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214 THE CONDOR Vol. XVII to the Arctic coast of Alaska. The earliest birds were noted at Point Barrow May 15, 1882, and May 25, 1883. But already by this date the species has appeared on the Mackenzie near the mouth of the Liard. By what route do these birds reach their destination ? They do not come from the south, for the species is vnlrnown in southern Canada at any time of the year. The nearest part of the Pacific Ocean is to the southwest near Sitka, but the birds do not come by that route, for the birds of this part of the country have been closely watched for several year? and the. only spring record of the Yellow-billed Loon is that of a straggler seen on Admiralty Island May 25, 1911. They do not come up the valley of the Yukon, for this species is not known anywhere in the interior of Alaska. The only possibility left is that they come from the Arctic Ocean to the northward. But all the lakes between Great Slave 'Lake and the Arctic Ocean are still covered with ice and so is the delta of the Mackenzie River. Thus apparently the only solution of the problem is a migra- tion at a single flight from the open waters of the Arctic Ocean across 700 miles of frozen country to the open water near Great Slave Lake. This supposition also requires that the birds pass Point Barrov? off-shore many days before they were noted at that place. Thus the spring route from eastern Asia wonld be first a 2000 mile trip northeast to Bering Strait, then 500 miles still northeast to round Point Barrow, then 500 miles east to the coast of Mackenzie, and then finally 700 miles south--in the spring--to Great Slave Lake. Trnly a most remarkable route, but who will suggest a route more plausible ? The route is apparently reversed in the fall. The species is common on Great Slave Lake until the middle of September, and Sir John Franklin says that near there at Fort Enterprise this species was the last water bird to leave, October 26, 1820. By this time the smaller lakes and streams were closed by the ice, .but .there would still remain enough open water in the larger lakes and the Mackenzie River for the birds to work their way north in the early winter the 700 miles to the open Polar Sea. Then there woald still remain a 3000 mile trip to their winter home and they wonld be passing Point Barrow in November weeks after the last of the birds which nested there had disappeared, for the latest fall date at this place is September 25, 1897. And so this article closes with a reiteration of the opening paragraph: The migration route of the Yellow-billed Loons which visit Great Slave Lake is the most incomprehensible problem of migration on the North American continent. Washington, D.C., August 18? 1915. NOTES ON THE NESTING OF THE WHITE-TAILED PTAi?MIGAN IN COLOl?ADO By W. C. BRADBURY WITH FIVE PHOTOS N MAY 7th of this year (1915) I sent out a party of four young men, with team, camera, camping outfit and equipment, for the purpose of col- lecting the rarer varieties of eggs and birds nesting at high altitudes, this in the interests of the Colorado Museum of Natural History, Denver. Com- mencing at the foot-hilis near Morrison, Colorado (altitude 5750 feet above sea-