Most pigeons have scales on their feet (and not feathers).
However, some pigeons have a genetic variation (or two) that gives them feathers on their legs and feet (a lot of feathers or a little bit).
Foot feathering comes from variations in two genes: slipper and grouse. A bird that has the feathery versions of both slipper and grouse have an extreme form of foot feathering, called muff.
Slipper
The slipper gene comes in two versions, or alleles: ‘slipper’ and ‘no slipper.’ Pigeons inherit two copies of the slipper gene, one from each parent.
Grouse
The grouse gene is completely separate from the slipper gene. It too comes in two versions: ‘grouse’ and ‘no grouse.’ And as with slipper, pigeons inherit two copies of grouse, one from each parent.
Muff
Grouse and slipper work together to make an extreme form of foot feathering, called muff. The largest muff (the most feathering on the feet) occurs when a bird has two copies of the ‘slipper’ allele and two copies of the ‘grouse’ allele.
Different allele combinations of slipper and grouse make birds with in-between amounts of foot feathering.

Indian Fantail Pigeon – with normal feet (scales and not feathers)

American Fantail Pigeon with some feathers on its feet

Saxon Shield Owl Pigeon with long feet feathers

Reverse Winged Pouter with extreme feet feathers
Source of information: Learn.Genetics. http://learn.genetics.utah.edu
Photographer: Martina Nicolls
Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM