A handful of winter thrushes
By James Duncan
Communities & Wildlife Officer
Autumn - as nature's last hurrah prior to the bleak winter months, its spectacular blaze of golden glory typically marks the arrival of a mind-boggling number of avian visitors. As the leaves change, the seeds fall and the Ivy flowers, the hedgerows burst with a glut of juicy fruits, packed full of energy and nutrients. Whilst a trio of thrush species are always here in Sussex relishing this feast, they're joined by a pair of family members from the continent.
But what exactly is a thrush? Well, the word stems from the old English throstle, a poetic name for a Song Thrush. They're all small or medium sized passerines ('perching' birds that comprise more than half of all bird species) and are most closely related to the Old World (Africa, Europe & Asia) flycatcher family. The six species we typically see here in Britain all belong to the genus Turdus, the 'true thrushes,' though the family Turdidae is one of the most species rich avian genera on the planet. All are migratory, even those that we perhaps assume (through regular familiarity) are not.
As we move toward the cold, dark nights of winter, which will you see? Well, one that you won't is the summer breeding Ring Ouzel, a bird of Northerly upland slopes and gorges, surprisingly hard to spot in Sussex during their seasonal journeys to and from the Atlas Mountains of North Africa. You will, however, see many of its similar resident cousin; our most numerous thrush - the Blackbird. Not many would struggle to identify an adult male, though females and juveniles may prove more challenging with sooty brown plumage and diffuse mottling, making them more confusable with other family members. A low, direct, dashing flight is distinctive and look out for their characteristic habit of 'drooping' wings and 'jerking' the tail when on the ground. Their hyper alert nature and 'fleeing' flight style harks back to a time when they were once a shy, retiring species of dense woodland, something their versatility has now radically altered. Though most British individuals are resident, many arrive here from Scandinavia and Russia to avoid the harshest of winter weather.
So, onto the thrushes with 'thrush' in the name. The most familiar is of course the Song Thrush, a bird whose bold repertoire of assertive, repeated musical phrases punctuates many a winter day, though they often sing all the way through to the end of July. Outside of the breeding season, they're typically of solitary nature and you may be alerted to their presence though a feeding habit - that of 'hammering' snail shells open on a suitable natural anvil. They're a nervous, skittish bird, frequently unapproachable and often shy away from extended time in the open. Their warm brown upper parts contrast with those of the 'colder' grey-brown Mistle Thrush and they're rather short-tailed and compact. Should you disturb one, it'll usually flow low and fast in a jerky manner, rapidly diving back into cover, often uttering its subtle call, "zit" before taking to flight. If it happens to pass overhead, look out for rusty-buff underwing coverts (their armpits).
The Mistle Thrush is the larger relative of the two. They tend to display more complex patterning on the face, more variegated wings and bolder rounded spots that extend all the way from the breast to the flanks and lower belly; in contrast to the 'sprinkling' of arrow-shaped spots on the Song Thrush. Their 'armpits' are white (only visible in flight) and they're a bolder, longer-winged and more alert bird than the retiring Song Thrush. If flushed, look out for a powerful, undulating flight (rather woodpecker-like) with a tendency to rapidly gain height after take-off. As a whole they're rather more social and may be seen foraging in small groups, well away from cover, or chattering away in a frenzied manner within the tree canopy. Their harsh, dry, rattling calls are extremely distinctive and carry long distances. When in full song, they most resemble the Blackbird, though the tone is undoubtedly more desolate, with a faster tempo and a complete absence of squeaky notes. Whereas Song Thrushes usually sing on until July, Mistle Thrushes typically conclude their repertoire by late Spring. Their diagnostic habit of singing willingly from exposed perches in stormy weather has earnt them the colloquial name of 'stormcock.' Both species undertake extensive migrations from Northerly and Easterly regions of the Palearctic, overwintering in a broad front across the Mediterranean and Middle East, though British & Western European birds are to a large extent resident.
So, what about the two that arrive specifically to plunder the autumnal berry harvest? The most numerous is the highly nomadic Redwing, a bird with a tiny breeding grasp in Scotland, its true stronghold the subalpine Boreal forests of Northern Europe. An approximate one million may descend upon the UK each winter, arriving en masse most typically in October. Many won't finish their journey here, continuing on to the shores of the Mediterranean. They're a nocturnal migrant, their high-pitched but wispy flight call, "seeef" often giving away their whereabouts on misty nights. Major shifts in population take place year on year as they respond to weather and feeding conditions, with some individuals in some years taking entirely different routes. A compact Starling-sized thrush, the Redwing is highly distinctive with a prominent pale supercilium (stripe over the eye), pale submoustachial stripe (think chin stripe), rusty red flanks and 'armpits.' Typically they're evasive birds and should you flush them, the entire party may take to flight, flying high and landing in distant treetops. Keep your eyes and ears peeled for them moving quickly along hedgerows, where a slow approach will pay dividends. Once fully gorged on fruit and berries in late winter, they'll often move into open areas in search of earthworms.
Another seasonal nomad is the resplendent Fieldfare (main image). Unlike the Redwing, the Fieldfare is resident across a broad swathe of central Europe, though also doesn't favour the lack of feeding opportunities at Arctic latitudes in winter. Hence, three quarters of a million may arrive in the UK and in Southern Europe each winter. Their movements, as with Redwing, are fully determined by resource availability - should the fruit harvest in Scandinavia fail owing to brutal conditions, huge flocks may descend upon our orchards as they gorge on unpicked apples. Similar in size to the stocky Mistle Thrush, the Fieldfare is heavily built, long winged and tailed and has the same white 'armpits.' Colouration is of course markedly different, the Fieldfare's russet wings and back unique amongst our six, the dark tail and light grey rump helping to differentiate it in flight. It's another highly gregarious species and you may be drawn to their noisy flocks by their 'camera shutter-like' calls. In similarity with Mistle Thrush, they display a bold, upright posture when foraging and are viciously territorial in much the same manner. Late in winter, they will also forage regularly in open fields and grassy areas, joining an assortment of Blackbirds, Mistle Thrushes and Redwings.