Two closely related duck species often seen in the spring and late fall are the scaup.
Hunters often refer to them as “bluebills” and aptly so. Both possess a light blue bill. While trying to tell the two species apart can be a challenge in the field, knowing a few of their key differences may aid in a positive identification.
The scaup are diving ducks, often found in rafts with other diver species like ring-necked duck, common goldeneye, redhead, canvasback and ruddy duck.
While seeing one on a shallow pond or marsh is not out of the question, the more productive places to look are generally deeper bodies of water.
When in breeding plumage, male scaup have a greenish or purplish head, black breast, a vermiculated gray and black back, white sides, black rear and blue bill. Female scaup are generally brown overall with a darker brown head. Females of both species also have white around the base of the bill, which can be more exaggerated in greater scaup.
A suite of field marks are key for comparing and discerning the two species. In males and females, head shape plays a large role. Greater scaup tend to have a more robust and gently rounded head profile. Lesser scaup have a small inflection point or “corner” near the rear of the head. This can make the head of the lesser scaup appear peaked. An actively diving lesser scaup can sometimes appear to have a more rounded head. This is because the diving activity may flatten out the crown feathers.
Tricky birds like this should either be left unidentified as “scaup species” or patience may be needed to eventually observe the bird at rest. A resting Lesser Scaup will usually show the correct head shape.
Head color is another thing to pay attention to. Greater scaup tend to show a green iridescence in head coloration, whereas lesser shows purple. Head color, however, is not a totally diagnostic feature of either species. Lesser scaup can often show green head coloration or a combination of green and purple as well.
There are a few other differences in male scaup. The white side patches tend to have thin light brown barring in “lesser.” The lack of this barring in “greater” makes them appear to have “whiter” sides. Greater scaup is slightly larger than “lesser” at about an inch longer and three inches more wingspan. Greater scaup also have a larger, broader bill. The “nail” at the end of the bill is larger is “greater” than in “lesser.” Lastly, the white found throughout the secondary and primary feathers is more extensive in “greater” than in “lesser.”
Look for either scaup species during their peak migration in the spring and fall. March is essentially the spring peak for both species in Iowa, especially the “greater.” The peak of migration for “lesser” begins in March and spills over into April.
The Mississippi River hosts the largest numbers for greater scaup during spring migration and is perhaps the best place to look for them in Iowa. In Linn County, Cedar Lake in Cedar Rapids and Pleasant Creek SRA north of Palo are good places to look for either species during migration. In Johnson County, Hawkeye WMA, Terry Trueblood RA and Coralville Lake are productive locations.
Cone Marsh in Louisa County can host a nice variety of both diving and dabbling duck species. Keep an eye out on small ponds, even in urban areas. Either species may persist in small numbers into the winter months if open water persists. Check roller dams and reservoir tail water areas as well as areas kept open on rivers by industrial water influx.
MARCH BIRDS
— Waterfowl, waterfowl, waterfowl. Cone Marsh and Hawkeye WMA are top places to watch migrating waterfowl. Keep the hunting seasons in mind and wear hunter orange if out birding on public lands. The Mississippi River also hosts a large number of waterfowl in migration. Green Island WMA also can be great when peak numbers and diversity coincide.
— Gull watching can be pretty good in March. Cedar Lake and Coralville Lake, if still iced over in places, sometimes host a nice diversity. Look for herring, lesser black-backed, glaucous, and Iceland gulls. Getting good at herring and ring-billed gull identification is the best place to start a journey to becoming good at gull identification. Gulling is the most challenging form of birding by far.
— Look for Sandhill Cranes at Cone Marsh WMA in Louisa County. While many cranes migrate through Eastern Iowa, many will actually stay to breed in marshy areas. Listen for their loud, trumpeting-like sound.
PHOTOGRAPHY ADVICE
This month’s advice is short, but can make a world of difference in photo quality. Clear lens covers that are made to protect the lens from scratching, dust, etc. are not recommended.
Shooting through an extra layer of glass can severely diminish the quality of photos, often making them seem fuzzy. A hood is a good way to protect the lens from scratches and other elements, such as rain. A hood also serves to shade the lens from sunlight or other light sources, preventing glare and lens flare.
Brandon Caswell has undergraduate degrees in biology, anthropology and geology. He enjoys bird-watching and nature photography. He helps instruct introductory and advanced courses in environmental science and geoscience at the University of Iowa. Email brandon.caswell83@gmail.com
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Bird-watching: Duck, duck, goose - The Gazette
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