Dr. Walkinshaw (1938) says of the usual song: "Uttered at the rate of five or six times per minute, the song lasts slightly over one second. It is given all day long from the time of arrival until the young have left the nest and has been heard as late as the 16th of August (1931). The frequency is much greater during the early nesting season and during the earlier hours. During midday on warmer days the number of times per hour seems much less. Later, from four until near sundown, it again increases. During late nesting, when the young are about to leave the nest, the rate again decreases, but it is heard several days after the young leave the nest." Aretas A. Saunders tells me that the songs are pitched at C´´´´ or B´´´, and the call note, _tseek,_ at A´´´. _Field marks._--The golden swamp warbler could hardly be mistaken for anything else. The rich, brilliant yellow of the head and breast, sometimes almost orange on the head, only slightly paler in the female, the absence of wing bars, and the large amount of white in the tail will distinguish it. _Enemies._--Dr. Walkinshaw (1941) says that the house wren is a serious competitor with the prothonotary warbler in Michigan, contending with it for nesting sites in the bird-boxes. The cowbird is a persistent enemy of this warbler in spite of its hole-nesting habits; perhaps if the warbler nested in deeper holes it might find some relief from this pest. Among 70 sets of eggs of this warbler in the J. P. Norris collection, 18 contain cowbirds' eggs. Dr. Friedmann (1929) found no less than 36 records of such parasitism in the literature, and says: "As many as four eggs of the Cowbird have been found in a single nest together with four of the Warbler's. There are several cases on record of doubled-storied nests of this bird, with a Cowbird's egg buried in the lower story. Such cases are, however, not common, and usually the Warbler seems to make no attempt to get rid of the strange eggs." E. M. S. Dale wrote to me of a nest, found near Toronto in 1933, that contained seven eggs of the cowbird and none at all of the warbler! Snakes sometimes destroy the eggs or young. _Fall._--Dr. Walkinshaw (1938) says that "the majority of the Prothonotaries leave our rivers [Michigan] by the second or third of July. One may canoe some years a good many miles during the latter part of July or the early part of August without finding a single Prothonotary, whereas in other years many groups can be found. The majority evidently are early migrants. Very few remain until late August or early September, the latest date being September 9, 1934, at Battle Creek." The 1931 A. O. U. Check-List states that this warbler apparently crosses the Gulf of Mexico in migration "and is not found in Mexico north of Campeche," but probably some migration is along the coast of Texas and Mexico, as suggested by George G. Williams (1945).