The purpose of annual hunting regulations is to keep harvests at levels compatible with a population's ability to maintain itself. The regulatory tools that exist to do this are framework regulations and special regulations. Framework regulations are the foundation of annual regulations and consist of the outside dates for opening and closing seasons, season length, daily bag and possession limits, and shooting hours. Although the earliest and latest dates within which states may hold hunting seasons are set by the Migratory Bird Treaty Act, in practice most frameworks dates have been more restrictive; historically, dates close to October 1 through January 20. Under the Act, season lengths may not exceed 107 days. In practice, season lengths have fluctuated with bird abundance. Traditionally, season lengths have varied by Flyway, with seasons being the longest in the Pacific Flyway and the shortest in the Atlantic Flyway, reflecting differences in the abundance of birds, number of hunters, and other factors. The number of birds of a species or group that can be harvested in a day is defined as the daily bag limit. Traditionally, bag limits have been large for birds that are highly productive, very abundant, short-lived, or lightly hunted. Flyway differences exist, with daily bag limit being most liberal in the Pacific Flyway and most restrictive in the Atlantic Flyway, for the same reasons that the season lengths differ. Shooting hours limit the time of day when migratory birds may be harvested, and have rarely been changed except when hunting seasons have become very restrictive. Since 1918, one-half hour before sunrise to sunset has been the traditional shooting hours.
Special regulations consist of framework regulations that are applied on a small scale. These consist of split seasons, zones, and special seasons. States have been allowed to divide their hunting period for most species and groups of birds into 2 or sometimes 3 nonconsecutive segments in order to take advantage of species-specific peaks of abundance. Zoning is the establishment of independent seasons in 2 or more areas (zones) within a state for the purpose of providing more equitable distribution of harvest opportunity for hunters throughout the state. Generally, special seasons focus on those species considered to be more lightly utilized than others. Special seasons are usually, but not always, in addition to the regular season. Special seasons currently exist for some teal, wood duck, sea duck, and resident Canada goose populations.
There are a number of other regulatory tools. Closed seasons occur when a species' abundance is insufficient to withstand harvest. For example, canvasback seasons, which currently are open, have been closed in the recent past. Permits are effective regulatory mechanisms that allow hunters to take a limited number of birds of a certain species. Recent examples of the use of permits have been with some Canada goose populations and with tundra swans. Quotas are defined as predetermined apportionments of a limited resource. Recent examples of quotas have been with some Canada goose and sandhill crane populations.
Harvest regulations are published annually in the Federal Register; opportunity for public comment is part of the regulatory process.