Monday, December 13, 2010

Silver-eye, wax-eye or white-eye


Zosterops lateralis, the little silver-eye, is not so numerous in the Wairarapa as it is up north where huge flocks congregate in the winter and descend upon berry producing trees and shrubs in their hoards. Hurrying from tree to tree, from one garden to another, with a continuous, noisy twitter, or uttering short plaintive notes, they set about distributing seeds, mindless as to what is is they are casting about, and with no concern at all as to whether the seeds are native or obnoxious. Poroporo keeps on sprouting in my garden here, undoubtedly spread by silver-eyes.

Now that the house sparrow numbers are very much in decline, the silver-eye is probably New Zealand's most numerous bird, far out numbering the more obvious starlings which tend to get the blame for the silver-eyes' crimes against orchardists. Silver-eyes have a particular fondness for fruit. They happily eat their way through a wide range of fruits, including apples, kiwi fruit, feijoas, figs, grapes, pears and persimmons. Their pointed beaks can break the skin of fruit more readily than other birds, and once the skin is broken it allows other birds the opportunity to feast. But as Buller said, “It far more than compensates for this petty pilfering by the wholesale war it carries on against the various insects that affect our fruit trees and vegetables”.

The silver-eye is a small olive–green bird with white rings around the eyes. They have a fine tapered bill and a brush tipped tongue like the Tui and Korimako, the bellbird, for drinking nectar. There are many species in Africa, southern Asia, and the south western Pacific, but it is the Tasmanian sub–Australian species which migrates to the eastern states of the Australian mainland in winter which colonised New Zealand. They were recorded in New Zealand as early as 1832 but it was not until 1856 that they arrived in very large numbers. It is assumed that a storm caught a migrating flock in Australia and diverted them here. The Maori name, Tauhou, means “stranger”.
Their success as a species has probably a lot to do with their varied diet which is mainly comprised of insects, fruit and nectar, but they will also readily take fat, cooked meat, bread and sugar water from bird tables.
They are delightful, busy little birds and are strongly territorial and are often seen fluttering their wings aggressively at another bird. I have seen them cuddling up in pairs on a branch busy preening and feeding each other. With their white ringed eyes set close together, they look so much like clowns. And then to see them with a bright red cotoneaster berry in their beaks, the picture is complete.

Thursday, December 02, 2010

The Persecution of rooks in New Zealand

On the local radio throughout this spring, Greater Wellington Regional Council was once again asking people to report on rookeries in the area. This pursuit of rooks brings into question Regional Council's pest strategies especially in relation to birds.

Rooks are a minor agricultural pest, certainly no worse than say yellowhammers, so why is one being pursued and not the other? It would seem that one of requirements of the Biosecurity Act is that pest control must be cost effective, so the yellowhammer is too numerous and widespread to eradicate but the rook is apparently a viable target for eradication. Both birds were introduced from Europe in the 19th century, as bio-control agents. These birds are not a threat to native or endemic species.

In perusing the voluminous amount of data on Regional Council pest strategies on line, I have managed to glean that over a period of twenty years 2002-2022 at a cost of $60,000 a year it is proposed to eradicate the rook. Part of that budget goes towards putting up helicopters to find the rookeries.

There is no similar proposal to eradicate more serious pests such as mustelids or rats as like the yellowhammer they are not cost effective. Possums are dealt with because of necessity for tb control.

However, there is an operational budget for the control of pests, cats, mustelids, rats, in a buffer zone around Mount Bruce, the wildlife sanctuary in the Wairarapa. The budget for one year 2007-2008 was $34,300. I was not able to glean what the long term strategy is for the buffer zone.

Now in looking at all this, the logic somehow escapes me. To eradicate the rook, a minor agricultural pest on a par with yellowhammers, will cost 1.2 million over 20 years. Given what has happened to the Kiwi at Mount Bruce, the losses from mustelid attacks, should we not be spending that money on increased pest control in the buffer zone around Mount Bruce and leaving the poor rook alone?