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Bobwhite Population Dynamics

Long-term hunting success on a premiere quail hunting plantation in Red Hills; wise management has increased quail survival and recruitment resulting in record bobwhite densities

Long-term hunting success on a premiere quail hunting plantation in Red Hills; wise management has increased quail survival and recruitment resulting in record bobwhite densities.

This hen was originally banded as a chick (see wing tag) and later radio-tagged to monitor her survival and reproduction.

This hen was originally banded as a chick (see wing tag) and later radio-tagged to monitor her survival and reproduction.

Even on the best managed lands in the world, bobwhite populations fluctuate. In fact, quail populations, especially at high densities, can double (or halve) across a period of 2-3 years. Managers strive to produce high density quail populations for a quality hunting experience and reduce variation in population size from year to year. A hallmark of the managers Tall Timbers works with is to be able to produce quality bobwhite hunting year after year.

Bobwhite populations are a function of their demographic rates. The Game Bird Program focuses on understanding how demographic rates are influenced by internal (nutrition, behavior, genetics) and external factors (habitat management, weather, food supplies, and predation). Then we conduct studies to determine how management influences key demographic rates and how much influence these have on fall populations.

Some fundamental but important aspects of quail populations:

For all the demographic variables that potentially affect bobwhite populations, our research indicates that survival of adults, nesting rate, and chick survival are often the most important variables. Nesting success, fertility rate, renesting rate, and others are important, but less likely to drive populations. That is bobwhite populations are highly sensitive to some demographics, like survival, but less so to others, like nesting success (unless the situation is severe).

Adult survival rate drives our quail populations. Percent quail survival on Tall Timbers averages about 20% over the long term but can vary from less than 10% to 40%. These shifts in survival rate largely determine if populations are going to increase or decrease from fall to fall. Importantly, it appears that regional factors often affect survival rates. Chick survival is another key demographic for bobwhites. In years with low chick survival, populations stagnate or decline, despite good nesting rates.

Pinelands survival

Seasonal survival and quail productivity: long-term monitoring helps us find trends in demographics, and then determine causes and management actions

Bobwhite populations are linked to annual survival rates

Bobwhite populations are linked to annual survival rates

Seasonal survival has important implications for bobwhite populations.  If over winter survival is low, typically due to avian predation, then this reduces the number of breeders in the population the following spring.  If summer survival is low, then the opportunity for hens to renest is reduced as few survive the breeding season.  When summer survival is low, nest success is an important parameter because hens often only get one chance to nest.  If summer survival is high, nesting success is less important to fall populations because hens readily renest.  There is a point, however, when nest success becomes very low that even with high adult survival rate populations can be greatly reduced.

Nest survival is important but less so than adult and chick survival rates

Nest survival is important but less so than adult and chick survival rates.

There is a temporal aspect to demographics.  Strong nesting and chick production in May and June is important to growing bobwhite populations.  Late season nesting is often helpful to make a hatch a bumper year, or help when earlier hatches failed, but overall are less important to fall populations because fewer hens (perhaps only 30-40%) remain from spring.

Applying our understanding of how demographics affect populations is important because it is directly related to management.  Managers strive to increase annual survival rates without reducing nest productivity will ultimately sustain higher bobwhite densities over time.  How timber management and burning are applied is critically important to bobwhite survival rates and nesting activity.

Our long-term research on Tall Timbers and in Albany provides a unique perspective on how bobwhite populations operate demographically.  We can track trends in demographics over time, and also compare populations that increase or decrease relative to their demographics for a given year.