Bird watch news
Blackbird
Turdus merula
As last month’s feature bird was the Song Thrush, this month we will look at its close relation, the Blackbird. Both belong to the thrush family or Turdidae and were introduced to New Zealand in the 1860’s. There are no native thrushes and they are the only representatives of this group in New Zealand. Blackbirds are native to Europe, the Middle East and North Africa. Like the Song Thrush, Blackbirds are widespread in all habitats across New Zealand except high alpine. They have even spread to the Chatham, Kermadec and Sub-Antarctic Islands.
They eat invertebrates, such as spiders, beetles, caterpillars, and grubs, frequently tossing aside dead leaves in search of tasty morsels. Like Song Thrushes, they often hunt for worms under lawns, though they like to stick close to the cover of shrubbery. They also eat fruit.
A mature male blackbird is black with an orange bill and orange ring around each eye. Females are brown, often with streaks on their undersides. They use the same nesting territory each year, which is defended by the male through threat displays and calls. From August to December a pair will produce 2 to 3 broods, each with 2-6 eggs. The female is solely responsible for incubating the eggs, but both parents feed the chicks. We have a breeding pair that returns to our garden each year and the male seems to be a very devoted father. He appears to be the primary caregiver of the fledglings, perhaps because mum is busy incubating the next brood.
At dawn and dusk, the male will find a high vantage point from which to sing his melodious song, distinctive from the Song Thrush’s by its lack of repetition.
Male
Female
Backyard Bird Monitoring Data: A tale of two birds
It is easy to see why some species are more abundant than others. Flightless native species unaccustomed to predators have their work cut out. More of a mystery is why two closely related species of similar size, diet, breeding behaviour, etc should fare differently. While the blackbird and song thrush are both abundant, from the results of our garden surveys blackbirds outnumber song thrushes by almost 2 to 1 (more precisely 1.79 to 1).(NB: Both Annesbrook and Wakatu had very small sample sizes, which may explain opposite trend). Both blackbirds and song thrushes nest in our garden. For the most part, they seem to co-exist peacefully, often foraging in close proximity, but occasionally altercations erupt. From my observations, the blackbirds are more aggressive and usually the ones doing the chasing. The graph on the bottom left compares the averages of blackbirds and song thrushes of garden surveys in which birds are fed with those in which birds are not fed (from February 2008 to January 2011). Feeding results in increased numbers of blackbirds and no change in the numbers of song thrushes recorded. Perhaps their stroppiness enables blackbirds to more successfully take advantage of resources such as food and nesting sites. This is only one of many possible explanations and I would be interested to hear your thoughts and observations.
