Acid Rain

   Of all the threats facing the loon, acid rain is the most serious. Jeff 
Fair of the New Hampshire Loon Preservation Committee calls it the 
"most insidious" threat to loons. Rawson Wood, Chairman of the North 
American Loon Fund, terms it the "most urgent issue for loons." 
Nearly all scientists, even electric company scientists, admit that 
there is an acid rain problem, but there is considerable debate 
regarding the specific solutions, timing and costs of control measures. 
While most coal and utility representatives argue for more research 
and no action, environmental groups point out that every nation in 
the western world, except the United States, is committed to at least 
a thirty percent reduction of acid-causing pollutants (SO2 and NOx1 
gases). Indeed, several United States scientific organizations, 
including the National Academy of Sciences, recommend an 
immediate control program.

   This debate is critical for loons. It requires little scientific 
sophistication to realize that fish-less lakes will become loon-less 
lakes. Because they mainly feed on rough fish and minnows which 
are less sensitive to acid rain than most game fish, loons might stay 
around after a lake's walleye and trout populations have 
disappeared. Unfortunately, the maps of acid-sensitive lakes and the 
maps of the common loon's breeding range overlap all too well. Both 
cover the Laurentian Shield like a blanket of acidic snow.

   Two studies conducted in the 1980s have provided several 
important pieces to the loon/acid rain puzzle. Scientists expected to 
find poorer breeding success for loons on lakes with higher acidity. 
However, Karl Parker, then a graduate student at Syracuse 
University in New York, found that loons on heavily acidified lakes in 
the Adirondack Mountains produced chicks at comparable rates to 
those on well-buffered lakes. The loons on the acidic lakes seemed to 
be able to cope by spending more time procuring food items for their 
chicks and by switching from small fish (the typical food for chicks) 
to larger fish or crayfish, prey items less sensitive to acidity. Parkers 
even observed adult loons flying to the lake with fish in their bills.

   Robert Alvo, then a graduate student at Trent University in 
Peterborough, Ontario, studied loons on acidic lakes in the Sudbury, 
Ontario region from 1982 to 1984. Alvo predicted that loons living on 
highly acidic lakes in the Sudbury area (one of the areas most 
severely affected by acidification in North America) would have low 
reproductive success. Unlike Parker, Alvo found that common loon 
breeding success was significantly lower on low alkalinity (poorly 
buffered) lakes. This was not due to avoidance of these lakes by 
loons, fewer eggs laid, or poor hatching success for eggs, but to the 
effects of acidification.

   Like Parker, Alvo observed loons feeding their young unusually 
high amounts of non-fish items like algae and aquatic invertebrates. 
However, on these highly acidic lakes there did not seem to be 
enough food to keep the chicks alive through the eleven week period 
before flight. Unfortunately, the adult loons apparently did not 
recognize that there was insufficient food for the young on these 
lakes. Their strong sense of year-to-year fidelity to nesting lakes 
kept the adults coming back to poor quality lakes.

   The acidification of lakes does not seem to affect adult loons. The 
failure of fish to reproduce, however, means that there are few or no 
small fish for the chicks. The adults eat larger fish which can 
withstand moderate amounts of acidification. Even when there are 
few or no larger fish, the adults can still cope by flying to other lakes 
to feed. This, of course, means that the adults end up spending less 
time on their nesting lakes tending the nest and defending the 
territory from intruders. The flights are also energy-expensive for 
loons which typically don't have to fly often during the summer. 
These factors in an indirect way may also be adding to the problems 
with brood survival.

   Why were the effects of acid rain on loon reproduction evident in 
Ontario but not New York? No one knows for sure, but it is likely the 
result of more acidic input over a longer period of time for the 
Ontario lakes. The picture in Ontario may very well be the state of 
affairs in upstate New York if lake acidification continues.

   Acid rain is an issue vital to North American wildlife. Not just loons 
but many species of ducks, especially black ducks, game fish and 
perhaps even our forests are threatened by the continuing emissions 
of coal-fired power plants. Based mainly in the Ohio River Valley, 
these outdated facilities will have to be replaced or modified to keep 
the cry of the loon a common sound on northern lakes. There is time 
to act, but precious little time to waste.