Editing Common loon (section)

== Predators and parasites ==

Adult common loons have few predators, although [[bald eagle]]s will attack incubating birds. Attacks by sharks in winter have also been recorded.<ref name="Evers2010" /> When a predator approaches (either the loon's nest or the loon itself), the common loon sometimes attacks the predator by rushing at it and trying to stab it with its dagger-like bill, aiming its attacks either at the predator's abdomen or the back of its head or neck, which may be deadly to predators up to the size of a fox or raccoon.<ref>{{Cite journal|journal=Bird Observer|issue = 3 |year=2004|volume = 32|last1= Davies |first1=William E. |pages=202–204|url=http://www.birdobserver.org/Portals/0/PDF_open/bo32-3-web.pdf?ver=2017-02-10-105735-433#view=Fit| title=About the cover. Common loon}}</ref>

Eggs are taken by a number of mammals, including [[American mink]], [[striped skunk]], [[North American river otter|otters]], foxes and [[raccoon]]s, with the latter being responsible for nearly 40% of all nest failures. Birds such as [[herring gull]]s, [[northern raven]]s and [[American crow]]s will eat unattended eggs. Because their nests are at the water's edge, common loon eggs are especially vulnerable if the adult is absent.<ref name="Evers2010" />

Chicks may be killed by [[common snapping turtle]]s, large gulls, bald eagles and large fish such as [[northern pike]] and [[largemouth bass]]. The eagle in particular is a significant predator of chicks.<ref name="Evers2010" />

Internal parasites of the common loon include many species of [[helminths|worms]], including [[trematoda|flatworms]], [[cestoda|tapeworms]], [[nematode]]s and [[acanthocephala|spiny-headed worms]].<ref>{{Cite journal|last1=Daoust|first1=Pierre-Yves|last2=Conboy|first2=Gary|last3=McBurney|first3=Scott|last4=Burgess|first4=Neil|year=1998|title=Interactive mortality factors in common loons from maritime Canada|journal=Journal of Wildlife Diseases|volume=34|issue=3|pages=524–531|doi=10.7589/0090-3558-34.3.524|pmid=9706561|s2cid=24447180}}</ref> High levels of worms may result from feeding changes due to low availability of fish, and can lead to illness and death.<ref name= kinsella>{{cite journal | last1=Klnsella | first1=J.M. | last2=Forrester | first2=Donald J. | title=Parasitic helminths of the common loon, ''Gavia immer'', on its wintering grounds in Florida | journal=Journal of the Helminthological Society of Washington | volume =66 | issue=1 | pages=1–6 | year=1999 | url=http://bionames.org/bionames-archive/issn/1049-233X/66/1.pdf }}</ref> Protozoal infections including one caused by ''Eimeria gaviae''<ref>{{Cite journal|last1=Montgomery|first1=Roy D.|last2=Novilla|first2=Meliton N.|last3=Shillinger|first3=Robert B.|date=1978|title=Renal coccidiosis caused by ''Eimeria gaviae'' n. sp. in a common loon (''Gavia immer'') | jstor=1589663 |journal=Avian Diseases|volume=22|issue=4|pages=809–814|doi=10.2307/1589663|pmid=749899}}</ref> and [[avian malaria]] have been recorded in this loon.<ref>{{cite journal|last1=Martinsen|first1=Ellen S. |last2=Sidor|first2=Inga F. | last3=Flint | first3=Sean | last4=Cooley | first4=John | last5=Pokras | first5=Mark A. |year=2017 | title=Documentation of malaria parasite (''Plasmodium'' spp.) infection and associated mortality in a common loon (''Gavia immer'') | journal=Journal of Wildlife Diseases | volume=53 | issue=4 | pages=859–863 | doi=10.7589/2016-08-195 |pmid=28665230 |s2cid=4391165 }}</ref> The [[black fly]] ''[[Simulium|Simulium annulus]]'' is closely associated with the common loon to which it is attracted to chemicals in the [[uropygial gland]] secretions as well as by visual and tactile cues. This fly is detrimental to loons, their preferred hosts, transmitting blood-borne parasites and viruses, and causing nest abandonment when numbers are high.<ref name="wein">{{cite journal|last1=Weinandt|first1=Meggin L. |last2=Meyer|first2=Michael|last3=Strand|first3=Mac|last4=Lindsay|first4=Alec R.|year=2012|title=Cues used by the black fly,''Simulium annulus'', for attraction to the common loon (''Gavia immer'')|url=http://commons.nmu.edu/cgi/viewcontent.cgi?article=1010&context=facwork|journal=Journal of Vector Ecology |volume=37|issue=2|pages=359–364|doi=10.1111/j.1948-7134.2012.00239.x|pmid=23181860 |s2cid=768681 |doi-access=free|url-access=subscription}}</ref><ref>{{Cite journal|last1=Piper|first1=Walter H.|last2=Tischler|first2=Keren B.|last3=Reinke|first3=Andrew|year=2018|title=Common loons respond adaptively to a black fly that reduces nesting success|journal=The Auk|volume=135|issue=3|pages=788–797|doi=10.1642/auk-17-239.1|s2cid=90934731|url=https://digitalcommons.chapman.edu/cgi/viewcontent.cgi?article=1202&context=sees_articles|doi-access=free}}</ref> External parasites include [[ischnocera]]n [[bird louse|feather lice]], although these are not found on the bird's head.<ref name=Rothschild>{{cite book |last1=Rothschild |first1=Miriam |author-link1=Miriam Rothschild |last2=Clay |first2=Theresa |title=Fleas, Flukes and Cuckoos. A Study of Bird Parasites |year=1953 |publisher=Collins |location=London |page =[https://archive.org/details/fleasflukescucko00roth/page/153 153] |url=https://archive.org/details/fleasflukescucko00roth}}</ref>

[[Botulism]], acquired by eating infected fish, can lead to paralysis and drowning. [[Aspergillosis]] is another cause of emaciation and death.<ref>{{cite book|chapter=Causes of mortality in common loons|last1=Franson | first1=J.C.| last2=Cliplef | first2=David J. |title=Proceedings from the 1992 Conference on the Loon and its Ecosystem: Status, management, and environmental concerns|pages=2–12|year=1992|publisher=US Fish and Wildlife Service}}</ref> Outbreaks sometimes lead to thousands of deaths.<ref name= MNFI>{{cite web |last1= Gibson|first1= J.W. |title = ''Gavia immer'' Brünnich Common Loon| work=Michigan Natural Features Inventory |year=2007| pages=1–6| publisher=Michigan State University |url= https://mnfi.anr.msu.edu/abstracts/zoology/Gavia_immer.pdf }}</ref>