The Lesser Scaup (Aythya affinis) is a small North American diving duck known for its distinctive blue bill and habit of rafting in large flocks on open water. Scaup have a fairly complex life cycle that revolves around breeding, migration, molting, and wintering in different habitats across North America.
What are the identifying features of the Lesser Scaup?
Lesser Scaup are medium-sized ducks with a length of 16-20 inches and weight of 1.5-2.4 pounds. The adult males have a rounded head with a purple sheen, black feathers on the back and tail, a white side panel, and a light blue bill. Females are mottled brown overall with a white patch around the base of the bill. Both sexes have yellow eyes. In flight, Lesser Scaup show white on the undersides of the wings. They are very social and gather in large flocks on lakes, rivers, and coastal waters.
Where does the Lesser Scaup breed?
Lesser Scaup breed in the northern prairie states and provinces of the United States and Canada. The key breeding states include North Dakota, South Dakota, Minnesota, and Montana. They nest near ponds, lakes, marshes, and rivers with abundant aquatic vegetation for food and cover. Males establish and defend breeding territories on the water. Females build nests on the ground near water, concealed by vegetation. The nests consist of down lined depressions and hold around 9 eggs. Females care for the eggs and ducklings on their own.
When does breeding occur?
Lesser Scaupbreeding occurs between April and July. Courtship begins in April when large flocks break up and pairs begin to form. Egg laying typically peaks in May and June. The female incubates the eggs for around 21-27 days before they hatch. The ducklings fledge in around 40-45 days, usually in July. Early hatched young have the best chance of survival due to declining wetland resources through summer. Males depart before the young fledge.
How many broods do Lesser Scaup produce?
Lesser Scaup normally only produce one brood per year. The female lays and incubates one clutch of eggs and cares for the resulting ducklings. She may re-nest up to two times if the first nest fails early enough in the season. This allows time for a new clutch to hatch and fledge before winter. Most Lesser Scaup breed for the first time at age one.
What do Lesser Scaup eat?
Lesser Scaup forage mainly on aquatic invertebrates and some aquatic plants. Their diet consists of:
- Insects
- Mollusks
- Crustaceans
- Worms
- Snails
- Fish eggs
- Algae
- Duckweed
- Pondweed
They dive underwater to find food in ponds, lakes, rivers, and estuaries. Males and females form large flocks that forage together. Ducklings eat mainly aquatic insects and other small invertebrates.
When and where does migration occur?
Lesser Scaup undergo lengthy migrations in spring and fall between breeding and wintering areas. In spring, they migrate north in April and May. They follow flyways over land from winter sites to reach breeding grounds. In fall, Lesser Scaup gather on northern staging lakes starting in early August. They migrate south from September to December, gathering on the Great Lakes and other major bodies of water during migration. Males and females migrate separately.
Typical migration patterns are:
- Spring: March to May
- Fall: September to December
Major migration corridors include:
- Mississippi Flyway
- Central Flyway
- Pacific Flyway
Where does the Lesser Scaup winter?
Lesser Scaup winter along both the Atlantic and Pacific coasts of North America. The highest concentrations occur in:
- Chesapeake Bay
- Long Island Sound
- Coastal Texas
- Coastal California
Some birds also overwinter along the Great Lakes, Gulf of Mexico, interior rivers, and reservoirs. They gather in large rafts on open water and dive to feed on mollusks, crustaceans, and aquatic insects.
How long is the typical lifespan of a Lesser Scaup?
The typical lifespan of a Lesser Scaup in the wild is relatively short due to high predation on eggs, ducklings, and adults. Only around 25% survive past their first year. Those that do survive may live around 5 years on average. The longest known lifespan in the wild is over 17 years.
What are the main threats to Lesser Scaup?
Lesser Scaup face a variety of natural and human-related threats throughout their range. These include:
- Habitat loss and degradation – Draining and development of wetlands reduces nesting and migration habitat.
- Invasive species – Mollusks that compete with native food sources.
- Pollution – Oil spills, chemical runoff, plastic trash.
- Overharvesting – Historic overhunting impacts population numbers.
- Predators – Foxes, skunks, racoons, and birds prey on eggs and young.
- Disease – Avian cholera outbreaks can kill thousands in a season.
Conservation efforts aim to protect key wetland habitats and limit harvesting and pollution threats.
What is the conservation status of Lesser Scaup?
The Lesser Scaup has an IUCN status of Least Concern. Its global population is estimated at around 3.5 million. However, numbers have declined over the past few decades, prompting increased conservation actions. The 2012 North American Waterfowl Management Plan calls for monitoring, habitat protection, and restoration to support Scaup populations.
Conclusion
In summary, the Lesser Scaup is a small diving duck with a broad range across North America. Its life cycle includes breeding in the northern prairies in summer, migrating south in fall and wintering along the coasts. Males and females form pairs during spring migration to nesting grounds. Females lay around 9 eggs and care for the ducklings on their own. The ducks forage on aquatic invertebrates and migrate in large flocks. Threats from habitat loss and other factors have caused declines in recent decades. Ongoing conservation efforts aim to maintain healthy Scaup populations into the future.