‘That’s a buzzard!” says Richard Gregory, gesturing at a tall birch tree stump 50 metres or so away, from which a flapping streak of brown and white has just disappeared. “That was a buzzard. That’s one of the ones I was telling you about. It’s back.”

When Gregory was a young child, toddling around the green bits of Cheshire with a monocular, a glimpse of a buzzard made for a thrilling day out – though he was mad about birds by the age of four, he was in his teens before he ticked the large raptor off his list. Now, though, thanks to reintroduction projects and legal protections, its number and that of several other birds of prey is on the up in Britain. We glimpse another one, as it happens, a few minutes later, and while I suppose there is just a possibility it was the same bird on a second swoop, I’m counting that as a double sighting.

The recovery in recent decades of Britain’s raptor population is welcome for a number of reasons. Firstly, it means I was right after all that time I spotted a red kite while driving up the A1 and everyone else in the car said I was talking rubbish. Secondly, it’s a snatch of good news in what could otherwise seem an unrelentingly grim picture.

These are bad days to be a bird. A study released this week found that the most common birds in Europe are declining at an alarming rate, and that is not an idle term. By studying 30 years of data across 25 countries, conservationists estimated that there are now a brain-boggling 421 million fewer birds flapping across the continent’s skies than were around in 1980.

House sparrows alone account for a third of that decline, with 147 million fewer birds, a drop of 62% of their total population; starling numbers have fallen by 45 million or 53%; skylarks are down by 37 million (46%). Yes, the marsh harrier has recovered a bit, and feral pigeons and ring necked parakeets are doing well in cities, but overall, concluded the report, “global biodiversity is undergoing unprecedented decline”, and some of the species taking the hardest hit are birds which were once, not so long ago, abundant in our skies.

Gregory, one of the report’s authors, is also the head of species monitoring and research at the RSPB, so the fact that bird populations were on the slide didn’t exactly come as a surprise. All the same, he says, he had a genuine start when he first tallied the numbers.

“You can’t really call it the Eureka moment, because it’s not good news. But yes. It’s a shock.”

We are ambling between lovely mature oaks and pines at the bird conservation charity’s reserve at The Lodge in Bedfordshire, while delicate yellow-brown birch leaves flutter down like confetti. November is not generally a great time of year to count birds – most species’ populations are monitored in the breeding season, when they are singing their tiny bird hearts out about love and new housing – but for Gregory, who says he can recognise the calls of 450 native species, any walk through woodland is an aural adventure.

Another buzzard … this time in Glen Lyon, Scotland. Photograph: Russell Cheyne/Reuters

It’s principally agricultural intensification that is behind the crisis, he says (“hear that chip-chip-chip-chip? That’s the alarm call of a wren”), though there are examples of good farming practice if you look for them (“There’s a little goldcrest above our heads, that very high pitch pspspspspsps. They’re lovely.”)

It can be exhausting, he admits, having an internal voice constantly identifying birdsong, particularly when he finds himself awake for the dawn chorus.

Above all he wishes that policy-makers would take more notice. “We’re sleepwalking into disaster, and there’s no response to it, the governments and others don’t seem to be responding to this level of loss or even noticing it, that’s my personal view.”

The coalition says it has put in place incentives for farmers to protect wild habitats, and will introduce a new scheme next year “designed to be even more targeted and effective”. This week the government unveiled a 10-year strategy to protect bees and wasps – they’re screwed too – that started with a call to gardeners not to mow lawns so often.

Little steps in gardens and patios can help our birdlife too, says Gregory, even if you’re the kind of urbanite who couldn’t pick a flamingo out of a lineup. Seed mixes (not peanuts) left out in winter, nesting boxes tacked to exterior walls, water features in beds.

And if you struggle, in all truth, to muster a great deal of concern for the corn bunting given all the other craziness going on, he advises applying a spot of self-interest.

“Birds play a role in removing pests – there’s a robin there on the fence, look – in dispersing seeds, in scavenging dead rabbits and things in the environment. And they have their aesthetic role too. If they go we will lose both the utilitarian benefit to nature, and the more feed-your-soul side … this is interesting. It’s a flock of fieldfares that have come from Scandinavia …”