Portions of this story originally appeared in the Tall Timbers Quail Management Handbook
Predator control has a long history in game management. Over time, the pendulum on managing predators had swung from the thoughtless killing of predators, to their protection, so that through the 1990s, most bobwhite professionals believed predator control was an outdated and ineffective management tool.
But, over the years managing predator populations has become yet another tool in maintaining huntable quail populations and is part of a solid management plan.
The list of quail predators is long and includes mid-size or “meso” mammals, raptors, and snakes. This predator dynamic has changed over time, as well due to human intervention.
Removal of top-level predators like red wolves and the Florida panther, and the loss of the fur market, have allowed meso mammal numbers to rise and with them, the need to manage their populations to help ground-nesting species like bobwhite quail and wild turkey. Hawk and owl numbers remain steady after decades of federal protection and organochlorine pesticide bans. Add in coyotes, armadillos, and fire ants and quail face a lot of obstacles to survival.
While it is unlikely that changing dynamics in predator communities are the definitive cause for occasional bobwhite declines, there is also little doubt that bobwhite are affected by property-level increases in predator numbers.
Research at Tall Timbers has focused on understanding how predators limit quail numbers and what practices can be introduced to increase quail. In the past, it was something local managers were convinced was important, but had not been resolved by research. Today, our bobwhite management system strikes a balance we call predation management and is driven by the findings of biologists and implementation of different techniques to reduce the risk of predation on bobwhites.
Nest Predation Studies
One of our first efforts in the 1990s was to identify what predators were actually depredating quail nests. Even though quail had been studied for 80 years, up until then there was no definitive study on quail nest predators.
While researchers and managers guessed at what depredated nests based on signs at the nest, these results were not verified. We were interested in which predators were actually destroying nests, determining if they left reliable signs at the nest site to help identify them, and how their relative importance as a nest predator was related to their relative abundance.
A 10-year study in the Red Hills monitored 790 nests with 24-hour infra-red surveillance video equipment, and documented 242 predation events. Some of our suspicions were confirmed— and there were some surprises.
Mammals (primarily raccoons, possums, armadillos, and bobcats) were the main nest predators on our study areas. At the time, armadillos were not considered much of an egg eater, neither were bobcats. Another surprise was the low numbers of cotton rats, foxes, and coyotes observed.
Coyotes are a minor quail nest predator, and it has been suggested they may actually benefit quail by reducing other more common species of predators, such as fox. A contrary opinion is that they also prey heavily on cotton rats and other small mammals that can buffer quail from avian predators. Such are the complexities of the issue.
Cotton rats had been considered a major nest predator of quail for decades. Now we know that they are rarely nest predators (occasionally taking an egg or two). Rather they eat the egg shells after other predators break open the eggs.
This was just one of many behaviors of predators that made signs at the quail nest unreliable to identify nest predators.
The level of snake predation on nests was also a new finding. Some snake species, such as gray rat, corn snake, and king snake, were significant predators of quail nests in some years. Snake densities on managed quail lands can be very high, so it was not a surprise that snakes were a major nest predator.
When a smaller snake depredates a nest, they often consume only a portion of the clutch and the adult quail will resume incubation after the snake leaves, even encouraging it to leave with occasional pecks and aggressive displays.
Having a complex predator community also raised the concern of compensation, that is, does reducing mammal nest predators allow snakes and fire ants to find more nests, and then nullify the effects of reducing mammal nest predators?
Our studies indeed identified some compensation for removal of meso mammal nest predators, but the result was not complete compensation, and varied from site to site.
Even when meso mammals are reduced through trapping, nest success still rarely exceeds 70%, and more typically fluctuates between 40 and 65%. In this case, snakes and ants increase their rate of depredation, thereby partially compensating for the removed mammal predators.
The next step in understanding the effects of nest predators was relating their abundance to quail demographics, to determine if there was a correlation between them.
To do so, we developed a method to “index”, or measure, what we coined as the “predator context.” The predator context is the abundance/activity of different meso mammal nest predators on a property— and it varies from place to place.
To measure the predator context, we relied on scent stations, a sand ring with a scent tablet in the middle, to attract predators that leave their foot print. This simple system, when properly distributed throughout a managed quail land, provides a picture of the predator index.
Some areas have large numbers of coyotes and few fox, others have large numbers of armadillos, etc., and the different mixes provided insights into which predators had the greatest effect on nesting.
The Predator Index was then compared to measures of reproductive success obtained from radio-tagged quail measured on study sites across the Southeast. Our early findings showed a significant negative correlation between meso mammal predator numbers and nesting rate, nesting success, and total population productivity.
It was apparent that production of young quail was correlated to the abundance of nest predators. This was an important data set, because it was the first to show a relationship between predator context and quail demographics.
Simply put, the more nest predators a site had, the less likely there would be a good hatch.
It is important to clarify that having a high predator index did not preclude having a good hatch, but reduced the odds of having a good hatch. Likewise, having a low predator abundance did not ensure a good hatch, but increased the odds of one.
This messy result can perplex some, but the reality is that predator-prey relationships in the Southeast are extremely complex, and predation on quail is affected by weather, drought, food supplies, buffer species, the predator context, and more.
Increasing the odds of a good hatch helps increase bobwhite populations, as managers are always managing against time, and the bad things that happen to quail populations. Taken collectively, this data suggested that when predator abundance is high, reducing their numbers should result in increased quail numbers, or reduced variation in quail numbers, or both.
Predator Removal Research
Our correlative research to this point provided us with the knowledge to conduct a predator removal study to look at the effects on quail populations. Up to this date, there had been a lot of conjecture, but there were no properly-designed studies in the Southeastern U. S. that had the necessary background information to conduct sound experiment.
The Cooperative Predator Management project was forged in 2000, between the University of Georgia, Tall Timbers, the Albany Quail Project and the USDA Wildlife Services.
A monumental undertaking, this study was partly an outgrowth of illegal predator control on some private lands, and inconsistent legal methods permitting managers to conduct predator control. Clearly some information was needed to help both managers and policy makers find a solution to predation.
The Cooperative Predation Management Study was a seven-year study, and was the largest known predator-prey study on northern bobwhites to date. The study included four study sites in two states, >4,000 radio-tagged bobwhites, >4,900 mammalian predators removed, and nearly 1,300 nests monitored.
After one year of pretreatment data, known nest predators were reduced on two of the sites for three years, while the other two served as controls. The treatments were then switched for another three years. We monitored radio-tagged quail for their survival and reproduction, placed surveillance video cameras on nests, captured and banded broods, measured nest predator abundance, and censused quail in the fall.
Despite a severe drought during the project, and an outbreak of the contagious distemper virus on some study areas, radio-tagged bobwhites incubated more nests on trapped sites (0.77 nests per hen) than on non-trapped sites (0.59 nests per hen) and fledged an additional 1.7 chicks per hen on trapped sites.
This equaled a 44% increase in recruitment on trapped versus non-trapped sites—a significant increase in chick production. Predator numbers, as measured by the Predator Index, were lower during trapping, but about the same number of animals were removed each year, indicating how quickly these populations rebounded and/or reoccupied these sites once trapping stopped for the year.
Fall quail populations were generally higher on sites with a low Predator Index, and in most cases trapping was required to obtain this low index, but the results were variable. Fall populations on some of the sites responded dramatically to predator removals, whereas others less so, potentially a result of severe drought experienced or compensation by other predators. On one site, snakes partially compensated for the reduction in mammals by eating more quail nests.
It is good to remember that the predator community on bobwhites is much larger than the meso mammals, which is one more reason why predation management is a system, not just reducing one group of predators through trapping.
Sites with the lower predator index had higher than average populations more often than not, and these occurred when nest predators were trapped.
From a management perspective, an important result of predator trapping was that it increased chick production, and lowered variation in nesting demographics from year to year. This is a key result, as our management philosophy to reduce annual variation in populations is just as important as having high densities of quail. When quail are declining regionally due to weather, predator control reduced the decline, allowing for a faster recovery under better weather conditions.
So, predator control may not eliminate a decline when times are tough, but may reduce the level of decline. Managing to reduce variation in quail populations is important to maintaining high quail densities because it takes years to recover from a serious decline.
The predator index monitoring technique was refined and is now commonly being used on numerous properties, and year-round trapping with a special permit became a reality in Georgia, and other states as a result of this study.
The basics of predator management
Predation management is using both preventative and direct methods to reduce the effects predators have on survival and nesting of bobwhites. There are four major methods to manage predators.
First, increase suitability of habitat for quail to reduce the risk of predation.
Second, reduce the suitability of a property for some predators, by removing the habitat they rely on.
Third, provide supplemental feed to increase buffer prey species and reduce predation on adults and nests.
Fourth, monitor your nest predator population, and use trapping methods to reduce their number when necessary.
Collectively, predation management helps reduce, but never eliminate, the effects of predators on bobwhites. Predation management requires consistent and meticulous dedication to the application of habitat management, monitoring, and mammalian predator reduction when needed, to ensure long-term success and optimize bobwhite density.
