Lake Hornborgasjön is situated in south-western Sweden, and is one of the most interesting wetlands in the country. The Lake Hornborgasjön Bird Observatory was formed in 1983 by local volunteers, before the lake restoration process during the 1990’s. The aim was to ensure proper monitoring of the outcomes of the lake restoration from a biodiversity point of view, mainly focusing on the avian fauna. Since then, several census and survey projects have been running continuously, covering the following areas and species:

• Waterfowl monitoring: Simultaneous counting of all waterfowl (in this case extended to swans, geese, dabbling and diving ducks, grebes, rails, waders, herons, gulls and terns) in predefined sectors covering the entire lake during autumn and spring migration periods
• Monitoring birds on shoreline meadows: Using line transects the number of birds utilizing the shoreline meadows for breeding or foraging are counted twice annually, during breeding season.
• Cranes: monitoring of the number of staging cranes during spring and autumn migration (presented in detail at the first IBOC conference; Hermansson et al., 2014).
• Geese: the number of moulting Grey-lag geese and Canada geese in the lake area is counted in June every year.
• Species-specific counting of breeding birds: Swans, White-tailed eagles, Marsh harriers, Kestrels, Black-headed gulls, Black terns and Common terns, Black-necked grebes and Great reed warblers are counted every year. Some years, also the numbers of breeding Crested grebes, Red-necked grebes, Cormorants and Grey herons are being counted.
• Bird ringing, primarily of passerines, terns, gulls, waders and raptors.