{{short description|Species of bird}} {{Use dmy dates|date=August 2020}} {{Speciesbox | image = Podiceps auritus (13909539717).jpg | image_caption = ''Podiceps auritus auritus'' in breeding plumage in Saint Petersburg, Russia | image2 = Horned Grebe (Podiceps auritus) in winter plumage, Scarborough Marsh, Maine, USA.png | image2_caption = ''Podiceps auritus cornutus'' in winter plumage in Scarborough Marsh, Maine. | status = VU | status_system = IUCN3.1 | status_ref = <ref name="iucn status 12 November 2021">{{cite iucn |author=BirdLife International |date=2018 |title=''Podiceps auritus'' |volume=2018 |article-number=e.T22696606A132066871 |doi=10.2305/IUCN.UK.2018-2.RLTS.T22696606A132066871.en |access-date=12 November 2021}}</ref> | genus = Podiceps | species = auritus | authority = (Linnaeus, 1758) | range_map = Slavonian Grebe-location-map-en.svg | range_map_caption = {{legend0|#F1F53D|Breeding range|border=1px solid gray}} {{legend0|#F58821|Winter range|border=1px solid gray}} | synonyms = *''Colymbus auritus'' {{small|Linnaeus, 1758}} *'''''Pliodytes lanquisti''''' {{small|Murray, 1967}} *''Podiceps dixi'' {{small|Brodkorp, 1963}}? *''Podiceps howardae'' {{small|Storer, 2001}}? *''Podiceps pisanus'' {{small|(Shufeldt, 1913)}}? }}
The '''horned grebe''' or '''Slavonian grebe''' ('''''Podiceps auritus''''') is a relatively small and threatened species of waterbird in the family Podicipedidae.<ref name="iucn status 12 November 2021"/> There are two subspecies, ''P. a. auritus'' (Slavonian grebe), which breeds in Eurasia, and ''P. a. cornutus'' (horned grebe), which breeds in North America.<ref name="HBW">{{Cite book|last1=del Hoyo|first1=J.|last2=Elliot|first2=A.|last3=Sargatal|first3=J.|year=1992|title=Handbook of the Birds of the World|publisher=Lynx Edicions|volume=1|pages=193–194|isbn=978-84-87334-10-8}}</ref><ref name="BLI">{{Cite web|url=http://www.birdlife.org/datazone/speciesfactsheet.php?id=3640|title=Horned Grebe Podiceps auritus|year=2015|website=Birdlife International}}</ref><ref name="BWP">{{cite book | last=Cramp | first=Stanley | title=Handbook of the Birds of Europe, the Middle East and North Africa: Volume 1 Ostrich to ducks | publisher=Oxford University Press | publication-place=Oxford London New York | date=1977 | isbn=0-19-857358-8 | pages=97–105}}</ref> The Eurasian subspecies is distributed over most of northern Europe and northern Asia, breeding from Iceland east to the Russian Far East.<ref name="Fjeldså">{{Cite journal|last=Fjeldså|first=Jon|year=1973|title=Distribution and Geographic Variation of the Horned Grebe Podiceps auritus (Linnaeus, 1758).|journal=Ornis Scandinavica|volume=4|issue=1| pages = 55–86| issn=0030-5693 | doi=10.2307/3676290 | jstor=3676290 | url=https://www.researchgate.net/publication/279956314 }}</ref> The North American subspecies spans most of Canada and some of the United States.<ref name=":1">{{Cite journal|last=Stedman|year=2000|title=Horned Grebe (Podiceps auritus)|journal=The Birds of North America|volume=505|doi=10.2173/tbna.505.p}}</ref> A small population was cited in Greenland in 1973,<ref name="Fjeldså"/> but is not mapped or further mentioned by subsequent authors.<ref name="HBW"/><ref name="BWP"/><ref name="BLI"/>
The American name 'horned' refers to the orange-yellow crest feathers located above and behind the eyes, called "horns". The English name, originally 'Sclavonian', is first attested by George Montagu in his 1802 ''Ornithological Dictionary'',<ref name="Montagu">{{cite book | last1=Montagu | first1=G. | last2=Bensley | first2=T. | title=Ornithological Dictionary; Or, Alphabetical Synopsis of British Birds | publisher=J. White | issue=v. 1-2 | year=1802 | url=https://archive.org/details/ornithologicald01montgoog/page/n258/mode/2up | access-date=2025-09-30 | page=13-PP10}}</ref> from ''Sclavonia'', an old name for northern Prussia, referring to the species' main breeding area in Europe;<ref name="Lockwood">{{cite book|last = Lockwood| first = W. B.|title = Oxford Book of British Bird Names|publisher = Oxford University Press|year = 1984}}</ref> the spelling was emended (without any reason given) to the current 'Slavonian' by Hartert in 1912.<ref name="s686">{{cite book | last1=Hartert | first1=Ernst | last2=Jourdain | first2=F. C. R. | last3=Ticehurst | first3=Norman F. | title=A hand-list of British birds, with an account of the distribution of each species in the British Isles and abroad | publisher=Witherby | publication-place=London | year=1912 | doi=10.5962/bhl.title.8013 | doi-access=free | page=157}}</ref>
==Taxonomy== The horned grebe was formally described in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his ''Systema Naturae'' under the binomial name ''Colymbus auritus''.<ref>{{cite book | last=Linnaeus | first=Carl | author-link=Carl Linnaeus | year=1758 | title= Systema Naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis | volume=1 | edition=10th | page=135 | publisher=Laurentii Salvii | location=Holmiae (Stockholm) | language=Latin | url=https://www.biodiversitylibrary.org/page/727040 }}</ref> Linnaeus specified the type locality as Europe and America but this has been restricted to Vaasa in Finland.<ref>{{ cite book | editor1-last=Mayr | editor1-first=Ernst | editor1-link=Ernst Mayr | editor2-last=Cottrell | editor2-first=G. William | year=1979 | title=Check-list of Birds of the World. Volume 1 | edition=2nd | publisher=Museum of Comparative Zoology | place=Cambridge, Massachusetts | pages=149–150 | url=https://www.biodiversitylibrary.org/page/16108789 }}</ref> The horned grebe is now one of the nine species placed in the genus ''Podiceps'' that was introduced in 1787 by the English naturalist John Latham.<ref name=ioc>{{cite web| editor1-last=Gill | editor1-first=Frank | editor1-link=Frank Gill (ornithologist) | editor2-last=Donsker | editor2-first=David | editor3-last=Rasmussen | editor3-first=Pamela | editor3-link=Pamela C. Rasmussen | date=December 2023 | title=Grebes, flamingos | work=IOC World Bird List Version 14.1 | url=https://www.worldbirdnames.org/new/bow/grebes/ | publisher=International Ornithologists' Union | access-date=19 July 2024 }}</ref> The genus name combines the Latin ''podex'' meaning "vent" and ''pes'' meaning "foot". The specific epithet ''auritus'' is Latin meaning "-eared" or "long-eared", and the subspecific name ''cornutus'' means "horned".<ref>{{cite book | last=Jobling | first=James A. | year=2010| title=The Helm Dictionary of Scientific Bird Names | publisher=Christopher Helm | location=London | isbn=978-1-4081-2501-4 | pages=[https://archive.org/stream/Helm_Dictionary_of_Scientific_Bird_Names_by_James_A._Jobling#page/n311/mode/1up 311], [https://archive.org/stream/Helm_Dictionary_of_Scientific_Bird_Names_by_James_A._Jobling#page/n62/mode/1up 62]}}</ref> <gallery mode = packed heights = 160px> Slavonian Grebe (Podiceps auritus auritus) juvenile Kaldbakstjarnir.jpg|juvenile ''P. a. auritus'' Slavonian Grebe (Podiceps auritus auritus) immature Kaldbakstjarnir.jpg|immature ''P. a. auritus'' Slavonian Grebe (Podiceps auritus auritus) breeding Kaldbakstjarnir 1.jpg|adult ''P. a. auritus'' in moult from breeding to winter plumage, calling </gallery>
==Description== The species can be recognised by its orange-red and black breeding plumage, its black and white non-breeding plumage, and its characteristic "horns". It is {{cvt|31–38|cm}} long, has a wingspan {{cvt|55–74|cm}} wide and weighs {{cvt|300–570|g}}.<ref name=":1" /> It has a moderately long neck, flat forehead and a rear crown of black feathers. Its beak is straight and pointed, with a white tip.
The breeding plumage has bright erectable "horns", black fan-shaped cheek feathers and an overall red-and-black colour. The neck, flanks, lores and upper-chest are chestnut brown, while the crown and back are black. The belly is a dull white. Males are slightly larger and brighter than females but are generally indistinguishable.
The non-breeding plumage is overall black and white. The neck, chest and cheeks are white, while the back and crown are a dull black-grey. The border between the crown and the cheeks extend in a straight line behind the eyes. The winter plumage does not have the "horns".
Juveniles appear similar to a non-breeding adult except they are a slightly duller shade of white and their back is tinged with brown. The line separating the cheeks and crown is less distinct and their beak is paler.<ref name="HBW"/> The chicks are fluffy, with a dull grey back, a white belly and distinct black-and-white facial and neck striping.
===Subspecies and distribution=== Two subspecies are accepted:<ref name=ioc/> {| class="wikitable " |- ! Summer !! Winter !! Scientific name !! Common name !! Summer distribution !! Winter distribution |- |120px || 120px || ''P. a. auritus'' (Linnaeus, 1758) || Slavonian grebe || Small populations in Iceland, Scotland, and Norway, and extensively from Sweden eastwards through Russia, northern Kazakhstan and northwest Mongolia to the Russian Far East in south Chukotka, Sakhalin and the Kamchatka Peninsula (east Russia) || Inshore waters of the Atlantic coast of Europe from Iceland and Norway south to northwestern France, in the eastern Mediterranean Sea, the Black Sea, and the Caspian Sea, and the Pacific coasts of Asia from northern Japan, Korea, south to eastern China.<ref name="HBW"/> |- |120px || 120px || ''P. a. cornutus'' (Gmelin, JF, 1789) || Horned grebe || Subarctic south and central Alaska mainland, central and western Canada from Yukon east to northwestern Ontario, but also a small disjunct population on the Magdalene Islands in the Gulf of St. Lawrence in Quebec,<ref>{{Cite web|url=http://www3.mffp.gouv.qc.ca/faune/especes/menacees/fiche.asp?noEsp=6|title=Horned Grebe List of wildlife species threatened or vulnerable in Quebec|year=2010}}</ref> and the northern tier of west-central contiguous USA states from northeastern Washington to Minnesota || Inshore waters of the Pacific and Atlantic coasts of North America, from southern Alaska south to California and the northern Gulf of California, and Nova Scotia south to Texas.<ref name="HBW"/> |- |}
The subspecies are physically similar in measurements, but differ subtly in plumage, with ''P. a. auritus'' darker, having a blacker back and crown, and orange-yellow lateral crown tufts in breeding plumage; and ''P. a. cornuta'' paler, with greyer back and crown, and straw-yellow tufts.<ref name="BWP"/><ref>{{Cite journal|last=Parkers|year=1952|title=Geographic variation in the Horned Grebe|journal=Condor|volume=54|issue=5|pages=314–315|doi=10.2307/1364948|jstor=1364948}}</ref>
A third subspecies ''P. a. arcticus'' <small>Boie, 1822</small> has sometimes been accepted for the population in coastal Norway, Iceland, and Scotland,<ref name="Fjeldså"/> but is now treated as synonymous with nominate ''P. a. auritus''.<ref name="BWP"/><ref name="HBW"/>
In winter plumage, it is often confused with the black-necked grebe, which is only slightly smaller in size and has similar colouring but is differentiated by a steeper forehead, a more slender, slightly uptilted bill, duskier cheeks, and a fluffier rump.<ref name="BWP"/><ref name=":0">{{Cite web|url=https://www.sararegistry.gc.ca/virtual_sara/files/cosewic/sr_horned_grebe_0809_e.pdf|title=COSEWIC Assessment and Status Report on the Horned Grebe Podiceps auritus.|year=2016}}</ref>
=== Vocalisation === Young begin calling for begging purposes in a slightly trilled peeping noise, similar to that of a domestic chick. As they mature, their song changes to a more adult-like chittering.<ref name="BWP"/> Their typical advertising call is loud and nasally "''aaarrh''" descending in a pitch and ending in a trill.<ref name=":2">{{Cite web|url=https://www.allaboutbirds.org/guide/Horned_Grebe/lifehistory|title=Horned Grebe|year=2016|website=All About Birds}}</ref> They use other calls during copulation, alarm and breeding ceremonies that are slightly variable from the advertising call. Horned grebes are extremely vocal during breeding, territory establishment and defence.<ref name=":1" /> Their song is subdued during autumn migration and at wintering sites.<ref name=":2" />
== Habitat == thumb|Chicks swimming alongside an adult ''P. a. cornutus'' in breeding plumage, Alaska The species breeds primarily in boreal and subarctic regions with a frost-free period of around 90 days or less,<ref name="BWP"/> but also in temperate zones, including prairies and parklands.<ref name=":1" /> They breed in small to moderately sized (0.5-10 ha) shallow freshwater ponds, marshes and shallow bays on lake edges with beds of emergent vegetation.<ref name=":0" /> They prefer lakes less than 2.5 m deep, with submerged vegetation, rather than bare gravel, silt or mud lakefloors,<ref name="BWP"/> and marginal vegetation with sedgess, rushes, and bulrushes along with large areas of open water.<ref>{{Cite journal|last=Faaborg|year=1976|title=Habitat selection and territorial behavior of the small grebes of North America|journal=Wilson Bull|volume=88| pages = 390–399}}</ref> This habitat provides a suitable site for nest material, anchorage, concealment and protection for young. It readily uses lakes surrounded by trees or forest.<ref name="BWP"/>
During migration, they will stop along lakes, rivers and marshes. Following migration, they winter in marine environments, including off estuaries and bays or sandy beaches; in some places, for example in Norway, large numbers congregate on inland lakes.<ref name="Fjeldså" />
== Behaviour == === Food and feeding === thumb|A Slavonian grebe ''P. a. auritus'' with a recently caught fish, Saint Petersburg, Russia
Horned grebes dive underwater using their large feet for agile manoeuvrability to feed on aquatic arthropods, fish and crustaceans.<ref name=":1" /> They will also catch airborne insects on the water's surface. Underwater they swallow or capture large prey and re-emerging at the surface to manipulate the fish headfirst.<ref name=":4" /> They usually feed solitarily or in small groups of up to five individuals.<ref name=":4">{{Cite journal|last=Storer|year=1969|title=The behaviour of the Horned Grebe in spring|journal=Condor|volume=71|issue=2| pages = 180–205|doi=10.2307/1366078|jstor=1366078}}</ref> During the summer, aquatic and airborne arthropods are preferred, whereas winter selection favours fish and crustaceans.<ref name=":1" />
As with other grebes, the horned grebe has an adaptation for swallowing fish whole. They will eat their own feathers from a young age, so that their stomach has a matted plug that functions as a filter to hold fish bones until digestion.<ref name=":2" />
=== Breeding === thumb|Adult ''P. a. auritus'' on nest with two eggs, Russia [[File:Podiceps auritus MHNT.ZOO.2010.11.39.7.jpg|thumb|Egg at Muséum de Toulouse]]
Horned grebes are monogamous and develop their relationship through elaborate mating routines. There are four pair bonding ceremonies; discovery ceremony, weed ceremony, head-shaking ceremony and triumph ceremony.<ref name="BWP" /><ref name=":4" /><ref name=":6">{{Cite journal|last=Fjeldså|first=J.|year=1973|title=Antagonistic and heterosexual behaviour of the Horned Grebe, Podiceps auritis|journal=Sterna|volume=12| pages = 161–217}}</ref> The discovery ceremony begins with advertising displays, which include an upright posture, erect "horns" and sounding of their advertising call. Then, both male and female engage in bouts of penguin dance and preening. This initial pair bonding ceremony is to ensure correct species identification, sex and compatibility.<ref name=":4" /> The weed ceremony follows the completion of a successful discovery ceremony. The male and female will dive, retrieve weeds and rise in synchronisation. The pair will come breast-to-breast with their weeds then turn side by side to continue swimming. This weed-rush can continue multiple times until both individuals are satisfied.<ref name=":4" /><ref name=":6" /> Finally, the head-shaking ceremony and triumph ceremony are performed for primarily established pairs.<ref name="BWP" /> Once copulation is to take place, it always occurs on a platform nest built by the pair.<ref name=":4" /><ref name=":6" />
Horned grebes usually arrive at breeding grounds in pairs or solitarily to seek out a mate in the spring or early summer.<ref name="HBW" /> A pair may nest entirely alone or in a loose colony that typically contains approximately 20 breeding pairs, each pair nesting some distance from the others.<ref name=":1" /> During nesting, horned grebes are known to defend their nests very aggressively.<ref name=":6" /><ref name="HBW" /> Nests are built from plant matter and are most commonly affixed to emergent vegetation otherwise built on land or in shallow open water.<ref name=":7"/> Depending on location the eggs are laid between April and September, with June being the most common month.<ref name="HBW" /> The females lays a single clutch of three to eight eggs,<ref name=":7">{{Cite journal|last1=Ferguson|last2=Sealy|year=1983|title=Breeding ecology of the Horned Grebe, Podiceps auritus, in southwestern Manitoba.|journal=Canadian Field-Naturalist|volume=97|issue=4 | pages = 401–408|doi=10.5962/p.355041 |doi-access=free}}</ref> which are coloured white, brownish or blueish green.<ref name=":1" /><ref name=":2" /> These eggs measure {{convert|58|by|39|mm|in}} on average.<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=69}}</ref> Both males and females share incubation time for 22 to 25 days.<ref name="HBW" /><ref name=":7" /> When the young hatch, they can swim and dive within the first few days, although they must be kept warm by their parents for up to 14 days.<ref name=":1" /> During this time, the juvenile chicks can often be seen riding on the backs of their swimming parents right in-between the wing and the back.<ref name=":2" /> Later the horned grebe will take their first flight at 55–60 days old.<ref>{{Cite web|url=https://www.audubon.org/field-guide/bird/horned-grebe|title=Horned Grebe Podiceps auritus|website=Audubon Guide to North American Birds}}</ref> The species finally reaches sexual maturity at two years old.<ref name="HBW" />
== Conservation status == The total North American population is estimated at between 200,000 and 500,000 individuals<ref name=":0" /> and the Eurasian population at 12,900 to 18,500 mature individuals.<ref name="BLI" /> The global population has declined by 30% over the last three decades and by 79% within North America.<ref name=":0" /> This is due primarily to human disturbance, forestry operations around breeding sites, fluctuating water levels, and stocking of lakes with rainbow trout that compete for aquatic insects.<ref name="HBW" /> They are also frequently caught in nets, vulnerable to oil spills and diseases.<ref name=":0" /><ref name="HBW" /> Between 1985 and 2001, grassland and wetland drainage amounted to 5% global habitat loss.<ref name=":0" /> The western Canadian population is listed as being of special concern and the breeding population on Magdalen Islands is listed as endangered.<ref name=":0" /> Due to global declines, the International Union for Conservation of Nature uplisted the status from least concern to vulnerable in 2015, resulting in conservation and research action plans.<ref name="BLI" /> The small population in northern Scotland is in severe decline, with only 26 pairs in 2021, a decline of 58% over the previous 26 years.<ref>{{cite journal |last1=Eaton |first1=Mark |display-authors=et al |title=Rare Breeding Birds in the UK |journal=British Birds |date=2023 |volume=116 |issue=11 |pages=634–635}}</ref>
==Fossils== A handful of fossil species, such as the Pliocene aged ''P. howardae'', ''P. pisanus'' and ''P. solidus'', and the Pleistocene aged ''P. dixi'' have been described to be related to or perhaps some of them might be pre-Holocene material of the horned grebe.<ref name="Olson&Rasmussen2001">{{Cite journal |last1=Olson |first1=S. L. |last2=Rasmussen |first2= P. C. |year=2001 |title=Miocene and Pliocene birds from the Lee Creek Mine, North Carolina. |journal=Smithsonian Contributions to Paleobiology |volume = 90 |issue = |pages = 233–365|doi=10.5479/si.00810266.90.233 |url=https://www.biodiversitylibrary.org/part/351988 }}</ref><ref name="Storer2001">{{Cite journal |last1=Storer |first1=R. W. |year=2001 |title=A New Pliocene Grebe from the Lee Creek Deposits. |journal=Smithsonian Contributions to Paleobiology |volume = 90 |issue = |pages = 227–231|doi=10.5479/si.00810266.90.227 |url=https://www.biodiversitylibrary.org/part/351987 }}</ref><ref name="Ksepkaetal2013">{{Cite journal |last1=Ksepka |first1=D. T. |last2=Balanoff |first2= A. M. |last3=Bell |first3= M. A. |last4=Houseman |first4= M. D. |year=2013 |title=Fossil grebes from the Truckee Formation (Miocene) of Nevada and a new phylogenetic analysis of Podicipediformes (Aves). |journal=Smithsonian Contributions to Paleobiology |volume = 56 |issue = 5 |pages = 1149–1169| doi = 10.1111/pala.12040 |bibcode=2013Palgy..56.1149K |s2cid=83938510 | url = https://onlinelibrary.wiley.com/doi/full/10.1111/pala.12040|url-access=subscription }}</ref> However while ''P. howardae'' and ''P. dixi'' are regularly recognized as fossil material of the horned grebe by some authors, ''P. pisanus'' and ''P. solidus'' are argued to be valid species that are close to the ancestry of the horned grebe.<ref name="Zelenkov2013">{{cite book |last1 = Zelenkov | first1= N. V. |year= 2013 |chapter= New finds and revised taxa of Early Pliocene birds from Western Mongolia. |editor-last1=Göhlich|editor-first1=U. B.| editor-last2=Kroh|editor-first2=A. | title = Paleornithological Research 2013-Proceedings of the 8th International Meeting of the Society of Avian Paleontology and Evolution.|series=Natural History Museum Vienna, Vienna |volume = |pages = 153–170 |chapter-url= https://www.researchgate.net/publication/259357289}}</ref>
==References== {{Reflist}}
{{Grebes}} {{portalbar|Birds|Animals|Biology}}
{{Taxonbar|from=Q192058}} {{Authority control}}
horned grebe Category:Holarctic birds horned grebe horned grebe