Appearance

Hooded Mergansers have 10 functional primaries, 16-18 secondaries (including 4-5 tertials), and 18-20 rectrices. Wings are moderately pointed and tail is long and graduated. No geographic variation in appearance or molt strategies reported.

Molts

Molt and plumage terminology follows Humphrey and Parkes (1959) as modified by Howell et al. (2003, 2004) and Pyle (2005). Hooded Merganser exhibits a Complex Alternate Strategy (cf. Howell et al. 2003), including complete prebasic molts, an incomplete preformative molt, and limited to partial prealternate molts in both first and definitive cycles (Bent 1923, Palmer 1976, Hohman et al. 1992, Pyle 2008; Fig. 4). Note revised plumage terminology of Pyle (2005) reverses previous terminology for prebasic and prealternate body-feather molt; thus, the prealternate molts result in cryptic summer body feathers for wing molt, and the prebasic molts result in colorful plumage aspects of males. The preformative (female) or second prebasic (male) molt results in definitive plumage aspect.

Prejuvenile (First Prebasic) Molt

Complete, May-Jul, in the nest. Completed 75–80 d after hatching.

Preformative Molt

("First prebasic" and/or "first prealternate" molt of previous terminology). Incomplete molt, Aug-Mar, commencing on or near breeding grounds and completing on non-breeding grounds. Variably protracted, with some to all molt occurring on breeding grounds, stopover sites, or winter grounds, depending on individual. Includes some to most body feathers, sometimes 1-4 tertials and a few proximal lesser secondary coverts, usually at least two central rectrices, and up to all 18-20 rectrices; the remaining secondaries and primaries are retained (Pyle 2008). Males may average more complete feather replacement than females, as found in other ducks.

First Prealternate Molt

(Part of "first prebasic molt" of previous terminology). Molt absent-limited, Jun-Aug, occurring primarily on or near breeding grounds. Includes some head and back feathers to hide colorful formative feathers of males; likely more limited or absent in females. Males may dessert breeding grounds to undergo some or all of this molt. Study needed.

Definitive Prebasic Molt

(Includes "definitive prealternate molt" of previous terminology). Complete, Aug-Oct, primarily on discrete molting grounds away from breeding grounds (Hohman et al. 1992), especially in males. Males desert females during breeding to begin molt. Females may commence molt on breeding grounds and both sexes may complete molt on non-breeding grounds after departing molting sites. Primaries, secondaries, rectrices, and most to all wing coverts replaced synchronously, resulting in flightlessness for up to 3-4 weeks.

Definitive Prealternate Molt

(Part of "definitive prebasic molt" of previous terminology). Partial molt, May-Jul, on or near non-breeding grounds. Includes most to all body feathers of upperparts but few if any tertials, wing coverts, or other flight feathers; may average more extensive in males than females due to need to replace or cover colorful plumage, providing crypsis for flightless wing-molt period.

Plumages

Following based on detailed plumage descriptions of Roberts (1955), Oberholser (1974), Palmer (1976), and Cramp and Simmons (1977); see Carney (1964, 1992) and Pyle (2008) for age/sex-related criteria; color photos in Burk (1984), Carney (1992; wing). Sexes show similar aspects in Juvenal Plumage but are dimorphic thereafter.

Natal Down

(Jun-Jul). Ducklings precocial, down-covered at hatch. Brown on back and upper breast; cheeks buffy or rufous; throat, lower breast, and belly white. A grayish spot on each side of back caudal and medial to trailing edge of wing, and at base of each side of tail. Trailing edge of inner wing grayish white or buffy. Male and female similar in plumage aspect. See also Nelson 1993.

Juvenal Plumage

(Jul-Oct). Head brownish gray with small crest (more like hairy fringe) and poorly defined whitish chin. Wings brownish, with less white than in Definitive Basic Plumage (below). Secondary coverts narrower, more rounded, and paler brown with darkish tips. Proximal greater coverts and secondaries have some white, but distal-most greater coverts (e.g., corresponding to s1-s3) with reduced or no white. Tertials straight, comparatively short and acutely pointed, dark brown, usually without longitudinal white stripes at rachis; often very frayed at ends. Rectrices brownish, tapered with notched ends. Breast and sides brownish fuscous, feather margins pale. Abdomen white with brownish mottling. Sexes not distinguishable without cloacal examination; however, males slightly larger with potentially longer and more pale-striped tertials.

Formative Plumage

(Nov-Jun). The first white-bellied plumage. Female as in Juvenal Plumage (above) but with crest feathers darker and more elongated, head and body increasingly mixed with darker or more rufous tinged feathers of Definitive Basic Plumage in female (see below); chin more distinctly white, and formative tertials (sometimes replaced in Dec-Feb) with indistinct whitish shaft streaks. Male as in Juvenal Plumage but gradually attains some blackish and or white in head, back and breast and rufous in flanks of Definitive Basic Plumage in male (below); usually does not attain full breeding aspect of adults. In both sexes wing feathers as in Juvenal Plumage: outer primaries faded, brownish, and worn; body plumage variably mixed with paler brown juvenal feathers; and replaced formative rectrices (often mixed with juvenal rectrices) blackish brown, slightly tapered with broadly rounded ends, and not notched.

First Alternate Plumage

(Jun-Sep). Female similar to Formative Plumage of female (above). Male similar to Formative Plumage of male (above) but black and white feathers of head, upperparts, and breast replaced or covered with brownish feathers, obscuring bold patterning and providing crypsis for wing molt.

Definitive Basic Plumage

(Oct-Jun). Female plumage brownish overall, particularly head, neck, and upperparts; bushy rufous or cinnamon crest; chin sharply defined, white; upper throat also white (although sometimes flecked with brown), as are lower breast and belly; upper breast slaty; sides brownish; undertail coverts grayish. Male with large, black-bordered, white crest; rest of head and neck black with greenish sheen; back black; breast white with 2 black stripes extending down the foresides; abdomen white; sides and flanks rufous or tawny with vermiculated gray and black; uppertail coverts brownish gray with narrow buffy edging; undertail coverts white, speckled, or mottled dusky. Wing of both sexes differs from that of Juvenal Plumage (above) by being darker brown with more white: secondary coverts broader, more squared, and darker brown; greater coverts (including those corresponding to s2-s3) and secondaries distinctly tipped white (averaging broader white tip in male); tertials curved distally, elongated, and black, with longitudinal white shaft stripes through center (usually broader and more pronounced in males); outer primaries fresher and duskier. Wing lining and axillars white. Rectrices of both sexes rectrices uniformly blackish with broadly rounded ends, and not notched.

Definitive Alternate Plumages

(Jun-Sep). Both sexes similar superficially to Definitive Basic Plumage in female (above), but some colors of Definitive Basic male (above) present under replaced alternate feathers. General appearance a muted, dusky brown; crest small and dusky. Wing and tail as in Definitive Basic Plumage of each sex.

Bare Parts

Bill And Gape

In hatchlings upper mandible brownish slate; lower mandible, lamellae, tomia, and base of bill at commisure yellowish pink to light orange; nail reddish brown, pinker at tip; upper egg tooth pale dull yellow, yellowish or pinkish white; lower egg tooth yellowish white, translucent and scale-like. First-cycle and older female with upper mandible blackish green with orange edge; lower mandible muted orange or yellowish. First-cycle male with bill brownish green with orange edge, becoming darker in spring; Adult male with bill black, duskier and paling to yellowish at base in Jun-Sep.

Iris

In hatchlings moderately yellowish brown (Nelson 1993). In females iris brownish buff or brownish olive. In males iris similar to females in first cycle, becoming bright yellow in adults. Color can be used to sex Definitive Alternate birds in the field.

Legs And Feet

In hatchlings toes and tarsi grayish olive, yellowish on inner web of toe 2 and on lobe of hallux (toe 1); webs olive or brownish gray (Nelson 1993). Feet not gray as depicted by Delacour (1954) or reddish as depicted by Millais (1913) or contrastively colored as indicated in Bellrose (1980). In older females toes brown, olive gray or dusky yellow, web darker. In older males toes vary from yellow to light olive to light brownish, webbing dusky to black.