Hi Billanddeb, and welcome. As the RSPB puts it, 'All birds their nests and eggs are protected by law: the Wildlife & Countryside Act of 1981. This makes it an offence, with certain exceptions, to deliberately take, damage or destroy the nest of any wild bird while it is in use or being built.' The exceptions referred to are if the nest would constitute a threat to public safety or public health.
It's hard to judge whether the birds would feel distress as we would understand it at being moved on, but this would mean breeding failure for them this year, as territories are established in early spring.
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Thanks Aiki. We have starlings nesting too, so it looks like we'll be having a rather large family this year. It will be interesting, noisy, messy (with the gulls) and the birds are already costing me a fortune in food. Ce la vie! Thanks again for your help.