Editing Black-throated loon (section)

==Behaviour==
[[File:Gavia arctica taking off.jpg|thumb|A black-throated loon taking off]]
Like other loons, this bird does not take flight well; it takes off by pattering on a "runway" of water.<ref name="Pielou2012">{{cite book|last=Pielou|first=E. C.|title=A Naturalist's Guide to the Arctic|url=https://books.google.com/books?id=QQuqAAAAQBAJ&pg=PA203|date=31 July 2012|publisher=University of Chicago Press|isbn=978-0-226-14867-0|page=203}}</ref> While flying, it makes a barking "kwow" [[flight call]].<ref name="PetersonMountfort2001">{{cite book|last1=Peterson|first1=Roger Tory|last2=Mountfort|first2=Guy|last3=Hollom|first3=P. A. D.|title=A Field Guide to the Birds of Britain and Europe|url=https://books.google.com/books?id=s12BdfjtWtsC&pg=PA9|date=15 December 2001|publisher=Houghton Mifflin Harcourt|isbn=978-0-618-16675-6|page=12}}</ref>

===Breeding===

[[File:Black throated loon family feeding on Lake Sträken, Sweden.jpg|thumb|Black-throated loon family feeding on [[w:sv:Stråken (Mullsjö)|Lake Stråken]], Sweden]]

This species usually nests on the ground<ref name="Petersen1979">{{cite journal|last=Petersen|first=Margaret R.|title=Nesting ecology of arctic loons|journal=The Wilson Bulletin|volume=91|issue=4|year=1979|pages=608–617}}</ref> within about {{convert|1|m|ft}} of the lake it breeds at.<ref name="Hakeetal.2005"/> This loon also sometimes nests on vegetation, like ''[[Arctophila fulva]]'', that has emerged from lakes. The nest site is often reused the next year.<ref name="BergmanDerksen1977"/> The nest itself is oval-shaped<ref name="Petersen1979"/> and built mostly by the female<ref name="Sjolander1978"/> out of heaped plant material like leaves and sticks.<ref name="Hauber2014">{{cite book|last=Hauber|first=Mark E.|title=The Book of Eggs: A Life-Size Guide to the Eggs of Six Hundred of the World's Bird Species|url=https://books.google.com/books?id=evQvBAAAQBAJ|date=1 August 2014|publisher=University of Chicago Press|location=Chicago|isbn=978-0-226-05781-1|page=53}}</ref> The nest is about {{convert|23|cm|in}} across. Families of black-throated loons often move their nest site from the original nest ponds they inhabited to wetlands nearby after the chicks reach two weeks of age. The journey is generally less than {{convert|150|m|ft}}.<ref name="BergmanDerksen1977"/>

In the southern portion of its range, this loon starts to breed in April, whereas in the northern parts of its range, it waits until the spring thaw,<ref name="hbw"/> when there is adequate water for it to take off.<ref name="Petersen1979"/> It usually arrives before the lake thaws, in the latter case.<ref name="Sjolander1978">{{cite journal|last1=Sjolander|first1=Sverre|title=Reproductive behaviour of the black-throated diver ''Gavia arctica''|journal=Ornis Scandinavica|volume=9|issue=1|year=1978|pages=51–65|issn=0030-5693|doi=10.2307/3676139|jstor=3676139}}</ref>

Before copulation, the female hunches its neck and swims close to the shore until it finds a suitable place and then lies down on the shore. The male sometimes adopts the same posture as the female. During this time, the only vocalization made is a one note "hum". During copulation, the male, coming ashore, mounts the female and occasionally flaps its wings loudly. After this, the male returns to the water and {{birdgloss|preens}} itself. The female stays ashore for a maximum of about 23 minutes and usually starts to build the nest.<ref name="Sjolander1978"/>
[[File:Gavia arctica MWNH 1918.JPG|thumb|Eggs, Collection [[Museum Wiesbaden, Germany]]]]
The black-throated loon lays a clutch of two, very rarely one or three,<ref name="hbw"/> {{convert|76|by|47|mm|in}} eggs that are brown-green with darker speckles. These eggs are incubated by both parents for a period of 27{{nbsp}}to 29{{nbsp}}days,<ref name="Hauber2014"/> with the female spending the most time incubating. During incubation, this bird turns its eggs. The interval between when they are turned is very irregular, ranging from one minute to about six hours.<ref name="Sjolander1978"/> After they hatch, the mobile young are fed by both parents for a period of weeks.<ref name="Hauber2014"/> The chicks fledge about 60{{nbsp}}to 65{{nbsp}}days after hatching, and achieve sexual maturity after two to three years.<ref name="hbw"/>

Nesting success, whether or not at least one chick will hatch from any given nest, is variable year to year, ranging from under 30% to over 90%.<ref name="BergmanDerksen1977"/> For clutches of two eggs, the average nesting success is about 50%, whereas in clutches with only one egg, this rate is about 60%.<ref name="MudgeTalbot1992"/> The nesting success is influenced most by predation,<ref name="Petersen1979"/> and flooding.<ref name="MudgeTalbot1992">{{cite journal|last1=Mudge|first1=G. P.|last2=Talbot|first2=T. R.|title=The breeding biology and causes of nest failure of Scottish black-throated divers ''Gavia arctica''|journal=Ibis|volume=135|issue=2|year=1992|pages=113–120|issn=0019-1019|doi=10.1111/j.1474-919X.1993.tb02822.x}}</ref> Some of the adults that lose their clutch early in the incubation period renest. Most of the time, only one chick survives to fledge, the other dying within seven days of hatching.<ref name="BergmanDerksen1977">{{cite journal|last1=Bergman|first1=Robert D.|last2=Derksen|first2=Dirk V.|title=Observations on arctic and red-throated loons at Storkersen Point, Alaska|journal=[[Arctic (journal)|Arctic]]|year=1977|volume=30|issue=1|pages=41–51|doi=10.14430/arctic2682|url=https://arctic.journalhosting.ucalgary.ca/arctic/index.php/arctic/article/download/2682/2659|doi-access=free}}</ref> In Scotland, a study concluded that a single pair usually fledges a chick, on average, 25% of the time per year.<ref name="hbw"/> This can be increased by artificial means, such as constructing rafts for loons to nest on.<ref>{{cite journal |last=Hancock |first=Mark |year=2000 |title=Artificial floating islands for nesting Black-throated Divers ''Gavia arctica'' in Scotland: construction, use and effect on breeding success |journal=Bird Study |volume=47 |pages=165–175 |doi=10.1080/00063650009461172 |issue=2 |doi-access=free |bibcode=2000BirdS..47..165H }}</ref> Whether or not there is at least one chick fledged is influenced by the density of fish in the breeding lake; a lake with a higher density of fish usually reduces the chance that a pair will fledge a chick, even though this loon feeds mainly on fish. There are two factors that might contribute to this; the first being that aquatic insects, an alternative food source for chicks, are more dense when there are less fish, and the second being that a higher density of fish means more [[northern pike]], a predator of small chicks.<ref name="Eriksson1986">{{cite journal|last1=Eriksson|first1=Mats O. G.|title=Reproduction of black-throated diver ''Gavia arctica'' in relation to fish density in oligotrophic lakes in southwestern Sweden|journal=Ornis Scandinavica|volume=17|issue=3|year=1986|pages=245–248|issn=0030-5693|doi=10.2307/3676833|jstor=3676833}}</ref>

===Feeding===
A top predator in the [[pelagic zone]] of some subarctic lakes,<ref name="AmundsenLafferty2009">{{cite journal|last1=Amundsen|first1=Per-Arne|last2=Lafferty|first2=Kevin D.|last3=Knudsen|first3=Rune|last4=Primicerio|first4=Raul|last5=Klemetsen|first5=Anders|last6=Kuris|first6=Armand M.|title=Food web topology and parasites in the pelagic zone of a subarctic lake|journal=Journal of Animal Ecology|volume=78|issue=3|year=2009|pages=563–572|issn=0021-8790|doi=10.1111/j.1365-2656.2008.01518.x|pmid=19175443|doi-access=free|bibcode=2009JAnEc..78..563A }}</ref> this bird feeds on fish and sometimes insects, [[mollusc]]s, [[crustacean]]s, and plant matter.<ref name="hbw" /> The black-throated loon usually forages by itself or in pairs, rarely feeding in groups with multiple species.<ref name="BaltzMorejohn1977">{{cite journal|last2=Morejohn|first2=G. Victor|year=1977|title=Food habits and niche overlap of seabirds wintering on Monterey Bay, California|journal=[[The Auk]]|volume=94|issue=3|pages=526–543|last1=Baltz|first1=D. M.}}</ref> It dives from the water,<ref name="De GraafTilghman1985">{{cite journal|last2=Tilghman|first2=Nancy G.|last3=Anderson|first3=Stanley H.|year=1985|title=Foraging guilds of North American birds|journal=Environmental Management|volume=9|issue=6|pages=493–536|doi=10.1007/BF01867324|issn=0364-152X|last1=De Graaf|first1=Richard M.|bibcode=1985EnMan...9..493D|s2cid=85418857}}</ref> at depths of no more than {{convert|5|m|ft}}.<ref name="Bundy2009">{{cite journal|year=2009|title=Breeding and feeding observations on the black-throated diver|journal=Bird Study|volume=26|issue=1|pages=33–36|doi=10.1080/00063657909476614|issn=0006-3657|last1=Bundy|first1=Graham|doi-access=free}}</ref> Just before diving, this loon stretches and holds up its neck until it is erect and at full length. It usually jumps slightly upwards before diving.<ref name="BNA">{{cite journal|last=Russell|first=Robert W.|year=2002|title=Arctic Loon (''Gavia arctica'')|journal=The Birds of North America|doi=10.2173/bow.arcloo.01 |editor-last=Rodewald|editor-first=P. G.|access-date=11 July 2017|url=https://birdsna.org/Species-Account/bna/species/arcloo|url-access=subscription}}</ref> These dives are frequent, with an average of about 1.6 dives per minute. Most dives, about 80% of them, are successful, and those that are successful are usually shorter than those that are unsuccessful, with an average of 17 seconds for each successful dive, and 27 seconds for each unsuccessful dive. These dives usually only result in small items, and those that yield larger pieces of food are usually more than 40 seconds, where this bird catches quick-swimming fish.<ref name="Bundy2009"/>
[[File:Parelduiker in haven en op zee-4961855.webm|thumb|left|A video of a black-throated loon foraging]]
When it is breeding, the adult usually feeds away from the nest, foraging either at the opposite end of the breeding or at lakes near the breeding lake. When foraging for newly hatched chicks, the adult forages in the lake where the nest is or in nearby lakes, returning after a prey item has been caught. When the chicks are older, they usually accompany both of the parents, swimming a few metres behind them. The strategy that predominates immediately after hatching is generally still employed when the chicks are older, but at a reduced rate.<ref name="Jackson2002">{{cite journal|year=2002|title=Between-lake differences in the diet and provisioning behaviour of black-throated divers ''Gavia arctica'' breeding in Scotland|journal=Ibis|volume=145|issue=1|pages=30–44|doi=10.1046/j.1474-919X.2003.00119.x|issn=0019-1019|last1=Jackson|first1=Digger B.}}</ref> The chicks are fed only one item of prey at a time. The young are also able to capture food themselves at least 36 days after hatching, although they are still fed daily up until about 70 days of age.<ref name="Sjolander1978" />

The diet of black-throated loon chicks varies, the prey in the breeding lake being a major factor. For the first eight days, chicks are usually fed [[three-spined stickleback]]s and [[common minnow]]s if they are found in the breeding lake. If they are not present, then the chicks are brought up mainly on small invertebrates until about eight days, when they are able to take [[trout]] of about {{convert|100|mm|in}} in length. Although in these chicks trout makes up the majority of their diet, they are still fed invertebrates in large numbers. In all lakes, [[salmonid]]s make up an important part of the chicks' diet after eight days. Salmonids, especially those between {{convert|100|and|240|mm|in}}, are important in the diets of older chicks. Eels are also an important food for older chicks.<ref name="Jackson2002" />