| Diving ducks | |
|---|---|
 | |
| Greater scaup,Aythya marila | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Anseriformes |
| Family: | Anatidae |
| Subfamily: | Anatinae |
| Tribe: | Aythyini |
| Genera | |
See the text | |
Thediving ducks, commonly calledpochards orscaups, are a category ofduck which feed by diving beneath the surface of the water. They are part ofAnatidae, the diverse and very largefamily that includes ducks,geese, andswans.
The diving ducks are placed in a distinct tribe in the subfamilyAnatinae, theAythyini. Whilemorphologically close to thedabbling ducks,[1] there are nonetheless some pronounced differences such as in the structure of thetrachea.mtDNAcytochromeb andNADH dehydrogenasesubunit 2sequence data indicate that the dabbling and diving ducks are fairly distant from each other, the outward similarities being due toconvergent evolution.[2]Alternatively, the diving ducks are placed as asubfamilyAythyinae in the family Anatidae which would encompass all duck-like birds except thewhistling-ducks.[3][failed verification]Theseaducks commonly found in coastal areas, such as thelong-tailed duck (formerly known in the U.S. as oldsquaw),scoters,goldeneyes,mergansers,bufflehead andeiders, are also sometimes colloquially referred to in North America as diving ducks because they also feed by diving; their subfamily (Merginae) is a very distinct one however.
Although the group iscosmopolitan, most members are native to theNorthern Hemisphere, and it includes several of the most familiar Northern Hemisphere ducks.
This group of ducks is so named because its members feed mainly by diving, although in fact theNetta species are reluctant to dive, and feed more like dabbling ducks.
These are gregarious ducks, mainly found on fresh water or onestuaries, though thegreater scaup becomes marine during the northern winter. They are strong fliers; their broad, blunt-tipped wings require faster wing-beats than those of many ducks and they take off with some difficulty. Northern species tend to bemigratory; southern species do not migrate though thehardhead travels long distances on an irregular basis in response to rainfall. Diving ducks do not walk as well on land as thedabbling ducks; their legs tend to be placed further back on their bodies to help propel them when underwater.
Threegenera are included in the Aythyini. Themarbled duck which makes up themonotypic genusMarmaronetta, however, seems very distinct and might have diverged prior to the split of dabbling and diving ducks as indicated by morphological and molecular characteristics.[1][2] The probably extinctpink-headed duck, previously treated separately inRhodonessa, has been suggested to belong intoNetta,[1][4] but this approach has been questioned.[5]DNA sequence analyses have found it to be the earliest diverging member of the pochard group.[6] The molecular analysis also suggests that thewhite-winged duck should be placed into amonotypic genusAsarcornis which is fairly close toAythya and might belong into this subfamily.[2]
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