Hi Stella, welcome to WAB.
Your neighbour has no right to tell you what to do in your own garden, as long as what you are doing is legal and not creating a nuisance or a health/safety hazard. Feeding garden birds is perfectly legal and you've clearly taken all reasonable steps to ameliorate any possible nuisance.
Any further actions by your neighbour could be construed as harrassment.
Put this website
Garden Law Discussion :: Index in your favourites, just in case the situation escalates.
Good luck,
T2