LIFE HISTORIES OF NORTH AMERICAN DIVING BIRDS. 3 



season. It was almost impossible to count or even to estimate the 

 number of western grebes in this colony, for the nests were scat- 

 tered over a wide area among the reeds or bulrushes {Scirpus 

 lacusfris), and many of them were beyond our reach in water too 

 deep to wade; there were certainly hundreds, and perhaps over a thou- 

 sand of them. The nests were floating in water 2 feet deep or more 

 and consisted of compact masses of rubbish, dead and rotten reeds, 

 mixed with a few green flags, and plastered with soft slimy vege- 

 table substances. They were generally anchored to growing bul- 

 rushes in plain sight, but some were well concealed from view in 

 thick clumps. They were built up from 3 to 5 inches above the 

 water and measured from 18 to 25 inches in diameter, the inner 

 cavity being from 7 to 9 inches in diameter. We were surprised to 

 find the bodies of a large number of these grebes lying dead on or 

 near their nests, during both seasons, and were unable to account 

 for it; sometimes two bodies were found at one nest. Muskrats 

 were quite common in this slough, and a pair of minks had a den 

 on the island; perhaps the latter may have indulged in a midnight 

 massacre. In another deep-water slough, near Crane Lake, we 

 found a small colony of 12 or 15 pairs of western grebes nesting 

 among the cat-tail flags (Typha latifolia), where the nests were often 

 well concealed in thick clumps. 



Although they were not so shy and retiring about their breeding 

 grounds as the other grebes, I was never able to surprise a western 

 grebe on its nest until one cold, rainy day when I waded into the 

 slough and saw the birds sliding off their nests all around me, 

 swimming away almost under my feet and bobbing up unexpectedly 

 near me; the sun came out soon afterwards and I longed for my 

 camera; I tried to repeat the experience later but never succeeded. 

 Apparently they sit more closely in wet weather, but under favor- 

 able circumstances do not find it necessary. Evidently both sexes 

 assist in incubation. They seldom, if ever, cover the eggs with the 

 nesting material as other grebes do. I once flushed a female ruddy 

 duck from a clump of bulrushes, but a careful search revealed 

 nothing but grebes' nests and later I took from a grebe's nest two 

 eggs of the western grebe and an egg of the ruddy duck. The 

 smaller grebes also occasionally lay an egg in a western grebe's 

 nest. 



In North Dakota the western grebes breed abundantly in some 

 of the sweet-water lakes, generally in deep water and often among 

 the tall canes and wild rice which grows 8 or 10 feet high. The 

 extensive marshes of tall canes {Phragmites connmunis) bordering 

 the Waterhen River in Manitoba form a safe and almost inaccessi- 

 ble breeding resort for this species where large numbers find a con- 

 genial summer home. The water in these marshes is too deep to 



55916— 19— Bull. 107 2 



