Chestnuts are one of the more difficult birds to sex. There are a few guidelines though that may assist in sexing the birds:

Walter Burgess: Sexing 101 - species # 2 - Five-coloured Mannikin or - Lonchura Quinticolor:

Walter Burgess: Sexing 101 - species # 3 - Java Sparrow - Padda oryzivora :

Walter Burgess: Sexing 101 - species # 4 - Timor Dusky Sparrow - Padda fuscata :

Walter Burgess: Sexing 101 - species # 5 - Moluccan Munia - Lonchura molucca :

Walter Burgess: Sexing 101 - species # 6 - Javan Munia - Lonchura leucogastroides :

Walter Burgess: Sexing 101 - species # 7 - Lonchura cucullata scutata - Bronze Mannikin :

Walter Burgess: Sexing 101 - species # 8 - Lonchura fringilloides - Magpie Mannikin (incorrectly called the Pied Mannikin) :

Walter Burgess: Sexing 101 - species # 09 - Lonchura cantans - African Silverbill :

Walter Burgess: Sexing 101 - species # 10 - Lonchura malabarica - Indian Silverbill :

Walter Burgess: Sexing 101 - species # 12 - Lonchura bicolor bicolor - Black-and-white Mannikin :

Walter Burgess: Sexing 101 - Species # 13 - Amadina fasciata - Cut-throat Finch :

Walter Burgess: Sexing 101 - Species # 14 - Amadina erythrocephala - Red-headed Finch :

Walter Burgess: Sexing 101 - species # 15 - Amandava amandava - Red Avadavat (Strawberry Finch) :

Walter Burgess: Sexing 101 - species # 16 - Amandava subflava - Orange-breasted Waxbill :

Walter Burgess: Sexing 101 - Species # 17 - Coccopygia melanotis - Swee Waxbill :

Walter Burgess: Sexing 101 - species # 19 - Lonchura maja - White-headed Nun :

Walter Burgess: Sexing 101 - Species # 20 - Lonchura punctulata - Nutmeg Mannikin (Spice finch) :

Walter Burgess: Sexing 101 - Species # 21 - Estrilda astrild - Common Waxbill :