Silkie Hen are available in Sunshine Islands.
To unlock the black Silkie Hen, you need to ship one S-Rank Egg. The only way to earn an S-Rank on your Eggs is to have your Chicken win the Chicken Festival on Summer 07. Your Chicken will need to have 8 or more hearts to be declared the winner.
Silkie Hens cost 4,500 G each, and produce 1 Silkie Egg every 3 days. You can hatch more Silkie Hens by hatching Silkie Eggs.
Eggs and Silkie Eggs can be converted to Mayonnaise by using the Mayonnaise Maker machine.