From Silent Spring (I’d remind you that these irrigation projects were courtesy of the US Government):
Such poisoning of waters set aside for conservation purposes could have consequences felt by every western duck hunter and by everyone to whom the sight and sound of drifting ribbons of waterfowl across an evening sky are precious. These particular refuges occupy critical positions in the conservation of western waterfowl. They lie at a point corresponding to the narrow neck of a funnel, into which all the migratory paths composing what is known as the Pacific Flyway converge. During the fall migration they receive many millions of ducks and geese from nesting grounds extending from the shores of Bering Sea east to Hudson Bay — fully three fourths of all the waterfowl that move south into the Pacific Coast states in autumn. In summer they provide nesting areas for waterfowl, especially for two endangered species, the redhead and the ruddy duck. If the lakes and pools of these refuges become seriously contaminated, the damage to the waterfowl populations of the Far West could be irreparable.
What has become of the redhead and the ruddy ducks?
Here is the Cornell Lab of Ornithology’s assessment of the Ruddy’s prospects today. Here is the Cornell Lab’s assessment of the Redhead Duck’s prospects. A fun research project for someone interested in the environment is to go through the book, now 50 years since publication, and revisit the passages like the ones above. That one was from p.46. Here is one from p. 48:
Meanwhile, the nesting colonies of the grebes dwindled — from more than 1000 pairs before the first insecticide treatment to about 30 pairs in 1960. And even the thirty seem to have nested in vain, for no young grebes have been observed on the lake since the last DDD application
Extra points to those of you who know who authorized the spraying.
From this NOAA report it looks like there are around 470 nesting pairs in Clear Lake, even as the report indicates that such an estimate is likely an underestimate of the number of nests. I have no way to verify the 1000 number or the 30 number Carson cited above.