They’re custom and they look pretty comfortable.
From the article:
“Meet Gator the goose, who wears custom sandals which were made for him by his owners so his feet don’t get sore after too much walking on concrete. Bob and Lauree Strouse designed the fancy footwear to protect his webbed feet on the pavements of St Augustine in Florida. Described as a ‘rescue goose’ by his owners, Bob and Lauree picked up their pet from the side of a lake filled with hungry alligators calling him ‘Gator Bait’, a name which has since been shortened.”