JF Ptak Science Books Quick Post
This title sounds a little stretched and disingenuous, but it is not, not really--there was a plan to destroy periscopes of subs, rendering them ineffectual while submerged, and it did involved exploding birds, so the title to this quick post is largely true.
The article/note explaining it all appeared in the February 1918 issue of Popular Mechanics, which is reproduced here in full. It is brief and to the point: a falcon would be trained to hunt a metal tube protruding from water, which is would attack while carrying a pouch of high explosives around its neck that would detonate when it came into contact with water. No more periscope, no more sub, no more falcon.
It does seem to be a wooden-cog reaction to a metal gear problem...and very off-putting.
I haven't seen very many bits on using animals as actual weapons of mass destruction, though the ones I recall catapulted diseased animals over and into enemy lines, and a few other truly bad things not worth repeating. But I must say that I found this approach to warfare particularly repugnant, even for warfare of desperation.