| Redhead | |
|---|---|
 | |
| Adult male, Maryland | |
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| Adult female with young, Montana | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Anseriformes |
| Family: | Anatidae |
| Genus: | Aythya |
| Species: | A. americana |
| Binomial name | |
| Aythya americana (Eyton, 1838) | |
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Breeding Year-round Migration Nonbreeding | |
| Songs and calls |
Theredhead (Aythya americana) is a medium-sizeddiving duck. The scientific name is derived fromGreekaithuia, an unidentifiedseabird mentioned by authors includingHesychius andAristotle, andLatinamericana, of America.[2] The redhead is 40–56 cm (16–22 in) long with an 74–84 cm (29–33 in)wingspan; the weight ranges from 1,030–1,080 g (36–38 oz),[3][4] with males weighing an average of 1,080 g (38 oz) and females an average of 1,030 g (36 oz).[4] It belongs to the genusAythya, together with 11 other described species. The redhead and thecommon pochard form asister group which together is sister to thecanvasback.[5] Thiswaterfowl is easily distinguished from most other ducks by the male's copper colored head and pale blue bill during thebreeding season;[6] from its close relativecanvasback it is distinguished by the more rounded head, shorter bill, and (in the males) yellow, not red, eye. The Eurasiancommon pochard is even more similar, but very rarely overlaps in range; it also differs in having a red eye, and a more acute, less rounded head shape.[4]
Other names that have been used for the redhead include red-headed duck and the red-headed pochard.[7]
The redhead is in the familyAnatidae (ducks, swans, geese) and genusAythya (diving ducks). There are currently no acceptedsubspecies of the redhead.[7]
The twosyntype specimens ofFuligula americana Eyton (Monogr. Anat., 1838, p.155) are held in the vertebrate zoology collections ofNational Museums Liverpool atWorld Museum, with accession numbers NML-VZ D829 (male immature) and NML-VZ D829a (female adult).[8] The specimens were collected in North America and came to the Liverpool national collection viaThomas Campbell Eyton’s collection[9] and the13th Earl of Derby’s collection which was bequeathed to the city of Liverpool.[8]
The redhead and thecommon pochard form asister group which itself is sister to thecanvasback.[5] This group is then sister to themonophyletic group consisting of the white-eyes (hardhead,Madagascar pochard, and the sister speciesferruginous duck andbaer's pochard) and scaups (New Zealand scaup,ring-necked duck,tufted duck,greater scaup,lesser scaup).[5]
The redhead is apochard, a diving duck specially adapted to foraging underwater. Their legs are placed further back on the body, which makes walking on land difficult. The webbing on their feet is larger thandabbling ducks and their bills are broader to facilitate underwater foraging. In addition, pochards have a lobed hind toe.[7] No pochard has a metallic coloredspeculum, something that is characteristic of other ducks.[10]
During breeding season, adult males have a copper head and neck, with a black breast. The back and sides are gray, the belly is white and the rump and tail are black. Male bills are pale blue with a black tip and a thin ring separating the two colors. Non-breeding males lose the copper color and instead have brown heads. The eyes are yellow, one of the most obvious distinctions from canvasback and common pochard, which have red eyes.[6][4]
Adult females, however, have a yellow to brown head and neck. The breast is brown, the belly is white and the rest of the body is a gray to brown. The female bills are slate with a dark tip that is separated by a blue ring. Females remain the same color year round.[6] The eyes are brown, as in all otherAythya species.[4]
Duringbreeding season, redheads are found across a wide range ofNorth America, from as far north as Northern Canada, south to the Caribbean in winter. Their preferred areas include theintermontane regions ofBritish Columbia,Alberta,Saskatchewan,Manitoba, and the Dakotas with some small localities inOntario,Quebec and southern United States. These pochards then migrate south to winter in warmer climates. These areas include southern United States where breeding does not occur and extends to Mexico, Guatemala, Cuba, and the Bahamas.[7][6] In both seasons, redheads use wetlands as their main habitat.[6]
Small, semi-permanentwetlands in non-forested country where the water is deep enough to provide denseemergent vegetation is considered ideal breedinghabitat for redheads.[7][11] When wintering, redheads switch to large areas of water near the coast that are protected from wave action, but can also be found inreservoirs,lakes,playa wetlands,freshwater river deltas,coastal marshes,estuaries andbays.[7][6][11]
Redheads do not have manypredators and are most likely to die of disease or indirect human impact. These ducks are considered less desirable as table fare than their puddle duck cousins like themallard. However, their beautiful plumage makes them a targeted species for waterfowl hunters looking to focus on diving ducks. Adults can be preyed upon bynorthern river otters,red-tailed hawks,great horned owls,bald eagles,golden eagles and to a greater extent,minks.[12] Most predation comes in the form of duckling predation and egg foraging.Northern pike andsnapping turtles are known to eat ducklings whereasskunks,minks,crows andmagpies will steal and eat redhead eggs.[7][12]
TheNorth American Waterfowl Management Plan for redheads is 760,000 North American birds.[13] The population size has increased in the past few decades to well over 1.4 million birds.[6] Redheads make up 2% of North America's duck population and only 1% of its harvested ducks.[13] Populations may be stable because of restrictive bag limits for the species. In addition, the species uses semi-permanent and permanent wetlands to breed and these habitats are less likely to be affected by drought. For future management of the species, organizations are looking intowetland conservation.[13]
Redheads begin to leave their winter range in late January and February with the northernmost birds migrating by late April. In western North America, migrants begin arriving in Oregon, British Columbia and Colorado in February. In central North America, migrants arrive as soon as temperatures open wetlands and lakes, which can range from late February (Nebraska) to early May (Alberta, Manitoba and Iowa). In theGreat Lakes region and north-eastern North America, migrants will also arrive as soon as bodies of water open up.[14]
Western birds migrate throughGreat Basin to thePacific Coast. In British Columbia, fall migration begins in September and continues through October. TheGreat Salt Lake region is of particular importance to migrants in western United States. Central North American redheads will begin migrating earlier, around August/September and go through the Great Plains to theTexas coast. Eastern populations will migrate through theGreat Lakes region to theAtlantic Coast or Florida from October to November. Most redheads winter along theGulf of Mexico (offshore Louisiana, Florida and Mexico). However, eastern populations will winter in South Carolina.[14]
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Redheads flock together onlakes and other bodies of water, butmigrate in pairs, which are formed in December or January through elaboratecourtship rituals.[7] Unpaired redheads migrate together in a ‘courting party’ that can be up to 25 individuals strong, enabling them to find a mate within the group.[7] The pair bonds are established yearly through a long courtship process. Males begin this process through neck-kinking and head throwingdisplays while emitting a cat-like call.[14] The male continues by initiating a neck-stretching display while producing a cough-like call. If interested, the female produces inciting calls towards the male while performing alternate lateral and chin lifting movements. The male then swims ahead of her and turns the back of his head towards the female.[7] Once courtship is finished, the two birds are paired for the year. The male initiatescopulation by alternating bill dipping andpreening dorsally towards the female, upon which the female may return to the male.[10]
Once copulation is completed, female redheads begin formingnests. They are built with thick and strong plant material in emergent vegetation, such ashard stem bulrush,cattails andsedges, over or near standing water.[7][12] Redheads do not defend theirterritory orhome range; they are insteadsocial while in their breeding ground. This is thought to facilitatebrood parasitism on other pochards, which is particularly prevalent on the part of younger, less experienced redhead females.[7] In this process, redheads lay their eggs in other pochards’ nests, including thecanvasback,ring-necked duck andgreater andlesser scaups, and this parasitism by redheads reduces the hatching success of other pochards’ eggs, especially those of thecanvasback.[7] The parasitic relationship between the redhead and other pochards promotes hybridization between the species; redheadhybrids with thering-necked duck,canvasback and thegreater andlesser scaups have been found.[10] Canvasback × redhead hybrids can be fertile.[15] Brood sizes range from 5 to 7 young, with the mother abandoning the chicks at 8 weeks old, 2–4 weeks before they are capable of flight.[13]
There is little information on redheadvocalizations outside of breeding calls. When the neck is fully extended in the neck-stretching display, males emit a cat-likewheee-oww.[7][10] Males may also produce a soft coughing call, although this call is less frequent.[7] Females emit a softerrrr note when inciting a male.[7]
All pochards have similardiets that include both plant and animal materials. Redheads undergo aniche switch when breeding and when wintering. During the breeding season, redheads will eat as much animal matter as possible, includinggastropods,mollusks and insect larvae.[7][6] They will eat the occasional grass and otheremergent vegetation.[6] However, once they fly south, redheads will change their diet to include mostly plant material, consisting ofpondweeds,wild rice,wild celery,wigeon grass,bulrushes,muskgrass andshoal grass.[7][6]
Gastropods known as food ofAythya americana include:Acteocina canaliculata,Acteon punctostriatus,Anachis avara,Anachis obesa,Caecum nitidum,Calliostoma sp.,Cerithidea pliculosa,Cerithium lutosum,Crepidula convexa,Diastoma varium,Melanella sp.,Mitrella lunata,Nassarius acutus,Nassarius vibex,Natica sp.,Neritina virginea,Odostomia trifida,Olivella minuta,Olivella watermani,Polinices sp.,Pyramidellidae,Pyrgocythara plicosa,Rissoina catesbyana,Sayella livida,Turbonilla sp.,Turbonilla interrupta andVitrinella sp.[16]
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