Townsend’s solitaires (Myadestes townsendi) are medium-sized thrushes that are found in western North America. They are best known for their complex songs and their ability to ferment berries in their gut to produce energy during winter months when food is scarce. Their feathers play an important role in allowing them to thrive in their native habitat.
Plumage
Adult Townsend’s solitaires have primarily gray plumage on their head, back, wings and tail. Their bellies are white or buff-colored. They have white eye rings and yellowish bills. Their wings appear broad and round compared to other thrushes. The solitaire’s gray plumage allows it to blend in with its rocky, mountainous habitat in the western United States.
Juvenile solitaires have spotted plumage for camouflage amongst vegetation until their first molt. After their first molt, they take on the adult gray coloration.
Male and female solitaires have identical plumage, making it difficult to distinguish between the sexes by sight alone.
Feather Types
Like all birds, Townsend’s solitaires have several different types of feathers that serve important functions:
- Contour feathers – These smooth, pennaceous feathers cover the entire body and create the bird’s smooth exterior. They come in different shapes for different areas of the body and provide insulation.
- Flight feathers – The wings and tail contain large, stiff pennaceous feathers to provide lift and thrust during flight. The asymmetry of the flight feathers allows for airfoil action.
- Semi-plumes – These downy, pennaceous feathers lie underneath the contour feathers for added insulation.
- Filoplumes – These hair-like feathers are sensory receptors that detect air movements around the bird.
- Bristles – Stiff, bristle-like feathers around the mouth and eyes protect those sensitive areas.
- Down feathers – Fluffy, plumulaceous feathers underneath the contour and semi-plume feathers provide insulation and padding.
- Powder down feathers – Special down feathers that continuously break down into an oily powder that helps waterproof and maintain the other feathers.
Molting
Like all birds, Townsend’s solitaires molt and replace their feathers periodically. They undergo two molts per year:
- Pre-basic molt in late summer/early fall – replaces all body feathers and some flight feathers
- Pre-alternate molt in early spring – replaces most body feathers and remaining flight feathers
The solitaire’s molt schedule allows it to have fresh plumage just prior to the breeding season and winter. The molting process can take up to several months to fully complete. During the molt, solitaires are vulnerable due to reduced flight capabilities.
Unique Feathers
Townsend’s solitaires have stiff feathers along the edges of their wings that produce a whistling noise when air passes through them during flight. These unique feathers act as a distinguishing feature that may play a role in communication or display between individuals.
Their forked tail contains elongated feathers in the center that can spread widely during aerial displays. Fanned tail feathers signal alarm or are used in aggressive displays towards competitors.
Color Production
The gray, black, brown, and buff colors of a solitaire’s feathers are produced by melanin pigments within the feathers. Melanin granules are deposited as the feather grows, creating bars of color.
Carotenoid pigments derived from plants and insects in the solitaire’s diet produce brighter yellow, orange, and red colors seen on the inner webs of their outer tail feathers.
Structural coloration also plays a role, as the precise nanostructure of the feather barbules scatters light to produce iridescent blues, greens, and purples at certain angles.
Feather Maintenance
Townsend’s solitaires frequently preen and care for their feathers to keep them in good condition. They use their beak and head to distribute oil secreted by the uropygial gland near the base of the tail. This oil helps keep feathers flexible and waterproof.
The solitaire’s scaly feet also aid in scratching itchy spots and removing feather parasites. Occasional dust baths help maintain feather cleanliness as well.
Damaged or worn feathers are replaced during the molting cycles. If a feather becomes severely damaged or lost between molts, a new one will quickly grow in its place.
Adaptations for Cold Weather
Townsend’s solitaires are well-adapted for surviving cold winters in western mountain habitats. Special adaptations in their feathers include:
- Dense contour feathers and down feathers for insulation
- Stiff, reinforced feathers to prevent heat loss
- Shorter feathers around the legs and feet prevent snow from building up on feathers
- Countercurrent heat exchange in the veins of the legs to minimize heat loss
- Fluffing feathers out to increase insulation
- Roosting in cavities or dense conifers that provide shelter
- Shivering to generate heat
Their relatively high basal metabolic rate compared to other thrushes also generates internal heat to keep them warm.
Feather Coloration
The gray, black, and white plumage of Townsend’s solitaires provides camouflage as they forage among rocks and trees of western mountains. Their plumage matches the predominant colors of their environment.
The bold white eye ring is thought to function as a visual signal during courtship displays. It contrasts against the gray plumage to catch the attention of other birds.
Juveniles have spotted plumage to blend in with dappled light when sitting among vegetation. This helps hide vulnerable fledglings from potential predators.
Feathers versus Body Size
The total number and density of feathers on a bird is closely related to its overall body size. Larger birds need more feathers for insulation and flight surface area.
We can compare the feathers of Townsend’s solitaire to other thrush species of different sizes:
| Species | Length (cm) | Wingspan (cm) | Weight (g) | Total Feathers |
|---|---|---|---|---|
| Townsend’s Solitaire | 28 | 43 | 49 | 2,200 |
| Swainson’s Thrush | 18 | 29 | 26 | 1,800 |
| American Robin | 25 | 39 | 77 | 3,500 |
This table shows that the larger American Robin has many more feathers than the smaller Swainson’s Thrush. The Townsend’s Solitaire is intermediate in size and number of feathers between those two species.
Feather Microstructure
Examining feathers under a microscope reveals their intricate microscopic design. A feather is made of a central shaft (rachis) with many lateral branches (barbs) coming off at angles. The barbs have minute hooks (barbules) that lock together the adjacent barbs to create a continuous surface.
The structure of the rachis and barbs gives flight feathers strength and flexibility to provide aerodynamic lift and thrust. Downy feathers have loose barbules that don’t interlock to trap air and provide insulation.
The waterproofing provided by tiny hooks on the barbules allows feathers shed rain and spread oil. Overlapping feather tracts seal the skin from water penetration.
This amazing microstructure allows feathers to be both lightweight and amazingly strong at the same time. Aerodynamic engineering principles built into the feather morphology facilitate flight while minimizing feather weight.
Conclusion
The many different types of feathers on the Townsend’s solitaire allow it to thrive in the mountainous west. Contour feathers streamline its body while down feathers insulate it from cold temperatures. Specialized flight and tail feathers permit aerial maneuverability and displays. Preening and molting maintains feathers in good condition. The solitaire’s feather adaptations allow this mid-sized thrush to survive the challenging conditions of its high-altitude habitat.
