JarL, 191'8 EARLY AUTUMN BIRDS IN YOSEMITE VALLEY 19 Rock Wren'(galpinctes obsoletus obsoletus). One seen August 31; heard once Or twice afterwards. Western House Wren (Troglodytes aedon parkrnani). Common but not very num- erous. Last one seen September 15. Western Gnatcatcher (Polioptila caerulea obscura). The only one seen was taken September 25. Western Bluebird (gialia mexicana occidentalis). A complete family of Western Bluebirds lived in front of Camp Curry, but the specie, s was seldom noted elsewhere. A small flock, in company with Audubon Warblers, was seen on September 20 near the foot-bridge west of Yosemite Village, but it did not stay long. APPRO?I?JATE DATES OF DEPARTURES Black-headed Grosbeak (Zamelodia melanoceghala). None seen after September 20. Lazuli Bunting (Passerina amoena). Very scarce toward the end of September; an immature taken September 28. Western Warbling Vireo (ireosylva gilva swainsoni). Nu?nerous during latter part of August, but disappeared before middle of September. Cassin Vireo (Lanivireo solitarius cassini). Numerous at first, gradually growing scarcer, but a few still in valley on September 28. California Yellow Warbler (Dendroica aestiva brewsteri). D?sappeared early in September. Golden Pileolated Warbler (Wilsonia pusilla chryseola). Last goticed September 22. Western House.Wren (Troglodytes aedon parkmani). Last one seen September 15. San Francisco, November 1, 1917. A NOTE ON THE TRACHEAL AIR-SAC IN TIIE RUDDY DUCK By ALEXANDER WETMORE N A PAPER published recently' the writer described a peculiar air-sac in the male Ruddy Duck (Erismatura jama.icensis) that was developed from the trachea, and was capable of inflation through a slit behind the larynx until it forlncd a pronounced swelling on the neck. The dissections on which these ob-' servations were based were made in the field in the summer of 1915, and during the following winter. Other observations on this peculiar development were made in the summer of 1916, but through the writer's absence in the field it was found impracticable to include them in the paper quoted, which was then in press. On May 29, 1916, and on subsequent dates several adult Ruddy Ducks were captured alive in shallow ponds in the marshes at the mouth of Bear River, Utah. These ducks often were found in narrow channels that, though two feet deep or more, were barely wide enough to allow a boat to pass. As we came down ?hese narrow runs the ducks swam on ahead until finally they came out into ponds where the water was not more than six or eight inches in depth. When closely pressed these birds chose to dive rather than attempt a laborious effort at flight. Under these conditions it was often possible to capture them alive and un- injured. In the clear water they could be seen swimming rapidly, both feet stroking vigorously together, with wings held close at the sides and the head turn.. ing quickly as they sought an avenue of escape. On examining the males I was surprised to find that normally the tracheal I On Certain Secondary Sexual Characters in the Male Ruddy Duck, ?rlsmatu?ajamaicensis (Omelin) Proc. U.S. Hat. Mus., vol. 52, Feb. 8, 1917. pp. 479-482. '
