168 THE CONDOR Vol. XXII ~ 
hole was lined with vegetable fibers and contained three babies, just hatched 
and with eyes not yet opened. The next day I found them covered with a 
thin growth of long black down. The mother kept to the nest most of the 
time, but I observed the father hunting through the grass in the vicinity more 
than onee. The babies remained in the nest about two weeks. 
Young birds have been seen to fly as early as the end of June at the lower 
elevations; and as late as August 12 I have found them in the same stage at — 
higher altitudes. I have not been able to determine whether the mountaineers 
are second broods or not. Regularly, as early as the middle of August, the 
Juncos are in small flocks. | 
Yellowstone Park, Wyoming, June 28, 1920. 
THE FUNCTION OF POWDER DOWNS IN HERONS 
By ALEXANDER WETMORE 
WITH TWO PHOTOS 
ITE curious fluffy, greasy tracts of feathers found in patches on the breast 
and pelvic region in herons and occurring at random in various other 
eroups of birds, even in the Passeriform order, have been the subject of 
considerable speculation and comment. Some time ago I had opportunity to 
study their development in the young of a few species of herons and from 
these observations was able to settle definitely their function so far as con- 
cerns this group of birds at least. Observations were made first while rearing 
a young Great Blue Heron (Ardea h. treganzar), and were checked and verified 
in the young of the Snowy Heron (Egretta c. candidissima), Black-crowned 
Night Heron (Nycticorax n. naevius), and Bittern (Botaurus lentiginosus). It 
is interesting to note that my findings verify a possible function of these tracts 
as suggested by Newton and Gadow (Dictionary of Birds, 1896, p. 654). 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 uti- 
lizing 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 
