I've watched the postings on ant invasion problems and the questions
around whether boric acid is safe to use around birds.  I remembered
hearing many years ago of a baby poisoned by a mixup of boric acid
mistaken as milk powder...fatally poisoned as I recall.  So here is what
I dug out of "Dangerous Properties of Industrial Materials", Seventh
Edition, ed: Sax and Lewis, 1989 p 544:
        Boric Acid:
        "A human poison by ingestion and possibly other routes.
Moderately toxic by skin contact and subcutaneous routes in humans.
Poison experimentally by inhalation and subcutaneous routes.  Moderately
toxic experimentally by intraperitoneal and intravenous routes.  Human
systemic effects by an unspecified route:  wakefulness, anorexia, nausea
and vomiting.  Ingestion or absorption by other routes may also cause
diarrhea, abdominal cramps, erythematous lesions on skin and mucous
membranes, circulatory collapse, tachycardia, cyanosis, delirium
convulsions and coma.  Death has occurred from ingestion of less than 5
grams in infants and from 5 to 20 grams in adults.  Chronic exposure may
result in borism (dry skin, eruptions, and gastrointestinal
disturbances).  Experimental reproductive effects.  Mutagenic data.  A
human skin irritant.  Commonly used in the home as a cleaner and
insecticide...."
        There is also a long list of toxicity data by various routes on
various mammals, but no one seems to have set about deliberately
poisoning birds with it.  I would assume it is generally poisonous to
just about everything, although perhaps rather large doses are required
to be fatal.  Most of the mammal lethal dose (to 50% of an experimental
population) numbers are in the range one to four grams per kilogram body
weight.
        Way up north here ants seem to be a very seasonal problem, with
invasions mainly around spring thaw time.  Since they are hive animals,
there is little point in killing the individuals, because the hive will
keep on sending out explorers as long as any workers are left.  Maybe
the best that can be done is plug points of entry by tracing the little
nippers' trails with a tube of silicone caulking in hand.
        Hope this bit of info on boric acid gets around!
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