Morphological differences and migration patterns of greater and lesser snow geese in New York State

Lesser (Chen caerulescens caerulescens, LSGO) and greater snow goose (Chen caerulescens atlantica, GSGO) populations have increased substantially in the past 50 years. The light goose conservation order established in 1998 (Canada) and 1999 (U.S.) aimed to increase snow goose harvest and stabilize populations because breeding ground abundance was thought to negatively impact arctic ecosystems. In the Atlantic flyway, where LSGO and GSGO are both available for harvest, techniques to differentiate subspecies in the field using morphology may be helpful for harvest management because mid-continent LSGO are similar to 16 times more abundant than GSGO (n < 1,000,000). We investigated percentages and spatial distribution of LSGO and GSGO in the spring harvest in NY as this information could be useful for snow goose population and harvest management decisions. We developed a discriminant function analysis (DFA) using heads from snow geese harvested during spring 2016 to 2018 and were able to differentiate between LSGO and GSGO with 95.5% accuracy. Based on the DFA results, we estimated that spring harvest in New York state was 80% GSGO and 20% LSGO. Using band recoveries from autumn and spring harvests, we also identified that GSGO harvest occurred farther west during spring than autumn and in the 2010s than prior two decades. Our results indicate that GSGO comprise most snow goose harvest in New York state and provide evidence for a shift in spring migration patterns of GSGO since the 1990s.

Automated summary

The populations of lesser and greater snow geese have significantly increased in the past 50 years. Measures were taken in Canada and the United States in 1998 and 1999, respectively, to stabilize the populations and increase the harvest. Differentiating between the subspecies using morphology can be helpful for managing the harvest. Analysis of the spring harvest data in New York state shows that 80% of the harvest consists of greater snow geese, indicating a shift in their migration patterns since the 1990s.