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 July, 1911 NESTING NOTES ON DUCKS OF THE BARR LAKE REGION, COLO. 123 several species are omitted, as I have endeavored to include in these notes only such data as will add to the general fund of information on this subject. MALLARD ( Anas platyryncos) 'During our numerous trips through the Barr Lake district we found the Mallard one of the commonest ducks. A very large flock wintered on the larger lakes; during spring and fall migration flocks of Mallards were always in evidence, and during the summer months pairs and single birds were quite common. It was therefore rather surprising that despite careful and persistent searching, we found but two nests of this species during three seasons' work. Both of these, however, were quite out of the ordinary and are worthy of description. On May 11, 1907, while wading out from shore through a sparse, burnt-over b'ig. 38. MALLARD'S NEST ON MUSK-RAT HOUSE, SHOWING DETAILS OF NFT CONSTRUCTION growth of cat-tails, skirting asmall lake, a female Mallard flushed noisily from a large musk-rat house and revealed a beautiful set of eleven eggs deposited in a hollow, scraped in the dead cat-tails and debris forming the house, and well lined with down. The house was very conspicuous, standing over two feet above the surface of the water surrounding it, and the nest was an open one as can plainly be seen from the accompanying illustration (Fig. 37). There was no apparent attempt at concealment. The female flushed when we were fully thirty yards from the nest, and the male swam about well out of gunshot. A week later (on the eighteenth) we succeeded in approaching to within ten feet of the brooding female, who was in plain sight even froni a considerable dis- tance. The nest was in much the same condition as on the preceding visit, but the downy lining was much less in edence. On the twenty-fourth we found that