Super Starlings
Murmurations are marvelled at by millions of people every year – but there is so much more to Starlings than just a wonder of nature
Murmurations may grab the headlines, but there is so much more to this great bird
The days are shortening, winter is near, and a ritual is about to re-start. Each evening, birdwatchers and members of the public will soon be assembling at certain favoured sites to await the arrival of masses of Starlings at their roosts. The gathered admirers will be duly enthralled by the hypnotic movements of the murmurations. Every so often, TV camera crews will also be there to record the meld of excitable flocks of birds and people.
These days the Starling has become almost synonymous with these spectacular roosts, which may number a million birds at their peak in deep winter. At the same time, the species itself, as a staple of our avifauna, is in steep decline; since the mid-1970s breeding numbers have declined by 66% and there is a similar pattern across northern Europe. As the Starling has become less familiar as a bird of gardens, roofs and playing fields all year round, it has become more of a glamorous celebrity of winter headlines – Strictly Come Roosting, you might say.
But there is more to the Starling than its glamorous nightly rituals. Flocks might have star quality, but the bird as an individual is intriguing, even during the chores of the day. And perhaps the best way to demonstrate this is to examine what a winter Starling might do away from crowds, when it is one outside a million.
Poor table manners
As soon as dawn breaks, the roost disbands and birds go off for the day to feed. As a rule, individuals return to the same place that they were feeding the day before, often to the same field and the same corner of the same field; indeed, studies suggest that resident birds, in particular, stay more or less in the same feeding areas all year.
Such resident individuals will typically stay in small flocks or even parties, close to their breeding territories. The migrants, however, which comprise the bulk of the roost, are not attached to any particular sites and can move around more freely. They often feed in larger flocks than their British-breeding colleagues.
Starlings are infamous for their ability to guzzle a great deal of food quickly, something considered to be poor table manners compared to those of birds preferred by Middle England, such as Blue Tits and Robins.
This is partly an adaptation to eat quickly and get out of the way of
predators, but if Starlings could feed faster, they would. In contrast to pigeons, for example, they have no crop for storage, and it has been calculated that, if it were physically possible to consume more in a stretch, Starlings could satisfy their daily requirements in a single hour, at least if they were eating grain. In practice, feeding takes a great deal longer.
Starlings are omnivores, foraging for animal food and vegetable matter throughout the year. In the summer they mainly take a variety of invertebrates, but in the autumn and winter the diet switches towards a much higher proportion of seeds and berries. Famously, as the diet changes, so the Starling’s gut adapts; under a vegetarian diet, the overall gut is longer, the gizzard (the muscular bit that grinds down food) is larger and the intestinal villi (minute projections that line the gut wall and increase the surface area of digestion) become longer. The gut is about 28cm long in May, rising to about 39cm in January, and is about 4g heavier, the bird itself being some 75-90g in all. Changes in gut length can occur remarkably quickly, being complete within about 14 days.
Soil probing
While a Starling can acquire the vegetable component of its diet very quickly and easily, unfortunately it cannot survive on seed or fruit alone, and must hunt for invertebrates for some essential nutrients. These are much more difficult to find, and the hunt is more time consuming.
It involves probing the bill into the soil under short-sward grassland and hoping to wrestle an edible item from its hiding place in the earth. One of its favourite foods is leatherjackets, the larvae of craneflies (or ‘daddy long-legses’).
These are mostly nocturnal and dig themselves deeper into the soil by day, often out of reach – anywhere over 2.5cm and they are safe. Starlings have two special adaptations for soil-feeding. Their bill is laterally narrow, so when a bird opens its bill in the soil, the eyes rotate forward, allowing it to peer in with better forward vision. It also has extremely strong protractor muscles, the ones that open the upper mandibles; so it probes into the ground and opens the bill while still immersed, a method known as prying, making a small hole into which it can look for prey.
Taking into account the Starling’s tendency to eat quickly, it might come as a surprise to realise that this bird has a relatively well-developed sense of taste. Experiments in the laboratory have shown that Starlings can detect different concentrations of salts, tannins, citric acid and sugars. They can differentiate sucrose, which they cannot digest, from other sugars which are more beneficial. How this affects their foraging technique isn’t yet clear, but it does at least put a different complexion on our views of the Starling as a gormless, guzzling glutton. Perhaps we should include a cup of tea on the bird table?
It turns out, too, that Starlings have a discerning sense of smell. When nestbuilding, they smell out herbs that are rich in volatile compounds (Yarrow is a favourite) and add this green material to the nest at regular intervals. It seems that this boosts the immune system of subsequent chicks, but the male mainly brings green leaves early on in construction. It seems that the females are discerning of males with sensitive noses.
Nest-building is, of course, mainly in the future, although Starlings will sometimes bring sticks to their nest-holes even in mid-winter. One spring-like activity that is prevalent at the moment, however, is singing. During the day, Starlings often
punctuate their foraging duties
THE STARLING’S DAY, THEREFORE, CONSISTS OF PERFORMING, PROBING, PRYING AND PREENING, AMONG OTHER THINGS
with short periods of rest, when they preen and sing. At these day-roosts, both males and females sing, and nobody is sure why they do it. In autumn, it could possibly be connected to acquiring a territory, but in winter this isn’t clear.
Deprived upbringing
The song is varied but structured, with two main types, loud Whistle Songs and softer, longer Warble Songs. In the breeding season, the Whistling Song is heard in territorial exchanges between males, while the more rambling, quieter Warble Song is for mate attraction. Males have between 20 and 70 different motifs in their songs, depending partly on age – the repertoire improves the older a bird gets – and the individual. Females prefer males with longer, more varied Warble Songs, and the song-rate is also an indication of fitness.
Remarkably, birds which have suffered from unpredictable food supply in early nest life, grow up to sing less often, for shorter periods and with less variety, forever held back by their deprived upbringing. The different motifs in a repertoire are copied from neighbours and from the environment, and this leads to some impressive mimicry, for which the Starling is justly famous.
Apart from imitating such species as Buzzards and Blackbirds, Starlings can imitate non-avian sounds such as car alarms, phones and human whistles and words. All contribute to increase the repertoire and make the bird more attractive to nearby females. The Starling’s day, therefore, consists of performing, probing, prying and preening, among other things. The winter days are short, of course, and it won’t be long before absolutely every Starling is preparing to join the main event of its existence, the great roosting-time gathering and murmuration. No Starling could fail to join in such a momentous event.
Except that Starlings can, and often do. One of the many fascinating things about a big Starling roost is that not everybody does attend. While the migrant Starlings from the continent usually attend, not all the residents do. Some roost in their nest-holes instead. Who can blame them?
Although a Starling’s olfactory sense does diminish in the winter, it is tempting still to think the smell must be horrendous.
And maybe a niffy night in the roost is not to everyone’s taste?