I agree with glsammy, whilst it's easy enough to get too close that you might spook a bird and it flies off to another perch, you're probably never really close enough to cause it any distress or affect it's welfare.
In fact, in the past, I've even climbed trees to get better photos of an owl and, despite only being 30ft away, the owl never showed any of signs of distress. Last week I was out in the Peaks where a Robin was so comfortable with us being around that he sat just a couple of feet away and stayed there for 5 minutes.
Each occasion is different and as long as you don't chase birds around the park or stick your lens in their nest, you can usually get quite close without causing any harm.
It's a fair comment from Helen as some general advice for anyone who goes out taking pictures of birds, but on this occasion I don't think it really applies as glsammy's pics are obviously taken from quite a distance. I'm just gutted that I wasn't standing next to him when he took the pics
