Hi
We have a wood pigeon who regularly visits our garden for food. He has become quite friendly with the whole family and now eats out of our hand and sits with us. We have a problem with magpies in our neighbourhood- the blighters are everywhere and very intimidating to most other birds. I know think they are attacking the pigeon- saw this the other day- and when he came for breakfast this morning he is looking very dishevelled. Are they picking on him because of us??
As Hazel says it is down to territory.
Nature can be very harsh at times to itself, its all about survival plus, if a species sees a weakness in another of its own or another species, it is natures way of keeping the blood line strong, even though it seems so harsh.
Enjoy what you see, watch and you'll find it fascinating, but sometimes harsh.