194 THE .CONDOR Vol. XllI CANVASBACK ( Marila valisineria) Probably the most important feature of our field work at Bart was that of establishing beyond question, the Canvasback, as a Colorado breeder. Although we made a special effort throughout the three seasons to locate nests of this species, one was all that we discovered, and judging from the few ducks seen, as compared with the number of individuals of the other species, we were no doubt very fortu- nate in finding the one nest. On May 31, 1907 we found a fine set of ten Ruddy's eggs in an excavation in the side of a large musk-rat house. Upon returning to this nest on June 8, we found another and newer nest in the same musk-rat house containing eight fresh eggs of the Canvasback. This was also an excavation in the side of the house, much deeper than that of the Ruddy (the eggs being fully eight inches from the Fig. 66. NEST AND EGGS OF RUDDY IN EXPOSED POSITION ON TOP OF MUSKRAT HOUSE entrance), and higher above the water line. The cavity was fairly well lined with white down, quite a quantity of which was also scattered about the entrance of the burrow. A week later (June 15) the full complement of fourteen eggs had been deposited, and covered with a thick layer of down. The female was surprised not far from the nest and afforded us a splendid opportunity for identification. These eggs hatched on or about July 6. RUDDY Dvc? ( Eristnatttra./anzaicensis) Judging from the numbers of Ruddy Ducks seen throughout the three seasons on all the smaller marshy lakes, we should have found them nesting in considerable numbers, but three nests and a mixed set was the best that we could do.
