Editing Common loon (section)

==Status and conservation==
Since 1998, the common loon has been rated as a species of [[Least-concern species|least concern]] on the [[IUCN Red List of Endangered Species]]. This is because it has a large range – more than {{convert|20000|km2|abbr=on}} – and because it has a stable population trend that does not warrant a [[Vulnerable species|vulnerable]] rating. It also has a large population size of 612,000 to 640,000 individuals. The estimated breeding population ranges from 1,400 to 2,600 mature individuals in Europe.<ref name="iucn status 19 November 2021" /> Over half of the breeding population in North America is found in Ontario with 97,000 territorial pairs, and in Quebec with 50,000 territorial pairs. About 2,400 individuals occur in each of the maritime provinces of Canada—Nova Scotia and New Brunswick. British Columbia accounts for 25,000 territorial pairs. In far northern Canada, about 50,000 territorial pairs are known to occur, and 12,500 to 15,000 territorial pairs occur in the [[Prairie Provinces]] of Alberta, Manitoba, and Saskatchewan. In the United States, the largest breeding population is present in Alaska with 3,600 to 6,000 territorial pairs. The U.S. Great Lakes region has 5,900 to 7,200 territorial pairs which accounts for over half of the breeding population in the United States. There are about 100 territorial pairs in the northwestern U.S. states of Washington, Idaho, Montana, and Wyoming. About 2,250 territorial pairs are found in New England and New York. In winter, 3,500 to 4,500 individuals are found in the United Kingdom, and even fewer individuals are found in the western European coastline and in Iceland. Along the Pacific Coast, about 184,000 to 189,000 adults and 31,000 to 32,000 juveniles are found, and along the Atlantic Coast, 423,000 to 446,000 adults and 72,000 to 76,000 juveniles are found.<ref name="Evers2010" />

The common loon is listed under Appendix II of the [[Convention on the Conservation of Migratory Species of Wild Animals|Convention on the Conservation of Migratory Species]], and in Article I under the European Union (EU) [[Birds Directive]].<ref name="iucn status 19 November 2021" /> It is one of the species to which the [[Agreement on the Conservation of African-Eurasian Migratory Waterbirds]] (AEWA) is applied.<ref>{{Cite web|url=http://www.unep-aewa.org/en/species/gavia-immer|title=''Gavia immer'' {{!}} AEWA|archive-url=https://web.archive.org/web/20160816145045/http://www.unep-aewa.org/en/species/gavia-immer|archive-date=16 August 2016|access-date=12 July 2017}}</ref> In Europe it appears in 20 Important Bird Areas ([[Important Bird Area|IBAs]]), including Ireland, Svalbard, mainland Norway, Iceland, Spain, and the United Kingdom. It is also a listed species in 83 [[Special Protection Area]]s in the EU [[Natura 2000]] network.<ref name="iucn status 19 November 2021" /> The [[United States Forest Service|USDA National Forest Service]] has designated the common loon a species of special status, and in the upper Great Lake regions of the [[Huron-Manistee National Forests|Huron-Manistee]], [[Ottawa National Forest|Ottawa]], and [[Hiawatha National Forest|Hiawatha]] national forests as a regional forester sensitive species.<ref name=":4">{{Cite journal|last=Tischler|first=Keren B.|date=2011|title=Species Conservation Assessment for the Common Loon (''Gavia immer'') in the upper Great Lakes|url=https://www.fws.gov/uploadedFiles/tischler_common_loon_2011.pdf|journal=USDA Forest Service, Eastern Region|pages=1–59}}</ref>

=== Threats to status and conservation ===

==== Effects of mercury and acid rain pollution on health and brood productivity ====
The common loon is a key indicator of [[Mercury (element)|mercury]] deposition in aquatic environments due to its position at the top of the [[food chain]].<ref name=":10">{{Cite journal |last1=Evers |first1=David C. |last2=Savoy |first2=Lucas J. |last3=DeSorbo |first3=Christopher R. |last4=Yates |first4=David E. |last5=Hanson |first5=William |last6=Taylor |first6=Kate M. |last7=Siegel |first7=Lori S. |last8=Cooley |first8=John H. |last9=Bank |first9=Michael S. |last10=Major |first10=Andrew |last11=Munney |first11=Kenneth |date=2008-02-01 |title=Adverse effects from environmental mercury loads on breeding common loons |url=https://doi.org/10.1007/s10646-007-0168-7 |journal=Ecotoxicology |language=en |volume=17 |issue=2 |pages=69–81 |doi=10.1007/s10646-007-0168-7 |pmid=17909967 |bibcode=2008Ecotx..17...69E |s2cid=17769869 |issn=1573-3017}}</ref> The main contributors to elevated mercury concentrations in aquatic environments are coal burning power plants, waste incineration, and metal production.<ref name=":19">{{Cite web |title=Threats to Loons |url=https://www.adkloon.org/threats-to-loons |access-date=2022-03-07 |website=Adirondack Center for Loon Conservation |language=en-US}}</ref> Although environmental mercury (Hg) is naturally occurring, [[methylmercury]] ({{chem2|CH3Hg+}}, sometimes written as {{chem2|MeHg+}}) is a biologically toxic form that accumulates throughout aquatic environments in the northeastern United States.<ref name=":20">{{Cite journal |last1=Schoch |first1=Nina |last2=Glennon |first2=Michale J. |last3=Evers |first3=David C. |last4=Duron |first4=Melissa |last5=Jackson |first5=Allyson K. |last6=Driscoll |first6=Charles T. |last7=Ozard |first7=John W. |last8=Sauer |first8=Amy K. |date=April 2014 |title=The Impact of Mercury Exposure on the Common Loon (Gavia immer) Population in the Adirondack Park, New York, USA |url=https://bioone.org/journals/waterbirds/volume-37/issue-sp1/063.037.sp116/The-Impact-of-Mercury-Exposure-on-the-Common-Loon-Gavia/10.1675/063.037.sp116.full |journal=Waterbirds |volume=37 |issue=sp1 |pages=133–146 |doi=10.1675/063.037.sp116 |s2cid=85674745 |issn=1524-4695}}</ref> Methylmercury, a [[neurotoxin]], has been shown to have a wide range of behavioral, reproductive, and survival effects on the common loon.<ref name=":21">{{Cite journal |last=Schoch |first=Nina |date=2006-01-01 |title=The Adirondack Cooperative Loon Program: Loon Conservation in the Adirondack Park |url=https://digitalworks.union.edu/ajes/vol13/iss2/5 |journal=Adirondack Journal of Environmental Studies |volume=13 |issue=2 |issn=1075-0436}}</ref> Previous research has found a correlation between mercury levels and [[pH]], with more acidic aquatic environments being at the highest risk for elevated methylmercury concentrations.<ref name=":22">{{Cite journal |last1=Yu |first1=Xue |last2=Driscoll |first2=Charles T. |last3=Montesdeoca |first3=Mario |last4=Evers |first4=David |last5=Duron |first5=Melissa |last6=Williams |first6=Kate |last7=Schoch |first7=Nina |last8=Kamman |first8=Neil C. |date=2011-10-01 |title=Spatial patterns of mercury in biota of Adirondack, New York lakes |url=https://doi.org/10.1007/s10646-011-0717-y |journal=Ecotoxicology |language=en |volume=20 |issue=7 |pages=1543–1554 |doi=10.1007/s10646-011-0717-y |issn=1573-3017 |pmc=3175042 |pmid=21691858|bibcode=2011Ecotx..20.1543Y }}</ref> Once mercury enters the water, it is taken up by fish and spread throughout the food chain.<ref name=":19" /> Resulting from this transmission of mercury, there is a significant positive correlation between mercury levels in fish and mercury levels in male, female, and chick blood of common loons; consequently, an increase in mercury concentration in the blood of common loons and fish was seen with a decrease in local aquatic pH.<ref name=":16">{{Cite journal |last1=Champoux |first1=L. |last2=Masse |first2=D. C. |last3=Evers |first3=D. |last4=Lane |first4=O. P. |last5=Plante |first5=M. |last6=Timmermans |first6=S. T. A. |date=September 2006 |title=Assessment of mercury exposure and potential effects on common loons (Gavia immer) in Québec |url=http://link.springer.com/10.1007/s10750-006-0066-7 |journal=Hydrobiologia |language=en |volume=567 |issue=1 |pages=263–274 |doi=10.1007/s10750-006-0066-7 |issn=0018-8158 |s2cid=10621451}}</ref> Although there have been reductions in recent years in acidifying emissions, there has been limited biological recovery in these lakes most likely due to climate change.<ref name=":6">{{Cite journal |last1=Bianchini |first1=Kristin |last2=Tozer |first2=Douglas C. |last3=Alvo |first3=Robert |last4=Bhavsar |first4=Satyendra P. |last5=Mallory |first5=Mark L. |date=October 2020 |title=Drivers of declines in common loon (Gavia immer) productivity in Ontario, Canada |url=https://linkinghub.elsevier.com/retrieve/pii/S0048969720332447 |journal=Science of the Total Environment |language=en |volume=738 |pages=139724 |bibcode=2020ScTEn.73839724B |doi=10.1016/j.scitotenv.2020.139724 |pmid=32531589|s2cid=219620784 }}</ref> Research has shown that warmer summer temperatures can inhibit reestablishment of cold-water fish species in acidified lakes and droughts brought on by increased summer temperatures can further acidify lakes.<ref name=":6" />

Although the common loon is able to decrease their methylmercury levels by molting and laying eggs, continued consumption of fish with raised methylmercury levels prevents these mechanisms from effectively lowering methylmercury levels.<ref name=":21"/> Mercury concentrations have been shown to vary by the sex and age of common loons. Male common loons were found to contain the highest blood mercury concentration likely due to the fact that they tend to consume bigger fish with higher mercury concentrations.<ref name=":17">{{Cite journal|last1=Schoch|first1=Nina|last2=Glennon|first2=Michale J.|last3=Evers|first3=David C.|last4=Duron|first4=Melissa|last5=Jackson|first5=Allyson K.|last6=Driscoll|first6=Charles T.|last7=Ozard|first7=John W.|last8=Sauer|first8=Amy K.|date=April 2014|title=The Impact of Mercury Exposure on the Common Loon ( Gavia immer ) Population in the Adirondack Park, New York, USA|url=http://www.bioone.org/doi/abs/10.1675/063.037.sp116|journal=Waterbirds|language=en|volume=37|issue=sp1|pages=133–146|doi=10.1675/063.037.sp116|s2cid=85674745|issn=1524-4695}}</ref> Females contained the second highest blood mercury concentration with differences between the males likely being due to the fact that females can expel mercury into the eggs they lay.<ref name=":16" /> Juveniles had the lowest blood mercury concentration.<ref name=":18">{{Cite journal|last1=Burgess|first1=Neil M.|last2=Meyer|first2=Michael W.|date=February 2008|title=Methylmercury exposure associated with reduced productivity in common loons|url=http://link.springer.com/10.1007/s10646-007-0167-8|journal=Ecotoxicology|language=en|volume=17|issue=2|pages=83–91|doi=10.1007/s10646-007-0167-8|pmid=18038272|bibcode=2008Ecotx..17...83B |s2cid=40571426|issn=0963-9292}}</ref> Scientists found that the data from juveniles helped to best indicate the local mercury availability as they are fed exclusively from their natal territory.<ref name=":16" />

Elevated levels of mercury have been associated with changes in foraging and [[brooding]] behavior among adult common loons, especially in higher concentrations.<ref name=":18" /> Studies have found that elevated levels of methylmercury are associated with lethargy and decreased time spent foraging in adult common loons.<ref name=":10" /> A different study carried out in the [[Adirondack Mountains]] found that elevated levels of methylmercury are associated with reduced diving frequency in adult common loons.<ref>{{Cite journal |last=Stewart |first=Paul A. |date=January 1967 |title=Diving Schedules of a Common Loon and a Group of Oldsquaws |journal=The Auk |volume=84 |issue=1 |pages=122–123 |doi=10.2307/4083265 |jstor=4083265 |issn=0004-8038|doi-access=free }}</ref> One study found that brood productivity was reduced by half when female blood mercury levels exceeded 4.3 μg/g and productivity completely failed when female blood mercury levels exceeded 8.6 μg/g. These results are related to fish mercury levels of 0.21 μg/g and 0.41 μg/g, respectively.<ref name=":18" /> As mercury levels and pH are correlated, scientists have found that brood success decreases with decreasing pH such that environments with a pH at around 4.5 exhibited reproductive success below a calculated positive growth rate threshold.<ref name=":6" /> An association has also been observed between elevated blood methylmercury levels and aberrant incubation patterns.<ref name=":10" /> Adult common loons with high levels of methylmercury were found to spend less time incubating and in the nest, increasing the risks of [[predation]] and the eggs overheating/overcooling.<ref name=":10" /> Together, the effects of heightened methylmercury levels on parenting behaviors may contribute to lower chick survival rates. One study in Maine and New Hampshire found that high levels of methylmercury in parents are associated with a significant decrease in the number of fledged young, with common loons in the highest risk group producing 41% fewer fledged young than common loons with low levels of methylmercury.<ref name=":10" />

==== Mercury deposition in the Adirondack Mountains ====
The common loons of the [[Adirondack Mountains]] are particularly affected by methylmercury as the acidity of the lakes provides an environment conducive to converting environmental mercury to methylmercury.<ref name=":20" /> One study found that 21% of the male Adirondack common loon and 8% of the female Adirondacks common loon sampled were at high risk for detrimental impacts such as behavioral and reproductive abnormalities.<ref name=":20" /> In the Adirondacks, [[bioaccumulation]] factors for methylmercury were found to increase up the food chain, leaving common loons at the highest risk for detrimental effects from methylmercury.<ref name=":20" /> [[Spatial analysis]] indicates that the highest aquatic mercury concentrations are found in the southwestern portion of the Adirondacks, an area with lakes heavily affected by acid rain.<ref name=":22" /> Organizations such as the Adirondack Loon Center and the Adirondack Cooperative Loon Program spearhead loon conservation efforts in the Adirondacks by performing research, engaging the public, and informing public policy.<ref name=":21" />

==== Breeding range decline ====
The common loon's breeding range has moved northward, the species breeding as far south as Iowa a century ago.<ref name=":5">{{Cite web|url=http://seagrant.wisc.edu/birds/Common_Loon_conservation.html|title=Common Loon Conservation Status- Migratory Birds of the Great Lakes – University of Wisconsin Sea Grant Institute|last=Wiland|first=L.|date=2007 |archive-url=https://web.archive.org/web/20170712112025/http://seagrant.wisc.edu/birds/Common_Loon_conservation.html|archive-date=12 July 2017|access-date=12 July 2017}}</ref> It too is adversely affected by [[acid rain]] and pollution, as well as lead poisoning from fishing sinkers (especially those that are about the size of the grit stones they ingest<ref>{{Cite journal | last1=Franson | first1=J. Christian | last2=Hansen | first2=Scott P. | last3=Pokras | first3=Mark A. | last4=Miconi | first4=Rose | date=2001 | title=Size characteristics of stones ingested by common loons | jstor=1369696 | journal=The Condor | volume=103 | issue=1 | pages=189–191 | doi=10.1650/0010-5422(2001)103[0189:scosib]2.0.co;2| s2cid=86704804 | doi-access=free }}</ref>) and mercury contamination from industrial waste.<ref name="locke">{{cite journal | last1=Locke | first1=L.N. | last2=Kerr | first2=S.M.| last3=Zoromski | first3=D. | title=Lead poisoning in common loons (''Gavia immer'') | journal=Avian Diseases | volume=26| issue=2 | pages=392–396 | year=1982 | doi= 10.2307/1590110 | jstor=1590110 | pmid=7103895 | citeseerx=10.1.1.514.3406 }}</ref> Heavy metals such as mercury may be partially removed through biological processes such as excretion or deposition in feathers, but their adverse effects are [[biomagnification|magnified]] through concentration of the toxic elements in organs such as the liver. Eggs shells may also contain metal contaminants,<ref name="burger">{{cite journal | last1=Burger | first1=Joanna | last2=Pokras | first2=Mark | last3=Chafel | first3=Rebecca | last4=Gochfeld | first4=Michael | title=Heavy metal concentrations in feathers of common loons (''Gavia immer'') in the northeastern United States and age differences in mercury levels | journal=Environmental Monitoring and Assessment | volume=30 | issue=1| pages=1–7 | year =1994 | doi=10.1007/BF00546196 | pmid=24213705 | bibcode=1994EMnAs..30....1B | s2cid=24178181 }}</ref> leading to low reproductive productivity. High levels of heavy metals are linked to loons being in poor condition,<ref name="Scheuhammer">{{cite journal | last1=Scheuhammer | first1=Anton M. | last2=Wong | first2=Allan H.K. | last3=Bond | first3=Della | title=Mercury and selenium accumulation in common loons (''Gavia immer'') and common mergansers (''Mergus merganser'') from Eastern Canada | journal=Environmental Toxicology and Chemistry | volume=17 | issue=2 | pages=197–201| year=1998 | doi=10.1002/etc.5620170209 | s2cid=85336567 }}</ref> males being affected more because they eat larger fish.<ref name="MNFI" />

The common loon has also faced a decline in breeding range due to hunting, predation, and water-level fluctuations, or flooding. Some environmentalists attempt to increase nesting success by mitigating the effects of some of these threats, namely terrestrial predation and water-level fluctuations, through the deployment of rafts in the loon's breeding territories.<ref>{{Cite journal|last1=Desorbo|first1=Christopher R|last2=Taylor|first2=Kate M.|last3=Kramar|first3=David E. | last4=Fair | first4=Jeff | last5=Cooley | first5=John H. | last6=Evers | first6=David C. | last7=Hanson | first7=William | last8=Vogel | first8=Harry S. | last9=Atwood | first9=Jonathan L. |date=2007 | title=Reproductive advantages for common loons using rafts | journal=Journal of Wildlife Management | volume=71 | issue=4 | pages=1206–1213 | doi=10.2193/2006-422|bibcode=2007JWMan..71.1206D |s2cid=85992979|issn=0022-541X }}</ref> In addition, artificial floating nesting platforms have been provided for the common loon in some lakes to reduce the impact of changing water levels due to dams and other human activities.<ref>{{Cite journal|last1=McIntyre|first1=Judith W. | last2=Mathisen | first2=John E. | date=1977 | title=Artificial islands as nest sites for common loons | journal=The Journal of Wildlife Management | volume=41 | issue=2 | pages=317–319 | doi=10.2307/3800613 | jstor=3800613 }}</ref> The common loon abandons lakes that fail to provide suitable nesting habitat due to shoreline development. It is endangered by personal water-craft and powerboats that may drown newly born chicks, wash eggs away, or swamp nests.<ref name=":5" /> It is still considered an "injured" species in Alaska as a result of the [[Exxon Valdez oil spill]].<ref name=":4" />

=== Lead poisoning ===
In a 2003 survey of [[New England]] dead loons, lead poisoning from fishing weights accounted for about half of the deaths, and other human factors directly caused the death of 52% of the observed 522 loons.<ref>{{Cite journal |last1=Sidor |first1=Inga F. |last2=Pokras |first2=Mark A. |last3=Major |first3=Andrew R. |last4=Poppenga |first4=Robert H. |last5=Taylor |first5=Kate M. |last6=Miconi |first6=Rose M. |date=April 2003 |title=Mortality of Common Loons in New England, 1987 to 2000 |journal=Journal of Wildlife Diseases |volume=39 |issue=2 |pages=306–315 |doi=10.7589/0090-3558-39.2.306 |issn=0090-3558|doi-access=free |pmid=12910757 }}</ref>