Birdwatching in Bulgaria - Tour company site with photo gallery. - http://www.birdwatchingbulgaria.net/
Birdwatching Bulgaria - Overview, checklist, birding areas, tours, and information about the country. - http://www.birdwatchingbulgaria.com/
Birding in Bulgaria - Tour company site with checklist of Bulgarian birds and information on important wetlands and their birds. - http://www.viapontica.com/