BIOLOGICAL DATA AND HABITAT REQUIREMENTS
WILDLIFE SPECIES: Cygnus buccinator | Trumpeter Swan 



TIMING OF MAJOR LIFE HISTORY EVENTS : 
Pair formation - Trumpeter swans most often form pair bonds when they
are 2 or 3 years old, and first nest when they are 4 or 5 years old.
Most pairs remain together year-round and bond for life [2,18,23].

Nesting - In the Copper River area of Alaska, the Greater Yellowstone
area, and Red Rock Lakes National Wildlife Refuge, egg laying normally
begins in late April or early May and is completed about mid-May [4,17].
In interior Alaska, egg laying begins later than in the above areas
[17].  In Alberta, the eggs are layed in mid-May [2].

Clutch size and incubation - Each breeding pair uses only one nest and
the female lays five to six eggs [2,14,17].  If the eggs are destroyed
the pair will probably not renest [2].  The incubation period is 33 to
37 days [3,4,18].

Cygnet development and fledging - Trumpeter swan cygnets grow rapidly
[4].  They are fully feathered in 9 to 10 weeks, but are unable to fly
until 13 to 15 weeks in Alaska and 14 to 17 weeks in Montana [4,17].
Cygnets remain with their parents throughout their first winter.  They
separate from their parents the following spring, but siblings may
remain together into their third year.  Family bonds are strong;
subadult siblings may rejoin with parents after nesting ends or in
subsequent winters [23].

Molt - Nonbreeding subadults molt first.  Most nonbreeders in Alaska
begin their molt in late June or early July.  At Red Rock Lakes, the
molt may be completed as early as June [4].  It is rare for both members
of a breeding pair to be flightless at the same time.  The male of the
pair usually molts first.  Some paired birds may begin to molt as early
as nonbreeders.  Many, however, delay a month or longer.  Some trumpeter
swans are flightless until early September in Alaska and until October
in Montana.  Trumpeter swans are normally flightless for about 30 days
[4].

Migration - The seasonal movements of trumpeter swans in the Greater
Yellowstone region are limited to local flights between breeding habitat
and contiguous wintering areas.  No molt migration is known.  Breeders
molt in the general vicinity of nesting territories [17].

In Alaska, trumpeter swan populations migrate south in shifts.  This
occurs from September until very late in the year, with times and
distances varying depending on severity of the weather.  Trumpeter swans
move from interior regions in September, as total freeze-up occurs by
the first week in October.  By mid-October, they have usually left
Kenai, located on the coast.  On the Copper River Delta, many swans
remain until about mid-November.  They arrive at Lonesome Lake, British
Columbia, beginning October 20 through October 25 [17].

Life span - Trumpeter swans may live up to 35 years in captivity but
usually do not live more than 12 years in the wild [2].


PREFERRED HABITAT : 
Breeding habitat - Trumpeter swans nest on the margins of interconnected
shallow marshes and lakes, lakes within forest or sagebrush habitat,
and oxbows of rivers [18].  They prefer stable, quiet, shallow waters
where small islands, muskrat houses, or dense emergent vegetation
provide nesting and loafing sites.  Nutrient-rich waters, with dense
aquatic plant and invertebrate growth, provide the best habitat [3,23].

Nests are built in water 1 to 3 feet deep [4].  Trumpeter swans build a
platform nest made of emergent vegetation.  The nest is often located on
a muskrat house, beaver lodge, or small island [18].  In Alaska,
trumpeter swan nests are built 10 to 600 feet (3-183 m) from shore,
depending upon cover and water depth.  Occasionally, a nest is located
on or near the shoreline of a small inlet in a large lake [10].
 
Winter habitat - Winter habitat must provide extensive beds of aquatic
plants and water that remains ice-free.  In the Greater Yellowstone
region, cold temperatures and ice restrict trumpeter swans to sites
where geothermal waters, springs, or outflow from dams maintain ice-free
areas.  In winter, trumpeter swans use shallow lakes, streams, and ponds
that do not entirely freeze over during the winter months [18,23].
Pacific Coast trumpeter swans use both esuaries and freshwater habitats,
and feed in pastures and croplands [23].  Good winter habitat also
contains a certain amount of level and open terrain, allowing these large
birds to loaf or fly without restriction of movement or visibility [3].


COVER REQUIREMENTS : 
Tall emergent vegetation provides shelter and cover for trumpeter swans
[10].  Adults may remove vegetation around the nest until the nest is
surrounded by open water.  This provides good visibility and protection
from land predators [2].  During winter, trumpeter swans prefer open
sites with few trees or shrubs to obscure their vision while feeding
[23].


FOOD HABITS : 
Trumpeter swans eat the roots, stems, leaves, and/or seeds of a variety
of aquatic vegetation, and they occasionally eat insects [2].
Initially, young cygnets eat large aquatic insects and snails.  Cygnets
feed on the water's surface and often depend on the adults to stir up
the water around them.  Within 2 to 3 weeks the cygnets start to eat
aquatic plants [2].

Trumpeter swans feed on the following:  the tubers of duck potato and
sago pondweed (Potamogeton pectinatus); the stems and leaves of sago and
other pondweeds (Potamogeton spp.), water milfoil (Myriophyllum
verticullatum), muskgrass (Chara spp.), waterweed (Elodea canadensis),
and duckweed (Lemna triscula); the seeds of yellow pond lily (Nuphar
polysepala), water shield (Bransenia schreber), smartweed (Polygonum
spp.), sedges (Carex spp.), and spikerush (Eleocharis spp.); and the
stems and roots of grasses and sedges [2,3,4,17].


PREDATORS : 
Predation is of little consequence in determining overall trumpeter swan
population levels, but may be an important cause of death to preflight
cygnets [3].  Except for man, trumpeter swans have few natural enemies
after flying age is reached.  Coyotes (Canis lutrans), river otters
(Lutra canadensis), minks (Mustela vison), and golden eagles (Aquila
chrysaetos) have been blamed for cygnet deaths in Yellowstone National
Park and Red Rock Lakes National Wildlife Refuge [20].  The following
species also occur in trumpeter swan habitat and could potentially prey
on trumpeter swans:  black bears (Ursus americanus), grizzly bears (U.
arctos), lynx (Lynx canadensis), bald eagles (Haliaetus leucocephalus),
greathorned owls (Bubo virgianus), mountain lions (Felis concolor),
bobcats (Lynx rufus), striped skunk (Mephitis mephitis), red fox (Vulpes
vulpes), raccoons (Procyon lotor), and gulls (Larus spp.) [20].


MANAGEMENT CONSIDERATIONS : 
The commercial swanskin trade, coupled with sport hunting and habitat
destruction, reduced the species to near extinction by 1920.  The
trumpeter swans' traditional migration patterns and knowledge of
important winter and spring habitats were lost as the swans neared
extinction.  Although recovery efforts have increased swan numbers,
historic migratory paths have not yet been restored.  As a result,
virtually all the breeding trumpeter swans of Canada and the Greater
Yellowstone Ecosystem share the same high-elevation winter habitat in
the Greater Yellowstone Ecosystem.  Increasing numbers of wintering
swans, concentrating on this limited, harsh winter habitat are
vulnerable to catastrophic losses.  Reduced flows during drought, heavy
ice formation, unusually severe winter weather, disease, or
environmental pollution could destroy a large portion of the
mid-continental population during a single winter [23].

Trumpeter swans are sensitive to human activities on their breeding
grounds.  Intrusions by humans at nesting wetlands have caused temporary
and permanent nest abandonment as well as movements from breeding and
staging areas [2,11].  Trumpeter swans will not nest on lakes
intensively developed for recreation.  The swans are most sensitive to
disturbance from mid-April to mid-June [2].

Cygnet survival is associated with spring weather and favorable water
levels.  It is extremely important to properly manage water levels so
that nest flooding is avoided and growth of aquatic vegetation is
encouraged through nutrient cycling [18].

Management efforts currently focus on ensuring adequate stream flows,
protecting and enhancing nesting and wintering habitat, and restoring
southward migration to lower elevation habitats [23].


REFERENCES : 
NO-ENTRY

Related categories for Wildlife Species: Cygnus buccinator | Trumpeter Swan