Two techniques for gendering animal characters are tertiary sexual characteristics (like eyelashes) and adding "human" gender traits to animals (like wider hips and humanlike breasts), whether in a subtle fashion or not. Here are the standard masculine and feminine characteristics for each form.
Anthro, Furry, Or Petting Zoo Person (PZP)
Masculine: male human build, wider shoulders, mens' clothing (usually fully dressed), accesories (like a baseball cap), often has humanlike head hair (feathers that look like human head hair if a bird), thicker eyebrows, sometimes smaller eyes
Feminine: female human figure, wider hips, usually has humanlike breasts, womens' clothing (usually fully dressed), accesories (like a purse, a bow/bows, and/or jewelery), very commonly has humanlike head hair (feathers that look like human head hair if a bird), thinner eyebrows, eyelashes, wider eyes, sometimes bigger eyes, more slender muzzle in canids
Semi-Anthro, Demi-Furry, Or Borderline Petting Zoo Person (BPZP)
Masculine: part male human build, part animal build, wider shoulders, mens' clothing (either half-dressed or fully dressed), accesories (like a baseball cap), sometimes has humanlike head hair (feathers that look like human head hair if a bird), thicker eyebrows, sometimes smaller eyes
Feminine: part female human figure, part animal figure, wider hips, sometimes to oftentimes having humanlike breasts, womens' clothing (either half-dressed or fully dressed), accesories (like a purse, a bow/bows, and/or jewelery), sometimes has humanlike head hair (feathers that look like human head hair if a bird), thinner eyebrows, eyelashes, wider eyes, sometimes bigger eyes, more slender muzzle in canids
Critter or Funny Animal
Masculine: less curvaceous bipedal animal build, mens' clothing (often half-dressed), accesories (like a baseball cap), very occasionally has humanlike head hair (feathers that look like human head hair if a bird), thicker eyebrows, sometimes smaller eyes
Feminine: more curvaceous bipedal animal figure, sometimes wider hips, womens' clothing (often half-dressed), accesories (like a purse, a bow/bows, and/or jewelery), occasionally has humanlike head hair (feathers that look like human head hair if a bird), thinner eyebrows, eyelashes, wider eyes, sometimes bigger eyes, more slender muzzle in canids
Feral or Natural Stance Animal
Masculine: less curvaceous animal build, darker skin/fur/feathers/scales/e.t.c., accessories (like a collar, e.t.c.), rarely has humanlike head hair (feathers that look like human head hair if a bird), thicker eyebrows, sometimes smaller eyes
Feminine: more curvaceous animal figure, lighter skin/fur/feathers/scales/e.t.c., accessories (like a collar, e.t.c.), rarely to very occasionally has humanlike head hair (feathers that look like human head hair if a bird), thinner eyebrows, eyelashes, wider eyes, sometimes bigger eyes, more slender muzzle in canids, sometimes more slender animal body shape
Another technique is to omit gender clues (except the biologically accurate ones) altogether or gendering only through voice and/or commentary (other characters referring to the character either as he, his and him if male or she and her if female).
