www.trakus.org is a reference site containing tens of thousands of photos and lots of accompanying data, which was established to collect and share anonymous information about the birds species that can be found in their natural habitats across Turkey.

www.birdtheme.org is an incredible database where every bird themed stamp can be found. It was the site I referred to the most while putting this collection together – it still is. Simply a boon for those interested in bird themed stamps.

www.delcampe.net is an online marketplace and auction house for stamps with trustworthy users that also comes in handy for price-checking.

PostBeeld has a vast amount of stock. More than 200,000 different postage stamp series, in various conditions. However, the strongest point of PostBeeld is its stock turnover. Almost every day they add hundreds to thousands of stamps to their inventory, so each time you visit postbeeld.com you are almost always likely to find something of interest to you for your collection.