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Food & Habitat
Diet – what do mohua eat?
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 mohua feeding habits:
"Mohua 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 mohua 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
Mohua 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 mohua feeding together, but today with fewer mohua 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 mohua feeding flocks, attracted by the insects dislodged, but not eaten, by the mohua 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 (Mohua 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.
Mohua on the Routeburn Track holding an insect in its bill (Photo: Michael Eckstadt)) 
This young mohua 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 mohua live?
Red beech is the favoured habitat of mohua (Photo: Michael Eckstadt)
Forests with large red beech (Nothofagus fusca) trees are preferred by mohua 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 mohua 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 mohua (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 mohua 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!
Mohua prefer beech forests as habitat as pictured here in a Mountain Beech (Nothofagus solandri var. solandri) tree at Glenorchy (Photo: Michael Eckstadt)
Web: To read more about predator control techniques used in the Eglinton Valley to protect mohua and other native wildlife click this link
www.doc.govt.nz
Web: To read more about the Chalky Island to Eglinton Valley mohua transfer sponsored by the Mohua Charitable Trust click on this link
www.mohua.co.nz (pdf)
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