Ancient instincts behind epic journey

Some are being seen in the region now, with 12 on fields in the lower Derwent valley between York and Selby resting and refuelling as they move northwards.

The Greenland wheatear is of the leucorhoa race, slightly larger and with a stronger pink buff colour on the breast than the oenanthe race that breeds here.

They also tend to have a more upright posture.

The main arrival is later than British wheatears as they follow a route used by many waders and waterfowl moving up from Africa, across Continental Europe to the British Isles and then to Iceland. From there they move on to western Greenland and eastern Canada.

With no prevailing winds to help them, particularly this month, their progress is a steady one which also gives time for their breeding grounds to be fully thawed out. But it is in autumn that their return to Africa,becomes even more remarkable. They do not begin their return migration until late August which gives them more time after breeding to build up reserves of body fat for their journey.

It was once thought that their return was in two stages, first to southern Europe then to Africa.

But analysis of the body weights, wing length and timings of departures from Greenland, compared with the arrival times and measurement of birds arriving on an island off the Moroccan coast – backed up by sightings from ships in the Atlantic suggest that at least some of the wheatears make a single-hop crossing of the Atlantic of at least 1,500 miles. This is a staggering achievement, particularly in a bird that,at about one ounce is only slightly heavier than a sparrow, but it seems that such crossings, particularly with a favourable tailwind, are perfectly feasible.

The wheatears in western Canada and Alaska also return to Africa in the autumn but they cross the Bering Straits before heading southwards across the vast expanse of Asia, an incredible 15,000km or more, but at least with the opportunity to rest and refuel on the way.

Wheatears breed in a broad belt from Alaska and Arctic Canada across Eurasia to eastern Siberia, yet without exception, they all winter in Africa, obviously a deeply imprinted and ancient instinct perhaps dating from a time when the world's land masses looked very different.

Red-rumped swallows continued to be seen over the weekend with two over Wawne in East Yorkshire and one remaining this week at the Rother Valley Country Park in South Yorkshire.

The elegant wood sandpiper has been seen on passage at several sites with three at the Pulfin and High Esk reserve in East Yorkshire,three at the Fairburn Ings reserve near Castleford and two at the Watton reserve in East Yorkshire. A spotted redshank was also at Fairburn.

In the Yorkshire Dales 12 dotterels were seen near Malham Tarn.

There has been a good passage of whimbrels with more than 146 in a roost at Wheldrake Ings near York and 15 at Woodmansey, East Yorkshire.

At Wheldrake 16 of the whimbrel were caught as part of a long-running research project including two that had been caught a fortnight previously. In that time their weight had increased from 330gms to 550gms showing the importance of the valley for migrating birds.