Editing Grebe (section)

===Feathers===
Grebes have unusual [[feather|plumage]]. On average grebes have 20,000 feathers, the highest among birds. The feathers are very dense and strongly curved. In the larger species feathers are more dense but shorter, while the opposite is true in smaller species where the feathers are longer but less dense. 

The density and length of feathers is correlated exponentially with heat-loss in cold water. For this reason grebes invest plumage maintenance the most in birds in terms of duration of time and energy. The [[uropygial gland]]s secrete a high concentration of paraffin. The secretion provides a dual purpose of protecting the feathers from external parasites and fungi, as well as waterproofing them.<ref name="Fjeldså2004" />{{Rp|33–36}} When [[preening]], grebes eat their own feathers and feed them to their young. The function of this behaviour is uncertain, but it is believed to assist with [[pellet (ornithology)|pellet]] formation, excreting out internal parasites and protecting their insides from sharp bone material during digestion.<ref>{{cite journal|last=Simmons|title=Feather-eating and Pellet-formation in the Great Crested Grebe|journal=Br. Birds|volume=49|pages=432–435|year=1956|url=http://www.britishbirds.co.uk/search?model=pdf&id=3147|access-date=2013-02-22|archive-date=2016-04-15|archive-url=https://web.archive.org/web/20160415043309/https://britishbirds.co.uk/articles/search-articles/?id=3147&model=pdf|url-status=live}}</ref> The [[ventral]] plumage is the most dense, described as very fur-like. By pressing their feathers against the body, grebes can adjust their [[buoyancy]]. In the nonbreeding season, grebes are plain-coloured in dark browns and whites. However, most have ornate and distinctive breeding plumages, often developing chestnut markings on the head area, and perform elaborate display rituals.<ref name="EoB" /> The young, particularly those of the genus ''Podiceps'', are often striped and retain some of their juvenile plumage even after reaching full size.<ref name="Fjeldså2004" />{{Rp|36–39}}

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| image1            = Great Crested Grebe chick, Earlswood Lakes, Surrey (3522706435).jpg
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| caption1          = A [[great crested grebe]] (''Podiceps cristatus'') chick with its downy feathers and striped head
| image2            = 2016.10.30.-02-Wagbachniederung Oberhausen-Rheinhausen--Haubentaucher.jpg
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| caption2          = A great crested grebe in nonbreeding or winter plumage
| image3            = Пірникоза 6013.jpg
| caption3          = A pair of great crested grebe in breeding plumage as they perform a courtship ritual
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