Neighbours started keeping Chickens

Yorkie1

Any restrictive covenant is trumped by s.12 Allotments Act 1950 (I think it is from memory), which says that irrespective of any provisions in leases or other documents relating to land ownership (I'm paraphrasing), it is legal to keep chickens as long as they don't cause a statutory nuisance (noise, smells etc).

spinningsheep

I agree, the OP needs to speak to the neighbour. If you just point out it's location in relation to your bedroom window, they may just move it. If not you will simply need to suck it n see. Wait, you may be surprised.