By JOHN WALSBY
Reports from Christchurch last spring indicate that a programme of encouraging residents to plant more native trees appears to have succeeded in drawing birds such as the tui and bellbird back into the suburbs.
On the Auckland isthmus the odd tui can still be seen and heard in gardens near parks and reserves with plenty of mature trees but it may be more than a century since the bellbird's glorious song was heard.
There is a slim chance they may eventually be seen again around the city for over the summer I had several reports of bellbird sightings along the coast north of the Harbour Bridge; possibly birds recolonising the mainland from the sanctuary of Tiritiri Matangi.
The tui and bellbird feed mainly on nectar and small fruit to support their energetic lifestyles and will remain in an area only if there are good supplies all year round.
As mature puriri trees usually have flowers throughout the year they used to be a good source of nectar for honeyeaters during winter when blossom on other natives is scarce.
Today, however, there are too few puriri and the birds welcome ripe fruit or a flush of flowers on introduced trees.
A month ago tui were gorging themselves on the glut of persimmons in my garden and now they are partying elsewhere in the district among the flowers of an introduced ornamental, the flame coral tree.
Several species of flame trees have been introduced, all from warmer regions, and as they are frost tender they are most vigorous in the north and near the coast.
The most common, Erythrina x sykesii, a hybrid of American and African species, is a large, fast-growing tree with a spreading canopy, popular in parks and gardens for its scarlet flowers and the shade it offers in summer.
It is flowering early this year, with its bright red tongues of floral fire flaring up before it has lost all of last season's leaves.
It is unusual for trees from tropical climes to drop their leaves in winter like deciduous trees from cool temperate regions and it is tempting to suggest that it might be to benefit the pollination of the flame coral tree's flowers.
On branches bare of foliage the flowers stand out like bright red beacons and access is not obstructed by the large new leaves that do not usually sprout until spring, towards the end of flowering.
Like our native kowhai, the flame tree belongs to the pea and bean family, the Leguminosae, which also includes such plants as wisteria, lupin, clover, broom, gorse and kaka beak.
Typically the five petalled flowers of this family have a prominent flag petal and two lateral wing petals to attract pollinators.
The remaining pair are opposed like hands in prayer to form a keel that encloses the stamens and style to protect them.
Only when suitable insects land on the flower to feed from the nectaries do the keel petals part to expose the anthers and style tip so that pollen can be dabbed on and received from the pollinator.
As a variation from the normal arrangement, the flame coral tree's flower has an enlarged flag petal but reduced, hidden, wing petals and its keel petals are too small to enclose its elongated stamens and style.
Clearly it is not designed to be pollinated by insects, for their hairy bodies could never contact the anthers while they sipped nectar.
Rather it is modified for pollination by the plumage of honeyeating birds and in New Zealand the flowers have a magnetic attraction for tui.
Outside Auckland, tui can frequently be seen in groups of up to a dozen partying together on the sweet nectar but as this hybrid-cross is sterile, pollination never results in seed pod formation so the plant can be propagated only from cuttings.
<i>Nature Watch:</i> Native birds partying on foreign flame tree
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