A hardy bird that has adapted well to the unforgiving environment of bitterly cold and windswept estuaries
Dominic Couzens explains how this hardy bird has adapted well to tough living conditions
ONE OF THE great sights of birding is the mass of waders on an estuary, flying back and forth around high tide. There is something satisfying about appreciating how waders roost in large numbers when the tide is high, but go back on to the mud once the tide falls, and how different waders then spread out over different kinds of ooze. Over the years, I have been so overwhelmed by the sumptuous shorebird displays, that I tend to overlook other birds that are affected by the depth of water.
Several categories are: estuarine wildfowl, especially Shelducks and Brent Geese; cormorants and, to a lesser extent, gulls and terns. All these are wedded to tidal cycles. And then, how about a left-field addition to this list, a bird that you wouldn’t instantly assume was in such company – the Twite? It doesn’t have long legs, or a long bill. But, in parts of its range, it is just as much an estuarine bird as the most committed Redshank or Dunlin. Rather than seeking out worms, crustaceans or molluscs in the mud itself, however, the Twite subsists on the seeds of estuarine plants that grow in patches regularly inundated by the tide, especially the Glassworts (Salicornia spp) and Seablite (Suaeda maritima).
The Twite feeds by hopping over the mud and perching on the plants themselves. However, it can only do this when the tide allows. As the water comes in, flocks of Twite feeding far out on the mud, usually without competition from other shoreline seed-eaters such as Snow Buntings and Shore Larks, are forced towards the inner saltmarsh. At high water, they will feed in adjacent fields, often flocking with these other birds, and even Linnets. However, once the tide retreats, the birds return to their extreme feeding grounds. Glasswort, the Twite’s staple, is often abundant where it occurs, and forms extensive ‘forests’ of branched, succulent forms that look a little like mini Christmas trees (or at least, those sorts of
spindly Christmas trees you buy from the back of lorries.) On big estuaries, patches of Glasswort can be very extensive and can occur a considerable way from shore. There are also several different species that occur on different parts of a saltmarsh. These plants don’t all set seed at the same time, either, meaning that at least some are available for most of the Twites’ winter stay from October to February. There are also other saltmarsh plants available if their staples run out, such as Sea Aster, and on cultivated fields these birds aren’t so sniffy that they avoid such common stuff as Dandelion seeds, or Shepherd’s Purse or even Chickweed. However, the seeds of saltmarsh plants are unusually high in nutrients, and thus highly favoured. Twites do have some exotic tastes, though; they are among a very few songbirds known to consume seaweeds, presumably in times of food shortage. The Twite’s most favoured estuaries – the Wash, the Humber and Morecambe Bay – attract large flocks, often hundreds strong. Apart from allowing the birds to feed far away from humankind, these estuaries offer a habitat that is frequently bitterly cold, unforgivingly windswept and also very damp. The birds can hide among the plants and keep their heads down, but they cannot avoid inclement conditions entirely. This, though, lies at the heart of the Twite’s uniqueness as a species. Twites are defined by their hardiness; they thrive in conditions that other, similar species cannot cope with. One of their previous country names, now obsolete, was Mountain Linnet. But they have no specific attachment to mountains, neither in the winter nor in the breeding season, so a better nickname would be something like Tough Linnet or Seriously Hard Linnet (or maybe No Linnets.) Instead they are drawn to treeless places, open to the full force of the elements, lacking in both sun and warmth. The Twites that winter in saltmarshes are mainly from the population that breeds in the Pennines, which is one of the species’ strongholds. Once you reach properly up north, though, in the Hebrides, Shetlands and Orkneys, where Linnets fear to tread, Twites are abundant and typically stay close to the breeding areas all-year-round. Here, they typically build the nest on or close to the ground, among low, thick vegetation. Heather or Bracken suffice, and Gorse bushes are used in Scotland. Twites, though, are experts at using all kinds of different places for the nest site, including under rocks and boulders and even on cliff ledges. On the latter, they might rub shoulders with birds such as Puffins and Guillemots, which must make a pleasant change from hordes of wintering waders. The nest is bulky and extremely well
built, typical of finches, and ideal for chicks that are being brought up in a chilly climate.
A Twite feeding quirk
One of the quirks of the Twite, also shared by its sun-loving relative the Linnet and, to a greater or lesser extent by most other finches, is that it feeds its young not on insects but on the regurgitated paste of seeds that it has ingested. If you forgive the association, it is hard not to think of tough nestling Twites being fed on good Scottish porridge, and the analogy isn’t so far off. Other species of finch, such as Goldfinch and even Hawfinch, always add some insects to the mix, but it seems that Twites don’t normally do so. It doesn’t seem to do them any harm. The Twite, in common with other finches, has a long breeding season and will sometimes squeeze three broods into a busy summer, not finishing until well into August. And why shouldn’t it carry on? Being such a confirmed seed-eater, it makes sense to continue breeding when there are still abundant seeds around. When the young hatch they soon join into large flocks with the adults, and hundreds may be seen together. There is some, highly intriguing evidence that siblings sometimes associate for much longer than is normal for a typical songbird. It is thought that most brood-mates of small passerines simply drift apart as soon as they fledge, but sibling Twites have been found in the same part of a wintering flock when more than two years old. Whether this is typical, or just a quirk, is not known. One very important trick you need when you live in a chilly, wind-blasted climate is to find a secure place to roost every night. And here, Twites show an adaptability that borders on the ingenious. They have been recorded sleeping in all manner of places, likely and unlikely. They are often in thick ground vegetation, such as Bracken or heather, in stubble or cut crops and will also use hollows on the ground. They roost in reedbeds quite frequently. The Twite has been recorded in slopes of boulder scree, on houses and in walls, and inside the thatch of a building. They have been known to construct their own tunnels in the snow. My top favourite, though, is an observation of Twites nestling down within the downy inflorescences of cotton-grass in the middle of a pond. Soft and cosy, this must rank as a top-notch comfortable airy B&B. It isn’t quite in keeping with the bird’s tough guy image, though. On most nights, Twites roost communally – not close, but within contact calls of their kind. And in that respect, they are once again united in behaviour with the noisy waders that shift and settle on the tidal estuaries around our shores.
Subtly plumaged is a polite way of describing this LBJ With good views, the ‘drab’ plumage of the Twite is complemented with glimpses of the pink rump
Twites usually spend the winter months in flocks