126 BULLETIN 135, UNITED STATES NATIONAL MUSEUM 



In the young great blue heron powder-down tracts produced functional 

 feathers soon after the contour and flight feathers had burst their sheaths and 

 the bird began to preen and care for its plumage. The heron in question had 

 been taken from the nest while still too young to know fear of man, and as I 

 reared it by hand it became devoted to me, though fierce and truculent toward 

 all others. As its plumage developed I noted that the bird constantly rubbed 

 the bill in the powder downs, and on examination found that the heron was 

 utilizing the greasy, powdery substance given off by the tracts to dress and oil 

 the contour feathers. The bill was worked in among the powder downs until a 

 small amount of the exuviae had gathered at the tips of the mandibles and then 

 contour or wing feathers were pulled rapidly through the bill, anointing them 

 with this oily substance. At once return was made to the powder downs after 

 which other feathers were treated in turn until the whole of the body and wing 

 plumage had been properly dressed. I had no difficulty in observing the process 

 as, when permitted, the heron until practically grown delighted in standing upon 

 my knee as I sat in a chair. I was able to place my fingers in beside the tip of the 

 bill, in the powder downs, to feel the mandibles gently nibbling at the downy feath- 

 ers and then to see the bill withdrawn with its sides covered with the grayish 

 powder. Following this I observed as it was passed over other feathers. This 

 process was repeated daily whenever I cared to see it. At the same time I dis- 

 covered by examination that the uropygial gland, the usual source of oil for 

 feathers, seemed undeveloped and remained in a nonfunctional condition until 

 the heron was pratically grown. The bird in early life paid no attention to this 

 gland, but worked in either pelvic or pectoral down patches. The actual devel- 

 opment of the oil gland I did not observe as the heron at this stage became so 

 vicious toward others that I was forced to discourage its tameness until finally 

 it left the laboratory. 



Parenthetically I may add that although on various occasions I examined 

 powder-down tracts in living and in dead herons I was unable to observe that 

 these tracts were luminous, in spite of numerous records on the part of others 

 to the contrary. 



DISTRIBUTION 



Breeding range. — Western United States except the Pacific coast 

 region. East to Montana (Damson County and Fallon) ; Wyoming 

 (Sheridan and Fort Laramie) ; central Colorado (Crow Creek, Weld 

 County, Brighton, and Arkansas Valley, probably); New Mexico 

 (Carlsbad); and Texas (Kerr County, probably). South to central- 

 western Texas (Tornillo Creek near Boquillas) ; Sonora (Guaymas) ; 

 and northern Lower California (Salton River) . West to Lower Cali- 

 fornia (Salton River) ; southeastern California (Pehcan Island, Salton 

 Sea and the Colorado River near Riverside Mountain); Nevada 

 (Truckee River and Pyramid Lake) ; and Oregon (Klamath Lake, 

 probably). North to Washington (Yakima Valley, probably and 

 Cheney) ; and Montana (Great Falls, probably and Dawson County, 

 probably) . 



Winter range. — Mexico, and southwestern United States. North 

 (rarely) to Idaho and Wyoming (Yellowstone Park) . East to New 

 Mexico (Dona Ana) ; and Texas (Fort Clark and Brownsville) . South 

 and west to the west coast of Mexico (Manzanillo). North to Ari- 



