Dragging the marsh with a rope was ineffectual in finding nests. The birds flushed long before the rope neared them. I found nests of the sparrows by using a blind. From a blind I would determine the approximate location of a nest by watching the movements of the adult birds. Then I would either make a direct search of the vegetation or move the blind closer to find the actual site. Many hours were spent in blinds. I had two in operation throughout the breeding season, and it was from these that most of the data on behavior were accumulated. Observations were made by means of a 7 x 50 coated binocular and on occasions by means of a 19.6x spotting telescope. DESCRIPTION OF THE AREA The intensive work was carried out on the marshes west of the town of Lavallette in Ocean County, New Jersey. Further observations were made at other localities in the county, in particular at the Chadwick marshes (plate 6), one mile north of the Lavallette site, where many of the Ammospizas were banded. The breeding Ammospizas of the localities are the nominate races, _A. c. caudacuta_ (Gmelin) and _A. m. maritima_ (Wilson). Characteristic of the sand beaches of the Atlantic coast of the United States are offshore bars which, when exposed, form long bays parallel to the coastline. These bays become surrounded by marshes that in turn are inhabited by the two species of _Ammospiza_. The birds prefer the marshes closest to the ocean (plate 6). I made trips to the marshes on the mainland side of upper Barnegat Bay and found only a few Sharp-tailed Sparrows and no Seaside Sparrows in residence. The island of the Lavallette marshes that I worked on was approximately 1400 feet long and 600 feet wide. One-third of the east central end of the island was covered with sand fill, pumped there several years before the study was begun (plate 1, fig. b). The island was also ditched. The four east-west ditches are spaced 125 feet apart; the two ditches perpendicular to these are 340 feet apart and are situated in the western portion of the island. These ditches, originally dug as a means of decreasing the mosquito population, are one foot wide and almost three feet deep. The excavated earth is deposited in a row paralleling the ditch. The entire island, excluding the sand fill is not more than two feet above normal high tide. In August, 1955, abnormally high water, a result of hurricane "Connie", rose four to five feet and covered all but the tops of the bushes and a few mounds of sand. Low tides expose no mud flats for the edges of the marsh are nearly vertical banks and the water along the edges is more than one foot deep.