Editing Common pochard (section)

== Ecology ==
These are gregarious birds; they form large flocks in winter, often mixing with other species of diving duck.{{sfn|Madge|Burn|1988|p=247}} They are strong fliers; in direct, flapping flight, they can reach speeds of {{convert|22|–|24|m/s|mph|abbr=on}}.{{sfn|Henningsson|Johansson|Hedenström|2010|p=94}}

=== Food and feeding ===
Common pochards feed on plant material (including seeds), small fish, [[Mollusc|molluscs]], and other [[Aquatic invertebrate|aquatic invertebrates]].{{sfn|The Wildlife Trusts|2021|ref=The Wildlife Trusts}}{{sfn|RSPB|2021|ref=RSPB}} They feed primarily by diving to retrieve items from under the water's surface; however, they will also upend and dabble at items on the water's surface. They do most of their feeding at night.

They regularly forage in close association with [[Bewick's swan|Bewick's]] and [[Whooper swan|whooper swans]], two species that trample underwater sediment to excavate food. Studies have shown that this behaviour greatly increases the food intake rate of the pochards, as they glean food items that drift away from where the swans are trampling. This rate can be double what it would be if the birds were feeding on their own.{{sfn|Gyimesi|van Lith|Nolet|2012}}

=== Breeding ===
[[File:Aythya_ferina_MHNT.ZOO.2010.11.20.4.jpg|thumb|Eggs from the collection of the [[Museum of Toulouse]]]]
The female builds a [[Bird nest#platform|platform nest]] of plant material, with a shallow cup lined with [[Down feather|down feathers]] near its centre. This is placed either on the ground within {{convert|10|m|ft|0|abbr=on}} of the water's edge or in the water with the platform rising above the water's surface. It is always located in dense cover. The female lays one egg daily until her [[Clutch (eggs)|clutch]]—typically 8–10 [[egg]]s—is complete. Only then does she begin [[Egg incubation|incubation]]. The eggs are greenish-grey and broadly oval, measuring {{convert|62|x|44|mm|abbr=on}} on average. They are incubated by the female and hatch synchronously after around 25 days. When off the nest the female will cover the eggs with down. The young are [[precocial]], [[nidifugous]] and can feed themselves. They fledge when aged 50–55 days.{{sfn|Cramp|1977|p=567}}

Like many ducks, common pochards suffer a high rate of parasitic egg-laying, a behaviour also known as egg dumping. Studies have shown that as many as 89% of nests in some areas contain one or more eggs not laid by the incubating female.{{sfn|Št́ovíček|Kreisinger|Javůrková|Albrecht|2013|p=369}}{{sfn|Petrzelkova|Klvana|Albrecht|Hořák|2013|p=103}} The percentage of parasitic eggs may reach as high as 37% of all eggs laid in some populations.{{sfn|Petrzelkova|Klvana|Albrecht|Hořák|2013|p=103}} There appears to be little cost to the incubating female for accepting eggs that are not her own, and indeed she will roll any egg left close to her nest into her clutch.{{sfn|Dugger|Blums|2001|p=717}}{{sfn|Hořák|Klvaňa|2009}} However, if the number of parasitic eggs exceeds six, she is twice as likely to abandon her nest.{{sfn|Dugger|Blums|2001|p=721}} Females sometimes lay their eggs in the nests of other duck species as well; red-crested pochards are unwitting hosts in some areas.{{sfn|Amat|1993|p=65}}

Levels of nest predation can be high, particularly for nests located in upland areas. Those located on islands, or over water (on artificial platforms) do significantly better, presumably because water deters at least some [[mammal]]ian predators.{{sfn|Albrecht|Hořák|Kreisinger|Weidinger|2006|p=788}} Nesting success depends on a number of factors, including the age of the female, her body mass, the date the nest was started, and the size of the clutch. Older, heavier birds are more successful than younger, lighter ones. Smaller, earlier-laid clutches are less likely to be abandoned than larger, later ones.{{sfn|Blums|Mednis|Clark|1997|p=919}}