This is not an exhaustive or a complete subject. It is likely to change over time, with edits, additions and deletions, and is simply a collection of my thoughts based on many years of experience. You should follow your instincts, and you must always seek your own professional advice.
Jackdaws are common birds and are the leaders in nest building!
They can create very large nests from twigs and small sticks. These nests can block chimney pots and flues and would be a problem if left unattended.
With a roof space, the nests can get very large indeed, as shown by these images..:
Disclaimer: Anything posted in this Blog is for general information only and it is not in any way intended to provide any advice, legal or otherwise, on any general or specific matter that you can rely on. You should always seek your own legal and surveying advice.