Tomtit
Encyclopedia
The Tomtit, Petroica macrocephala, is a small passerine
bird in the family
Petroicidae
, the Australian robins. It is endemic
to the islands of New Zealand
, ranging across the main islands as well as several of the outlying islands
. It has several other English
names as well. There are several sub-species showing considerable variation in plumage
and size. The species is not threatened and has adapted to the changes made to New Zealand's biodiversity
.
The Tomtit is one of four species of the genus
Petroica
found in New Zealand, the ancestors of which having colonised from Australia
. The species was once thought to have been descended from the Scarlet Robin
, although more recent research has questioned this. It seems likely that there were two colonisation events, with the North Island Robin and the South Island Robin descended from one event and the Black Robin
and Tomtit from another.
There are five subspecies
of the Tomtit, each species being restricted to each of the following islands or island groups, North Island, South Island, the Snares Islands, the Chatham Islands and the Auckland Islands. Four of these five subspecies have been elevated to full species in the past (the Chatham subspecies was retained with the South Island Tomtit),, but genetic studies have shown that these subspecies diverged relatively recently. The Māori
name of the North Island Tomtit is Miromiro, while the South Island Tomtit is known as Ngirungiru.
. The male North Island
subspecies has black head, back, wings (with a white wing bar) and a white belly. The subspecies from South Island
, the Chatham Islands
and Auckland Islands
are similar but have a yellow band across the breast between the black head and white belly. The females are brown instead of black. The Snares Island subspecies is entirely black, and is known as the Black Tit.
The island subspecies of Tomtits show a striking variation in body size, being considerably larger than their mainland relatives, a tendency known as the island rule
. Birds from the main islands weigh around 11g, but birds from Snares Island weigh in at 20 g.
, feeding on small invertebrates such as beetle
s, caterpillars, spider
s, moth
s, weta
, earthworm
s and flies. Fruit is taken during the winter and autumn. Most subspecies feed in vegetation, waiting on a perch and watching for prey. Insect
s are also gleaned from branches and leaves. The Snares subspecies feeds on the ground as well, in a similar fashion to the New Zealand Robin
.
Passerine
A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...
bird in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Petroicidae
Petroicidae
The bird family Petroicidae includes roughly 45 species in about 15 genera. All are endemic to Australasia: New Guinea, Australia, New Zealand and numerous Pacific Islands as far east as Samoa. For want of an accurate common name, the family is often called the Australasian robins. Within the...
, the Australian robins. It is endemic
Endemic (ecology)
Endemism is the ecological state of being unique to a defined geographic location, such as an island, nation or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. For example, all species of lemur are endemic to the...
to the islands of New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
, ranging across the main islands as well as several of the outlying islands
New Zealand Outlying Islands
The New Zealand outlying islands comprise nine island groups, located in the subtropics and subantarctic, which are part of New Zealand but lie outside of the New Zealand continental shelf. Although considered as integral parts of New Zealand, seven of the nine island groups are not part of any...
. It has several other English
English language
English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...
names as well. There are several sub-species showing considerable variation in plumage
Plumage
Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
and size. The species is not threatened and has adapted to the changes made to New Zealand's biodiversity
Biodiversity of New Zealand
The biodiversity of New Zealand, a large Pacific archipelago, is one of the most unusual on Earth, due to its long isolation from other continental landmasses. Its affinities are derived from Gondwana, from which it separated 82 million years ago, New Caledonia and Lord Howe Island, both of which...
.
Taxonomy and evolution
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Petroica
Petroica
Petroica is a genus of Australasian robins, named due to their red and pink markings. They are not closely related to the European Robin nor the American robin...
found in New Zealand, the ancestors of which having colonised from Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. The species was once thought to have been descended from the Scarlet Robin
Scarlet Robin
The Scarlet Robin is a common red-breasted Australasian robin in the passerine bird genus Petroica. The species is found on continental Australia and its offshore islands, including Tasmania...
, although more recent research has questioned this. It seems likely that there were two colonisation events, with the North Island Robin and the South Island Robin descended from one event and the Black Robin
Black Robin
The Black Robin or Chatham Island Robin is an endangered bird from the Chatham Islands off the east coast of New Zealand. It is closely related to the New Zealand Robin . It was first described by Walter Buller in 1872. The binomial commemorates the New Zealand botanist Henry H. Travers...
and Tomtit from another.
There are five subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
of the Tomtit, each species being restricted to each of the following islands or island groups, North Island, South Island, the Snares Islands, the Chatham Islands and the Auckland Islands. Four of these five subspecies have been elevated to full species in the past (the Chatham subspecies was retained with the South Island Tomtit),, but genetic studies have shown that these subspecies diverged relatively recently. The Māori
Maori language
Māori or te reo Māori , commonly te reo , is the language of the indigenous population of New Zealand, the Māori. It has the status of an official language in New Zealand...
name of the North Island Tomtit is Miromiro, while the South Island Tomtit is known as Ngirungiru.
- North Island Tomtit P. macrocephala toitoi
- South Island Tomtit P. m. macrocephala
- Chatham Island TomtitChatham Island TomtitThe Chatham Island Tomtit is a subspecies of Tomtit found on some of the smaller islands of New Zealand....
P. m. chathamensis - Auckland Island Tomtit P. m. marrineri
- Snares Island Tomtit P. m. dannefaerdi
Description
The Tomtit is a small (13 cm, 11 g) bird with a large head and a short billBeak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
. The male North Island
North Island
The North Island is one of the two main islands of New Zealand, separated from the much less populous South Island by Cook Strait. The island is in area, making it the world's 14th-largest island...
subspecies has black head, back, wings (with a white wing bar) and a white belly. The subspecies from South Island
South Island
The South Island is the larger of the two major islands of New Zealand, the other being the more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman Sea, to the south and east by the Pacific Ocean...
, the Chatham Islands
Chatham Islands
The Chatham Islands are an archipelago and New Zealand territory in the Pacific Ocean consisting of about ten islands within a radius, the largest of which are Chatham Island and Pitt Island. Their name in the indigenous language, Moriori, means Misty Sun...
and Auckland Islands
Auckland Islands
The Auckland Islands are an archipelago of the New Zealand Sub-Antarctic Islands and include Auckland Island, Adams Island, Enderby Island, Disappointment Island, Ewing Island, Rose Island, Dundas Island and Green Island, with a combined area of...
are similar but have a yellow band across the breast between the black head and white belly. The females are brown instead of black. The Snares Island subspecies is entirely black, and is known as the Black Tit.
The island subspecies of Tomtits show a striking variation in body size, being considerably larger than their mainland relatives, a tendency known as the island rule
Foster's rule
Foster's rule is a principle in evolutionary biology stating that members of a species get smaller or bigger depending on the resources available in the environment. This is the core of the study of island biogeography. For example, it is known that pygmy mammoths evolved from normal mammoths on...
. Birds from the main islands weigh around 11g, but birds from Snares Island weigh in at 20 g.
Behaviour
The Tomtit is mostly a insectivoreInsectivore
An insectivore is a type of carnivore with a diet that consists chiefly of insects and similar small creatures. An alternate term is entomophage, which also refers to the human practice of eating insects....
, feeding on small invertebrates such as beetle
Beetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
s, caterpillars, spider
Spider
Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...
s, moth
Moth
A moth is an insect closely related to the butterfly, both being of the order Lepidoptera. Moths form the majority of this order; there are thought to be 150,000 to 250,000 different species of moth , with thousands of species yet to be described...
s, weta
Weta
Weta is the name given to about 70 insect species endemic to New Zealand. There are many similar species around the world, though most are in the southern hemisphere. The name comes from the Māori word 'wētā' and is the same in the plural...
, earthworm
Earthworm
Earthworm is the common name for the largest members of Oligochaeta in the phylum Annelida. In classical systems they were placed in the order Opisthopora, on the basis of the male pores opening posterior to the female pores, even though the internal male segments are anterior to the female...
s and flies. Fruit is taken during the winter and autumn. Most subspecies feed in vegetation, waiting on a perch and watching for prey. Insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s are also gleaned from branches and leaves. The Snares subspecies feeds on the ground as well, in a similar fashion to the New Zealand Robin
New Zealand Robin
The New Zealand Robin or Toutouwai , Petroica australis, is a sparrow-sized bird found only in New Zealand, where it has the status of a protected endemic species. The birds are sparsely distributed through South Island and Stewart Island/Rakiura, although the distribution is not continuous...
.