One nest, that of a Seaside Sparrow containing four young, became fouled with excrement when the young were nine to ten days old. It is interesting that these young were cared for only by a male, at least for the last four days of nest life, and that one of the young birds died two days before the others left the nest. This male's mate was probably a female that I banded on June 18 (the young left the nest on June 23) and never saw again. A female, whose mate was probably killed by me on June 15, continued to incubate the three eggs until they hatched on June 29, but deserted the nest when the young were two days old. This female was seen again on August 1 more than 500 yards from her nest site on the island immediately north of the study area. Devotion of parent passerine birds to the young typically increases with the growth of the young (Nice, 1943:245). This may explain why the mateless female deserted its nest when the young were only two days old, whereas a mateless male continued to care for his six-day-old young. The death of one nestling, and the eventual fouling of his nest may indicate that the job was too much for one adult to perform. The correlation of increasing devotion of the parents with increasing age of the young was further illustrated by the distraction display, noted by me, on the part of a pair of Seaside Sparrows on the day their young left the nest. As I lifted the four nine-day-old young from the nest for weighing, they began to give the distress call. This attracted the parents from the feeding area approximately 60 yards away. The two adults ran around on the ground within ten feet of me giving the _tsip_ note and fluttering their wings. Several times the adults flew within a few feet of me, making a vibrating sound with their wings. Although I realized the function of this display, it was distracting nevertheless. ACKNOWLEDGMENTS I am indebted to Assistant Professor Harrison B. Tordoff for comments and suggestions throughout the preparation of this manuscript, and to Mr. Stuart W. John who photographed the birds and the habitat scenes. The aerial photograph of the study island is reproduced with the permission of Fairchild Aerial Surveys, Inc., and the photograph of Lavallette and Chadwick through the kindness of the Lavallette Yacht Club. The drawings were made by Mr. John R. Beeder. Additionally I wish to express my gratitude to Dr. Dean Amadon, Mr. H. Lyman Sindle, and Mr. Lester B. Woolfenden for help and advice in certain aspects of the field work. SUMMARY A comparative study of the breeding behavior of the Seaside Sparrow and Sharp-tailed Sparrow was made in New Jersey in 1955.