by Steve Westerman

Wharfedale Naturalists Society

IN the last couple of weeks, grey wagtails (Motacilla cinerea) have started to reappear along the river Wharfe, where it flows through Ilkley. They nest in crevices between rocks, or tree roots, or in man-made structures (e.g., the bridges), and are a relatively frequent sight in all but the coldest months. They seem to disappear in the winter, but many probably don’t travel far. For example, a UK ringing study found 40 per cent of winter recoveries were within 10km of the birds’ summer locations (where they were ringed). However, consistent with a search for less harsh environments, of those birds from the north of England that travelled more than 100km for the winter, all were recovered further south.

The name – grey wagtail - doesn’t do justice to the birds’ appearance (see photograph). This small (approx. 18cm), attractive bird has bright yellow underparts (less extensive in the female). They have pale over-eye (supercilium) and sub-moustachial stripes and, in the breeding season, the male has a black throat. Their name, however, does provide a good behavioural description. When standing or moving around on the ground they persistently flick their long tails.

Grey wagtails can best be seen when the river level is relatively low. They walk among the rocks in the stream searching for invertebrates. They will also take insects in mid-air – and often stand on a rock scanning above for passing prey. When they spy something that looks tasty, they will ‘jump’ – with a short, rapid burst of flight – to take it out of the air – before returning to their vantage point. In the summer months adults can be seen performing these activities to feed fledglings that perch amongst the rocks, or at the edge of the river, waiting for their next meal.

Life isn’t always easy for these cheerful-looking birds. As with many small birds, numbers suffer when winters are harsh. Although the effects of water acidification doesn’t seem to present the same problems that it does for dippers, they do have to be vigilant for predators.

One bright summer morning I was quietly photographing a grey wagtail that was feeding among rocks in the middle of the river. Suddenly, my attention was taken by a blur of activity in the corner of my eye. Something dark-coloured had swooped down. I presumed that perhaps a crow or a blackbird had landed. However, when I looked again the wagtail was gone. The intruder was a sparrowhawk. It had taken the wagtail, and was now perched – with its prize – in a nearby tree. It’s always exciting to see a sparrowhawk, but...