ROUGH-WINGED SWALLOW 429 



what through their skins. They are coated with streaks of gray 

 down. They develop rapidly. Within one week they assume some- 

 what the aspect and plumage of tlie adults. When they are ready 

 to leave the nest, at the lapse of 12 days, they are pale bro'vyn but 

 cannot vrell be differentiated from the adults while on the wing. I 

 went to the trouble to collect and examine young just out of the nests. 

 Superficially their forms seemed more like bank swallows than like 

 their adult parents." 



Skutch (MS.) continues: "When 13 days old the nestlings were 

 well feathered, but they remained in the burrow a full week longer, 

 gaining strength to fly." Thus, he considers the nestling period 

 to be 20 or 21 days. Weydemeyer (1933), out of a total of 34 nests 

 under observation, gives the following dates of young in nest : June 

 8, 1921, to July 9, 1928. In nine other nests, the young left the nest 

 by July 22, 1931, to July 29, 1930. 



The roughwing raises one brood during the season. 



Plumages. — At the time of leaving the nest the young birds are 

 similar to their parents in size, feathering, and length of wing and 

 tail, but the first primary lacks the roughness of the adult feather; 

 indeed, it is probable that nearh'^ a year passes before the young 

 birds acquire this saw edge that gives them their name. Also, the 

 plumage is tinged with rufous or cinnamon, especially on the throat 

 and upper breast; the wing coverts and tertials are margined with 

 the same ruddy tint. 



Dwight (1900) says: "First winter plumage acquired by a complete 

 postjuvenal moult after the birds have migi'ated southward in Sep- 

 tember, or very likely while they move leisurely along in flocks." 



The first nuptial plumage is apparently acquired by wear. Adults 

 have a complete postnuptial molt after they have migrated south- 

 ward, mainly in September or later. The sexes are alike in all 

 plumages. 



Food. — Howell (1924) says: "The food of the rough-winged swal- 

 low consists principally of insects, with a few spiders. Flies com- 

 posed nearly one-third (32.89 per cent) of the total. Ants and other 

 Hymenoptera are extensively eaten, and bugs to a lesser extent. 

 Beetles amounted to nearly 15 per cent of the food and included the 

 cotton-boll weevil, alfalfa weevil, rice weevils and flea beetles. A 

 few moths, caterpillars, dragonflies. Mayflies, and an occasional 

 grasshopper make up the remainder of this bird's food." 



Behavior. — In the field the roughwing appears as a sober-colored 

 little bird, plain grayish brown above and lighter below. At a dis- 

 tance it can easily be confused with the bank swallow, but when the 

 latter bird sweeps over the observer the breast band is readily de- 

 tected. If the two birds are seen "together, the larger size of ser- 

 ripennis and its more brownish appearance are at once apparent. 



