Latham's Snipe Gallinago hardwickii Population Trends in the Tokachi Plain, Hokkaido

Abstract

In the Tokachi Plain, eastern Hokkaido, the population trends of Latham's Snipe Gallinago hardwickii were clarified by comparing census results obtained in transect surveys made in late April to early July 1978-1991 with those in the same season of 2001. The average number of birds counted decreased significantly from 3.5±2.9 (average±SD)in 1978-1991 to 2.7±3.0 in 2001. Among the 38 2-km transects made, between 1978-1991 and 2001 the number of birds recorded decreased in 22 transects (57.9%), increased in 11 (28.9%), and remained the same in five (13.2%). When transects were classified into three types; A=agricultural land in both survey periods, B=agricultural land with woodland (more than 20% of the transect is adjacent to woodland) in both survey periods, and C=agricultural land in 1978-1991 which changed to agricultural land with woodland in 2001, the average numbers of birds decreased significantly in Type A habitat, but remained unchanged in habitat types B and C. Agricultural land with woodland is considered to be a favorable habitat because Latham's Snipe often utilizes isolated woods as a preferred nesting site. The results indicate that during the past 10 to 20 years the numbers of Latham's Snipe have decreased in agricultural land, but have remained basically unchanged in more-suitable habitats. Additionally, results showed that by 2001, 10% of 64 transects in which censuses were conducted in 1978-1991 had changed into habitat unsuitable Latham's Snipe. This suggests an overall decrease in the area of favorable habitat for this species in Hokkaido.