Saturday, January 1, 2011

Black-fronted terns in crisis

Black-fronted Terns Tarapiroe - Agile birds of the river under threat.

Peter Langlands

For me one of the defining moments of spending time on the river is watching the wildlife. In the South Island black-fronted terns are one of the most conspicuous of riverbed birds. They are constantly in flight, and like giant swallows capture all of their food on the wing. Often it is the tern’s call, which will alert me prior to sighting the birds. Often the terns will be seen gliding effortlessly up the river and will invariably fly into the wind when feeding. For me as an angler the experience of watching the terns is a welcome sight when tramping long distances up the riverbed. Sighting the terns makes the trip go quicker, and the distance between fish shorter. Without them the river would seem an empty place.

Yet as I write the black-fronted tern is classified as a critically endangered species. While they still appear to be very conspicuous, the species is in decline in many areas. A few terns can seem like a lot of birds as they are constantly flying up and down the river’s course. Yet often the some bird will be sighted throughout the day, giving an inflated impression of the numbers of terns. Also the terns we are sighting on the river may also be an aging population. Black fronted terns may, if we look at closely related species, live for at least twenty years.

The reason why terns are so endangered is that they are highly vulnerable to a multitude of factors during their breeding phase. They are ground nesting birds. Their nests consist of inconspicuous scapes in the stones and are easily run over by four wheel drives, stepped on accidentally by anglers, or dogs. Yet of greater concern is the predation of tern nests by stoats, and other introduced mammals, such as hedgehogs, which appear not be as innocent as thought. Wild cats can also wreck havoc on the terns breeding colonies. As terns require areas of open gravel to nest on, vegetation encroachment is also a major factor and greatly reduces the available space for nesting birds. Increasing numbers of black-backed gulls on the rivers also reduce nesting space for the terns. If these factors weren’t enough the terns also have to contend with natural floods, which will often wipe out an entire colony. The eggs and chicks are highly vulnerable and the chicks are also often run over accidentally.

Often you know you are in a tern colony when the birds swoop and squawk relentlessly, and will even when highly agitated lightly hit you on the head. At such times whether walking, or in a four-wheel drive, the best thing to do is to immediately vacate the area. The terns are sensitive to disturbance, and if the colony is in the early stages the birds will readily dessert the colony, after only a low amount of disturbance. Given the fact that the terns are colonial nesters on the riverbed they also literally “put all their eggs in one basket”.

Yet it is in our broader interest that anglers and trampers show concern for the terns, along with other endangered riverbed birds, such as the wrybill and black-billed gull, for these birds act as important icons when advocating water conservation. Terns are a marker of the health of the river. Surely without their presence on our open braided rivers, they would seem like very empty spaces. In the winter the terns vacate the rivers of the South Island to feed on coastal waters on the East Coast, with the Kaikoura region being an important feeding ground. Many birds also feed on the estuaries around the lower North Island.

Black fronted terns are only found in New Zealand (primarily a South Island bird during the breeding season). An estimate published in 1996 is of a population of only 5000 birds. They are critically endangered and as outdoor enthusiasts we must minimise our presence on their breeding colonies when fishing or four wheel driving, and have a responsibility to alert DOC of any riverbed activities that we see that may be putting the birds at threat. Hopefully things will not “tern out” for the worse, for this bird, which characterises the wilderness spaces, open spaces and prolific mayfly populations on our East Coast riverbeds. The black fronted tern is a treasure that is uniquely New Zealand’s.

Paradise in the city

Paradise in the city

Peter Langlands

Revised 140507

In a time when many native birds are declining it is good to celebrate the success stories. One such species, which has recently increased dramatically in numbers, is the Paradise duck (technically known as the Paradise Shelduck, also known by the Maori name of Putangitangi ). So named by Captain Cook, the paradise duck, or “parrie” for short, is only found in New Zealand. Once a rare sight outside of the high country in Canterbury, parries are now ubiquitous throughout lowland Canterbury and urban Christchurch.

During the 1950’s to 1980’s in Canterbury paradise ducks were often only found in high country regions, and extensive shooting had historically reduced their numbers. Paradise ducks are still shot, and are in some regions, such as the West Coast, an important component of the game birder’s bag. In the last few decades’ parries have shown a high level of adaptability and now paradise ducks roost on the top of buildings in the centre of Christchurch, where as in the not so distant past a cliff in a remote part of the high country would be a more typical setting! Just about every park in Christchurch has a pair of parries in it, often standing in stately manner, as if a centre piece, but much more lively than any statue.

Parries are thought to pair together for life, with the birds having different, yet, complimentary calls to each other. The male is jet black with finely speckled feathers. The female has a white head and chestnut coloured body. Unlike most other ducks, were the male is more colourful, the opposite is true for the paradise duck.

Since 1990 paradise ducks have moved into Christchurch, with the Avon and Heathcote Rivers providing routes for colonization for the birds, right into the city’s heart. Large willow trees, with holes in them, make ideal nesting site for the birds. The ducklings will jump out of the hole, sometimes situated many metres up a tree, and bounce on the ground with their resilient little bodies. The ducklings have a dramatic black and white stripped colouration often attracting the attention of people passing by. Large broods are often sighted and are testament to the fact that paradise ducks are nesting successfully in the “Garden City”.

Birds will often be grazing on lawns along the river bank. Rock statures and memorial plaques become roosting sites for parries, with high rise buildings in the background providing a striking setting. Paradise ducks, like other ducks such as mallards, grey ducks and the native black teal (another bird to recently re-colonize into the city’s rivers) have become fearless of people, often allowing approach to within arms length. Spring sees parries chasing each other with raucous fuss as they defend their prime riverbank real estate. The bird’s tameness combined with their comical, and at times very territorial nature, makes them an ideal subject matter for the photographer, or just an entertaining spectacle while having a picnic in the park.

We are lucky that these majestic birds have graced our city, in which paradise ducks historically thrived. It is good to see our native bird life flourishing in an urban environment. While flocks of paradise ducks in the high country may at times be viewed as a pest, to high country farmers, they area welcome sight in the city, bringing an element of the wild and open spaces with them. Whether perched on top of a building in the city’s centre, or on a cliff top in the high country, the paradise duck is an under stated, yet majestic, and iconic bird of our country, which is simply paradise.