How come you can hunt snow geese in the spring?

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In 1999, special late spring conservation seasons were implemented to reduce snow goose populations. The stated objective of management actions was to reduce the abundance of Central and Mississippi Flyway (CMF) light geese to 50% of the level of the late 1990s (peak estimate of 3.1 million in the US midwinter survey in 1998).

The abundance of CMF geese increased at an average rate of 3.5% per year prior to 1999 (1970-1999, P <0.001), after which Management Actions were implemented. Midwinter survey estimates declined for several years after 1999 (Graph 1) but rebounded to near 3.1 million in 2007. The estimated growth rate from 1999 to 2007 was 0.0 (P = 0.98). A growth rate near 0 is also estimated by Lincoln estimates (1.002, Pers. Comm. Alisauskas). (A 2007 midwinter index of 3.7 million CMF geese would have been expected if the population continued its pre-management action trajectory.)

Figure 1

Fig 1. Midwinter survey indices of Central and Mississippi Flyway light geese (Western Central Flyway and Midcontinent Populations) in the United States, 1970-2007.

For greater snow geese (GSG), the stated objective of management actions was to reduce abundance to a spring staging ground survey index of 500,000 geese.

The GSG population had increased at an average of 6.9% per year during 1970-1999 (P<0.001). During 1999-2007 the population has increased at 3.3% per year (P=0.126).

Population indices declined after management actions were implemented in Canada in 1999. New GSG survey methodology was implemented in 2004 which increased uncertainty about the population response to the management actions. The subsequent large increases in population indices could not be reconciled with available demographic data and may have been due to increased efficiency in the survey. Greater snow goose analyses suggest that the population has been at least stable (and probably declining) since the implementation of management actions in 1999 (CWS 2006). The preliminary 2007 estimate was 1,019,000.

It appears that liberalized seasons in the Altantic Flyway and management actions in Canada have at least reduced the annual growth rate of this population, but the population remains well above the Atlantic Flyway objective.

Figure 2

Fig. 2. Estimated number of greater snow geese during spring staging surveys.

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