I too have noticed my marans are often broody but not good mothers. The best mama chicken I've had was a split chocolate orpington named cocoa. She did a great job until she developed a sudden infection and died at 6 last year. My next best broodiest are turkeys. Then the legbars, then the marans. The legbars are descended from leghorns, and they still do better than the marans! The marans go broody way more often than the other hens, however. Sometimes I am tempted to get another orpington just to have a good broody chicken again!
in my climate orpingtons are not good mothers. it is too hot for them to cover the chicks. I like orpingtons but will never ever have them. my poor girl died due to heat at 11 mo.
I had other broodies that were good mothers: silkie, araucana, greek non standard hens and 1 black sex link.
I am glad to hear that legbars get broody too. I have just got 5 pullets and a cockerel of cuckoo legbars. they have been imported from italy and lay dark green (sort of olive) eggs. I googled cuckoo legbars and found nothing. has anyone ever heard of cuckoo legbars?