@goosepimple:
Not to say they're all capable mothers, as you obviously know firsthand, but I wouldn't brand an entire species as being inherently bad at mothering, because in my experience those that are incapable are only that way because humans have practiced interfering in the maternal process to raise the chicks themselves to gain security, so the mothers have lost maternal instinct and become incapable.
Given time, often with the help of kelp, and human tolerance of some losses as they learn, even non-mothers can often learn to become great mothers. But of course if you don't want to countenance losses to maternal learning hiccups, separation is best. I prefer the animals doing the work of rearing and tending their babies, not to mention that it improves their quality of life and health and therefore flavor

Not that I eat geese anymore, they were too attached to each other, another factor to consider... Anyway, kelp brings out great mothering (and fathering) and other instincts most incredibly, as well as general health, calm, and intelligence.
Also if you think (for example) that you're breeding pure white birds, give kelp for a year and you'll know for sure. The true genotype is only expressed in their phenotypes if they are receiving a complete nutrient profile spectrum, which commercial feeds do not provide, regardless of their claims. I've had hens I bought at over two years old go from all-white to yellow, black, red, etc. Their beaks, legs, eyes, feathers, eggshells, everything changes once they're receiving their true nutritional needs. Also kelp can turn white human hair its youthful color again. Last but not least I'd gain some fake eggs if you can, they're great for everything from helping shift broodies to fooling rats/vermin to curing eggeaters.