by Steve Westerman

Wharfedale Naturalists Society

IN my Nature Notes last month I talked about the Cuckoos that fly each year from sub-Saharan Africa to visit Ilkley Moor. The distances that these birds cover is just amazing. Over the last few weeks I’ve been watching some other species that make a similar journey.

Swifts regularly fly over parts of the moor and near the river, hunting for airborne insects. These are real long-distance travellers and most will over-winter in southerly parts of Africa.

A little further away from the town, I spotted some fledgling Swallows, perching obligingly on a telephone wire (see photograph). The parent birds had built a nest in a nearby old outbuilding. The fledglings didn’t have the long tail feathers of adults – and their beaks looked too large for their heads – but all the better for catching flies! Their migration journey will be similar to that of the Swifts.

On nearby moorland there are families of Wheatears. I watched one set of fledglings waiting impatiently on a rock whilst a parent bird scurried about looking for food to bring to them. For another family group a drystone wall provided a useful vantage point. In a couple of months these birds will be following the Cuckoos. Willow Warblers and Chiffchaffs nest in several places on Ilkley Moor. Physically, these species are difficult to tell apart, although their songs are discriminating. Interestingly, their migration journeys also differ. Some Chiffchaffs spend winter in the UK, some migrate to Mediterranean regions, and some push further on and skirt the Western Sahara. However, Willow Warblers, with slightly longer primary flight feathers, make a more demanding journey, deeper into Africa.

So, before long, these species (and more) will fly to the south of the UK, they will cross the channel, cross continental Europe, navigate the Mediterranean, and when they get to North Africa they will cross the Sahara Desert region, before finally reaching their winter homes. In the spring they will reverse the process – but then the journey is even more arduous as the desert area is more extensive and the winds are less favourable.

This incredible long-distance migration brings two questions to mind, for which I think there are only partial answers. First, how do these birds navigate so precisely with no GPS or physical map to refer to? Second, why has evolution has led to this particular behaviour? Given the difficulties and risks involved, Ilkley must have a lot going for it!

wharfedale-nats.org.uk