Trumpeter Swan

Scientific Name	Cygnus buccinator
Survival Strategy	Short-distance Migrant
Arrival in Upper Midwest	Late February to late March
Departure	October through November
Conservation Status	Least Concern

Phenology

Spring
Trumpeter swans arrive on their breeding grounds as the ice melts and take 2 to 4 weeks to build their mound-shaped nests. Egg-laying begins in late April to mid-May, with an average clutch size of 5 eggs.

Summer
Male and female trumpeter swans incubate the eggs, which takes 32 to 37 days. The cygnets fledge when they are almost three months old.

Fall
Fall migration occurs when, and if, open-water freezes up and puts the swan’s food supply out of reach.

Winter
The two most important goals for swans in winter, eating food and avoiding predators, require open water. They will migrate to the nearest ice-free lake or wetland if cold weather covers their current winter home in ice.

Behavior

Waterproof Coat
Swans use their bill to move oil from their uropygial gland near the base of the tail to their contour feather. The oil waterproofs this outer layer of feathers and keeps the insulating down feathers dry. The down layer can be up to 5 cm (2 in) thick, allowing the trumpeter swan to survive temperatures as low as -30°C (-22°F).

Unipedal Resting
In cold weather, swans often stand on one leg (unipedal resting). They lift the other leg next to the body to keep warm, cutting the amount of heat lost through their limbs in half. At times they will tuck their heads under a wing to protect them from the bitter cold.

Physiology

More Mass Holds More Heat
The large size of a trumpeter swan helps it maintain a body temp of 40°C (104°F). At nearly 13 kg (29 lb.), it is one of the heaviest flying birds globally, a little more than the weight of three gallons of milk.

Cold Feet, Warm Bird
Like other birds, swans use countercurrent heat exchange to conserve heat they would otherwise lose through their bare legs. The veins and arteries in a swan’s featherless legs are close to each other. Before the warm arterial blood gets to the bird’s feet, the veins absorb much of the heat and return it to the body. This exchange of heat keeps the feet colder, often just above freezing. Birds have little muscle or nerve tissue in their exposed legs and feet, so there is no need to waste energy keeping them warm.

Diet

Newly hatched cygnets will eat protein-rich insects and other small invertebrates for the first few weeks after hatching.

As adults, swans are almost exclusively plant-eaters, and they can eat more than 9 kg (20 lb.) of vegetation each day. Their diet includes sedges, rushes, and other aquatic plants. Swans are so buoyant that they are limited to aquatic food within reach of their necks. Imagine wearing an oversized life jacket and attempting to pick up a quarter from the deep end of a pool.

It is not unusual to see swans in corn stubble feeding on crop residue in the fall.

Lifespan and Mortality

In the wild, trumpeter swans can live for 20 to 30 years.

Predators
Eggs and young cygnets are the most vulnerable to predation. Their predators include bald eagles, foxes, coyotes, raccoons, ravens, and snapping turtles.

Adult trumpeter swans are occasionally preyed on by bobcats, gray wolves, and coyotes.

Death by Mistaken Identity
It is not legal to hunt trumpeter swans, but hunters sometimes shoot trumpeter swans by mistake due to their close resemblance to tundra swans and snow geese.

Power Lines
A significant cause of swan mortality is transmission line collisions. Transmission line companies have started installing Swan FlightTM Diverters to make the transmission lines more visible to birds.

Lead Poisoning
Lead poisoning through ingestion of ammunition and fishing tackle is lethal to most waterfowl. Eating one lead sinker or three lead pellets can kill an adult trumpeter swan in a matter of weeks. Lead shot has been prohibited for waterfall hunting nationwide since 1992.

A Success Story
In the early 1900s, the wild population of trumpeter swans was around 70, and they were on the brink of extinction. Through the efforts of wildlife professionals and private organizations, the population increased to more than 63,000 birds by 2015.

Climate Vulnerability

As the climate warms, the trumpeter swan population is projected to shift north, eventually out of the lower 48 states.

Never stop learning

Family Names: Female swans are called pens, male swans are cobs, and baby swans are cygnets.

Aerodynamics: To get airborne, trumpeter swans use running take-offs which require at least a 100-yard runway of open water.

References

The Trumpeter Swan Society https://www.trumpeterswansociety.org/welcome.html

Swans in Wisconsin https://dnr.wisconsin.gov/topic/WildlifeHabitat/swans.html

Mitchell, C. D. and M. W. Eichholz (2020). Trumpeter Swan (Cygnus buccinator), version 1.0. In Birds of the World (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.truswa.01

Johnsgard, Paul A., “Swans: Their Biology and Natural History” (2016). Zea E-Books. Book 38. http://digitalcommons.unl.edu/zeabook/38

2015 North American Trumpeter Swan Survey (PDF) https://www.trumpeterswansociety.org/file_download/inline/16524876-ce39-48cd-ae86-cb0b82756773

Swan FlightTM Diverter https://preformed.com/energy/distribution/wildlife-protection/swan-flight-diverter