In Hawke’s Bay, researchers from the University of Auckland are analysing the full range of rifleman conversation. Bioacoustic recording systems are paired with video cameras at nests to determine which calls are used when. Then, outside of the breeding season, the team is recording and analysing individual birds’ calls in order to detect any variations in calls between birds—differences from year to year, for instance, or between individuals and their parents. All this is to figure out whether riflemen are capable of vocal learning: whether they learn their calls as youngsters by imitating others.
“We think we’ve got a handle on bird sensory systems, but most information is based on very few species,” says study leader Kristal Cain. “New Zealand wrens are important for researchers the world over.”
If riflemen are capable of vocal learning, this is potentially a big deal. While most animals can make sounds, only a few are capable of learning specific calls and using them to communicate specific information. Whales, dolphins, bats, elephants, many songbirds and humans have this ability.
We have become very good vocal learners, but we’re also newbies at it on an evolutionary timescale. If we’re to understand how vocal learning evolved, we need to interrogate birds: they picked it up before we did.
But why pick the tiny rifleman for such a big assignment? There are plenty of great songsters and vocal learners in Aotearoa—tūī, kōkako and bellbirds.
Riflemen belong to a unique group of birds, the New Zealand wrens, which occupy an ancient branch on the tree of life. The lineage of these birds goes back further than any other songbird in the world, forming a previously missing link between parrots and songbirds. Wrens have been in Aotearoa longer than moa and kiwi—they are Gondwanan originals, like tuatara—but this heritage has only recently been identified.
Only two members of the wren family survive: the rock wren, which lives in the alpine zone, and the rifleman, which is scattered unevenly around the country, with fewer in the upper North Island. Sarah Withers reckons this is because the majority of populations of North Island riflemen live at higher altitude—many on mountains—which suits their tolerance for cold and their superpower of torpor. It’s also likely that there are fewer predators at higher altitude.
Time and Place: Since 126,000 years ago, in the Tarantian of the Pleistocene through today
The Rifleman, or Tītipounamu, is known only from New Zealand
Physical Description: Tītipounamu are very small, very round, perching birds, only reaching about 7 to 9 centimeters in total body length (that’s barely over 3 inches!) These birds are olive in color, with green undertones to the feathers. Their wings and tails are brown, and their backs also have brown spotting. Their necks are white, and they have yellowish bellies and rumps. The bills of Tītipounamu are moderate in length, and extremely pointed. The males are greener than the females, and the juveniles resemble the females before sexual maturity.
Diet: Tītipounamu feed primarily on insects, especially beetles, flies, and months, though they eat any sort of land arthropod generally.
By Lake Sylvan, CC BY-SA 2.0
Behavior: Tītipounamu forage in small groups and pairs in the forest, picking up food scraps near human camps and searching for invertebrates in tree trunks, branches, twigs, and leaves. They rarely spend time on the ground and are very restless while they forage, always ready to fly away at the slightest hint of danger. They flit back and forth between trees and shrubs, in search of food. It will start close to the ground and climb up the trunk, spiraling around it to look for food. They make sharp, fast, simple “zipt-zipt-zipt” calls that are actually ultrasonic!
Tītipounamu breed from August through February. They form long-term, monogamous pair bonds, which usually have two broods per breeding season. They have helpers, usually unpaired adult males for the first brood of the season, and then the first brood with the second brood. The parents work together to build the nest, making a dome-shaped nest out of sticks and gross with a side entrance tunnel. The nests are lined with dead leaves, moss, spider webs, and feathers. They’re usually placed in tree trunks or on branches, and they do use human nest boxes. The broods are two to five eggs that are incubated for three weeks by both parents. Both parents then help to feed the chicks for about a month. The fledged young are then fully independent at six weeks. Most young manage to fledge, though these numbers decrease in the second brood. Tītipounamu do not migrate, though they will move a little to look for food; the juveniles disperse a bit after leaving the family.
By Brian Ralphs, CC BY 2.0
Ecosystem: Tītipounamu live in beech and bine forests and associated scrub, especially very dense older ones with large numbers of understory plants. They are often found in remnant patches of native vegetation in cleared areas, and they can also be found in more human maintained habitats. They’re usually found in the uplands. These birds are often preyed upon by mammals such as stoats and introduced cats.
Other: Tītipounamu are not threatened with extinction, and they are in fact quite common. This is good, because they’re among some of the most unique birds - New Zealand Wrens, such as Tītipounamu, are the earliest-diverging group of perching birds, equally related to all other members of Passeriformes. There aren’t many living New Zealand Wren species today, making each one a unique window into a distinctive side branch of Passeriform evolution.
~ By Meig Dickson
Sources under the Cut
Gill, B. (2019). Rifleman (Acanthisitta chloris). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona.
Jobling, J. A. 2010. The Helm Dictionary of Scientific Bird Names. Christopher Helm Publishing, A&C Black Publishers Ltd, London.
Worthy, T. H., and R. N. Holdaway. 1996. Taphonomy of two holocene microvertebrate deposits, Takaka Hill, Nelson, New Zealand, and identification of the avian predator responsible. Historical Biology 12(1):1-24
#2672 - Acanthisitta chloris ssp. chloris - South Island Rifleman
AKA titipounamu. Originally described Anders Sparrman in 1787 as Sitta chloris, because he thought it was a nuthatch. In 1842 French ornithologist Frédéric de Lafresnaye made a portmanteau from the thornbill genus Acanthiza, and Sitta, and put the bird in it. Titipounamu means Vision of Greenstone. The English common name refers to the smart uniform of a NZ colonial regiment.
Aotearoa's smallest bird, and one of only two species left in its family. They feed on insects, fossicked from leaf-litter and plucked from the trunks of trees that the birds methodically explore. They prefer to live in thinly wooded forests, but land clearing has badly fragmented much of their habitat.
