Certhiidae

What is Certhiidae?

Certhiidae is a family of songbirds within the order Passeriformes that includes most of the birds known as tree creepers. These small, solitary birds are found throughout the woodlands of the Northern Hemisphere and typically range from 9.5 to 19 cm in length.¹²

Physically, they are characterized by downcurved bills, short and strong legs, and long, stiff tail feathers that act as a prop while they climb tree trunks in a spiral pattern to probe bark for insects. The family is primarily composed of the nine species in the genus Certhia, such as the common tree creeper.¹²

It is important to distinguish this bird family from the Cerithiidae, which refers to a family of aquatic gastropod mollusks (horn shells), and the Climacteridae, a separate family of Australian tree creepers that were formerly grouped with the Certhiidae.¹²³

How do treecreepers use their tails to climb trees?

Treecreepers are specialized for climbing vertically up tree trunks in search of insects. To facilitate this movement, they utilize their stiffened tail feathers as a prop against the tree bark, which provides essential support for their body as they ascend.²⁵

This climbing method typically involves the bird moving in short, vertical hops with both feet moving simultaneously. While this adaptation is highly effective for upward movement, it prevents the birds from descending the tree in the same manner; unlike the nuthatch, which can climb both up and down, treecreepers are generally restricted to upward locomotion.⁵

What are the main differences between Certhiidae and Climacteridae?

While both Certhiidae and Climacteridae contain birds commonly referred to as treecreepers, they are distinct families with notable differences in anatomy, behavior, and geography.

Key Differences

Feature

Certhiidae

Climacteridae

Common Name

Tree creepers

Australian treecreepers

Tail Structure

Stiffened; used as a prop for climbing

²

³

Not stiffened

²

Tongue

Standard

Brush-tipped

²

Nesting

Soft cup behind bark slabs

²

Tree hollows

²

Distribution

Northern Hemisphere

²

³

Australia and New Guinea

²

Evolutionary and Behavioral Context

The family Certhiidae consists primarily of the genus Certhia, which are solitary, brownish birds adapted for spiraling up tree trunks to probe bark for insects. In contrast, Climacteridae species exhibit behaviors more similar to honeyeaters or nuthatches, reflecting their distinct evolutionary path. While they were once grouped together, the Climacteridae are now recognized as a separate family, sometimes associated with the Sittidae or Meliphagidae.²³

We could dive deeper into the specific adaptations of other climbing birds, such as the woodpecker, to see how they compare to these two families.

How do nuthatches compare to treecreepers in their behavior?

Nuthatches and treecreepers exhibit distinct behavioral and locomotor patterns when navigating trees. The most significant difference lies in their movement: while treecreepers are generally restricted to climbing vertically upward in short, simultaneous hops, nuthatches can move with equal ease up, down, and around trunks and branches.²⁸

Locomotion and Foraging

• Treecreepers: These birds typically use their stiffened tail feathers as a prop against the bark to support their upward ascent. This specialized adaptation facilitates vertical climbing but prevents them from descending in the same manner.⁶⁸
• Nuthatches: Often called “upside-down birds,” nuthatches climb obliquely, using one foot for clinging and the other as a brace. This allows them to forage in areas that other birds, such as woodpeckers, cannot reach.²⁸

Feeding and Nesting

Nuthatches are known for their unique “hacking” behavior, where they wedge seeds into bark crevices and use the force of their bodies to pound them open with their bills. They also frequently store seeds in these crevices for later use. In contrast, treecreepers are primarily insectivorous, using their downcurved bills to probe bark for insects. Additionally, while both groups utilize tree cavities or bark for nesting, nuthatches are exclusively cavity nesters.²⁶