The easiest way to choose a bird collar size is to know your birds weight in grams. If you don't have a gram scale, you can find one on Amazon. Cone style bird collars can be trimmed to fit at both the neck and the perimeter, so if your bird is between sizes, order the bigger size. Find out more here.
All you need to know is your bird type and bird weight. If you don't know your birds weight, just google, "How much does (your bird species) weigh?"
Please know that, that most of our Cone Bird Collars can be trimmed to fit around the neck and perimeter. Our Neck Collars and Bird Vest styles have generous hook & loop allowing for minor fitting adjustments.