A lack of birdsong is hard to swallow for Roger Ratcliffe

If you are interested in birds, this spring has been strange and somewhat worrying. The proverb “one swallow does not a summer make” – meaning that a single instance doesn’t prove a point – ignores the fact that these glossy blue birds with red throats and forked tails arrive from sub-Saharan Africa not during the summer months at all but throughout April.

This year, though, whilst small numbers did make it to the UK on cue the majority failed to show up until the second half of May. The same was true of house martins, black and white cousins of swallows that commonly construct their nests with mud under the eaves of buildings. At Malham Cove in the Yorkshire Dales, where they attach their mud cups to the limestone cliffs, a friend tells me martins were two weeks later than normal. Elsewhere their appearance was spasmodic, more dribs than drabs, and one estimate in North Leeds put the number at just one fifth of the usual population. Swifts, another near relative of swallows, have been even more delayed.

All this reminded me of that classic bible of environmentalists, Silent Spring by Rachel Carson, in which she envisaged a spring without birdsong because of the widespread use of poisonous pesticides in agriculture.

More than half a century after the book’s publication, we have not reached the stage where blackbirds, song thrushes and a whole choir of other birds don’t provide us with a dawn chorus at this time of year, largely due to the revolutionary changes in environmental laws inspired by the book that banned the use of many chemical sprays.But, I tell you, walking across a sheep meadow in Nidderdale, North Yorkshire, on a sweltering day last week with every tree in leaf yet not a single swallow in sight is the closest I have ever come to experiencing Rachel Carson’s nightmare world.

So what’s going on? The meteorological explanation for the delayed movement of birds from Africa is that storms in France held up many species, and that unseasonal northerly winds effectively stalled the migration of smaller birds like swallows, house martins and members of the warbler family heading up from Africa.

The word “unseasonal” crops up again and again in relation to the effects of global warming, but when it starts to affect something like bird migration, an event that is carefully synchronised with the hatching of the insect life that birds require to feed their young, we should start to worry.

Mark Avery, the RSPB’s former conservation director who is now a highly respected campaigner against persecution of birds of prey on grouse moors, picked up on this in his blog, noting with concern that this year the beautiful song of the nightingale, another migrant from Africa, is for the first time absent from his local woodland. The no-show of nightingales and reduction in swifts and house martins around where he lives are, says Avery, as important to him as Brexit, interest rates and the cost of living. “In some ways, more important, because they are fundamental aspects of how the world is working, or not working.”

I have to agree. These indicators show the natural world is off kilter and should concern us all. Perhaps climate change is moving us towards a Silent Spring.

Roger Ratcliffe has worked as an investigative journalist with the Sunday Times Insight team and is the author of guidebooks to Leeds and Bradford. Follow him onTwitter @Ratcliffe