Thrush Bird

Thrush is an umbrella term used to define various species of birds that belong to the family  Turdidae. They share phylogenetic relations with old-world birds like Sylviidae and Muscicapidae. These birds have global distribution. They are the largest family of birds that are categorized into an order called Passeriformes. Since they are classified in this order and have the highest population density and species diversity, they are sometimes referred to as passerine birds. 

Thrush birds have a small body and feed on small insects and fruits. Multiple different genres are classified into the family, based on the genera there are different types of thrush. There are about 300 species of thrush that are classified into the Turdidae family. Some of the different species of thrush bird include the following, Grandala, Mountain bluebird, Western bluebird, Wood thrush, Song thrush, Hemit thrush, Black thrush bird, and American robin.

An important point to note is that the term “thrush bird” is also used to refer to birds that belong to different families. These birds are named so because they share morphological similarities with the members of the Turdidae family.

The article focuses on the general description of the bird. Diet and reproductive events are also discussed in the article. Apart from this the taxonomic classification of the bird is described in the article.

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Fig: A thrush bird

General Description

Thrush birds are generally considered as a bird with average size body size. There are more than 300 species that are classified as thrush birds. All these different species have different morphological features and ecological adaptations. A common characteristic that is found in all most all species is the size and shape of the body. None of the species is considered among heavy-bodied birds. 

The thrushes are considered to have a slender build of the body. The majority of the species have a long and slender bill. Another unique feature of these birds is that they are known to have booted taurus. The term refers to the covering of the lower legs. Generally, all birds are seen to have multiple scales that cover the lower part of the limb but thrush birds have a single scale that covers the entire lower part of the leg giving it a resemblance with boots. The body of thrush birds is also known to have dark coloured prominent spots on the ventral side of the body.

Apart from these common morphological generalizations, all different types of thrush share an evolutionary history and close phylogenetic relationship with the old world warbles and flycatcher. The taxonomic classification of these birds is also controversial as some evolutionary biologists classify these birds as a subfamily of the Muscicapidae family. 

The main reason for the debatable nature of the taxonomy is due to the similar food habits and ecology shared by the members of the Muscicapidae and Turdidae families. Since these birds have high species diversity they occupy almost all the geographical locations. The bird is known to have a wide range of distribution. 

 Taxonomic Classification

The systemic classification of animals and plants based on their similarities in morphology, anatomy and ecological adaptations is known as taxonomic classification. Taxonomic classification provides a basic understanding of the interspecies relationships, the study also deals with the phylogenetic and evolutionary relationship shared by the organism. Apart from these, the ecological and anatomical changes made during the course of evolution is also studied under this branch of science.

An important aspect of the taxonomic classification of thrush birds is that the term is used to define birds of different families, the taxonomic classification mentioned here encompasses the hierarchical order of categorization of different types of thrush bird that belongs to the Turdidae family. The taxonomic classification of the thrush bird is as follows.

They are classified under the kingdom Animalia, the primary requirement to be classified under this kingdom is the presence of multicellular body structure. The second most important feature is the cell type, the organism must have a eukaryotic cell structure. The kingdom is further classified into phylum.

Thrush birds are categorized into the phylum Chordata. The phylum consists of the members of the animal that has a notochord. There are 5 main requirements to be classified under this phylum. These 5 synapomorphies include the presence of a  notochord, dorsal hollow nerve cord, endostyle or thyroid, pharyngeal slits, and a post-anal tail. Since all types of thrush birds are known to meet these requirements they are rightfully characterized into the Phylum. The phylum can be further classified in class.

Thrush birds similar to all the birds are classified under the class of Aves. The characteristic feature of this class is the presence of wings among most of its members. Although some animals are classified under this class but lack the typical wings. The anatomical feature of these classes is the lightweight of the skeleton, the bone arrangements of the wings especially render them suitable for the ecological adaptation of aviation. Another important point to note is that all the members of this including thrush birds irrespective of the species are classified as warm-blooded animals, these animals are also termed endotherms. The significant feature of the class is the presence of feathers, toothless beaked jaws, a four-chambered heart, and a strong yet lightweight skeleton. Some of the important physiological features include the ability to lay hard-shelled eggs, and a high metabolic rate. Since the thrush birds satisfy all the necessary features they are rightfully categorized in this class

The class can be further divided into order. They belong to the order called Passeriformes. The members of this order are called passerines. The order is considered the largest order. More than 140 families are classified under this order and almost half of the total bird species diversity is categorized in this order. The most distinctive feature of this phylum is the arrangement of the toes. The three toes are pointing in the forward direction and one is pointed towards the back, this unique anatomical modification allows them to perch easily. Due to their ability to perch, the thrush birds are known as perching birds. The Passerines are divided into three suborders which are as follows, Acanthisitti is known as New Zealand wrens, Tyranni which is also known as suboscines, and Passeri which are sometimes referred to as oscines. Another important observation about the order is that most of the members of this order are omnivores. 

The order is divided into the family. The different types of thrush birds are classified in the family Turdidae. The family is known to consist of thrush birds, there are about 300 different species of thrush birds. Some of the common species that are classified as thrush birds include, 

• Turdus infuscatus, the black thrush bird

• Turdus merula, the common blackbird

• Turdus philomelos, the songbird

•  Turdus pilaris, the fieldfare

• Turdus migratorius, American robin

• Geokichla citrina, orange-headed thrush

• Zoothera dauma, Scaly thrush

• Tarsiger cyanurus, Red-flanked blue tail.

Morphological Features

Thrushes are known as medium-sized birds. The physical appearance of these birds are plump, the common characteristic of this group of birds is that they have soft plumage. The body size and weight vary according to different species of birds. One of the smallest birds of this group is forest rock thrush, the bodyweight of this bird is about 21 grams and the length of the body is 14.5 cm which when converted into inches is about 5.7 inches. The average weight of these birds is 43 grams. The largest known bird of the thrush family is the Great thrush. Body of these birds are approximately 128 to 175 grams, the size of the bird is approximately about  28 to 33 cm, when converted into inches they are about 11 to 13 inches long.  The colour of the birds varies greatly according to species. The generally found colours in the family of thrush birds include brown, black, grey and black spots on the body. Although these are some of the most commonly found colours., they are also found in red and blue colour. 

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An image of a thrush is shown above.

Anatomical Features

The most distinctive feature of this family is the presence of anisodactyl arrangement, it refers to the arrangement of the toe bones in such a manner that three bones point towards the forward direction. The fourth toes point towards the back. Hallux of the toe joins the toe and leg at approximately the same level as from the toe. This anatomical modification helps in perching. Another important point in the anatomy of the toe is the absence of webbed structure or joining.

Apart from the bone arrangement, some other anatomical modifications are a result of ecological adaptation. One such adaptation is the automatic pull of muscles behind the tibiotarsus. This anatomical modification helps in balancing their landing on the branch.

Almost all the birds of the thrush family have 12 feathers, with some exceptions where the number of feathers increases up to 16.they are also known to have comparatively stiff tails, this helps them in climbing trees.

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Fig: Thrush Bird Feet  Anatomy

Diet

The diet of thrush birds includes small insects and fruits. They also feed on seeds of fruits, nuts. They prey on small insects like mosquitos, fruit fly and beetles. Because they digest both plant-based products and hunt their food they are categorized as omnivores. 

Reproduction

All the types of thrush are classified as oviparous animals, that is they lay eggs. They are also considered seasonal breeders, the mating season generally ranges from late summer to spring. They are sexually reproducing organisms with internal fertilization. The eggs are laid in the nest of the bird. An interesting fact about these birds is that the chicks of these newly hatched eggs are altricial. The term is used to define birds that produce underdeveloped offsprings, the newly hatched birds do not completely developed eyes, wings or limbs. Parental care is very important, during this early developmental stage food is provided by the parental generation. The clutch size (number of offspring produced in a single mate) varies dispensing upon species. The average clutch size is 2 to 5 eggs per mating cycle.  The average lifespan of these birds is 3 years, but some species like the black thrush bird lives up to 2 years.

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Summary at a Glance

• Thrush birds belong to the family Turdidae

• They are classified into order Passeriformes.

• The common species of the birds include black thrush birds and song thrush.

• They have global distribution, the preferred habitat of these birds are geographical location with a warmer climate.

• They are oviparous animals.

• They are omnivores, the primary diet includes fruit seed and small invertebrates.

• The average life span is 3 years. 

• The most distinguishing feature of the birds of this family is the anisodactyl arrangement of the toe and altricial eggs.