These birds were produced as 'Murano Style' glass along with cats, penguins and I think there is a dog here on the board somewhere. They were made in Asia for Crystal Clear Collectables, Leonardo Glass and Badash Glass. The cat is still available from Amazon... I believe.
There are at least two for sale on eBay at the moment listed as Murano, and in the past I have seen them being sold on USA eBay for over $100 because they were described as Murano.
I will see if I can find the link to the dog!!