Starling birds are so familiar that birdwatchers all too often ignore them. Yet, if it were as rare today as it used to be its superb iridescent plumage would rank it as one of the most beautiful British Birds. The starling is one of our most common birds. More than six million pairs breed every year.
In the winter they are joined by at least 30 million more individuals that migrate here from northern and eastern Europe. Yet, up until the middle of the last century, the starling was relatively uncommon in Britain. The rise in the British population is part of a general pattern throughout Europe in which starlings have increased in numbers and spread westwards.
The reason for this population increase is not completely understood but an important factor is the bird’s ability to live on a wide variety of foods. Fruits, seeds, flying insects, caterpillars, grubs, earthworms, and household waste are all eaten, although the amounts taken of these different foods vary with the season.
In spring the starling’s diet consists mainly of insects and their larvae; in summer fruits become important; by winter these are replaced with seeds. Throughout the year, however, animal foods remain an important source of protein. Another reason for the starling’s success is that, during the last century or so, large areas of Europe’s indigenous forests have been cleared to create grassland for farming.
Close cropped grassland is the starling’s favorite habitat. One can often see those probing grassroots for invertebrates such as caterpillars, earthworms, and leatherjackets (the larvae of crane flies and a serious agricultural. During the breeding season, starlings spend most of their feeding time in grassland.
However, at other times of the year, they spread out into new habitats a necessity if they are to take full advantage of their omnivorous nature. Bushes, hedgerows, and trees are visited by starlings for fruits such as cherries, elderberries, and sloes. Moreover, they also search stubble fields, newly sown cereal fields, and farmyards for seeds.
People often ask how starlings gather so quickly and in such numbers when food is put out into a garden. Starlings have an excellent memory, especially when it comes to remembering places where food appears regularly and in abundance. These places are always under observation by at least one bird. When food appears, one starling flies down to investigate.
If it begins to peck, then all the other starlings nearby recognize this as a sign of food and fly down to join in. Within a very short time, a feeding flock has formed. The formation of a flock for feeding is advantageous for the flock members in that they can feed much faster than when they are on their own.
There are many more eyes on the lookout for predators such as cats and sparrow hawks. Against this, however, is the problem that a flock can grow too big for the food source, with the result that bickering and fighting ensue. The starlings’ omnivorous diet means that.
Depending on what they are eating, a large flock can either inflict great damage or be of great benefit. The starlings’ consumption of large numbers of leatherjackets is an obvious boon to the farmer but, on the other hand, they can devastate cherry orchards that are in fruit.
Roosting by the million
As well as feeding in flocks, starlings also roost in flocks. Sometimes more than a million birds gather together in night roosts, attracting large numbers of predators. In places such as Trafalgar Square, huge flocks can be seen wheeling around and darkening the sky at dusk.
Quite why starlings roost in such numbers is not yet known, but the advantages must be considered since they outweigh the attentions of predators. It may be that roosting presents a good opportunity for poorly fed birds to learn from their better-fed neighbors the location of good food supplies.
Nesting in letterboxes
The starling’s choice of nesting site shows again how well it takes advantage of opportunities presented by a man. Its most typical nest site is a natural hole, usually in a tree but also on a cliff. However, any hole of the right size and situation will do: cavities in the roofs of houses and farm buildings are especially popular, and on occasions, it even nests in letterboxes.
The breeding season begins in April. The male chooses his nest site and starts to build the nest a bulky affair of dried grasses decorated with fresh green vegetation and the petals of spring flowers. The breeding season is the only time of year when starlings are territorial.
The male defends a small territory around his nest site, but other breeding pairs are tolerated only a few yards away. Once the male has built his nest he tries to attract a female by flying inside the nest hole and singing. Once the male has a mate, she completes the nest, lining the cup with material that can range from fine grasses and feathers to string and cellophane.
Eggs and Young
Between three and six eggs may be laid, though the usual clutch is five. The eggs are small, about 3cm (1in) long, and clear pale blue or blue-green with no markings. Incubation is carried out mostly by the female and takes about 11 days. At first, the young chicks are blind and without any feathering, save for a few tufts of down.
But the chicks grow quickly since they are fed by both parents on a protein-rich diet of invertebrates; in the first 12 days their weight increases from 5g (oz) to 60g (20z). After the twelfth day, they virtually cease to add weight, but their feathers begin to develop rapidly, and by the time the chicks are 21 days old they are ready to leave the nest.
In most years the parents begin a second clutch of eggs. Between the first and second broods, starlings often swap partners. The female birds are moving on to join the males at the other nests. And the situation is further complicated by the fact that a few male starlings are polygamous, having two females occupying nearby nests.
Mimicry in birds
The starling’s song is not particularly musical but it is remarkable for its mimicry. Sometimes it mimics phrases from the songs of neighboring starlings, but it can also mimic the calls of other birds, including bullfinches, curlews, tawny owls, and green woodpeckers. It can even imitate mammal noises as well as inanimate sounds, such as telephones ringing.
Ornithologists have discovered that, with some species, if a male possesses a wide repertoire of songs it has a better chance of breeding successfully. This explains why starlings make such a variety of noises but not why they mimic ‘foreign’ sounds rather than create their own distinct sounds. That remains a mystery.
Starlings are closely related to those master-mimics, the mynah birds. Unlike the mynahs, however, starlings cannot imitate human speech. Mimicry is not confined to the starling family: parrots and jackdaws reproduce words, and many species imitate other birds.