The Mountain Bluebird belongs to the family Turdidae, which is the family of thrushes and relatives. This family contains a wide variety of familiar songbirds, including other bluebirds, robins, and thrushes.
The Mountain Bluebird (Sialia currucoides) is a small thrush native to the western United States and Canada. With its bright blue plumage and melodious song, it is a familiar sight in mountain forests and meadows. But what exactly is the taxonomic family that the Mountain Bluebird belongs to?
All living organisms are classified into hierarchical taxonomic ranks that group similar species together based on shared characteristics. The most basic rank is the species itself, followed by genus, family, order, class, phylum, kingdom, and domain. Understanding an organism’s taxonomy provides insight into its evolutionary relationships with other organisms.
In the case of the Mountain Bluebird, its scientific name reveals that it belongs to the genus Sialia and the species currucoides. Tracing the taxonomy further back, Sialia bluebirds belong to the family Turdidae. This places the Mountain Bluebird within a diverse family of medium-sized songbirds that occur worldwide.
Overview of the Turdidae Family
The family Turdidae belongs to the order Passeriformes, the perching birds or songbirds. With over 300 species, Turdidae is a large family found on every continent except Antarctica. It includes many familiar birds such as robins, bluebirds, and thrushes.
Some key features characterize the Turdidae family:
- Medium size, ranging from 15 to 25 cm in length
- Stocky bodies with long legs suited for hopping on the ground
- Pointed wings and short, rounded tails
- Slender bills, adapted for eating insects and fruit
- Excellent vocal abilities, with melodious songs and calls
- Drab plumage of browns, grays, and blacks (males are often brighter in color)
- Forage on the ground turning over litter to find invertebrates and fruit
The Turdidae encompass a diverse array of genera and species that occupy a wide range of habitats on all continents except Antarctica. Their diversity stems from an adaptive radiation resulting in many forms filling different ecological niches.
Major Groups within Turdidae
While diverse, the Turdidae family can be divided into several major subgroups:
- Thrushes: The true thrushes represent the largest group, including the widespread American Robin and Eurasian Blackbird. They are medium to large in size.
- Bluebirds: The three bluebird species of North America belong here, known for their brilliant plumage.
- Chats and chama: Old World species like the Stonechat, Whinchat, and Mocking Cliffs Chat belong to this group.
- Wheatears: Mostly Old World species that inhabit open country, including the Northern Wheatear.
- Dippers: Stocky, short-tailed songbirds adapted to aquatic habitats, like the American Dipper.
- Bush chats: Found in Africa, bush chats forage in dense undergrowth.
These groups represent some of the main evolutionary lineages within the Turdidae family. However, many relationships between genera remain uncertain and poorly resolved.
Distinctive Attributes of Turdidae
Let’s take a closer look at some of the distinctive traits that characterize this diverse family of songbirds:
Size and Shape
Turdidae species share a similar body plan and proportions. They have stocky, round bodies with long legs suited for hopping on the ground. The bill is slender and pointed, adapted for catching insects and eating fruit. Wings are broad and tails are medium-length to short, often held upright. Overall size ranges from 15 to 25 cm from head to tail.
Plumage
Most species have relatively drab plumage in various shades of brown, gray, and black. Exceptions include the brilliant blue shades of bluebirds. Sexual dimorphism occurs in some species where males have brighter, more decorative plumage than females. Juveniles typically resemble females with duller plumage.
Vocalizations
One trademark of this family is their vocal diversity and melodious songs. Many species have elaborate and complex songs, sometimes with regional dialects. Their voices are valued both for identifying birds by ear and for human enjoyment.
Habitat and Behavior
Turdidae frequent a wide range of habitats from forests to grasslands to alpine zones. Most forage on the ground turning over litter to uncover invertebrates or fruit. They hop along the ground in search of food. Most are solitary foragers outside of the breeding season when they form pairs or family groups. Migration is common in northern latitudes.
Reproduction
Cavity nesters make up a large portion of this family, excavating holes in trees or using natural cavities. Nest building with mud or grasses occurs in other groups. Clutch sizes range from 3 to 6 eggs. Both parents share incubation and feeding of nestlings. Many species have multiple broods in a breeding season.
Evolutionary History
The evolutionary origins of the Turdidae date back to the radiation of perching birds or oscines in the Oligocene, around 25 million years ago. Early thrushes diverged and spread across Eurasia and Africa. A later second radiation took place as thrushes expanded into the New World. Adaptive radiation led to diversification and speciation within the group.
Several factors likely contributed to their success and diversification:
- Adaptability to forests and more open habitats
- Ability to fly and migrate large distances
- Generalized omnivorous eating habits
- Cavity nesting or adaptable nest sites
- Bright plumage and melodious vocalizations for attracting mates
Today, this adaptable family occurs on every continent except Antarctica from the tropics through temperate and northern latitudes. Conservation threats come from habitat loss and fragmentation throughout their range.
The Mountain Bluebird’s Place in Turdidae
The Mountain Bluebird clearly exhibits all the classic features of its family Turdidae. A medium-sized thrush with stocky proportions, its vocal abilities and ground foraging behaviors align with related turdid species. Its ancestral lineage diverged early as a member of the bluebird group within the family.
Some specific turdid traits of the Mountain Bluebird include:
- Size ranges from 16 to 21 cm long with a wingspan around 30 cm
- Stocky shape with a medium length tail
- Male plumage brilliant sky-blue above and pale blue below
- Female plumage grayish-brown overall with some blue wings and tail
- Melodious warbling song, often delivered in flight
- Nest in cavities like old woodpecker holes
- Forage on the ground for insects and berries
- Migratory populations move south in winter
The Mountain Bluebird remains a fairly common species through mountain forests and meadows of the West. Its membership in an early New World lineage of Turdidae thrushes highlights the evolutionary history of this successful family of songbirds.
Conclusion
The Mountain Bluebird’s family membership reveals its place in the tree of life. As a member of the large and diverse Turdidae family of songbirds, it shares many traits and behaviors with related thrushes, bluebirds, and chats around the world. Its ancestral lineage diverged early as a New World bluebird, yet it retains the core attributes of its thrush family. Getting to know a bird’s taxonomic family provides insight into its evolutionary past and relationships with other species.