Heritage breeds.

A heritage breed, per the American Poultry Association, is one that is naturally mating, slow-growing (16 weeks or more to maturity), and has a productive lifetime of at least five years for hens, three years for roosters. They will brood their own clutches. They will out-perform commercial hybrids over a decade.

What they will not do is match a Cornish-Cross broiler at six weeks or a Leghorn-cross hybrid at peak lay. That is the trade. We keep these breeds because the trade is worth making.