Two once-widespread woodland birds have become so threatened that their numbers will be monitored by experts who track the UK’s rarest breeding birds, it was announced.

Populations of the lesser spotted woodpecker and the willow tit have plummeted since the 1970s.

Numbers of willow tits have fallen by 91 per cent and the lesser spotted woodpecker, the smallest of the UK’s woodpeckers, have dropped by more than three-quarters (76 per cent), the RSPB said.

The wildlife charity’s Mark Eaton said: “It is tragic to think that within many people’s memories these woodland birds were so widespread and now they are so rare.

“Since the 1970s, we’ve lost nine out of 10 pairs of willow tits and three out of four pairs of lesser spotted woodpecker, and in many areas these birds have disappeared completely.”

It is unclear exactly why numbers have fallen so significantly, but experts believe changes to woodland may be playing a role.

A lack of suitable management which would allow new growth and provides dead and decaying timber may be having an effect, while willow tits may also be hit by wooded areas drying out.

The RSPB said the declines were extremely alarming, with the birds disappearing altogether from counties where they were once found.

The situation has become so serious that the Rare Breeding Birds Panel, which has been charting the fortunes of the UK’s rarest nesting birds since 1973, will be collecting information on the number of breeding pairs which remain.

With any individual sightings of either of the species now of national significance, experts are calling on birdwatchers to submit records if they see them.

Reports produced by the panel aim to provide a snapshot of how the country’s most threatened birds are faring.

With the panel monitoring three other species for the first time - the long-eared owl, the short-eared owl and the Arctic skua – the list of rare birds which regularly or occasionally nest in the UK tracked by the experts now stands at 103.

The panel’s secretary Mark Holling said: “With so many species in trouble, these reports provide an essential snapshot of how our most threatened birds are faring.