From the Standard's write-up, these were glue-covered wooden sticks set next to a feeding station, which is the old "liming" method for catching small songbirds alive. That's why it takes planning: the bait draws them in and the sticks hold them.
It's specifically illegal. The Wildlife and Countryside Act 1981, section 5(1)(b), bans using "bird-lime or substance of a like nature" to kill or take any wild bird, and section 21(1) sets up to six months in prison and/or a level 5 fine (unlimited in England and Wales).
Anyone who finds lime sticks should leave them in place, photograph them and report to the police (Essex Police here) rather than pull birds off by hand: the wildlife hospital used a solvent spray to free them without tearing skin.
Section 5: https://www.legislation.gov.uk/ukpga/1981/69/section/5
Not legal advice.
