Food & Habitat
Diet – what do mōhua eat?
Mōhua are mainly insectivorous - meaning they eat mainly insects or spiders – but they are also known to eat some fruit. Often the first sign of a mōhua feeding above you in the forest is the rain of leaves and bark that they send down to the forest floor as they energetically pick off bark and moss from the trees hunting out their prey. Unable to feed on the wing, mōhua spend their time scrambling up and down tree branches and trunks, often upside down, probing crevices for grubs. They utilise their tail feathers to press into the branches until they are so worn down that they look like spines. Mōhua will occasionally feed on the forest floor but prefer to scratch through the leaf litter that accumulates in tree forks. Their favoured prey is beetles, caterpillars, spiders and moths.
Busy rummaging through the leaf-litter and moss looking for insects
(Photo: Michael Eckstadt)
The following extract from the Field Guide to Birds of New Zealand (1966) by Falla, Sibson and Turbott eloquently describes the mōhua feeding habits:
"Mōhua have a fondness for rooting through the accumulations of rubbish that fall down and collect in the [tree] forks… they grip the bark with one foot…dig their tail, which is supplied with spines, into the trunk, and scratch vigorously with the other foot sending down a shower of debris. In the search for insects mōhua thoroughly investigate the leaves, twigs, branches and higher portions of the trunk. The tail feathers rapidly become abraded. Their feeding actions are vigorous, hanging head downwards from a twig, or swinging on tips of smaller branches to examine foliage".
The spectacle of mixed feeding flocks
Mōhua usually feed in pairs or in small family groups over the summer breeding season. But come autumn and winter, it is time to get social and small family groups often come together to form roaming, feeding flocks that move together through the canopy. In times gone by some older folk can recall groups of over 100 mōhua feeding together, but today with fewer mōhua about it is an exciting moment to see groups of 20 or 30 birds feeding together in a raucous flock.
In the winter we are treated to even more of a spectacle when other bird species join the mōhua feeding flocks, attracted by the insects dislodged, but not eaten, by the mōhua as they flick up moss and leaves from the branches as they go by. Fantails (Rhipidura fuliginosa) join in the feeding frenzy and catch insects on the wing that are out of reach of the mohua. Browncreepers (Mōhua novaeseelandiae), bellbirds (Anthornis melanura) and yellow-crowned parakeets (Cyanoramphus auriceps) join in too, although the latter perhaps more for company than food as they are mainly herbivorous.
In special places such as Anchor Island, Fiordland, where the ecosystem is being restored to include bird fauna that had become locally extinct, small groups of saddleback or tieke (Philesturnus carunculatus) previously released on the island join in the feeding flocks too. These mixed flocks, including rare birds, go some way towards reminding us of what New Zealand’s forests must have been like before the impacts of man.
Mōhua on the Routeburn Track holding an insect in its bill
(Photo: Michael Eckstadt))
This young mōhua holds onto the side of a branch using his strong feet and legs while picking for grubs to eat under the moss and lichens. See how he uses his tail feathers as a prop against the branches
(Photo: J. van der Wetering)
Habitat – where do mōhua live?
The forests of the South Island of New Zealand are the natural habitats of the mohua. Historically podocarp-hardwood forests (including trees such as rimu, totara and miro) along the West Coast and Stewart Island were also home to the mohua, but today the only remaining mōhua populations survive in beech (Nothofagus spp.) forests. Mōhua mainly utilise the upper understory and canopy of the beech forests (25 – 45m high) but will occasionally come down to the ground to feed.
Red beech is the favoured habitat of mohua
(Photo: Michael Eckstadt)
Forests with large red beech (Nothofagus fusca) trees are preferred by mōhua probably because these trees often occupy the most fertile sites. Fertile soils have greater productivity and invertebrate biomass meaning more food is available. Red beech trees also usually contain more nesting holes for mōhua making them a favoured habitat. Dead standing trees play an important role in beech forests providing nesting sites for hole-nesting birds such as the mōhua (and roost sites for New Zealand’s only native land mammals, the long and short-tailed bats).
Did You Know?
Fertile forests support lots of invertebrates and are good homes for insectivores like mohua. But unfortunately introduced pests such as rodents and mustelids also thrive in these productive forest ecosystems and not only eat invertebrates but prey on mōhua too!
Most years the ecosystem balance in beech forests allows some native birds to co-exist in the forest with introduced mammals, but every 2 to 5 years when a large quantity of beech seed falls (known as a ‘mast’ event) the scales are tipped in favour of the mammals. After the heavy beech seeding the abundant quantity of food allows mouse and rat numbers to erupt, which in turn increases the number of stoats in the forest that prey on the abundant rodents. But as the summer turns to autumn the once abundant supply of beech seed dwindles, mice numbers drop and the still abundant rats and stoats in the forest turn to feathery prey – watch out mohua!
Mōhua prefer beech forests as habitat as pictured here in a Mountain Beech (Nothofagus solandri var. solandri) tree at Glenorchy
(Photo: Michael Eckstadt)
To read more about predator control techniques used in the Eglinton Valley to protect mōhua and other native wildlife click this link
To read more about the Chalky Island to Eglinton Valley mōhua transfer sponsored by the Mōhua Charitable Trust click on this link