Assertion: harrier's number | /r/CapableOf | dwindle by 20 per cent
Facets:
value: to 505 pairs
type: OTHER
Source sentences:
text: By rights, there should be as many 1,790 pairs of the birds known as "sky dancers" nesting in Scotland but, say conservationists, surveys show that illegal killing and disturbance saw numbers dwindle by 20 per cent to 505 pairs when they were surveyed six years ago.