I hatched two Indian Runner ducklings last week, and one is half the size of the other, they did hatch two days apart but the smaller one doesn't seem to have grown at all. This is the first time I've incubated and owned duck so I'm not sure what could cause this. I was wondering if this could indicate that the larger one is male? As well as being bigger he is also darker in colour. When the smaller one hatched it hadn't fully absorbed its yolk , however after a few hours it was absorbed, would that have effected her size? Other than being small she is doing very well, they're both fed ad-lib on chick crumb (a brand which is suitable for ducks) and they are both eating fine, and as you can see from the picture they are also adept swimmers, its only her size which I'm concerned about. I do apologize if I am asking silly question but I've only ever owned chickens so I'm not experienced with ducks. Any help is greatly appreciated. Thank You, Sammi.