Jim, I agree with most of the points you make regarding the two incidences I
described. Certainly, a sample of 2 is clearly too small to provide
conclusive proof of cause and effect that fireworks in urban settings are a
significant cause of bird mortality. And there are certainly the issues of
predators, noises other than fireworks, and numerous other things which scare
birds and could cause their nests to fail. However, probability analysis
would, I think, indicate that there is likely a connection here.

Consider the following. These are not just two completely random failed
nests. They are the only nests I have observed closely which were in
progress and doing fine prior to and until July 4. The Black-capped
Chickadee and Bewick's Wren nests I have followed in my yard have all fledged
long before July 4.

And consider the particulars of the two Robin's nests. The first nest
(1998), a point I did not mention in my previous post, was actually a 2nd
brood for the year. The first clutch of 2 eggs had fledged fine. So, it was
OK through the entire first brood cycle and to the point that the parent was
setting on a 2nd clutch. And it was OK until July 4, and then found failed
on July 5. The 2nd nest (2001), was only the first brood, but was fine
through the period of egg laying and incubation (incubation is shown in "The
Birders Handbook" to be 12-14 days) and to the point where the nestling
appeared to be about a week old. So this 2nd nest was OK for about 3 weeks
or so, and was OK when checked on July 3, but found failed on July 5.

It seems to me that the probability of both nests being fine for an extended
period leading up to July 4th and then being found failed on July 5th is very
unlikely to be to be a coincidence. It could be, but again, probability
analysis I think would suggest otherwise. I do, however, completely agree
with your suggestion that a viable study would consist of following many
nests over a period of several days on either side of July 4 and for several
years. And I also fully agree, that if fireworks were proved to be a
significant cause of bird mortality in urban settings, actually affecting
change with that information would be problematic at best.

Mark Johnston
Kent, WA