480 BULLETIN 2 03, UNITED STATES NATIONAL MUSEUM 



eggs of the Lousiana watertlirusli. The measurements of 50 eggs 

 average 19.1 by 14.6 millimeters; the eggs showing the four extremes 

 measures 20.8 by 15.0, 19.3 by 16.0, and 17.8 by 13.7 millimeters 

 (Harris). 



Young. — Nothing seems to be kno^n about the incubation, or about 

 the care and development of the young. 



Plumages. — Dr. Dwight (1900) calls the natal down deep olive- 

 brown, and describes the ju venal plumage of the northern waterthrush 

 as "above, deep olive-brown with cinnamon edgings. Wings and tail 

 darker, the coverts tipped with pale cinnamon. Below, primrose- 

 yellow heavily streaked on the chin and less heavily on the throat, 

 breast and sides with deep olive or clove-brown. Indistinct supercili- 

 ary line and orbital ring buff ; transocular stripe dusky." 



The first winter plumage is acquired by a partial postjuvenal molt in 

 July, which involves the contour plumage and the wing coverts, but 

 not the rest of the wings or the tail. Young and old are now prac- 

 tically indistinguishable. The sexes are alike in all plumages. Dr. 

 Dwight describes this plumage as "above, yellowish olive-brown in- 

 cluding wing coverts, without edgings. Below, straw-yellow, palest 

 on the crissum, the flanks washed with olive-brown, spotted on the 

 chin and streaked, except on the mid-abdomen and crissum, with black 

 veiled by overlapping whitish edging-s. Superciliary stripe and or- 

 bital ring pale ochraceous-buff ; transocular streak deep olive-brown ; 

 auriculars dusky. 



"First nuptial plumage acquired by marked wear, birds becoming 

 browner above and paler below, the veiling lost. It is possible there 

 is a very limited growth of new feathers about the head." Year-old 

 birds can usually be recognized by the paler and somewhat worn wings 

 and tails. 



Adults have a complete postnuptial molt in July. The adult winter 

 plumage is like that of the first winter, but the streakings below are 

 rather broader and the wings and tail are darker. Subsequent spring 

 plumages are produced by wear, as in the young bird. 



Food.— Fovhu^h. (1929) writes: "The food of the Water-Thrush 

 consists more or less of aquatic insects, beetles and their larvae, and 

 moths. It picks up dead and soggy leaves from crevices in the rocks 

 and throws them aside, thus uncovering lurking creatures on which 

 it feeds. According to Dr. Elliott Coues tiny molluscs and crusta- 

 ceans are eaten, and Arthur T. Wayne took one that had eaten a few 

 small minnows. Dr. B. H. Warren names small worms as one con- 

 situent of its food, and it also eats quantities of mosquitoes." 



Dr. Wetmore ( 1916) reports on the contents of four stomachs of this 

 species, including both races, collected in Puerto Rico, as follows : 



"Fly pupae and a few adults were present in three stomachs and 

 amount to 43 per cent of the total. Ants (24 per cent) , of which one 



