CKWRI :: Low Carryover From 2009 Drouth Is Impacting 2010 Quail Season

Low Carryover From 2009 Drouth Is Impacting 2010 Quail Season

South Texas Bobwhite Quail

By Colleen Schreiber
Reprinted from Livestock Weekly, November 4, 2010

            KINGSVILLE — Through the eyes of the avid bobwhite quail hunter (and perhaps even through the eyes of the bobwhite quail), things are looking pretty darn good right about now. In fact, they’ve been looking pretty darn good for most of 2010.
            To date, for South Texas, 2010 is the second wettest year over the past 100 years. What has made this record rainfall so ideal though is that it was perfectly timed for bobwhite quail — both reproduction and habitat. Rather than coming all at once, or during the fall and winter months, which has been the case over the last several years, the rains were well distributed over the first eight months of the year.
            In their annual quail forecast for the various regions, Texas Parks and Wildlife analysts report that in South Texas a wet winter, spring and summer along with relatively few 100-degree days made for ideal breeding and nesting conditions. It makes sense, then, that quail enthusiasts might be giddy with excitement. But hold on just one minute. Read on through the rest of that forecast and that giddiness likely turns to disappointment.
            The report reads: “The average number of bobwhites observed per route was 8.61 compared to 5.2 last year. This is well below the long-term mean of 18.6 and is predictive of a below-average hunting season.”
            The limiting factor, the report says, is low carryover. That makes sense given that in 2009 South Texas suffered through the worst one-year drouth in more than a century. From October 2008 through August 2009 the South Texas Plains only received 6.6 inches of rain according to the Falfurrias Weather Station. As a result, many landowners shut down quail hunting altogether.
            Fidel Hernández is an associate professor in the Department of Animal, Wildlife, and Range Sciences and holds the Alfred C. Glassell, Jr., Endowed Professorship for Quail Research at the Caesar Kleberg Wildlife Research Institute. Hernández, who has been with CKWRI for the past 12 years, is a South Texas native and has seen the boom and bust cycles even in his short tenure.
            Several South Texas properties managed specifically for quail cooperate with CKWRI on various quail research projects. One aspect of the research is conducting quail counts. Over the years, they’ve found that in South Texas, the best time of the year to conduct such surveys is in November because of late hatches. And because people generally don’t hunt quail in South Texas until December, waiting to get a more accurate count makes sense.
            So, Hernández hasn’t yet done quail surveys on these properties. However, Hernández agrees with TWPD’s general forecast for South Texas that counts will be lower than hunter expectations. He says it’s not unusual for quail enthusiasts to have high expectations in years when everything appears to be perfect in terms of reproduction and habitat, but being a scientist, he has a valid explanation as to why expectations often fall short of the mark in such situations. In looking at the growth rate of bobwhite populations in South Texas, CKWRI research finds that about 31 percent of the time the population is declining, 20 percent of the time it is stable, and 37 percent of the time it is increasing.
            The real take-home message, though, which is applicable, in particular, to the upcoming season, is that the probability of a population doubling only happens about five percent of the time and tripling is rare. Tripling only occurs about one percent of the time. Furthermore, quadrupling of a population does not appear to be biologically feasible.
            “It doesn’t matter how good the habitat is, and it doesn’t matter the locale,” Hernández says. “A quail in South Texas is capable of laying lays 12 eggs, and a quail in Florida is capable of laying 12 eggs regardless of its environment. Three or four nesting attempts are the maximum that is biologically possible.”
            So while the habitat looks great this year, and habitat does matter, Hernández reiterates that because most properties are starting with a low population, even if the population doubled, quail density will still be relatively low compared to the expectations based on habitat conditions. In fact, it typically takes two good years back to back, he says, for a quail population to return to above-average levels after a bust year.
            He offered still more data using precipitation as a benchmark to back up his points. Looking at rainfall January through August, which for quail is most critical, he came up with a rudimentary model to predict population growth. The fall density the previous year must be taken into account.
            Using a fall density of .2 bobs per acre (one bobwhite to five acres), the model indicated that it would take 16 inches of rain during that critical time period for the population just to be stable. With 20 inches it showed to be slightly increasing, but it took 25 or more inches during that critical eight-month period for the population to double and 30 inches for it to triple.
            “The point is that human expectations generally tend to be higher than what the population can actually produce,” he reiterates, “because South Texas rarely gets 25 inches of rain January through August.”
            It just so happens that 2010 is one of those rare years. Many places in South Texas, in fact, received upwards of 25 inches of rain during that ideal time. Again, though, the problem is that 2009 bobwhite density across much of South Texas was extremely poor, from .2 bobwhites per acre on the high end to .03 bobs per acre, which is one bobwhite per 20 to 30 acres, on the low end. Given all that, Hernández predicts that 2010 will be an average to slightly better than average year.
            Currently TWPD’s harvest recommendation for the 120-day bobwhite season is set at a 15 bird per day bag limit. Because the harvest regulation is arbitrary, it is theoretically possible to overharvest and exploit a population and drive it to extinction and be well within the legal regulations. TPWD’s harvest regulations are appropriate from a broad statewide perspective, but they are not designed to manage harvest on a smaller scale. In fact, CKWRI scientists argue that it is at the smaller spatial scale, even ranch by ranch, that harvest should be managed.
            CKWRI researchers have been working for the past four years to develop a way to better manage harvest, leave adequate breeding numbers and thus have a sustainable population not just in the good years but in the really poor years, and not just on a year to year basis but over a long period of time, for example, for the next 100 years. They call it sustained yield harvest.
            To develop a model for sustained yield harvest, three variables are necessary: fall density, spring density, and overwinter mortality.
            CKWRI’s quail research team recently developed a helicopter surveying technique for estimating fall and spring quail densities. The number of coveys counted during the helicopter-flown transects is correlated to density of quail. The technique was developed and tested not only in South Texas but in the Rolling Plains as well, and is considered an acceptable method.
            “It’s not perfect, but it is the best technique given the ones that are available,” remarks Hernández.
            Additionally, mortality estimates based on long-term field studies were developed for both South Texas and the Rolling Plains. Factors include mean survival time, mean clutch size, nest success, and chick survival. All of this biology, Hernández points out, went into the development of the model.
            “That’s the key factor,” he stresses. “The model is based on biology.”
            Again, the idea was to determine the level at which a population can be harvested each year if the goal is sustainability over a 100-year period. What they found was that approximately 20 percent of the fall population could be harvested year in and year out and the population would still be sustainable 100 years out. Above about 30 percent annual harvest, Hernandez says, the population becomes extinct at somewhere between 50 and 75 years.
            Northern latitudes, scientists say, can withstand higher harvest rates, perhaps as high as 40 percent. That may be explained in part by Fred Guthery’s population model which found that South Texas quail are better survivors but poorer producers, and up north they’re better producers and poorer survivors. Guthery, a former CKWRI quail scientist, now holds the Bollenbach Chair in wildlife ecology at Oklahoma State University.
            “The reason populations in the north can sustain a little higher harvest is because a large majority of them are dying, thus they retain the population by having higher reproduction,” Hernández explains. “In the south they tend to be a little bit better survivors, which means the more you hunt, the more breeders you’re likely taking out.”
            Still, Guthery’s model suggesting a 20 to 25 percent harvest for South Texas correlated to the newer model. Another interesting finding from the recent modeling study, Hernández says, is that at a 20 percent harvest rate, hunters actually have more opportunity, over the long term, to harvest birds than they would at a 40 percent harvest rate.
            “It’s a little counter-intuitive. At a 40 percent harvest rate, you’re harvesting more birds initially, but because the population is declining, you’re harvesting fewer and fewer birds as time goes on. So not only does a 20 percent harvest rate make the population sustainable, it offers the most hunting opportunity over the long haul.”
            Hernández noted that the 20 percent harvest rate would be for an average year. However, when starting from a particularly low spring density, that number might need to be adjusted.
            Density, he reminded, is measured in birds per acre.
            “A fall density of one bird per acre is phenomenal,” he notes. “Two bobwhites per acre are possible though fairly rare. At .5 bobwhites per acre, or one bobwhite per two acres, hunting starts to get good from about this level forward,” he continues. “At about .2 bobwhites per acre, or one bobwhite per 10 acres, at that level and down that’s a really low population.
            “So in theory, if you’re already starting at a bobwhite density of .2 in the fall, taking natural mortality into account, hunting could push the population way below what is needed for it to rebound. Thus, based on our modeling, the minimum spring density necessary for repopulation is about .2 bobs per acre.”
            Given all this, in simple terms, if the sustained yield harvest technique is used, a property with an estimated 1000 bobs, using the recommended 20 percent harvest rate for South Texas, hunting must cease once 200 quail are harvested.
            Currently Hernández knows of only one ranch that is using the sustained yield harvest method, but he’s hopeful that as more managers become aware of the technique and more quail managers begin using the helicopter surveying technique for estimating densities, it will become a standard in quail management.
            Possibly the best thing that the South Texas quail population has going for it, Hernández says, is that there are still many large contiguous tracts of land, and on these lands quail management is active, not passive. However, like many, he is becoming increasingly concerned about the monoculture stands of exotic grasses, particularly Kleberg bluestem and to an extent buffelgrass, which have moved in and have taken over prime quail habitat.
            Unlike buffelgrass, which offers some limited use for quail, Kleberg bluestem, Hernández says, has practically no merit for quail.
            “Kleberg bluestem is a sod-forming grass. It spreads like carpet,” he explains. “It doesn’t make for good quail nesting habitat, and the seed isn’t a good quail food. Plus, it’s really aggressive, more so than buffel.”
            Hernández and the team of CKWRI scientists have several studies on exotic grass invasion underway. Much has been learned, but as is typical with research, one overturned stone leads to another and another. That said, they are committed to finding some management solutions.
            The team of quail scientist also recently completed a 10-year study on the Encino Division of the King Ranch, and a new long-term project is now underway on the Santa Gertrudis Division. The focus of this study, in part, will be to find out if and to what level habitat manipulation mitigates the effects of drouth on quail populations.
            “We want to know how much can we really influence the quail population with habitat manipulation, and how much is really weather-related,” remarks Hernández. “We all preach habitat, habitat, habitat, but take a year like last year on places where they do all this habitat manipulation and even feed, and yet they still weren’t able to hunt quail.”
            The study is essentially just getting underway. The 2009 drouth made trapping of quail this past spring extremely difficult.
            “Just trying to get 10 quail radio collared was a hassle,” he says.
            The first phase of the project entails gathering a year’s worth of pretreatment data, such as the population before habitat manipulation is implemented. The second phase will involve habitat manipulation on an ecosystem level.
            “One area might need to be burned; another might need disking or brush control. We know what good quail habitat should look like, so it will be a matter of getting a piece of property to look like that, and then we’ll evaluate whether or not such manipulation affects the population year in and year out,” he reiterates.
            Hernández is hopeful that this study will definitively answer such questions, though the answers won’t come overnight.

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