English and Scientific names:

Common Merganser (Mergus merganser)

Number of individuals: 

1 adult female in breeding plumage.

Locality: LOUISIANA: 


Specific Locality:

Louisiana Universities Marine Consortium, 8124 Highway 56, Cocodrie

Date(s) when observed:

Feb. 10, 2009

Time(s) of day when observed:  

14:30 to 15:00 hours.


Reporting observer and address:

Russell Martin, Jr., Chauvin, LA.

Other observers accompanying reporter who also identified the bird(s):

John Conover

Light conditions:

Full sunlight. Bird was at 90% angle to sunlight (bird S.E., afternoon sun S.W.) compared to vantage point where observers were stationed. Observers were approximately 7 feet off the ground, viewing from a cement ramp behind the facility--bird was below line of sight, swimming in area with reflected sky light and reflected dark background of bulkhead along side of boat landing area behind bird. Distinguishing characteristics of bird were seen with both light and dark “backdrop” of reflected water.

Optical equipment: 

Zeiss 10X40B in excellent condition (6 years old)

Distance to bird(s): 

50 yards to 200 yards.

Duration of observation:

20 minutes. Bird was observed by other staff most of day.


brackish/salt water “lagoon” enclosed by bulkheads and rock levees, surrounded by salt marsh habitat approx. 1 mile north of Terrebonne Bay.

Behavior of bird: 

Bird swam most of time it was seen.  It was observed by J.C. flying away from observer in late afternoon.  At one time of day, it was observed near a lone Double-crested Cormorant. Workers noticed the bird swimming and probably feeding close to shore at boat launch.  It would swim towards center of “lagoon” as people walked nearby.


To the naked eye, bird appeared to be a common loon in general size and profile.  Upon looking through binoculars, however, it was clearly a merganser species.  Bird was initially observed swimming near a Double-crested cormorant, and was roughly a similar-sized bird; not noticeably smaller in size compared with cormorant, as would a Red-breasted Merganser.  Distance of bird to observers was never more than 200 yards, and usually no more distant than 100 yards. Bird swam with head upright for entire period that it was photographed. Large, wedge-shaped head apparent in profile, with a single crest of feathers at back of head. Bird was wide, in relation to size, much like a Canvasback, and very stocky in overall build. Beak of bird was much thicker than Red-breasted Merganser.  Sides and back of bird were a dull gray.  Bird had a clearly distinguished white patch on its chin. Chin patch ended abruptly above throat.  Throat was rich rusty color, as was neck and head of the bird; coloration much more distinct than Red-breasted Merganser.  A clearly defined thick white area was observed on lower half of throat. This marking wrapped completely around to lower back of neck (where it meets mantle). White appeared to abruptly end on sides of bird, almost as uniformly as it did on neck where it bordered rich brown color of throat.  Tail of bird was slightly above water line, parallel to surface. White wing patch barely observable on bird as it swam. In flight, large white wing patches were observed.  Wing patch was split by a very subtle, thin (gray) line separating greater coverts and secondaries; not a bold dark separation as seen in Red-breasted Mergansers. A close-up of photos taken shows distinctive facial features, including bill thickness at base of bill as bird looked at observers.  Eye of bird is brown, not red. Tail length of bird is easily seen, longer than one would expect to see in Red-breasted Merganser.


None heard.

Similar species:

All other N. American Mergansers eliminated by size and diagnostic features (both shape and proportion of bird, head/neck coloration, white patterns on chin and lower neck, and bill shape/size).  No other duck species share a combination of these elements that would confuse observers.

Photographs or tape recordings obtained?

Yes. Photographs were taken by J.C. and cropped close ups (with no color/contrast enhancement) are attached to this report.  Original images (app. 3 megs each) available upon request.

Previous experience with this species: 

Observer R.M. has extensive experience with the bird, having carved both sexes of the species and entered in international competition, based on in-hand frozen specimens.  Observer J.C. has minimal experience with species, having seen a flock in northern Michigan.

Identification aids: 

at time of observation:

None used.

after observation:

Sibley Guide to Birds, Google Image Search (for comparisons with immature/female Red-breasted Merganser).

Notes made from?  

Description written from memory and comparison between R.M. and J.C. of their impressions of physical characteristics of bird

Are you positive of your identification? If not, explain: 




Russell Martin, Jr.

Date and time: 

2/11/2009 (submitted by J.C. 2/18/09).