest migrants have been known to reach New England and Ohio before the end of March. The main flight passes through Massachusetts in May, a few birds lingering into June. In the interior and on the Pacific coast the dates are about the same. C. G. Harrold has taken it in Manitoba as early as April 29, but William Rowan (1926) says that the main flight comes along during the last week in May and the first few days of June, when it is abundant.
A. L. V. Manniche (1910) thus describes the arrival of the sanderling on its breeding grounds in northeastern Greenland:
The sanderling arrived at Stormkap singly or in couples respectively June 2, 1907, and May 28, 1908. In company with the other waders and large flocks of snow buntings, which arrived at the same time, the sanderlings would in the first days after their arrival resort to the few spots in the marshes and the surrounding stony plains, which were free from snow; here they led a miserable existence. Heavy snow storms and low temperature in connection with want of open water made the support of life difficult to the birds.
The temperature increased quickly and caused in a few days the places in which the birds could find food to extend very much. The areas free from snow grew larger and larger, and the ice along the beaches of small lakes and ponds with low water disappeared before the scorching sun; at the same time small ponds of melting snow were formed around in the field. Now the sanderlings would in couples retire from the party of other birds, and lead a quiet and tranquil life on the stony and dry plains. Now and then they would pay a visit to ponds of melting snow and beaches of fresh water lakes in order to bathe and seek food, and here they would join the party of other small waders as for instance Tringa alpina and Aegialitis hiaticula. According to my experience old birds would never resort to salt water shore.
Courtship.—The same observer tells us all we know about the courtship of the sanderling, as follows:
The pairing began toward the middle of June. The peculiar pairing flight of the male was to be seen and heard when the weather was fine, and especially in the evening. Uttering a snarling or slight neighing sound, he mounts to a height of some two meters from the surface of the ground on strongly vibrating wings, to continue at this height his flight for a short distance, most frequently in a straight line, but sometimes in small circles.
When excited he frequently sits on the top of a solitary large stone, his dorsal feathers blown out, his tail spread, and his wings half let down, producing his curious subdued pairing tones. He, however, soon returns to the female, which always keeps mute, and then he tries by slow, affected, almost creeping movements to induce her to pairing, until at last the act of pairing takes place; when effected, both birds rush away in rapid flight, to return soon after to the nesting place. I have also observed males in pairing flight without being able to discover any female in the neighborhood, and then, of course, without realizing the pairing as completing act. The male is in the pairing time very quarrelsome, and does not permit any strange bird to intrude on the selected domain. He seems to be most envious against birds of his own kin.
Nesting.—The sanderling breeds only in the far north, so far north that only very few Arctic explorers have found its nest. Strangely, however, the first recorded nest was found in a region where it rarely breeds and considerably south of its main breeding grounds. This was the nest found by Roderick MacFarlane (1908) on the barren grounds of northern Canada, of which he says:
On the 29th of June, 1864, we discovered a nest of this species in the barren grounds east of Fort Anderson. It contained four eggs, which we afterwards learnt were the first and only authenticated examples at that time known to American naturalists. The nest was composed of withered grasses and leaves placed in a small cavity or depression in the ground. The contents of the eggs were quite fresh, and they measured 1.44 inches by 0.95 to 0.99 in breadth, and their ground color was a brownish olive marked with faint spots and blotches of bister. These markings were very generally diffused, but were a little more numerous about the larger ends. They were of an oblong pyriform shape. The parent bird was snared on the nest. It is a very rare bird in the Anderson River country, and we failed to find another nest thereof.