I see that there is a cap of 1 listed for the Emerald Hatchling and the Topaz Hatchling. I have 2 Topaz Hatchlings and have the option to buy more. I have 1 Emerald Hatchling and have the option to buy more, so obviously they are not capped at 1 each. I can confirm, though, that th Emerald Sparrow and Topaz Sparrow each are capped at 1.