Reliable hunting bag statistics are a prerequisite for sustainable harvest management. Recently, Internet-based hunting bag reporting systems have been introduced in some European countries, e.g. Denmark, which may enable faster and more detailed reporting. However, reporting of waterfowl bags on a species-specific level may be biased from the individual hunters' ability to correctly identify species, particularly because juvenile birds can only be identified from subtle differences. We assessed hunters' ability to identify the five goose species huntable in Denmark. Identifications were made from a line-up of ten full-bodied geese including adults and juveniles. From a total of 2160 identifications made by active hunters, 85.5% were correct while 14.5% were assigned to a wrong species. Active hunters had on average an identification accuracy of 76.0%, highest for Canada goose (99.1%) and lowest for white-fronted goose (74.6%) and bean goose (73.7%). Identification accuracy was significantly lower for juvenile than for adult individuals of white-fronted and bean geese. Correcting the official Danish Bag Record (2013/2014) for identification accuracy, the bags of white-fronted and bean geese increase by 56.5 and 104.4%, respectively, while the bags of greylag and pink-footed geese decrease by 6.7 and 9.0%; the bag for Canada goose remains unchanged. Although identification accuracy is probably higher under field conditions, the study documents that inaccurate species identification is a source of bias in national bag statistics. Hence, improving identification skills by hunters is important to improve bag data accuracy when based on Internet reporting.
