Sitting, and relaxing. They then perceive no threat at all. You are lower, not towering over them as we do when we are standing, you are not moving so you can't be chasing them and your mind is on your cup of tea (or whatever) and not on gearing up to grab them or do anything to them.
If we put ourselves in their position, it makes sense. Suppose some person is staring at us, it makes us uncomfortable. Even when they aren't doing anything in particular, just that level of focus can affect the one being stared at. Then we are hugely bigger than a chook, imagine a GIANT was staring at us. It's a wonder any of them lets us be their friend up close.