THE PACKSADDLE BOBWHITE MORTALITY STUDY:

A FINAL 5-YEAR PROGRESS REPORT

 

Prepared by:

Stephen J. DeMaso, Upland Game Biologist, Oklahoma Department of Wildlife Conservation, OKC, OK 73105

Scott A.Cox,Wildlife Research Technician, Oklahoma Department of Wildlife Conservation, OKC, OK 73105

Scott E. Parry, Contract Wildlife Research Technician, Arnett, OK 73832

July 1997

 

 

A LITTLE HISTORY.……

 

Northern bobwhites are hunted in over 30 states. In Oklahoma, about 95,000 hunters harvest about 2.0 million

bobwhites annually. However, Oklahoma, like many states in the southeast, has not been immune from the steady decline in bobwhite populations since the early 1970's. Suspected reasons for the decreasing and fluctuating bobwhite populations in Oklahoma include habitat changes, changes in agricultural practices, weather, disease, predation, and overharvest. Other unidentified factors may also contribute to the declines.

 

A QUAIL PROBLEM...

 

Supplemental feeding is commonly used in Oklahoma and throughout the bobwhite's range in an attempt to enhance bobwhite populations. Supplemental feeding has been debated by wildlife biologists and managers as a valuable wildlife management technique. Many wildlife professionals believe that feeding may concentrate bobwhites, thereby increasing predation concentrated birds. Feeders may also increase opportunity for transmission of diseases and parasites.

 

INITIATION OF RESEARCH. ..

 

The Oklahoma Department of Wildlife Conservation (ODWC) initiated a bobwhite mortality study in the spring of 1990 in an attempt to understand the reasons for declining bobwhite populations. The goals of this study were to evaluate causes and rates of mortality, the effects of supplemental feeding on bobwhite survival, examine reproductive success, and spring and fall movements of bobwhites. The field work for this study began October 1, 1991.

 

LOCATION OF STUDY AREA. ..

 

The study is being conducted on the Packsaddle WMA, located in southern Ellis County, in western Oklahoma (figure 1). The area consists of rolling sand hills vegetated with shinnery oak mottes, plum thickets, sunflower covered blowouts and ragweed flats. On any given year, this native habitat may produce more than 1 quail/acre. Two study sites, each about 1200 acres, and a 1000 acre buffer zone are being used on the WMA. The eastern side of the study area contains supplemental feeders filled with sorghum {milo); one in the center of every 20 acres and is used as a treatment. In theory, the home range of a covey of bobwhites is about 40 acres, therefore, every covey on the feeder area should be exposed to supplemental food. The western side of the study area contains no feeders and is used as a control. The areas are separated by the buffer zone. Other wildlife management techniques used on the research areas include routine strip discing, prescribed burning, and seasonal cattle grazing.

 

RESEARCH METHODOLOGY AND FINDINGS. ..

 

Quail Density:

Line-transect-flush counts were conducted on horseback in the fall (October) to estimate bobwhite density prior to hunting season and in the spring {March) to estimate post-hunting density. Counts were conducted on both feeder and non-feeder areas. These counts give us an idea of reproductive success and over-winter survival. Bobwhite densities did not differ between feeder and non-feeder areas. Bobwhite densities averaged about 1 quail/2 acres in the fall and 1 quail/15 acres in the spring for the 2 study areas. Covey sizes averaged about 15.0 birds/covey in the fall and 9.0 birds/covey in the spring.

 

Quail Mortality:

To evaluate bobwhite mortality, radio telemetry was used to monitor activity of the birds on the study areas. Wild bobwhites were trapped and tagged with a leg band. In addition 3 to 4 birds/covey were fitted with radio

transmitters weighing about 6 grams. Transmittered birds were located daily and continuous trapping was required to replace birds that have died. This resulted in a constant sample size of 40 to 50 birds/study site (80 to 100 radioed birds total) being located every day. To eliminate bias due to trapping and/or handling, birds had to survive 7 days following capture before being included in the data analysis.

 

Causes of mortality were determined by examining physical evidence at the "kill site" where the transmitter was found and retrieved. Causes of mortality were classified as capture related, hunting, mammalian predation, avian predation, weather, and unknown (no evidence of what caused the bird's death. Entire birds found with no apparent cause of death were necropsied at the Oklahoma Animal Disease Diagnostic Laboratory at Oklahoma State University. Data on hunting mortality was collected during controlled bobwhite hunts on Packsaddle WMA. Data were collected at the check station from each bird harvested on the area (Table 2) .

 

QUAIL NESTING...

During the 1992 through 1996 nesting seasons we monitored 211 bobwhite nests. The preferred nesting sites were in native little bluestem grass clumps and the average clutch size was 14 eggs. We have also documented polygamous behavior. Of the birds alive on April 1 each year (223 females and 289 males) 37.7 percent of females and 9.3 percent of males successfully hatched greater than 1 nest. Nesting females that survived the nesting period incubated an average of 1.5 nests and surviving males incubated just over 1 nest. Of the

females that were successful on their initial nesting attempt, 24.3 percent attempted second nests. Female first

nests represented 56.6 percent, female renests 13.3 percent, female double-clutch attempts 6.2 percent, and male-incubated nests 23.9 percent of all nests located. Chicks hatched in only about half of the nests, the remainder of the nests were destroyed by predators (mainly snakes) .The average brood-rearing period was 39 days. Chick survival was monitored from hatching to 39 days old and 37 percent of the chicks survived, most dying within the first 3 weeks. On any given year, male bobwhites raise 5 to 35 percent of the broods. Adult bobwhites will adopt and/or abandon chicks within broods. Our data show that about 17 percent of the

broods end up with more chicks than were hatched from the nest.

 

QUAIL MORTALITY AND SURVIVAL FINDINGS ...

One thousand-one-hundred-fifteen bobwhites have been trapped, fitted with radio transmitters, and survived greater than 7 days. Capture mortalities accounted for 10.1% of total mortalities on the control area, hunting 14.1%, predation 65.2% (28.3% mammalian and 36.9% avian), unknown 3.3%, missing birds 5.2%, and winter weather 2.1% (Table 1) .On the feeder area capture mortalities accounted for 4.6% of all feeder area mortalities, hunting 15.5%, predation 67.0% (22.9% mammalian and 44.1% avian), unknown 5.3%, missing birds 6.9%, and winter weather 0.7% (Table 1) .Overall, capture mortalities accounted 7.5% of all mortalities, hunting 14.7%, predation 66.0% (25.7% mammalian and 40.3% avian) , unknown 4.3%, missing birds 6.0%, and winter weather 1.4% (Table 1) .None of the mortalities were determined to be the result of disease. Weather related deaths (whole carcasses) were determined to be the result of hypothermia and starvation, however, bobwhites in a weakened condition (or dead) due to severe weather or disease are easily predated and classified as such.

 

The only difference in cause-specific mortality between the control and feeder occurred in the avian predation category. AVIAN PREDATION WAS HIGHER ON THE FEEDER SITE! This may have been due to concentrating bobwhites around feeders during periods of severe winter weather. During the months of

January, February, April, and March the number of total mortalities on the control and feeder sites were

significantly different. Total mortalities were higher on the control site during February and December and mortalities were higher on the feeder site during January and April. Feeding does not biologically benefit bobwhites during periods of severe winter weather. It simply shifts the distribution of cause-specific mortality (i.e., Instead of starving to death bobwhites were more likely to be eaten by avian predators).

 

Average monthly survival rates of bobwhites did not differ between the control and the feeder site (Figure 2). However, during the month of February survival did differ between the control and feeder sites. We believe this was because of severe winter weather. Bobwhites on the feeder site had fewer mortalities caused by weather, but had higher predation and hunting mortalities. Average annual survival of bobwhites on the control site was 17.9 percent and 21.0 percent on the feeder site. The average annual survival of the sites combined was 19.8 percent.

 

Food is very rarely the factor limiting bobwhite populations in western Oklahoma. Therefore, money and time spent on habitat management is the best way to ensure long term stable bobwhite populations. For example, strip discing, controlled burning, and cattle grazing can be used to manage nesting cover and brood-rearing habitat. Many of the same plants (i.e., ragweeds, sunflowers, crotons, etc.) that make brood-rearing habitat are the same plants that provide late fall and winter food.

 

SOME INTERESTING FINDINGS. ..

One very interesting aspect of this research that has received regional and national attention is our documentation of long distance movements by bobwhites. It has long been understood that bobwhites undergo two periods of increased activity; the "spring breakup" and the "fall shuffle". During the fall shuffle we have observed almost half of the birds moving 2 miles or more from the research area. Ten to l5 mile movements were fairly common and we have observed quail moving as far as 37 miles! Movements in the spring

did not involve as many birds and the greatest distance traveled was 16 miles; movements of 4 to 5 miles were more common during the spring breakup.

 

CONCLUSION

Our data do not support the idea that quail feeders increase bobwhite survival or the number of bobwhites on the supplementally fed area. Also, our data show that avian predation is higher on supplementally fed areas. Bobwhite managers should concentrate time, effort, and financial resources toward habitat improvement programs which will minimize mortality from all sources and enhance survival during the nesting period. We believe the "quick fix" of quail feeders to supply food to wild bobwhites brings with it many problems and few solutions. Finally the food plot cliche from noted wildlife biologist Dale Rollins from Texas could also be used for feeders: "When you need em you can' t grow’em, when you can grow’em you don't need’em. With good

habitat and favorable growing conditions food is very seldom a limiting factor".

 

 

KEY FINDINGS FROM THE PACKSADDLE BOBWHITE MORTALITY STUDY

 

-Quail feeders did not increase bobwhite survival.

 

-Quail feeders did not increase bobwhite population numbers.

 

-Avian predation was higher on the supplementally fed area.

 

-Avian predation, mammalian predation, and hunting were the highest causes of mortality.

 

-Bobwhites in western Oklahoma can move large distances during the fall shuffle and spring breakup.

 

-23.9 percent of male bobwhites incubated nests.

 

-24.3 percent of female bobwhites attempted second nests.

 

-Five to 35 percent of bobwhite broods were raised by males annually.

 

-Bobwhite chick survival from hatching to 39 days was 37 percent.

 

-The average brood-rearing period for chicks was 39 days.

 

-Adult bobwhites will adopt and/or abandon chicks.

 

-17.0 percent of bobwhite broods ended up with more chicks than were hatched from the nest.

 

LOOKING TO THE FUTURE...

 

Research Goals

During the next five years we hope to learn more about the annual fluctuations in bobwhite populations. Bobwhite populations are directly correlated to reproduction, but the key to good fall populations is hatching many chicks and providing good habitat that satisfies their needs so a high percentage of them survive until November. This sequence of events is the least understood aspect of bobwhite life history. The first five years of the Packsaddle Project provided much insight to breeding behavior, nesting and hatching success, and chick survival, but many questions remain unanswered. Until very recently the technology to monitor bobwhite chick survival by actually having a radio transmitter attached to the chick was not available. The development of a micro transmitter weighing approximately half a gram now enables us to monitor chicks during the critical first few weeks of life. We are currently cooperating with OSU researchers and a full time graduate student is working with us on the Packsaddle using the latest "high tech" gadgets available to closely monitor bobwhite

chicks from the day they hatch until the day they die. Together we hope to start one of the most intensive quail

reproductive studies ever attempted.

 

SUCCESS BASED ON PARTNERSHIPS...

The Oklahoma Department of Wildlife Conservation sincerely appreciates very generous financial support for this project from the Grand National Quail Foundation of Enid. Without the very generous contributions from the GNQF this project would not have been possible. Several state chapters of Quail Unlimited have also been very helpful. These include Bluestem, Duncan; Eastern Oklahoma Quail Association, Poteau; Oklahoma City, Canadian County, El Reno; and Stillwater chapters as well as the Tulsa Bird Dog Club have also made significant monetary contributions to the quail mortality study. Additionally, the Oklahoma Quail Unlimited State Council and five member chapters (Great Plains, Weatherford; Bluestem, Bartlesville; North Central, Ponca City; Tri-County, Shawnee; and Northeast, Miami) have donated a four-wheel all-terrain vehicle as well as financial support. The Oklahoma City Chapter of Quail Unlimited has donated a four-wheel all-terrain vehicle, computer, and made the initial monetary contribution to purchase the first batch of chick radios. Mr. Mal Mixon, President of Invacare, assisted greatly with financial support for the study. All groups involved have

provided generous support and cooperation on this study and the ODWC invites continued assistance with the new bobwhite chick ecology study.

 

Oklahoma hunters provide financial support for this project through the Federal Aid to Wildlife Restoration Act, Oklahoma Project W-82-R, and from the purchase of hunting licenses.

 

 

 

Table 1. Percent of mortality of northern bobwhites by cause, Packsaddle WMA, Ellis County, Oklahoma, 1991-96.

 

 

Cause

Control
Percent

Feeder

Percent

Overall

Percent

Capturea

10.1

4.6

7.5

Hunting

14.1

15.5

14.7

Predation

65.2

67.0

66.0

     a. Mammalian

28.3

22.9

25.7

     b. Avian

36.9

44.1

40.3

Unknown

3.3

5.3

4.3

Missing

5.2

6.9

6.0

Weather

2.1

0.7

1.4

Disease

0.0

0.0

0.0

 

 a  Birds that have been monitored > 7 days, but were recaptured and mortality occurred in the trap.

 

Table 2. Annual controlled hunt statistics per hunt for northern bobwhites on Packsaddle WMA, Ellis

County, Oklahoma, 1990-96.

 

Year

No. of hunts

Total

Hunters

Mean No hunters/hunt

Mean no.

Birds

Harvested/hunt

Mean

Birds/hunter

Percent of birds

Harvested/hunt by age class

 

 

 

 

 

 

Adult

Young of Year

1990-91

11

132

722

65.3

4.7

15.7

84.3

1991-92

21

283

1,260

60.0

4.3

13.5

86.5

1992-93

22

252

1,150

47.7

4.3

13.8

86.2

1993-94

21

275

778

37.1

2.8

14.9

85.1

1994-95

21

417

1,249

59.5

3.0

19.3

80.7

1995-96

17

371

671

39.5

1.8

18.4

81.6

1996-97

16

350

1,248

78.0

3.6

9.5

90.5

*Note: The total acreage of the Packsaddle WMA has increased from 7,500 acres in 1990 to 15,000 acres in 1995 consequently the number of hunters/hunt has increased proportionately.


 

Fig. 1 Location of Packsaddle WMA, Ellis County, Oklahoma.

Fig. 2 Trends in mean  monthly-daily-survival-rate of radio-marked northern bobwhites on control and feeder areas, on Packsaddle WMA, Ellis County, Oklahoma, 1991-96.