BIOLOGICAL DATA AND HABITAT REQUIREMENTS
WILDLIFE SPECIES: Cygnus columbianus | Tundra Swan 



TIMING OF MAJOR LIFE HISTORY EVENTS : 
Age at first breeding - Tundra swans first breed when they are 2 or
3 years old.  They form lifelong monogamous pairs [10].

Nesting - Tundra swans start nesting in late May to late June depending
on location and weather [2,10].

Clutch size and incubation - Tundra swans generally lay a clutch of four
or five eggs [6,10].  The incubation period is 30 to 32 days [10].

Cygnet development and fledging - Tundra swan cygnets are generally able
to fly within 9 to 10 weeks.  The family remains together during the
fall migration, through winter, and during spring migration [10].

Molt - On the Yukon Delta, adult tundra swans molt between July and
August and regain flight within 35 to 40 days.  Nonbreeders, which
remain in flocks of 3 to 15 during the breeding season, regain flight in
late August and begin to congregate in sizable flocks [2].

Fall migration - Tundra swans migrate in family units, with several
families and probably some nonbreeding birds combining in a single flock
[2].  In the West, tundra swans leave major breeding grounds in Alaska
in late September and early October.  Marshes adjoining the eastern
shore of Great Salt Lake begin to receive tundra swans in mid-October.
Tundra swans begin arriving at the Malheur National Wildlife Refuge in
Oregon from mid- to late November and remain abundant well into
December.  In the Klamath basins of Oregon and California, wintering
tundra swans do not arrive in substantial numbers until late November
and early December.  On winter grounds adjacent to San Francisco Bay,
the swans are not present in great numbers until early December [2].

The eastern contingent of tundra swans passes across Minnesota,
Wisconsin, and Michigan, largely during November 5 to 15.  Tundra swans
on Chesapeake Bay slowly increase in numbers through December and reach
a peak in January [2].

Spring migration - Tundra swans begin leaving their winter habitat after
the first spring thaw [2].  Tundra swans from Chesapeake Bay cross
Pennsylvania to Lake Erie from the first week in March into early April.
Tundra swans leave their central California winter grounds in
mid-February, and within 3 weeks almost all have departed.  By early
April most have migrated north to Alaska and Canada.  The first swans
generally reach their breeding grounds on the Yukon Delta in late April
and almost all arrive by mid-May.  The western population of tundra
swans migrate earlier and more swiftly than its eastern counterpart [2].


PREFERRED HABITAT : 
Breeding habitat - Tundra swans usually breed on or near tundra ponds,
lakes, and sluggish rivers, and less often near sheltered tidal waters.
They tend to avoid areas near exposed marine coasts [1,8,10].

Nest sites - Tundra swans often select islets in tundra ponds and lakes
as nest sites [10].  Nests are also commonly located on the main shores
of lakes or ponds, heath tundras, hummocks in marshes or tidal meadows,
or more rarely, level stretches in marsh or meadow areas [2,15].  The
nest is an elaborate platform, 12 to 18 inches (30-45 cm) high, composed
of mosses, grasses, and sedges.  It resembles a muskrat house surrounded
by a moat.  In making the nest, the vegetation is plucked from around
the nest site, creating a circle of open water up to 15 feet (4.6 m) in
diameter [2].  In optimum habitat, several pairs of swans may have nests
very widely spaced but still in view of one onother [10].

Winter habitat - In winter, tundra swans use extensive shallow fresh and
brackish water. They are less frequently found on salt water.  Migrants
occur at ponds, lakes, flooded lowlands, slow-moving streches of rivers,
and estuaries [8,10].


COVER REQUIREMENTS : 
Tall emergent vegetation provides shelter and cover for tundra swans.
Adult swans remove vegetation around the nest until the nest is
surrounded by open water [2,10].


FOOD HABITS : 
Tundra swans eat the stems, seeds, and bulbous roots of aquatic plants,
and the seeds and young shoots of cultivated grains.  They also eat a
small amount of animal matter consisting mainly of the larvae of aquatic
beetles and dragon flies, worms, and mollusks [2,10].

Tundra swans feed on the following plants: foxtail (Alopecurus spp.) and
other grasses, wild celery, pondweeds, smartweeds, square-stem spike
rush (Eleocharis quadrangulata), arrowhead (Sagittaria spp.), coontail
(Ceratophyllum demersum), mermaid weed (Prosperinaca spp.), muskgrasses,
bulrushes, horsetail, wigeon grass (Ruppia maritima), and bur reed
(Sparganium spp.).  Rice and barley are eaten in stubble fields [2,10].
Tundra swans also feed on waste corn in both dry and flooded fields and
upon harvested potatoes.  These swans commonly fly as far as 10 to 15
miles (16-24 km) inland to glean waste corn and soybeans and to
browse upon shoots of winter wheat [2].


PREDATORS : 
Little information is available in the literature regarding predation on
tundra swans.  Bellrose [2] reported that nests have been destroyed by
gulls (Larus spp.) and foxes.  The following species also occur in
tundra swan habitat and could potentially prey on tundra swans: coyotes
(Canis lutrans), river otters (Lutra canadensis), minks (Mustela vison),
black bears (Ursus americanus), grizzly bears (U. arctos), bald eagles
(Haliaetus leucocephalus), mountain lions (Felis concolor), skunks
(Mephitis spp. and Spilogale spp.), and raccoons (Procyon lotor).  In a
few states, experimental hunting of tundra swans is allowed.  Generally,
a one swan per hunter limit is imposed [10].  Taking of tundra swan eggs
and the hunting of flightless molting birds by Native Americans are
significant mortality factors in some areas [10].


MANAGEMENT CONSIDERATIONS : 
The tundra swan is the most common and widespread swan in North America
[15].  Winter surveys of tundra swans during the 1950's in the United
States revealed an average population of 78,000.  This figure increased
to 98,000 during the 1960's and to 133,000 during 1970-74.  The lowest
population recorded from 1949 to 1974 was in 1950 at 49,000, and the
highest was 157,000 in January 1971.  Although the number of tundra
swans found on the winter surveys has varied considerably from year to
year, there has been a slow increase in the continental population over
the last 25 years [2].


REFERENCES : 
NO-ENTRY

Related categories for Wildlife Species: Cygnus columbianus | Tundra Swan