Quick Answer
Yes, Varied Thrushes do eat seeds as part of their diet. Varied Thrushes are omnivorous birds that consume a variety of food items including insects, berries, and seeds. Seeds, especially from trees and shrubs, provide an important source of nutrition and energy for these birds.
Varied Thrush Diet
The Varied Thrush (Ixoreus naevius) is a medium-sized songbird found along the Pacific Coast of North America. It breeds in coniferous forests from Alaska to California and winters in the Pacific Northwest down to northern California. Varied Thrushes are omnivores and their diet consists of both plant and animal material.
Some of the main food items in the Varied Thrush diet include:
Insects and Other Invertebrates
Varied Thrushes glean insects, spiders, and other arthropods from leaves, branches, and tree trunks. Some common insects eaten include beetles, caterpillars, flies, ants, and wasps. They use their slightly curved bill to probe into crevices and peel back bark to uncover hiding insects.
Berries and Fruit
These birds feed on a variety of berries and fruits when available. Some commonly eaten fruits include elderberries, blackberries, raspberries, salal berries, and wild cherries. They also may eat ornamental fruits from trees and shrubs near human habitation.
Seeds
Varied Thrushes regularly consume tree seeds, especially in the fall and winter when other foods may be scarce. Common tree species whose seeds they eat include pine, spruce, hemlock, alder, maple, and ash. The high fat content of seeds provides essential calories and nutrients.
Importance of Seeds in Diet
Seeds play an integral role in the Varied Thrush’s diet for several reasons:
High in Calories
Tree seeds and conifer seeds are very high in fat and calories, providing vital energy for Varied Thrushes, especially during migration and winter when food is limited. The high calorie content helps the birds maintain body heat and survive cold temperatures.
Nutrient Content
Seeds contain important nutrients like proteins, healthy fats, fiber, magnesium, potassium, and antioxidants. These nutrients help support muscle function, organ health, feather maintenance, and a strong immune system in thrushes.
Readily Available Food Source
Seeds are abundant and can be easily foraged from the ground or trees throughout much of the year. This makes them a reliable food source when insects, berries, or other prey may be scarce. The abundance of conifer forests in the Varied Thrush’s range ensures access to valuable seed food sources.
Preferred Tree Seed Species
Varied Thrushes will consume seeds from a wide range of tree and shrub species, but some seeds appear to be preferred when available:
Pine Seeds
Pine seeds from species such as Lodgepole Pine, Ponderosa Pine, and Sugar Pine are highly sought after by Varied Thrushes. The large, nutritious seeds are readily harvested from pine cones.
Hemlock Seeds
Seeds from Hemlock trees, including Western Hemlock and Mountain Hemlock, are an important part of the Varied Thrush’s diet. Hemlock trees produce large seed cones that provide abundant food.
Spruce Seeds
Sitka Spruce and Engelmann Spruce are two spruce tree species that produce seeds eaten by Varied Thrushes. The high fat content of spruce seeds makes them particularly valuable.
Maple Seeds
Varied Thrushes will eat the winged seeds of maple trees, including Bigleaf Maple and Vine Maple. Maple seeds provide protein and carbohydrates.
Alder Seeds
Red Alder seeds are consumed by Varied Thrushes, especially where alder trees are abundant. The small seeds provide fat and protein.
Tree Species | Examples | Benefits of Seeds |
---|---|---|
Pine | Lodgepole, Ponderosa, Sugar | Large, nutritious seeds; rich in fat and protein |
Hemlock | Western, Mountain | Abundant seed cones provide plentiful food |
Spruce | Sitka, Engelmann | High fat content of seeds |
Maple | Bigleaf, Vine | Winged seeds provide protein and carbs |
Alder | Red | Small, fat and protein-rich seeds |
Seed Foraging Strategies
Varied Thrushes employ different techniques to find and consume seeds:
Ground Foraging
Varied Thrushes forage among the litter on the forest floor searching for fallen seeds from trees overhead. Their camouflage plumage helps them blend in.
Bark Probing
The birds use their slightly curved bill to probe into crevices and under loose bark to find insects as well as uncover hidden seeds.
Fruit Plucking
They pluck whole cones and fruits directly from trees and shrubs and then extract the seeds while perched on a branch.
Seed Caching
Varied Thrushes sometimes hoard seeds, fruits, and insects by burying or hiding them as caches to eat later in winter.
Adaptations for Eating Seeds
Varied Thrushes have several physical and behavioral adaptations that allow them to effectively find and eat seeds:
Bill Shape
Their sturdy, pointed bill helps them open pine cones and probe into bark crevices to extract hidden seeds.
Vision
Excellent vision aids Varied Thrushes in spotting seeds on the ground or in trees while foraging.
Caching Behavior
Storing excess seeds helps ensure Varied Thrushes have food through harsh winters when prey is scarce.
Grit
Varied Thrushes ingest small stones or grit which aids in crushing and digesting hard seeds in their gizzard.
Fat Stores
They build up fat reserves in fall to survive cold winters. The fat calories from seeds directly support this process.
Importance of Seeds for Nestlings
In addition to eating seeds themselves, adult Varied Thrushes will feed seeds to their chicks when raised in nests:
Nutrient Content
The high protein and fat content of seeds helps fuel rapid growth and development in nestling thrushes.
Energy Needs
Growing nestlings have very high caloric needs. The concentrated energy content of seeds helps satisfy these requirements.
Feeding Frequency
Parent thrushes make frequent trips to the nest with beakfuls of nutritious seeds to quickly sate hungry offspring.
Fledgling Transition
As chicks grow, parents incorporate more seeds into feedings to help nestlings transition to foraging on their own.
Readily Available
The abundance of conifer seeds makes it an easy, plentiful food source for parent birds to collect and bring back.
Role of Seeds in Ecosystem
The seed eating habits of Varied Thrushes also have broader ecosystem impacts:
Seed Dispersal
Thrushes spread seeds through their droppings as they forage, helping plants propagate.
Tree Growth
Consuming seeds helps control overcrowding of seedlings under parent trees, allowing stronger growth.
Nutrient Cycling
Their droppings redistribute nutrients like nitrogen and phosphorus derived from seeds they eat.
Insect Control
By reducing insect populations, thrushes help prevent overgrazing damage to conifers caused by insects feeding on seeds.
Scavenging
Foraging for seeds on the forest floor helps remove and recycle biomass from the ecosystem.
Threats and Conservation
Some threats facing Varied Thrushes that can affect their seed eating habits include:
Habitat Loss
Logging, wildfires, and land clearing reduce crucial mature and old growth conifer habitat that provides seeds.
Invasive Species
Non-native plants can outcompete native trees that Varied Thrushes rely on for seeds.
Climate Change
Warming temperatures and drought conditions may decrease cone production in some seed-bearing trees.
Human Activity
Noise pollution, trapping, and urbanization may disturb foraging thrushes and limit access to key seed resources.
Conservation measures like preserving old growth forests, tree planting, and public education can help ensure Varied Thrushes continue to have access to the seed food sources they rely on. Monitoring thrush diets and seed availability will also elucidate their interdependence.
Conclusion
In conclusion, seeds form a critical part of the Varied Thrush’s diverse diet. Tree seeds like pine, hemlock, and spruce provide essential protein, fat, and calories. Varied Thrushes employ various strategies to locate and consume seeds, aided by adaptations like their sturdy bill and fat reserves. Seeds also help sustain Varied Thrush chicks in nests and play an important ecological role. Conservation of mature conifer habitat will help protect availability of this key food resource. Understanding relationships between birds and their food sources helps inform efforts to support forest ecosystem diversity.