176 MIGRANTS AND WINTER RESIDENTS 



waters within the District, but it is no uncommon 

 sight to see files of geese flying over, and they are 

 found in the markets and restaurants all through the 

 winter." (Avifauna Columbiana.) 



American Herring Gull; Sea Gull: Larus argentatus 

 smithsonianus. 



Back and wings pearl-gray, the wings with black mark- 

 ings; rest of plumage white. Length 2 feet. October to 

 March. Common, especially in spring. Flocks of this and 

 the following species may often be seen at low tide on the 

 mud flats along the Eastern Branch. 



Ring-billed Gull : Larus delazvarensis. 



Back and wings pearl-gray; wings marked with black and 

 white; rest of plumage white; bill greenish-yellow, encircled 

 near the end with a broad black band. Length 20 inches. 

 February to April 5; October to November. Very common. 



Bonaparte's Gull: Larus Philadelphia. 



Much smaller than the preceding. In summer, head and 

 upper neck dark slate color; back and wings pearl-gray; 

 rest of plumage white. Immature birds and adults in fall 

 without black head. Length 14 inches. April to May 5; 

 October to November. Common. 



Black Tern: Hydrochelidon nigra surinamensis. 



In summer, head, neck and under parts black; back, wings 

 and tail slate color; bill and feet black. In winter, forehead 

 and under parts white. Length 10 inches. Sometimes com- 

 mon in August and September. 



Loon: Gavia imber. 



Head and neck dark bluish-green, patches of mottled 

 white on throat and sides of neck; upper parts and sides 

 glossy black, conspicuously spotted with white; under parts 

 white. Length 2 l / 2 feet. September to April 25. Common. 



