In certain areas of the garden it does seem to have an effect, but where I normally feed the small birds, it has no effect on either the small birds or the crows and seagulls. I presume that their hunger overcomes any scarer, and if at all it's only for a short time, and I also have a dummy hawk and an owl but crows being what they are (clever) it takes them only a couple of days or so for them to suss out they have nothing to fear. Similar with seagulls! Really cant see anything, apart from bangers that would deter them. Hope this helps. chris.