Greater Scaup breed in shallow lakes and ponds in treeless wetlands. They gravitate towards wetlands that have higher ground to provide protection against the wind, areas with shallow water with abundant food, and areas with submergent and emergent vegetation. During migration, they rest and forage in the shallow waters of large lakes such as the Great Lakes and New York’s Finger Lakes. In the winter they use bays and shorelines on the Pacific and Atlantic coasts as well as the Great Lakes. Around 60–70% of the North American population spends the winter along the Atlantic coast and 20% spends the winter along the Pacific coast.Back to top
Greater Scaup eat aquatic invertebrates such as mollusks, insects, and crustaceans as well as aquatic plants, insects, and seeds. They forage primarily during the day, but will forage at night during the winter if disturbance from boats is too high during the day. To capture aquatic invertebrates in soft muddy substrates, scaup stick their bill into the mud and quickly open and close it while swimming forward. They tend to forage in waters less than 7 feet deep, but can forage and dive up to 23 feet in deeper water.Back to top
Greater Scaup nest on the ground, typically near the water’s edge in areas with dense cover from last year's growth of grasses and sedges. The nest is either on floating mats of vegetation or on solid ground that is not subject to flooding.
Females make a small depression on the ground and add grasses, other plant material, and downy feathers to make a saucer-shaped nest.
|Clutch Size:||5-13 eggs|
|Number of Broods:||1 brood|
|Egg Length:||2.4-2.7 in (6.2-6.9 cm)|
|Egg Width:||1.6-1.8 in (4.1-4.5 cm)|
|Incubation Period:||23-28 days|
|Egg Description:||Brownish olive-buff.|
|Condition at Hatching:|
Covered in down with eyes open. Ready to leave the nest in 24 hours.
Greater Scaup are members of the diving duck group, which catch food underwater unlike dabbling ducks (such as Mallards) that tip up to eat food just below the surface of the water. Scaup are good divers and can dive up to 23 feet underwater to retrieve aquatic invertebrates from the muddy lake and ocean bottoms. On the wintering grounds they form tight groups with each other and sometimes mix with other diving ducks. Greater Scaup are generally monogamous during the breeding season; they choose new mates every year, typically on the wintering grounds. During courtship, males gather in groups of up to 17 and surround a single female while calling. Males jostle and fight for a position near the female and throw back their heads or show the female the back of their head to grab her attention. In response to a pursuing male, females bob their heads, stretch their neck, and move their bill side to side while calling. After breeding males congregate on lakes with abundant food and plant cover to replace their feathers before flying south for the winter. Females are more likely than males to return to the same breeding sites the following year.Back to top
Greater Scaup are common throughout their range, but their populations are rapidly declining. Partners in Flight estimates the global breeding population is 780,000. The species rates a 12 out of 20 on the Continental Concern Score and is listed as a Common Bird in Steep Decline by Partners in Flight. Several factors may be contributing to the Greater Scaup’s decline, including warmer water in Alaska, contaminants, disturbance, habitat degradation, and hunting. Approximately 70% of the population along the Atlantic coast spends the winter in urbanized areas. In these areas, contaminants such as DDE and PCBs measured in tissues in 1993 and 1997 exceeded the guidelines set for safe human consumption. High levels of heavy metals such as mercury and selenium have also been found in tissues and eggs. Hunting could also impact the population, although the U.S. Fish and Wildlife Service carefully manages duck hunting and limits the number of individuals hunters can take every year based on population size. From 2012–2016 hunters took on average 69,366 Greater Scaup per year.Back to top
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