WINTER may still have a few nasty surprises for us, but there’s definitely a feeling of change in the air. As I open the back door I’m met with the joyful sound of birdsong.

Although the robins have been singing – rather wistfully – all winter, the cocks have now strengthened and elaborated their song. Blackbirds start early and sing late, serenading some of the beautiful sunsets we’ve seen in recent days, and the dunnocks, who’ve been flirting excitedly for weeks whenever there’s been a let-up in the cold, have chosen a nest site and the male’s sweet, rather wispy song greets visitors as they turn into our driveway.

So, it’s time to be listening for some of our summer migrants.

By early April chiffchaffs are usually vocal as they assert territorial rights and advertise for mates. I listen for them along the lower fringes of Middleton Woods. Their song is unmistakable – the – some might say rather tedious – reiteration of their name, chiff-chaff, chiff-chaff. They have a head start: they winter north of the Sahara, a shorter and less hazardous flight away, unlike the equally common willow warblers. These tiny olive-coloured birds come from wintering grounds south of the Sahara and I usually first hear them around the end of this month from the upper edges of Hebers Ghyll or from the small trees dotting the moor. The field guides advise us that chiffchaffs have dark legs whereas willow warblers’ legs are pale. However, once they sing, no-one could muddle the chiffchaff’s boring repetition with the cascade of silvery notes warbled by its paler-legged cousin.

The third warbler I shall be delighted to hear is the blackcap – a pale grey-brown bird with a sooty black cap and the voice of an angel. I think they’re actually as melodious as nightingales and without all that croaking and clicking! Blackcaps are of particular interest currently. In the 1980s a few overwintered in the UK. Numbers steadily increased and now most people will have seen one visiting feeders in winter gardens. In fact our support of winter birds with seed and fat -balls may have contributed to the success of this new strategy.

Now scientists from the BTO and Oxford and Exeter Universities are researching this phenomenon. Birds were ringed and 36 of them fitted with geo-locators. We already know one bird left its UK garden in March, flew to France and returned to the same garden in November. Further research should throw more light on why, how and how quickly birds can respond to climate and environmental changes.