There has been a study, and therefore a report on 244 British Wild bird species, and the report found as much as 27% of these birds were in trouble, of becoming extinct, and therefore urgent action is needed to protect these animals from becoming extinct.
Another bird which has suffered, and is suffering is the Curlew, showed in the pictured below.
The Curlew has declined by 42% in the last two decades.
There are many threats to birds in the UK, which is responsible for their decline. They are declining because of habitat loss. They are declining because of shooting. Sometimes poisoning. Most, if not all of the decline in birds is down to human activity.