
Hi,
My 3 year old does this very occasionally too, before breakfast. With her it's pure hunger, as she will then tuck straight into her breakfast - and there's nothing will make a Rough Collie eat if they're not hungry :D
She's definitely the 'supermodel' type - she is in sparkling health but stays very lean, despite being fed at least 50% more than her much larger daughter, who would put on weight if I let her. With the Mum, I aim to feed a bit more than she will eat in one meal, to ensure she's had all she wants, and could never get away with not giving her breakfast.
M.