INTERNATIONAL
COUNCIL
FOR
BIRD
PRESERVATION
Acid rain and birds:
howmuchproof
is needed?
Brent
A. Mitchell
HE
DELETERIOU
EFFECT
OF
ACID
rain on aquatic habitatsare well
documented (Schindler 1988).
The possibilitythat continued deposition of acid will result in further
acidification and alteration of wa-
tershedshas alarmed both the public
and the scientificcommunity. In large
areasof geologicallysensitiveterrain
in easternNorth America, many lakes
have lost over 40% of their original
alkalinity. Acidic depositionhasbeen
shownto affectadverselyphytoplankton, zooplankton, amphibians, and
fish. It is logical to project that such
adverseaffectswould ultimately harm
many typesof birds, but demonstrations of effectson broadly dispersed
populations
ofhighly
mobile
bird
spedes are difficult. Effects of acidifica-
tion on birds are not direct. Though
many speciesof birdsmay dependon
aquatic systems,they are not trapped
by them, unlike their fish or invertebrate prey. Moreover, our ability to
separatethe specificeffectsof acid
precipitationfrom the naturalfactors
that affect wildlife populations or
communities is limited. This limita~
tion is acute in the case of acid rain
effectson forest ecosystems,where a
host of subtle and interacting stress
agents frustrate simplistic analyses
(Addisonand Jensen1987). Despite
the difficulties,there is now evidence
thatmanybirds,especially
those
dependenton aquaticsystems,
arebeing
adversely
affected.
Research on the effects of acid rain
on wildlife did not begin formally in
North
America
until
1980. Because
CommonLoon (Gavia iraruer).Photograph/S.J. Lang/VIREO/LI 1/2/003.
234
AmericanBirds,Summer1989
PacificLoon (Gavia pacifica).Photograph/D.Roby and K. Brink/VIREO/R05/1/007.
of their feeding habits, attention has
been concentratedon, but not limited
to, waterfowl and loons. Studieshave
centered on changesin food abundanceand food quality, and the effects
of theseon reproductivesuccess.
Direct effectsof low pH or exposureto
metals are important factorsbehind
impaired reproduction and reduced
numbers of fish, amphibians, and
somegroupsof invertebrates,but the
effectson avian predatorsof fish and
invertebrate prey are still poorly
understood(e.g., Stensonand Eriksson 1989).
Because of differing tolerances to
acidity, decreasesin pH alter prey
abundance and diversity. The effect
on avian predatorsvariesaccordingto
the severity of the acidification and
the foraginghabitsof the bird species
(Blancher and McAuley 1987). Fisheaterssuch as loons, mergansers,herons, bitterns, ospreys, eagles, and
kingfishersare most obviouslyat risk
from decliningpH.
Prey abundancefor fish-eating birds
Common Loons( Gavia iraruer) require large amounts of food during
the breeding season (Parker 1988).
Loons feed on small fish, prey that is
sensitive to acidification, and the
Volume 43, Number 2
young remain on the natal lake for a
long time. Resultsof studiesof loon
breeding successin relation to lake
acidity have been mixed. In a major
study of small lakes in northern Ontario, McNicol et al. (1987a) found
that brood production of Common
Loons and Common Mergansers
(Mergus merganser) in northeastern
Ontario was higherwhere most lakes
the mostacidiclakes(pH 4.7) studied
by Parker (Alvo et al. 1988). Parker
did note that dives for fish were 21%
longerin the more acidic lakes.Loon
chicks in the Adirondack
area were
fed newts, tadpoles,and aquatic invertebratesin the absenceof fish;they
may have had more non-fish prey
sources available to them than did the
havefish and are not acidiccompared
loons near Sudbury (McNicol et al.
1987a). Recent work by McNicol in
to an area where most lakes are acidic
northern Ontario has shown that the
and fishless.
Both species
wereequally
probabilityof both loon chicksfiedging from two-chickbroodswas lower
on lakes with pH <6.3 comparedto
less acidic lakes (D. McNicol pers.
comm.). Lakes with low pH have
fewer types of alternate, invertebrate
abundant
in the stressed and
un-
stressedareas during the nest initiation period. Similarly, Alvo et al.
(1988) reported a significantpositive
relationshipbetweensuccessful
breeding of loonsand pH on 68 lakesnear
Sudbury, Ontario. (The area immediately surrounding Sudbury is extremely acidified and contaminated
with
metals
due to emissions
from
largenickel-coppersmelters;the study
area of Alvo et al. was over 30 kilo-
metersaway from Sudbury.)But Parker (1988) found no significantdifference between lake acidity and loon
reproductive successin the Adirondack region of New York State, another area where many lakes have
been acidified.One possibleexplanation is that the heavily acidified lakes
of the Sudburyareawereconsiderably
more acidic (minimum pH 4.0) than
prey.
In Sweden,Eriksson(1987) found
no relationshipbetweenbreedingsuccess and lake acidification
in Arctic
Loons(Gavia arctica). However, Arctic Loonsfed their youngaquatic invertebratesin addition to fish. Also,
becausesuccess
of diving birds at detectingfishpreyis dependentnot only
on fish density but also on transparency of water, Eriksson postulated
that such birds derive a short-term
benefit from the increased water clar-
ity in acidified lakes.
The only other piscivore whose
breedingsuccesshas been studied in
relation to lake acidity is the Osprey
235
ity to waterfowl (Haines and Hunter
1982). Furthermore, the declineof the
American
Black Duck has been coin-
cident with the progressivedecline in
the pH of precipitation over the past
30 years.
Primarily herbivorous outside the
breedingseason,dabbling ducks such
as the American Black Duck depend
on protein from animal sourcesfor
reproduction. The need for protein is
highestfor femalesbefore and during
egg-laying(for eggproduction)and for
ducklings(for rapid growth).
Slow duckling growth and low foraging efficiency caused by competition from fish for insectprey hasbeen
demonstrated in limited experimental studiesusing imprinted American
Black
Above.'
AmericanBlackDucks(Anasrubripes)Photograph/Steve
Holt/VIREO/h21/unacc.
Below.'Osprey(Pandionhaliaetus)Photograph/N.Abel/VIREO/a05/2/010.
(Pandion haliaetus; Eriksson et al.
1983). In Sweden decreasedproduction of young has occurred among
pairs breeding in areas with many
ø
acidified lakes. Distances between oc-
cupied nests have been shown to be
,?.•
shorterwherelargeareasof nonacidified lakessurroundthe nests(Eriksson
'•
•
1986).
Ducks
and
Common
Gold-
eneyes, (Bucephala clangula; DesGrangesand Rodrigue 1986; Hunter
et al. 1986). Eriksson demonstrated
that the absenceof fish provided some
compensatoryinsectfood availability
for Common Goldeneyesdue to reduced competition (Eriksson 1979).
DesGrangesand Hunter (1987) concludedthat, though competition from
fish is a complicating factor, it does
not negate the overall negative relationshipof acidity to American Black
Duck duckling growth and survival.
In Maine, McAuley and Longcore
(1988a, 1988b) found that young
Ring-neckedDucks (Aythya collaris)
Prey abundancefor non-fish-eating
survival was lower on acidic wetlands
birds
than on wetlandswith higherpH. The
difference was observed among older
Waterfowl, shorebirds, and many
passerines consume invertebrates
ducklings, ages corresponding to
feathergrowth and maximum weight
growth. This study was not complicated by the questionof competition
caught in aquatic systemsor flying
emergentinsectsthat haveaquaticlarval stages.Decreasesin pH eliminate
thoseinvertebrate speciesthat are intolerant. Most sensitiveare mayflies,
molluscs, crustaceans,leeches, some
caddisflies,odonates and water striders. Concern for acid rain effects on
In an initial study on man-made
wetlands in Maryland, Haramis and
Chu {1987) observeda reduced biomass of invertebrates in experimen-
waterfowlhasbeenpopularizedby the
Izaak Walton League (Hansen 1987).
Of particular concern is the statusof
the American Black Duck (Arias rubripes), which has declined significantly in the past30 years.The Amer-
tally acidified wetlands compared
ican Black Duck breeds over much of
eastern Canada and the northeastern
were more distressed,and spent less
United States where soil and water are
sensitive to acidification. Acidifica-
tion of surface waters is disruptive
to aquatic food chains (Bendell and
McNicol 1987; Bendell 1986; Bendell
1988)and may reducefood availabil-
236
with fish because all wetlands studied
contained fish.
to controls.
broods on
American
Black Duck
the acidified wetlands
showedlimited growth, alteredbehavior, and marked reduction in survival.
Ducklings on the treated wetlands
time foraging aquatically than did
control ducklings. The authors suggestedthat reducedavailability of invertebrateprey might be the causeof
reducedgrowth and survivalof juvenile American Black Ducks on acidified wetlands in the wild.
American Birds, Summer 1989
Birds reliant on flying insectsthat
have aquatic larval stagesmight also
be affected by increasesin wetland
acidity. In a study of Tree Swallows
( Tachycinetabicolor) near Sudbury,
Ontario,
Blancher
and
McNicol
(1988) observeda negativeinfluence
of wetlandacidity on threeaspectsof
reproduction: investment in eggsby
laying females, size and growth of
nestlings,and number of fledglings
produced. Swallows breeding near
wetlandswhere fish were presentlaid
earlier, but had smaller eggs and
clutch volumes, and slower growth
of primary feathers, than swallows
breedingnear fishlesslakes.
The Eurasian Dipper (Cinclus cinclus), an exclusivelyriverine species,
tent near acidic wetlands compared
to buffered sites.Tyler and Ormerod
(1985) noted that dippers breeding
along calcareous tributaries in the
southern Wye River in Wales are
known to lay particularly large
clutches.
In Scotland and Wales, calcium levels in two insect orders [Stonefly
Nymphs (Plecoptera)and Caddislarvae (Trichoptera)] increased significantlywith pH (Ormerodet al., 1988).
Calcium-richprey were found only in
circumneutral
streams. Differences in
pH accountedfor some variance in
eggmass.The authorsrelatedreduced
egg-shellthicknessto increasedstream
acidity.
(Ormerod and Tyler 1987). Delayed
elutch initiation, and significantly
Aluminum
Nyholm and Myherberg (1977) reported impaired reproductive capac-
ity in the Pied Flycatcher (Ficedula
hypoleuca)near an acidified lake in
Sweden.Egg-shellquality, clutch size,
hatchingsuccess,and incubationwere
poorer in nest boxes placed closer to
the lake than nest boxes more distant.
Similar impaired breeding was observed in the Bluethroat (Luscinia
svecica), Reed Bunting (Emberiza
schoeniclus) and Willow Warbler
(Phylloscopustrochilus). Aluminum
was found in the bone marrow of the
has been shown to be scarce on Welsh
and Scottish streams with low pH
which could haveimpactson eggproduction and growth of young.
Toxicity of metals
Concern has been raised regarding
affected Pied Flycatchers (Nyholm
1981). However, Ringed TurtleDoves (Streptopelia risoria) fed elevated aluminum levels in laboratory
smaller dutch and brood sizes, were
metal toxicity in birds feedingat or
diets failed to exhibit impaired repro-
recorded in dippers breeding along
acidic streams compared to those
breeding elsewhere.Mayfly nymphs
and caddisfly larvae are important
during rearing of the young, and are
espedallyscarcein acidic waters(Orroerod and Tyler 1986).
Lastly on the topic of food abundance, special note should be taken
that many of the studiescited above
reported not only changes in the
abundance of prey availability, but
lessdiversityin prey speciesof birds
feedingin acid-stressedenvironments
(e.g., McAuley and Longcore 1988b;
McNicol et al., 1987a; Blancher and
McNicol, 1988).
near acid stessedlakes, wetlands, and
duction or growth (Carriere et al.
1986). This discrepancymay be explained by differences in speciesresponseto aluminum or by higherconcentrations of phosphorus and calcium in the experimentaldiet than in
the natural food organisms.Ormerod
et al. (1988) found no evidencethat
aluminum in prey adverselyaffected
dippereggsin streamsin Scotlandand
streams. Acidification
increases the
solubility and mobility of a range of
highly toxic metals suchas cadmium
(Steinnes1989), aluminum, and lead.
Also, the biological availability of
methylmercury is increased at low
pH. Prey organismsfor many birds
have been found to accumulate
var-
ious metals in these perturbated en-
vironments.Conversely,acidification
of aquatic systemsmay reduce the
Wales. Moreover, aluminum concen-
concentration
relationshipwith stream acidity.
D.W. Spafling (pers. comm.1988)
fed three-day old American Black
Ducks and Mallards (Ariasplatyrhynchos)diets of varying concentrations
of caldum, phosphorus,and alumi-
of essential
elements
suchasseleniumand calciumin prey,
both of which may reducethe toxicity
of metals(Wren and Stokes1988).Of
particular interest in the caseof birds
may be this reduction in calcium,
trations in invertebrates
showed no
RingedTurtle-Dove(Streptopeliarisoria).B. Schorre/VIREO/S08/2/025.
Food quality
Irrespective of the abundance of
prey, the nutritional value of available
foods may be adversdy affected by
a'ddification. Mineral-rich foods, especially thosehigh in calcium suchas
snails, clams, crayfish, and amphipods, are important for egg production and for rapid growth in young.
But most of these organisms are
highly intolerant to acidity. Blancher
et al. (1987) found that snails,dams,
or pans of crayfish were brought to
Tree Swallow nestlingsin most nests
near circumneutral wetlands, but only
to a few nests near acidic wetlands.
Glooschenkoet al. (1986) foundthinner eggshells
with lower caldum con-
Volume43,Number2
237
Most of the field studies reviewed
num. Except for one concentration
containingextremelyhigh aluminum
(10,000 ppm), all concentrations
were
derived from studiesof aquatic invertebratesin Canada. All ducklingson
cur in prey organisms)and increased
incidence of hatchling mortality
(Scheuhammer1987).
Erikkson et al. (1989) compared
here are largely correlative because
causal relationships are difficult to
document in the field. Experimental
metal contents in liver tissues of 42
studies are easier to control and thus
the diet lowest in calcium and phos-
non-fledged Common Goldeneyes
phorusand 5000 ppm aluminum died
from acidic, circumnentral,and timed
lakes in Sweden.They found no sig-
establish causal relationships. These
studieshave helpedto identify mech-
w•thin two weeks. A diet of normal
calciumand phosphorusbut very high
aluminum had 92% mortality within
46 days.More AmericanBlackDucks
died on a greaterrangeof dietsthan
Mallards.
Results indicate
that both
speciesare sensitiveto aluminum, and
that Black Ducks may be more sensitive to diets varying in these three
elements than are Mallards.
Mercury
Althoughthemechanisms
arepoorly
understood, acidification of surface
watersmay enhancethe accumulation
of methylmercury, cadmium, and
lead in fish (Wiener 1987). Methylmercury accumulates in the food
chain, and dietary methylmercury is
readily absorbedby birds. At the top
of the food chain, birds can accumulate toxic amountsof methylmercury.
L. Alexander
has recovered thou-
sandsof dead Common Loons along
the Gulf coast of Florida since 1983,
most of which have been found to
have high mercuryconcentrationsin
their tissues(Mcintyre 1989).
In Ontario, Bart (1986) relatedsuccessfuluse of territories by breeding
Common
Loons and levels of mer-
cury contaminationin lakes along a
100-mile downstream
course from a
major mercurysource.His resultssuggestreductionsin egg laying and in
nest and territorial fidelity at mercury
concentrations from 0.3 to 0.4 ppm
in prey.
NestingEasternKingbirds(Tyrannus tyrannus) from an acid-stressed
area near Sudbury, Ontario, had
highermercury concentrationsin the
liver and feathers than populations
breedingbeside buffered lakes, and
the rate of masslossof eggswasfaster
on acid wetlands(Glooschenkoet al.
1986).
Ringed Turtle-Doves(Streptopelia
nsoria)subjectedto chronic,low-level
dietary exposure to cadmium, lead,
and methylmercuryhad an increase
in the percentageof infertile eggsin
the highestdose group (representing
maximum concentrationslikely to oc-
238
nificantly different concentrationsof
any of the 12 metalsanalyzedbetween
acidic and circumneutral
anisms of effects observed in the field.
But extrapolation of their results to
the wild must be reviewed with cau-
sites. How-
tion. For example,though studieson
experimental ponds yield important
of mercury was low-intermediate, information on the sensitivity of
American Black Ducks to pH, the
"singleindividualsfrom acidic lakes
ponds hardly resemble the natural
were so highly contaminatedthat the
risk of behavioral disturbances is not
breedinghabitatof the species--often
temporallyfloodedpoolsand ditches.
negligible."
Little is known about acid "pulses"in
these ephemeral pools and shallow
wetlands. Experimental studies must
Forest birds
be carefullydesigned,and positivere-
ever, thoughthe mean concentration
Evidence
of the fact of forest de-
clines and the roles of variousair pollutants in thosedeclinesis mounting
(MacKenzie and E1-Ashrey 1988).
While many air pollutantshavebeen
implicatedin effectsobservedin close
proximity to point sources,there is
substantialcontroversyover whether
observed declines in remote sites can
be attributedto anthropogenicagents
either directly or indirectly (Mitchell
1987). Trees are long-rivedand subject to a wide range of interacting
biotic and abiotic stresses,the mechanisms of which are poorly understood. The roles of various airborne
pollutantsin the declineof forestsare
complexand beyondthe scopeof this
paper.
As in the case of aquatic systems,
changesin forestcommunitieswill affect bird populations(Schreiberand
Newman 1988). The extent of forest
decline in North America is thus far
unknown, and few studieshave been
conducted on the effects of forest de-
cline on bird populations. However,
researchersat the University of Que-
bec at Montreal are monitoring six
passefinespeciesas bio-indicatorsof
the progressionof maple dieback (P.
Blancher,pers. comm.).
What's missing?
Due to the high costsof reducing
pollutant emissionscausingacid rain
and related air pollutants,many criticisms have been made of evidence of
acid-related effects on natural systems.
sults should serve to increase interest
in and fundingfor relatedwork in the
field.
Much of the most important work
has been conducted
in areas hardest
hit by air pollution,Schindler's"sledgehammer blows" (1987). They can not
alone predict responsesof ecosystems
to chronic, increasing, low-level
changesin soil and water chemistry
Nevertheless,they are meaningfulas
they have: 1) established
some of the
mechanismsof acidificationeffects,2)
begun to define pH levels at which
effectsbecome apparent in some spe-
cies, 3) prompted public concern, 4)
justified increasedmonitoring, and 5)
addedto the bundleof argumentsfor
abatement of air pollutant emissions
Work to date certainlyjustifiescontinued and increasedstudy. A thorough understandingof tolerancesof
birds is not only important to idenUfyingwhat populationsare at risk,but
can also make these speciesuseful
as bio-indicators of ecosystemstress
(e.g., McNicol et al. 1987b;Ormerod
and Tyler 1987). This may be especially true with respectto gaseousand
particulatepollutants,little studiedin
relation to wildlife (Newman and
Schreiber1988). Will we one day have
an avian/cadmium counterpart to
fish/pH indicators--a modem canary
in a coal mine? We won't know with-
out more toxicologicalinformation
Unfortunately,it is now impossible
to compare data from studiesof natural "control" sites;no place is untouched by atmospheric pollution
Differencesnow are only of degreeof
perturbation.As one investigatorput
American Bxrds,Summer 1989
xt, "the 'Grand Experiment'hasbeen
goingon for at least30 years."Science
•s only now learning how to observe
•t •n meaningfulways.
Researchpriorities and current
efforts
Researchefforts are underway to
bufid on the correlative evidence for
ac•d rain's effectson birds, to investi-
gatethe mechanisms
behindobserved
effects,and to take a more holistic
approachto observingecosystemresponseto anthropogenicstress(Table
1).
The U.S. Fish and Wildlife
Service
ac•drain programhastwo main components,researchinto biologicaleffectsand mitigation (R. K. Schreiber,
pers. comm.). Mitigation is done in
cooperationwith the states,and is
largely restrictedto liming of lakes
and streamsfor protection of fishery
resources. Research is divided into
b•rd work conducted at Patuxent National Wildlife Research Center in
Maryland and fish studies at the
Columbia National Fishery Research
Laboratoryin Missouri.
At Patuxent,researchers
are contin-
rang with original work, expanding
the number of experimentallyacidified ponds. For example, Spafiing's
prepareddiet studieswill be extended
by lacingpondswith metalsand allowingduckbroodsto feedon affected
prey. C. E. Grue is feedingEuropean
Starlings(Sturnusvulgaris)the same
chetsusedin Sparling'sstudy.
Severalmidwesternstatesare begin-
ning to look at levelsof mercury •n
Scotia. The Canadian Wfidhfe Service
Common Loons. For example, work
supportsa volunteer-basedloon monitoring program, the Ontario Lakes
Loon Survey, organizedby the Long
Point Bird Observatory.Nearly 500
lakes are surveyedyearly by volun-
has been done in Minnesota
to mon-
itor mercurycontentof loon feathers
(P. Strong,pers. comm.).
Blancher•ers. comm.) outlinesthe
approach taken by the Canadian
Wildlife Service'sLong-Range Transport of Airborne PollutantsProgram.
A team of biologistsis developinga
model designedto link lake acidityto
waterfowlproductionin acid-sensitive
regionsof easternCanada. In theory
it will be able to estimate the impact
of changesin acid emissionson the
potential for waterfowl to produce
young. A waterfowl reproductive
studyhas been initiated, focusingon
the breedingcondition of Common
Goldeneyes,and survival of marked
broodsin relation to wetlandsacidity.
Detailed work on the abundance of
important waterfowlfoodsin relation
to wetlandsacidity and fish community type is continuing.
Scheuhammer is continuing his
work (1987) on toxic effectsof dietary
metals.A currentstudylooksat reproductive effects of cadmium, lead and
aluminum
in combination
with low
levels of calcium. Another study to
investigateeffectsof mercury in combination with low levels of selenium
is planned.
Finally, a programto monitor longterm trends in waterfowl production
and statusof important prey in three
acid-stressedregionsof easternCanada is continuing. Waterfowl production is being assessed
by aerial survey
in almost 500 wetlands in Ontario,
and an additional
40 lakes in Nova
teers.
Importance of monitoring
The Ontario Lakes Loon Surveyzs
an example of public involvement m
monitoring sometimesreferred to as
"citizen science"(Bolze and Beyea et
a[. 1989). There is tremendousamateur interestin birds, which has often
been organized to obtain invaluable
information on number, distribution,
and reproductivesuccess.Similar bzrd
surveysare conductedfrom New England to the Great Lakes,organizedby
groupssuchas the Loon Preservation
Committee and supportedin part by
the North American Loon Fund.
A similar "citizen science" initiative
has recently been organized by the
National Audubon Society.Monitoring precipitationrather than affected
species,the Citizen's Acid Rain Monitoring Network dependson volunteer
samplersacrossthe United States. It
was set up to bring acid rain into the
public eye on a daily basis and to
producea nationwidegroundswellof
activism for the reduction of acid ram.
Such large-scale,long-term moni-
toring projectsare critical in percezving ecosystemresponseto chronic,
low-levelperturbations.But few governmentsare willing to dedicatesufficient resourcesto supportsuchlongterm monitoring. Schindler (1987)
Table 1. Major ecosystem
studieson the effectsof air emissionsin North America.
Name of study
Ecosystem
(location)
Pollutantstress
Northern coniferousforest(Ontario)
Acid deposition
Dorset Watershed Studies
Northern deciduousforest(Ontario)
Northern forest(Ontario)
MontmorencyExperimentalForestStudy
Northern
Acid deposition
Acid deposition
Acid deposition
ExperimentalLakesArea (ELA)
Watershed Studies
Turkey Lake ForestWatershedStudy
coniferous forest and associ-
ated lakes(Quebec)
Kej•mkujik CalibratedCatchment
Program
Kaybob Gas Plant Study
San BernadinoMountain Study
Hubbard Brook EcosystemProject
Northern coniferousforest(Nova
Scotia)
Acid deposition
Transition montane boreal forest
S02
(Alberta)
Mixed coniferousforest(California)
Oxidants
Northern mixed deciduous coniferous
Atmosphericdepositionincluding
Walker Branch WatershedStudy
forest(New Hampshire)
Mixed deciduousforest(TN)
WhitecourtGas Plant Study
IntegratedLake-WatershedAcidification
Study(ILWAS)
Mixed coniferousforest(Alberta)
Northeasterndeciduousforest(New
York)
?rom Schreiber and Newman
Volume 43, Number 2
acid and tace element
Atmosphericdeposition,including acid and trace element
SO2
Acid deposition
1988
239
hasnotedthat usefulmonitoringprojectsfor the future must be inexpensive
enoughto withstandvagariesin public
funding. They must also be simple
and verifmble, so that they are little
affected by personnel changes.Most
importantly, they must be highly sensitive to changesin ecosystems.To
satisfythese demanding criteria it is
important that monitoring be developed as a sciencein its own right.
Clearly, much work needs to be
effects of acidifi-
cation on birds, to establishthe causal
relationship, and to interpret these
findingsacrossbroad areasand whole
populations.But the evidenceto date
indicatesnegativeeffects,notably on
spedes of high public appeal, espedally Common Loonsand American
Black Ducks. Though the extent and
mechanismsof all pollutant effectsare
not known, thereis certainlycausefor
concern.
Unfortunately, uncertainty in one
area is often usedto argue postponement of public policy action, no matter how clearly indicated by evidence
from other areasof knowledge.
Evidence of indirect affects of at-
mosphericpollution on birds adds to
the proof of direct effectson aquatic
environments, synergisticeffects on
forests and human
ble mechanisms
health hazards to
provide an overwhelming argument
see
pollution and birds in Europe see
Goriup (1989).
ACKNOWLEDGMENTS
Peter J. Blancher, Donald K.
McNicol, and R. Kent Schreiberproinvaluable
information
and
commented on an early draft of the
manuscript. Any errors in fact or
interpretation are my own.
LITERATURE
CITED
ADDISON, P., and K. JENSEN. 1987.
Long-rangeair pollution effectson the
forest ecosystem.Trans. 52rid N. A.
Wildl. & Nat. Res. Conf pp. 665-676.
ALVO, R., D. J. T. HUSSELL, and M.
BERRILL. 1988. The breedingsuccess
of Common Loons (Gavia immer) in
relation to alkalinity and other lake
characteristics in Ontario. Can. J. Zool.
Common Loon (Gavia immer). Geoff
66: 746-752.
LeBaron/VIREO/L05/2/004.
BARR, J. F. 1986. Population dynamics
of the Common Loon (Gavia immer)
associatedwith mercury-contaminated
waters in northwestern Ontario.
No. 56.
BENDELL, B. E. 1988. Lake acidity and
the
distribution
and
abundance
of
water striders (Hemiptera: Gerridae)
near Sudbury, Ontario. Can. J. Zool.
66(10): 2209-2211.
-1986. The effectsof fish and pH on
distribution
and
backswimmers (Hemiptera: Notonectidae). Can. J. Zool. 64(12): 2696-
Cana-
dian Wildlife ServiceOccasionalPaper
the
for emission abatement.
for abatement
Hardngton (1988). For a reviewof air
vided
Implications for public policy
done to document
For details on the extent of abate-
ment minimally required see Schindler (1988). For a discussion
of possi-
abundance
of
--
2699.
and D. K. MCNICOL.
1987. Fish
predation, lake acidity and the compositionof aquatic insectassemblages.
Hydrobiologia 150:193-202.
BLANCHER,
P. J., and D. K. MCNICOL.
1988. Breedingbiology of Tree Swallows in relation to wetland acidity.
Can. J. Zool. 66(4): 842-849.
--,
C. J. FURLONGER and D. K.
Table 2. Relationshipof wetlandacidity to reproductivesuccessin nine studies.
Study•
1
2
3
4
5
6
7
8
9
Acidity
association
• Common
American
Eastern
Tree Eurasian
Loon Ring-necked
Duck
Black
Kingbird
Swallow
Dipper
Duck
Date of egglaying
Clutch Size
Eggshellthickness
Eggwaterloss
Egghatchability
Growth of young
Foragingefficiency
Survivalof young
Breedingsuccess
Food abundance
nd
0
nd
nd
nd
nd
nd
0
nd
0
nd
nd
nd
nd
--
0
---
nd
nd
0
nd
----
nd
nd
nd
nd
-0
0
nd
nd
0
nd
nd
-nd
nd
nd
nd
-nd
-nd
nd
nd
nd
---nd
nd
nd
nd
+½
+c
nd
nd
--nd
-nd
nd
nd
nd
0
0
-nd
nd
--
-nd
0
nd
-nd
nd
0
....
+½
0
nd
--
I = Alvo et al (1988);2 = Parker(1988);3 = McAuleyandLongcore(1988a;1988b);4 = Haramisand Chu (1987);5 and6 = DesGranges
and Hunter(1987);7
= Glooschenkoet al. (1986); 8 = Blancherand McNicol (1988): 9 = Ormerodand Tyler (1987), Ormerodet al. (1988)
nd= no data presented;0 • no relationshipobserved;- = negativerelationship;+ = positiverelationshipwith acidity.
Lack of fish and low pH wetlandsprobablyexplainsthis result.
adaptedfrom Blancherand McAuley, 1987
240
American Birds, Summer 1989
MCNICOL 1987 DletofnesthngTree
Swallows (Tachyctneta btcolor) near
Sudbury, Ontario, Summer 1986. Canadian
Wildlife
Service Technical
Re-
port SeriesNo. 31.
--
and D. G. MCAULEY.
HANSEN,
1987. Influ-
sourcesof experimentallyacidifiedwetlands. Pages 173-181 in A. W. Diamond and F. L. Filion, editors. The
Value of Birds. International
Council
for Bird Preservation Technical Publication No. 6.
Science and Technology. 23(6):645646.
pp. 636-644.
--
and J. RODRIGUE.
1986. Influence
of acidity and competition with fish on
the developmentof ducklingsin Quebec. Water, Air, and Soil Pollution 30:
743-750.
ERIKSSON, M. O. G. 1979. Competition
between
freshwater
fish and Golden-
eyes(Bucephelaclangula)for common
prey. Oecologia41: 99-107.
1986. Fish delivery, production of
HARRINGTON,
ERIKSSON, M. O. G., L. HENRIKSON,
and H. G. OSCARSON.
1989. Metal
contentsin liver tissueof non-fledged
Goldeneye, Bucepala clangula, duckhngs: A comparison between samples
from acidic, circumneutral, and limed
MCNICOL, D. K., B. E. BENDELL and
R. K. ROSS.
No. 62.
MCNICOL, D. K., P. J. BLANCHER and
B. E. BENDELL.
1987b. Waterfowl as
indicators of wetland acidification in
Ontario. ICBP Technical Publication
No. 6.
MITCHELL, B. A. 1987. Air pollution
and maple decline.Nexus 9(3): 1-13.
NEWMAN, J. R. and R. K. SCHREIBER.
1988. Air pollution and wildlife toxicology:An overlooked problem. Envi-
ronmental Toxicologyand Chemistry
7: 381-390.
1986. Association
of
Pollution 30: 553-567.
86.
HAINES, T. A. and M. L. HUNTER.
Waterfowl
and their
habitat:
Threatened by acid rain? Pages 177188 in Fourth International
Waterfowl
Symposium, Jan. 30, 31, and Feb. 1,
1981, New Orleans, La. Ducks Unlimited, Chicago,265 p.
Volume 43, Number 2
of aluminum
in causation
of defectiveformation of eggshellsand
of impaired breedingof wild passefine
birds.
Environmental
Research
26:
363-371.
--
and H. E. MYHRBERG.
1977. Se-
vere eggshelldefectsand impaired reproductive capacityin small passefines
in SwedishLapland. Oikos 29: 336341.
ORMEROD, S. J., and S. J. Tyler. 1987
GORIUP, P. D. 1989. Acidic air pollution
and birds in Europe. Oryx 23(2): 821982.
N. E. I. 1981. Evidence of
involvement
GLOOSCHENKO, V., P. BLANCHER,
J. HERSKOWITZ, R. FULTHORPE,
wetland acidity with reproductive parametersand insectprey of the Eastern
Kingbird (Tyannus tyrannus) near
Sudbury,Ontario. Water,Air, and Soil
1987a. Studies of the ef-
fectsof acidificationon aquatic wildlife
in Canada: waterfowl and trophic relationships in northern Ontario. Canadian Wildlife ServiceOccasionalPaper
NYHOLM,
w•ntenng•n the catchmentof the River
Wye, Wales Btrd Study 33 36-45
ORMEROD, S. J., K. R. BULL, C P
CUMMINS, S. J. TYLER, and J A
VICKERY. 1988. Egg massand shell
thicknessin Dippers Cincluscinclus•n
relation to stream acidity in Wales and
Scotland. Environmental
107-121.
Pollution
55
ORMEROD, S. J., N. ALLINSON, D
HUDSON, and S. J. TYLER. 1986
The distribution of breeding dippers
(Cinclus cinclus(L.); Aves) in relation
to stream acidity in upland Wales
FreshwaterBiology 16:501-507.
PARKER, K. E. 1988. Common loon re-
pages.
lakes in south Sweden. Arch. Environ.
Contam. Toxicol. 18: 255-260.
and S. RANG.
Re-
1988b. Foods of juvenile RingNecked Ducks: relationshipto wetland
pH. J. Wildl. Manage. 52: 177-185.
MCINTYRE, J. W. 1989. The Common
Loon cries for help. National Geographic 175(4): 510-524.
MACKENZIE, J. J. and M. T. EL-ASHREY. 1988. Ill winds: Airborne pollution's toll on trees and crops. World
Resources Institute, Washington. 74
1987. (The production of young in
Black-throated Diver, Gavia arctica, in
tus). V•r F•gelviirld 42: 293-300. (In
Swedish,Englishsummary).
control.
176.
Can. J. Zool. 64: 1961-1965.
mary).
, L. HENRIKSON, and H. G. OSCARSON. 1983. (Acid-rain--a future
dangerfor the Osprey,Pandion haliae-
rain
MCAULEY, D. G. and J. R. LONGCORE. 1988a. Survival of juvenile
Ring-NeckedDuckson wetlandsof different pH. J Wildl. Manage. 52: 169-
dion haliaetus) in southwestSweden.
southwestSweden).Viir Ffigelvdrld46:
172-186. (In Swedish, English sum-
W. 1988. Breaking the
deadlock on acid
sources 93: 1-4.
y•)ung
andnest
density
ofOsprey
(Pan--
in
Acid rain effects on waterfowl: Use of
Black Duck broods to assess food re-
Science and Acid Rain. Environmental
52nd N. A. Wildl. & Nat. Res. Conf
1987 Ac•d Rmn and
The Case for Concern
North America. Izaak Walton League
of America, Arlington, Virginia, 39 p.
HARAMIS, G. M. and D. S. CHU. 1987.
enceof wetland acidityon avian breedlng success.Trans. 52nd N. A. Wildl.
& Nat. Res. Conf, pp. 628-635.
BOLZE, D. and J. BEYEA. 1989. Citizen
CARRIERE, D., K. L. FISCHER, D. B.
PEAKALL, and P. ANGHERN. 1986.
Effects of dietary aluminum sulphate
on reproductive successand growth of
Ringed Turtled-Doves(Streptopeliarisoria). Can. J. Zool. 64: 1500-1505.
DESGRANGES, J. L. and M. L.
HUNTER, JR. 1987. Duckling response to lake acidification. Trans.
P W
Waterfowl
Dippers (Cinclus cinclus) and Grey
Wagtails(Motacilla cinerea)as indicators of streamacidity in upland Wales.
productionand chick feedingon acidified lakes in the Adirondack Park,
New York.
Can. J. Zool. 66:804-810
SCHREIBER, R. K. and J. R. NEWMAN
1988. Acid Precipitation effectson forest habitats: Implications for wildhfe
Conservation
Biology2(3): 249-259
SCHEUHAMMER, A.M. 1987. Reproductive effectsof chronic, low-level dietary metal exposure in birds. Trans
52nd N. A. Wildl. & Nat. Res. Conf,
pp. 658-664.
SCHINDLER, D. W. 1988. Effectsofac•d
rain on freshwaterecosystems.Science
239: 149-157.
ß1987. Detecting ecosystemresponses
to anthropogenicstress.Can. J. Ftsh
Aquat. $ci. 44: 6-25.
SPARLING, D. W. 1988. Dietary effects
of AI, Ca, and P on Black Duck and
Mallard ducklings. Abstracts of the
Ninth Annual Meeting of the Society
EnvironmentalToxicologyand Chemistry, November 13-17, 1988, Arhngton, Virginia.
STEINNES,
E. 1989. Cadmium in the
terrestrial environment: Impact of
long-rangeatmospherictransport. Toxicologicaland EnvironmentalChemtstry 19: 139-145.
STENSON, J. A. E. and M. O. G. ERIKSSON. 1989. Ecological mechanisms
important for the biotic changes•n
acidified lakes in Scandinavia. Arch
Environ. Contam. Toxicol. 18: 201206.
TYLER, S. J. and S. J. ORMEROD. 1985
Aspectsof the breedingbiologyof D•ppers Cinclus cinclus in the southern
catchment of the River Wye, Wales
Bird Study 32: 164-169.
WIENER, J. G. 1987. Metal contamination of fish in low-pH lakesand potential implications for piscivorouswddlife. Trans. 52nd N. A. Wildl.
& Nat
Res. Conf, pp. 645-657.
WREN, C. D. and P.M.
STOKES. 1988
Depressedmercurylevelsin biota from
acid and metal stressed lakes near Sud-
bury,Ontario.Ambio 17(1):28-30
Pages191-20&in A. W. Diamond and
F. L. Filion, editors. The Values of
Birds. International
Council for Bird
Preservation
Technical
Publication
No. 6.
ORMEROD, S. J. and S. J. TYLER. 1986.
The diet of Dippers Cinclus cinclus
--.QLF/Atlantic
Centerfor the
Environment,
39 South Main Street,
Ipswich, MA 01938
241