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A prime spot to see wild birds, Dunedin Botanic Garden gives us an amazing opportunity to observe 40 different bird species close-up in their own environment, write Clare Fraser and Mary Thompson.
The Dunedin Botanic Garden is like a well-stocked supermarket for birds - a supermarket that also offers a great choice of shelter and nesting sites in a variety of habitats, including ponds, streams, native bush and shrubs and trees bordering the lawns. For birds, the garden is just a small part of the bushy environs of the Dunedin town belt and the northern end of the city.
Forty bird species have been recorded in the botanic garden, more than half of which are New Zealand natives. Introduced birds are now more common in New Zealand than in their native European countries. In fact, an early purpose of the upper garden's aviary was to acclimatise these recent imports.
The garden is launching a guide to wild birds next Sunday. This has been developed in partnership with Birds NZ. It covers the 27 birds most often encountered in the garden, categorised into natives and introduced species, along with birds around the ponds and creeks.
Native birds often seen at the garden include tui, bellbird, kereru and fantail. But there are other less frequent flyers. Grey warblers give themselves away by their loud, wavering trill. Brown creepers are not common in the botanic garden, but can be detected by their noisy, buzzy chatter as they flit through the tree canopy feeding on invertebrates. Sadly, tomtits are now also rare in the garden but can occasionally be seen in bush areas.
Both welcome swallows and silvereyes and are considered native, because they self-colonised New Zealand from Australia and are now common. Silvereyes first arrived in the mid-1800s and welcome swallows in the mid-20th century. Silvereyes, or waxeyes, are now the most abundant native birds in New Zealand gardens.
Birds still visit from overseas; each year the shining cuckoo. They reappear every spring after their epic trip from their winter home in the Melanesian islands (Solomon Island area). Their distinctive song has a repeated upward whistle followed by downward notes, but it's hard to get a glimpse of the cuckoo, as it is usually high up and well camouflaged. They breed by laying an egg in the nest of a grey warbler, which is left with the job of feeding the foster chick.
Although there are more species of natives than introduced birds at the garden, numbers of introduced birds are far higher. Their commonness can make them seem less remarkable unless they do something unusual, such as the house sparrows that boldly visit people inside the cafeteria to find food. House sparrows are gregarious, noisy and unafraid of people.
A similar-looking bird but with opposite behaviour is the dunnock. Although it resembles and is often confused with a house sparrow, and is sometimes called a hedge sparrow, it is in a different biological family. It is quiet and unobtrusive, creeping mouse-like over the ground and under bushes to forage for invertebrates.
Its mating behaviour is particularly remarkable. A recent research study found that more than half the female dunnocks in Dunedin Botanic Garden were polygamous, having one or two additional male partners. Due to the communal effort, polygamous females had more success in raising chicks than their monogamous colleagues.
In comparison, there are two species of red-headed finch that look different from each other but are more closely related than the sparrow and dunnock. Goldfinch and redpoll are both seed-eating songbirds with a stout bill and colourful plumage. Although the redpoll has red in its name, its red head patch is smaller than the goldfinch's. Both fly in flocks and spend lots of time on the ground foraging for grass and weed seeds.
Chaffinches and greenfinches eat mostly seeds, too. Greenfinches are the largest finch in New Zealand and their heavy bill allows them to crack open seeds that other finches can't, including crops, leading to their pest status in some regions. They even attack the fruit buds of stone fruit trees.
Three similar-looking species - blackbirds, thrushes and starlings - forage on the lawns. If you look closer, these species can be easily distinguished. Starlings strut when looking for grubs on the ground - this is because they have a walking motion, whereas most birds hop. They leave holes on the ground, not because of their funky strut but because of their quirky bill action. Whereas most birds' bills work by clamping shut as they nip at food, starling's beaks are the opposite - the bill opens wide at the tip as they probe for earthworms, caterpillars, beetles, grubs and spiders.
Australian eastern rosellas were introduced to New Zealand in the early 1900s, beginning with Dunedin in 1910. Now they live throughout the North Island but Dunedin has the only South Island population. Sometimes people think these flocks of chattering multi-coloured parrots have escaped from a cage. Their habit of nesting in tree cavities may leave less habitat for native species.
These introduced birds spend a lot of time on the ground, unlike our surviving natives, which live up high, a habit that has kept them safe from introduced predators. A third habitat at the garden hosts both native and introduced birds - the ponds and creeks.
The ducks at the garden are mallards and not native to New Zealand. Although they were introduced from England, mallards here have evolved their own New Zealand look. Soon after their initial release in the 1870s, they started breeding with the native grey duck and now most New Zealand female mallards have a distinctive dark stripe through their eye.
Little pied shags sometimes visit rivers at the botanic garden, and there was a small nesting colony in trees near the pond for a year or two. Rock pigeons have adapted well to living alongside people so are attracted to the pond and information centre. Red-billed gulls and southern black-backed gulls also visit the pond but less so since visitors have been supplied with steamed flaked barley for feeding the ducks - seagulls can't digest it.
Whether they're native or introduced, a theme running through the bird world is flashy males and dowdy females. Bright colours make the males look healthy and attractive as a mate. That showiness would not work for females, as they need to be concealed and camouflaged while incubating eggs and protecting their chicks on the nest. Males are also the songsters of the bird world, to defend territories and attract a mate.
Clare Fraser is information services officer at Dunedin Botanic Garden and Mary Thompson is regional representative for the Otago branch of Birds New Zealand.