In response to Wayne Iverson's query, I quote the following from Life
Histories of North American Nuthatches, Wrens, Thrashers and their Allies,
by A. C. Bent, U. S. National Museum Bull. 195, 1948:

"Unfortunately for the dipper's welfare, it is too fond of the spawn and
small fry of salmon and trout, and it is tempted to feed on them freely
when and where they are easily available. This habit has made many enemies
for the dipper among sportsmen and especially among the managers of fish
hatcheries. The damage done to wild salmon and trout by this bird is
probably not serious under natural conditions, for these fish are known to
lay vastly more eggs than can ever hatch, many eggs eaten by the dipper are
known to be infertile, and vastly more fry are hatched than can possibly
survive; I have seen it estimated that, if all fish eggs hatched and the
fry grew to maturity, the oceans would soon be packed solid with fish.
Furthermore, the spawning grounds of both salmon and trout are mainly in
waters not frequented by the dippers, as these birds live mainly on the
rapid mountain streams rather than on the slower valley streams and
spawning grounds where they are rarely seen."

Bent goes on (for almost a page) to quote others to the effect that,
although dippers are (were) regularly shot by hatchery managers, they
actually did relatively little damage (although one quote mentioned 10,000
cutthroat fry taken from one hatchery during one winter!). Screening the
ponds was recommended, and that is what is done today to keep dippers and
other fish-eaters out of hatchery ponds. I think some of the mesh is
sufficiently large, however, so that dippers are the only birds that *do*
regularly partake of hatchery stock.

So you were fortunate, Wayne, to see something that all the old guys knew
about but the more recent books overlook. That is very commonplace, and I
am always amazed at how much information in Bent's life histories seems to
be lost from the modern literature on birds.

Dennis Paulson phone: (206) 756-3798
Slater Museum of Natural History fax: (206) 756-3352
University of Puget Sound e-mail: dpaulson at ups.edu
Tacoma, WA 98416