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Lesser
Scaup
PETIT
FULIGULE
Aythya affinis
(Eyton)
Abundant migrant throughout;
breeds province-wide in varying numbers.
A Lesser Scaup’s peaked head is
taller and narrower than a Greater Scaup’s, a distinction that is most easily
seen when it is sleeping or relaxing. When feeding, Lesser Scaup often compress
their crown feathers and present a more rounded profile when they surface
between dives. If such birds also show greenish iridescence in the head, they
are easily misidentified as Greater Scaup. The Lesser Scaup is the more
abundant of the two species in Manitoba. A scaup seen on a prairie slough in
summer is almost certain to be a Lesser, and this species is also by far the
commoner migrant in the prairie and parkland regions. Elsewhere, Greater Scaup
are sufficiently numerous that no assumptions can be made.
A few Lesser Scaup reach southern
Manitoba in late March, but the main migration is between mid-April and
mid-May, when the spring break-up is well advanced. Hundreds can then be seen
on lakes, rivers, marshes and sewage lagoons throughout the province. A peak
estimate of 12,000 Lesser Scaup was recorded at Delta in the last week of April
1971.1 Unlike the partly vegetarian Redhead, Canvasback, and
Ring-necked Duck, with which they often associate during migration, both scaup
species feed almost exclusively on aquatic invertebrates.2,3
The breeding range of this
species includes all of Manitoba, except near the Nunavut border.4 It
is the most abundant diving duck in the prairie pothole region, especially in
the Minnedosa-Erickson area and at Egg Lake, Saskatchewan, west of The Pas.5‑7
The Lesser Scaup is a much less common breeder in eastern Manitoba, but records
extend east to Oak Hammock Marsh and the Lac du Bonnet region, and northward to
Churchill; most nests in the south are initiated in June.8 Lesser
Scaup nests are vulnerable to mammalian predation, especially in drought years.9
In a 2.6-square-kilometre study area near Erickson, 51 pairs hatched 225 young
in 1957—a high-water year—but 65 pairs produced just 20 young in the dry summer
of 1958.10
Austin studied post-breeding
Lesser Scaup on sloughs near Erickson in 1982.11 They formed flocks
of up to 65 birds in the second half of July and were flightless for much of
August. Their numbers were augmented by migrants in late September, and flocks
of over 800 birds remained on the largest lake until a few days before
freeze-up. Lesser Scaup also appear at staging areas in southeastern Manitoba
around September 20, building to a peak in mid- to late October, when flocks
numbering in the thousands are not unusual. They form dense rafts on lakes,
often associating with smaller numbers of other diving duck species.
Spectacular flights of Lesser
Scaup sometimes pass through southern Manitoba in late fall. Hochbaum estimated
that 100,000 ducks, mostly Lesser Scaup, streamed southeastward over Delta in
one hour on 6 November 1947, at the peak of a three-day flight.12
Although scaup numbers are markedly reduced, this species remains by far the
most abundant diving duck in most areas during migration, and it is not unusual
to see several thousand in a day.
Some Lesser Scaup regularly
linger well into November, their numbers gradually declining until only a few
individuals can be found by the beginning of December. There are over a dozen
Christmas Bird Count records across southern Manitoba, with maxima of three
birds at Winnipeg in 1974, 2000 and 2001. At least one survived the 2000–2001 winter
at a sewage lagoon near Winnipeg, and several others have been recorded in mid-
or late February.
1 Siegfried 1974; 2 Rogers
& Korschgen 1966; 3 Bartonek & Hickey 1969; 4 Godfrey
1986; 5 Kiel et al. 1972; 6 Greenwood et al.
1995; 7 Townsend 1966; 8 Afton 1984; 9 Rogers
1964; 10 Rogers 1959; 11 Austin 1987; 12 Hochbaum
1955.
G.E. Holland, P. Taylor
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