In the case of certain island-inhabiting birds, however, some of these questions may be answered with a fair degree of certainty. Thus Ipswich Sparrows are known to nest only on Sable Island, off the Nova Scotia coast, and we are warranted in believing that the same birds, fate permitting, return to their sandy home year after year. Gannets (_Sula bassana_) nest in the western hemisphere only on three islets in the Gulf of St. Lawrence, and it is probable that the surviving individuals return each year to their former breeding grounds. The Terns of Muskeget and Penikese, forming the only two large colonies of these birds remaining on the Atlantic coast, return to their island retreats every spring; and actuated by this same love of home, the Brown Pelicans of the Indian River region of eastern Florida annually repair to a certain small island for the purpose of rearing their young. Many similar cases might be cited in confirmation of the belief—supported also by isolated observations on the mainland—that birds nest in the same locality throughout their lives, and, on occasion, may even occupy their previous season’s nest. As regards the manner in which these island-inhabiting birds arrive at the nesting grounds, as far as our recorded information goes, it seems that without relation to latitude they appear each spring with remarkable regularity, not straggling back a few at a time, but sending on an advance guard, which usually remains only a short time and is followed, a few days later, by apparently the entire colony. Thus, Mackay writes of the Terns of Penikese: “In 1893 the Terns arrived on May 10th, in the night, an advance guard of several hundred being noted early the following morning at daylight; these all left before noon of the 11th, and on the morning of the 12th, before daylight, immense numbers had again arrived.... In 1896 the Terns commenced to arrive during the night of May 9th; they were in evidence at daylight on the 10th, and continued to arrive all day, and on the morning of the 11th the usual colony had taken possession of the island.” (Auk, xiv, 1897, p. 284.) The migration of the island-nesting Terns in the tropics is apparently no less regular. Scott states that the Noddy arrived in the Tortugas “on April 20th in large numbers, but remained only two days; after inspecting their breeding grounds, all departed to return about a week later in greatly increased numbers, when breeding was almost at once commenced.” (Auk, vii, 1890, p. 306.)