A river made for kingfishers

The Cherwell rises in the uplands near Daventry and slips into Oxfordshire around Banbury, running south-east past Cropredy, Somerton and Islip before joining the Thames at Oxford. Along the way it changes character. In its upper reaches it is clear, shallow and gravel-bottomed; by the time it reaches the water meadows north of the city it has slowed and deepened, fringed with alder, willow and towering reed sweet-grass. That variety is exactly what makes it such good kingfisher country.

Kingfishers need three things from a river: clear shallows holding small fish, a vertical sandy or earthy bank for nesting, and low perches over open water to hunt from. The Cherwell provides all three along most of its length. Add the quiet stretches between villages, where bankside vegetation is left to grow and footfall is light, and you have one of the most reliable inland kingfisher rivers in the south Midlands.

Reading the water: where to look

Newcomers often scan the middle of the river and see nothing. Kingfishers work the edges. Focus your attention on:

• Gravelly riffles and shallows, where minnows, sticklebacks and bullheads shoal in the sunlight. These are the larders.
• Overhanging branches, especially alder and willow, one to two metres above the water. A good perch is a hunting station, and a bird may return to the same twig for days.
• Bends with an undercut or steep bank, which offer both a lookout and, in spring, a nesting site.
• Backwaters and side channels, which stay calm when the main river is running high and coloured.
• Bridges, sluices and weir pools, where fish concentrate and cover is close at hand.

The stretch between Islip and Marston, the meadows around Hampton Poyle, and the shaded walk through Mesopotamia towards the Thames all reward slow, patient scanning.

The low, direct flight — and other giveaways

You will usually hear a kingfisher before you see it. The call is a thin, sharp “pee” or a rapid double whistle, often given in flight and easy to mistake for a sparrow's alarm. Learn it and your success rate improves immediately.

The flight is unmistakable once you know it: fast, level and arrow-straight, skimming perhaps half a metre above the surface, with wings whirring in short bursts. It looks as though the bird has been fired along the river rather than flying over it. On dull days the upperparts read almost black; in sunlight the back turns a startling electric blue. If a low, direct shape shoots past with a flash of turquoise and a piping whistle, you have your bird.

The plumage itself is worth studying. Adults show deep blue-green upperparts, a rufous-orange belly and a long, dagger-like bill. Males have an all-black bill; females show a touch of orange-red at the base of the lower mandible. Juveniles are duller and greener, and often sit longer and more openly than adults — useful when you are learning.

Fieldcraft: how to sit and wait

Kingfishers are not shy so much as impatient. Sit still and they will often carry on feeding within a few metres; move and they are gone. A few habits will transform your chances:

• Arrive early. The first two hours after dawn are the most productive, though the hour before dusk runs it close.
• Position yourself behind bankside vegetation, not on top of it. Use a bush or trunk as a screen and keep your outline broken.
• Wear muted clothing and avoid sudden movements. Raise binoculars slowly.
• Expect to wait twenty minutes before the first whistle. Bring a cushion or a light seat and settle in properly.
• Work one stretch thoroughly rather than walking miles. Two hundred metres of good river, watched well, beats a five-mile trudge.

Binoculars of 8x42 are ideal for riverside work — bright enough under trees and wide enough in the field of view to catch a bird in flight. Keep dogs out of the water where banks are soft, and give any suspected nesting bank a wide berth between March and August.

The year on the Cherwell

Late winter and early spring are when the birds pair up and territorial calling peaks, often with spectacular chases up and down the river. Nesting tunnels are usually dug into vertical banks between March and May, with two or even three broods raised. Summer is family time: young birds sit on shaded branches and are fed noisily by their parents, which makes for excellent watching.

Autumn disperses the young birds, and by November many adults have shifted towards larger rivers and estuaries, though plenty stay on the Cherwell throughout. A hard frost, when smaller waters freeze, can concentrate birds on the faster, open stretches — a fine opportunity for anyone prepared to brave a cold morning.

Beyond the kingfisher

While you wait, the Cherwell will keep you entertained. Watch for grey wagtails bobbing on the riffles and little grebes slipping under the surface with a soft trill. Grey herons stand motionless in the shallows, mandarin ducks potter about beneath the alders, and reed warblers chunter from the fringe vegetation through late spring.

Look for the muddled tracks and droppings of water voles along grassy banks, and check stones and bridge ledges for otter spraint, which smells faintly of hay and fish. In summer, banded demoiselles flutter over the current like scraps of dark-blue paper, brown hawkers patrol the meadow edge, and a muntjac will sometimes bark from the far bank. The Cherwell is generous. Sit long enough beside it, and the kingfisher becomes one good thing among many.