AN EXPERIENCE WITH HORNED GREBES
(COLYMBUS AURITUS).
BY ALEXANDER D. DUBOIS.
Plates VIII-X
The southeastern portion of Teton County, Montana, lying in the prairie region east of the Rocky Mountains, comprises flat and rolling bench-lands, traversed at frequent intervals by coulees which are tributary to the Teton and Sun Rivers. On these benches are occasional shallow depressions which have no natural drainage. They form transient “prairie sloughs” which may be dry at one season and wet meadows or ponds of water at another.
The slough which afforded the present observations is a crescent-shaped depression, not more than ten or twelve acres in extent, curving about a knoll upon which stands a homesteader’s cabin. There are no lakes or water courses in the immediate vicinity. During the last few years the region has been rapidly transformed into grain farms. At the time these notes were made the meadow in question was bordered on three sides by plowed fields. The spring of 1917 was an extremely rainy one, following a winter of much more than normal snowfall. In consequence, the crescent-shaped meadow became a marshy sheet of water.
On the open water of this pond two Grebes were seen on several days in May. On the third of June, while walking around the pond scanning its surface with a field-glass, I was suddenly amazed to see a Grebe sitting upon a nest which protruded above the water amid the scant vegetation. Careful examination showed the bird to be Colymbus auritus. She slipped from the nest, as I slowly waded toward her, and swam about in the open water, anxiously watching my every movement. The interest was mutual. After watching the bird for some time I went up to the nest and found that it contained two eggs. Subsequent visits showed that the eggs were deposited at intervals of two days; the dates of the visits and number of eggs found at each visit being as follows: June 3 (2); June 5 (3); June 7 (4); June 9 (5); June 12 (6); June 13 (6).
Plate VIII.
1.