bedrock-samples/resource_pack/render_controllers/chicken.render_controllers.json

{
  "format_version": "1.8.0",
  "render_controllers": {
    "controller.render.chicken": {
      "geometry": "geometry.default",
      "materials": [
        { "*": "Material.default" },
        { "leg*": "Material.legs" }
      ],
      "textures": [ "texture.default" ]
    }
  }
}