_A. m. maritima_ is monogamous, the pair-bond being maintained throughout a breeding cycle. _A. c. caudacuta_ is promiscuous, relations between the sexes being limited to copulation. For _A. c. subvirgata_ a relationship other than promiscuity has been intimated (Lewis, 1920:587-589). Concerning observations of the nest he found at Yarmouth, Nova Scotia, Lewis wrote: "The nest was found after I had quietly watched the parent Sparrows for about an hour, while they were bringing food to their young.... The male sang from time to time from a piece of driftwood on the marsh about 30 feet distant from the nest. When I was examining the nest and the young birds, the parents made no demonstration for some minutes, but later they came near and uttered chip's, much like those of Savannah Sparrows." NESTS I found the nests of all eight pairs of Seaside Sparrows which nested on the Lavallette study island in 1955. Four nests were supported by marsh-elder bushes, three of which were dead. These nests were placed low enough to be hidden by numerous stems of black grass, as were the other four nests. Of the remaining four nests, three were placed in tussocks of black grass and the fourth one gained support mostly from cord-grass stems. The eight nests ranged from 9 to 11 inches (9.6 inch average) from the rim to the ground, the four nests in the bushes being the highest. The outside diameters of the nests ranged from 3 to 4.5 inches (3.9 inch average) and the outside depth varied between 2 and 3.5 inches (2.7 inch average). Seven of the nests had an inside depth of 1.5 inches; the other one was only an inch from the rim to the floor. The inside diameter of the cup varied between 2 and 2.5 inches. As mentioned above all eight nests were shielded by stems of black grass. Stems were not woven over the nests by the birds; rather it was the choice of the nest sites that resulted in the concealment. The only plant used for nest material was black grass. In all cases the black grass limited the directions from which the nests could be entered. Six of the nests were approached from a direction varying between northeast and southeast. The prevailing winds of spring and summer are from the south and southwest; the black grass consequently leans in the opposite direction. The remaining two nests were entered from the northwest. These were nests built in marsh-elder bushes where the grass stems were held upright by the branches of the bushes. One nest, built in a small dead marsh-elder bush, was tilted by the growth of stems of black grass which were used for support on one side. This tilting did not cause the contents to spill, but, I judged, did cause the adults to desert the nest.