Sam

The last category is injury or infection, which feels different again: warm, firm or sore to the touch, maybe with a scab or redness, and getting bigger over days rather than smaller over hours. Pecking from the others and rough handling are the usual routes.

So the three questions are when did it appear, what does it feel like, and is it shrinking. Soft, post-feed and shrinking is dinner. Anything else is a phone call.

One to be able to recognise because it is different and people confuse it with a food bulge. A soft puffy swelling that feels like air, slightly crackly under the fingers, like a little balloon. Not related to eating, and it can grow or move about.

That is air under the skin, usually after something has affected the air sacs or respiratory system. It needs a vet and it specifically needs you not to put a needle in it yourself, which people do.