The well-known Russian ornithologist Prof. Peter Sushkin described it as a distinct species from Bashkortostan (Bashkiria) in 1897, a highly acclaimed discovery. However, its breeding grounds never been discovered. Since then, there has been a long-standing debate over the taxonomic position of Anser neglectus. Taxonomists have argued that Anser neglectus belongs to the group of A. fabalis Lath. because of its close resemblance with A. f. fabalis.
At the beginning of the 20th century, large numbers of the Sushkin’s goose were observed in three winter quarters: on two lakes in the Republic of Bachkortostan, in the surroundings of the town of Tashkent in the Republic Uzbekistan, and in the puszta Hortobágy in eastern Hungary. It is a pity that taxonomists did not thoroughly compare the Russian and Hungarian ornithological papers concerning the former presence of Anser neglectus in these areas, because these rich sources refer to characteristics that would cast serious doubt on the classification of Anser neglectus as a subspecies, an individual variation or mutation of A. f. fabalis.
Sushkin’s goose, though a typical Taiga Bean Goose, distinguished itself from other taxa of the Bean Goose by its plumage, its field identification, by its specific “Gé-gé” call, the size of its bill, and by its preference for warm and dry winter haunts. A. neglectus should therefore be considered a separate, fully distinct species, sensu Stegmann (1935) and Stegmann in Schenk (1931/34), if we follow the established criteria in bird systematics of Tobias et al. (2010).
Between 1908 and 1911, an estimation of up to 150.000 individuals of A. neglectus wintered in the Hortobágy puszta. Approximate counts for both other winter quarters are not available. The last living birds were seen in the zoological garden of Budapest in 1934. Since then, A. f. fabalis and A. s. rossicus “Type neglectus” (i.e. A. f. fabalis and A. s. rossicus with a color of the bill and the legs, similar to the former A. neglectus) have been observed sporadically on the breeding grounds and in the winter quarters of both taxa. However, the true A. neglectus seems to be extinct. Its sudden disappearance may be related to the Tunguska event, the catastrophe in 1908 that may have caused genetic mutations. This hypothesis is considered to be the most likely, among other available hypotheses about its extinction.