the hooded merganser (lophodytes cucullatus) is a species of small duck .
it is the only extant species in the genus lophodytes .
the bird is striking in appearance; both sexes have crests that they can raise or lower , and the breeding plumage of the male is handsomely patterned and coloured .
the hooded merganser has a sawbill but is not classified as a typical merganser .
hooded mergansers are the second smallest species of merganser , with only the smew of europe and asia being smaller , and it also is the only merganser whose native habitat is restricted to north america .
a species of fossil duck from the late pleistocene of vero beach , florida , was described as querquedula floridana (a genus now included in anas), but upon reexamination turned out to be a species closely related to the hooded merganser; it is now named lophodytes floridanus , but the exact relationship between this bird and the modern species is unknown .
the hooded merganser is a sexually dimorphic species .
the adult female has a greyish-brown body , with a narrow white patch over the lower breast and belly .
she has a light reddish-brown crest extending from the back of the head .
during the nonbreeding season the male looks similar to the female , except that his eyes are yellow and the female's eyes are brown .
in breeding plumage the dorsal areas and the head , neck and breast of the mature male are mainly black with white markings; there are large white patches on either side of the crest , and they are particularly conspicuous when he raises his crest during courtship .
his lower flanks are a rich reddish-brown or chestnut in colour , and the breast and undersides are more or less white , extending into white stripes across the crop and breast .
in both genders there are narrower pencilled white stripes along the tertial wing feathers; when the bird is in repose , then if the tertial feather stripes are visible , they have the appearance of longitudinal white stripes along the bird's lower back .
[2]first-winter birds differ from adult females in appearance in that they have a grey-brown neck and upper parts; the upper parts of adult females are much darker  nearly black .
furthermore , the young birds have narrower white edges to their tertial feathers than adults do .
females of all ages are dark-eyed , whereas in males the eyes become pale during their first winter .
for preference the hooded merganser lives on small bodies of water such as ponds and small estuaries where there is ample emergent aquatic vegetation , but it also inhabits larger wetlands , impoundments , flooded timber , and rivers .
they prefer fresh water but do occur on brackish water bodies as well .
the hooded merganser is a diving predator that largely hunts by sight while under water .
most studies report that its diet varies according to circumstances , usually being dominated by fishes (44-81%) .
in addition it feeds on aquatic insects (13-20% of its diet) and other aquatic invertebrates such as crabs and crayfish (22-50%) .
males and females of the hooded merganser form monogamous pairs and they remain together until the female has selected a nesting cavity and completed laying her clutch .
after that , the male leaves the female to incubate and care for the brood .
females will actively seek out cavities in dead trees or artificial nest boxes such as those provided for nesting wood ducks .
they prefer cavities 415 feet off the ground .
breeding occurs anytime between the end of february and the end of june , depending on the region .
the female will lay a clutch of 7-15 eggs but only begins incubation when the last egg has been laid , thereby permitting synchronous hatching .
all hatchlings are consequently of the same size , which facilitates efficient parental care .
during incubation , the female may lose anywhere from 8% to 16% of her body weight .
like most waterfowl , hooded merganser hatchlings are precocial and usually leave the nest within 24 hours after they hatch; this is about long enough to accommodate synchronous hatching .
once they leave the nest , the young are capable of diving and foraging , but remain with the female for warmth and protection .
