Nesting Ecology of Rio Grande Turkeys Author(s): Dean Ransom, Jr., Orrin J. Rongstad and Donald H. Rusch Source: The Journal of Wildlife Management , Apr., 1987 , Vol. 51, No. 2 (Apr., 1987), pp. 435-439 Published by: Wiley on behalf of the Wildlife Society Stable URL: https://www.jstor.org/stable/3801031 REFERENCES Linked references are available on JSTOR for this article: https://www.jstor.org/stable/3801031?seq=1&cid=pdf- reference#references_tab_contents You may need to log in to JSTOR to access the linked references. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at https://about.jstor.org/terms Wiley and Wildlife Society are collaborating with JSTOR to digitize, preserve and extend access to The Journal of Wildlife Management This content downloaded from 128.227.251.4 on Tue, 09 Dec 2025 16:58:34 UTC All use subject to https://about.jstor.org/terms J. Wildl. Manage. 51(2):1987 WINTER HABITAT OF BLUE GROUSE * Hines 435 STANDING, K. M. 1960. Factors in relation to pop- ulation fluctuations in blue grouse. Ph.D. Thesis, Washington State Univ., Pullman. 182pp. WATSON, A., AND R. MOSS. 1979. Population cycles in the Tetraonidae. Ornis Fenn. 56:87-109. WEEDEN, R. B. 1964. Spatial separation of sexes in rock and willow ptarmigan in winter. Auk 81: 534-541. WHITE, G. C. 1983. Numerical estimation of sur- vival rates from band-recovery and biotelemetry data. J. Wildl. Manage. 47:716-728. WING, L. 1947. Seasonal movements of blue grouse. Trans. North Am. Wildl. Conf. 12:504-510. ZWICKEL, F. C. 1982. Blue grouse. Pages 63-65 in D. E. Davis, ed. CRC handbook of census meth- ods for terrestrial vertebrates. CRC Press, Inc., Boca Raton, Fla. S-, AND J. F. BENDELL. 1967a. A snare for capturing blue grouse. J. Wildl. Manage. 31:202- 204. - , AND . 1967b. Early mortality and the regulation of numbers in blue grouse. Can. J. Zool. 45:817-851. - , I. O. Buss, AND J. H. BRIGHAM. 1968. Au- tumn movements of blue grouse and their rele- vance to populations and management. J. Wildl. Manage. 32:456-468. Received 8 August 1985. Accepted 13 June 1986. NESTING ECOLOGY OF RIO GRANDE TURKEYS DEAN RANSOM, JR., ' Department of Wildlife Ecology, University of Wisconsin, Madison, WI 53706 ORRIN J. RONGSTAD, Department of Wildlife Ecology, University of Wisconsin, Madison, WI 53706 DONALD H. RUSCH, Department of Wildlife Ecology, University of Wisconsin, Madison, WI 53706 Abstract: The nesting ecology of Rio Grande turkeys (Meleagris gallopavo intermedia) was studied o Rob and Bessie Welder Wildlife Refuge (WWR), Sinton, Texas, during January-August 1983 and Radio telemetry was used to monitor the nesting activities of turkey hens. Twelve of 31 radio-tagged tu died during the study: 8 from predation, 1 from disease, 2 from trapping related injuries, and 1 f unknown causes. An annual hen survival rate of 0.73 was calculated from the total number of observation days and the known number of deaths. Ten (58%) of 17 instrumented hens reached incubation in 1983, but all nests were destroyed by predators. Two turkey broods were observed in 1983, one of 2 hens with 5 poults, the other 2 hens with 3 poults. In 1984, nesting data were gathered on 6 hens which reached incubation; 3 hatched eggs. Seven turkey broods totaling 8 hens with 40 poults were observed in August 1984. Nest sites were located in pastures deferred from livestock grazing. J. WILDL. MANAGE. 51(2):435-439 The population of wild Rio Grande turkeys, which occupies the Aransas River bottoms and surrounding uplands of the WWR, has declined from a high of approximately 700 (Watts 1969) in 1966-67 to <100 birds in 1983. In recent years, no broods have been observed by WWR personnel (J. G. Teer, pers. commun.). Although there have been several studies of the wild turkey on the WWR (Watts 1969, Smith 1977, Baker 1979b), none has directly investigated the nesting ecology of this popu- lation. Decreases in nesting attempts, nest suc- cess, or poult survival-all of which influence juvenile recruitment-could have played a part in this decline. This study was to determine whether reproductive failures by turkey hens wintering and breeding on the WWR and ad- jacent areas were responsible for the population decline. Financial support was provided by the Rob and Bessie Welder Wildl. Found. (WWF), Sin- ton, Tex., and the Coll. Agric. and Life Sci., Univ. Wisconsin, Madison. We gratefully ac- knowledge the assistance of several WWF stu- dents, as well as J. G. Teer, D. L. Drawe, and T. M. Yuill in trapping birds. We thank J. F. Rooke, P. H. Welder, H. Thomas, and N. E. Adams for access to their property. We also wish to thank W. Aschenbeck, of Cuero, Tex., for donating the domestic turkey eggs used in the simulated nest study. This is Welder Wildl. Con- trib. 301. STUDY AREA The study was conducted on the 3,158-ha WWR and 4,237 ha of the neighboring Rooke Ranch. The WWR is located along the northern boundary of San Patricio County, approximate- 'Present address: Caesar Kleberg Wildlife Re- search Institute, Texas A&I University, Kingsville, TX 78363. 435 This content downloaded from 128.227.251.4 on Tue, 09 Dec 2025 16:58:34 UTC All use subject to https://about.jstor.org/terms 436 TURKEY NESTING ECOLOGY * Ransom et al. J. Wildl. Manage. 51(2):1987 ly 11.3 km north of Sinton, Texas. The area is part of a grassland complex found along the Gulf 6f Mexico. Recently, however, it has de- veloped into a brush-grass complex, in part a result of its history of grazing by domestic live- stock (Drawe et al. 1978). The area receives an annual average rainfall of 89 cm, with most of the accumulation during late summer and fall. Drawe et al. (1978) described 16 plant com- munities occurring on the area, the most exten- sive community being honey mesquite (Proso- pis glandulosa)-mixed grass. There are 22 soil types ranging from heavy clays to fine sands. The WWR is operated as a working cattle ranch, which since 1974 has utilized a cow-calf operation in a variety of grazing systems and stocking rates. Prior to 1974, the WWR used steers in a continuous grazing system. There are 3 types of grazing systems currently in use on WWR: year-long continuous (CONT), a 3-herd 4-pasture deferred rotation (4PDR), and the short duration (SDG). The CONT pastures were grazed year-round with no deferment from grazing pressure. The 4PDR system involved 3 herds of cattle rotated between 4 pastures; graz- ing periods were structured such that each pas- ture was rested for 4 months while the other 3 were grazed for 12 months. The SDG is a sys- tem consisting of 10 pastures radiating out from a central water source. One herd of cows was rotated through the system. Each pasture was grazed for 2-3 days and rested for 18-27 days. Two other pastures were used in a switchback grazing system (2PSB). The pastures were grazed for varying periods of time by bulls and replacement heifers. The F. B. Rooke III Ranch was located in Refugio County, immediately across the Aran- sas River from the WWR. Part of the Rooke Ranch (1,776 ha) has been converted to agri- cultural crop production; the remaining 2,461 ha of this ranch is a cow-calf operation under continuous grazing pressure. METHODS Field research was conducted during Janu- ary-August 1983 and 1984. Wild turkeys were trapped in winter flocks using cannon nets and drop nets (Glazener et al. 1964). Birds were sexed, aged (Williams 1961), and weighed. Col- or-coded patagial wing tags (Knowlton et al. 1964) were placed on all birds caught. Solar- powered radio transmitters were fitted to tur- key hens caught in each year. Visual locations of instrumented hens were recorded daily dur- ing January-April, and only once/1-4 days during May-August to reduce disturbance to nesting and brood rearing hens. Daily and an- nual hen survival rates were determined using the methods of Trent and Rongstad (1974). Nests of radio-tagged hens were located after incubation had begun. Because we could not monitor hen movements closely enough during the laying period to determine the beginning of egg laying, hens were recorded as incubating only after 3 daily relocations placed the bird in the same spot. Nest sites were circled from a distance on an every-other-day basis after in- cubation had begun; in this fashion the approx- imate location could be determined. After the hen had left the nest-following a hatch, aban- donment, or nest predation-the exact nest lo- cation was confirmed and information on clutch size, nest success, and hatching success was re- corded. Clutch size was recorded as the number of distinct eggs remaining at the nest. Hatching success was calculated as the number of eggs hatched as a percentage of total eggs laid. Daily nest survival rates were calculated and expand- ed to the 28-day incubation period (Mayfield 1961). A simulated-nest study was conducted in 1984 to obtain additional information on nest pre- dation rates. Two groups of 18 nests each were placed in general areas used by nesting hens in 1983. Each nest consisted of a clutch of 5 do- mestic turkey eggs, which were observed over a 14-day period, simulating the laying period of wild turkeys (Bailey and Rinell 1967). The simulated nests were established after 1 May, 35-39 days later than initiation of the laying period of wild turkey hens on WWR in 1984. One group of nests was designated as a control, and the other as experimental nests. The control nests were treated in the same manner as real nests under incubation; they were approached and circled from a distance every other day. Experimental nests consisted of a permanently secured radio transmitter approximately 30.5 cm from the simulated nest. One end of a monofilament line was attached to an egg(s). The other end was attached to the lead wire which completed the battery-transmitter cir- cuit. In this manner, disturbance of the eggs would break the circuit and signal transmission would cease. A nest was recorded as destroyed if 1 egg was broken or missing from the nest. Instrumented hens that were successful in This content downloaded from 128.227.251.4 on Tue, 09 Dec 2025 16:58:34 UTC All use subject to https://about.jstor.org/terms J. Wildl. Manage. 51(2):1987 TURKEY NESTING ECOLOGY * Ransom et al. 437 bringing off a brood were located periodically to obtain brood counts and to determine poult mortality. During the months of June, July, and August, 55.7 km of pasture roads were travelled in the mornings and afternoons a minimum of 3 days/week to locate as many broods as pos- sible. RESULTS A total of 83 wild turkeys was trapped and marked in January of 1983; 27 hens (17 ad and 10 juv) were fitted with radio transmitters. The winter flocks were extremely trap shy in 1984; however, and we were able to recapture only 7 adult hens, 4 of which received transmitters. Nesting Radio failure and mortality reduced the sam- ple of 27 hens to 17 (8 ad and 9 juv) prior to nest initiation in 1983. Ten (4 ad and 6 juv) of the 17 hens were known to reach incubation, but all were unsuccessful, as a result of nest predation; only 1 hen renested but this also was destroyed by a predator during incubation. An unmarked hen was flushed accidentally from her nest, which also was later depredated. The remaining 7 hens never reached incu- bation, as determined by our technique. We do not know if these hens failed to attempt nesting or if they initiated egg laying and their nests were destroyed before incubation was reached. Mammalian predators were responsible for the destruction of 12 turkey nests (including the unmarked hen). Broken eggs were found in the nest bowl and scattered away from the nest. Most of the destroyed eggs were broken along the longitudinal axis, resulting in relatively neat angular edges with few tooth punctures. Based on simulated nest studies by Baker (1979a) and Pharris and Goetz (1980), it is our opinion that raccoons (Procyon lotor) were primarily re- sponsible for the nest destruction we observed. During 1984, nesting data were gathered on 6 hens, which initiated 8 and reached incuba- tion on 7 nests. One hen attempted 3 nests, reaching incubation on the Ist and 3rd attempt. This hen was killed by a predator at her 3rd nest. Three hens hatched a clutch of eggs and 2 hens' nests were destroyed; their nests were empty upon inspection. Hatching success for the 3 successful nests was 89%. Nest initiation dates (calculated by backdat- ing 14 days from the Ist day of incubation Table 1. Daily and 28-day nest survival rates for real, simu- lated control (S-C), and simulated radio-instrumented (S-R) turkey nests for 1983 and 1984 on the Rob and Bessie Weld- er Wildlife Refuge in south Texas. Total No. nests days Daily 28-day Nest de- ex- survival rate survival Year type stroyed posure (+95% CI) rate 1983 Real 11 144 0.924 ? 0.044 0.109 1984 Real 3 112 0.974 ? 0.030 0.478 1984 S-R 8 200 0.960 ? 0.028 0.318 1984 S-C 9 126 0.929 ? 0.046 0.127 [Blakey 1937, Mosby and Handley 19 from 2 to 24 April for 7 hens in 198 24 to 27 March for 5 hens in 198 clutch size was 11.1 eggs, ranging fr (N = 7) for both years of the study survival rates were significantly 0.07) in 1984 (0.974) than in 1983 ble 1). Seventeen of the 36 dummy nests were de- stroyed during the 14-day trial with a daily nest survival rate of 94.8% (Table 1). There was no significant difference (P > 0.10) in the daily survival rate between real, experimental-simu- lated and control-simulated nests in 1984. Nest Sites Nest sites were categorized into 2 broad vegetation classes: shrubs and herbaceous cov- er; 7 were under shrubs and 10 in herbaceous plant cover. Shrubs included Texas persimmon (Diospyros texana), spiny hackberry (Celtis pallida), and agarito barberry (Berberis trifo- liolata). Lateral screening cover was provided by residual old growth bunchgrass or vines, such as old man's beard (Clematis drummondii) and mustang grape (Vitis mustangensis), around the base of the shrub. Herbaceous cover used as nesting sites consisted of little bluestem (Andro- pogon scoparius), Canada wildrye (Elymus canadensis), switchgrass panicum (Panicum virgatum), silverleaf sunflower (Helianthus ar- gophyllus), spiny aster (Aster spinosa), old man's beard, and mustang grape. Nesting cover was >45 cm in height in all cases where shrubs were selected and in 50% of the cases where herbaceous cover was used. Nest Site Location Nests were widely distributed on the area but tended to be associated with permanent water (Fig. 1). They averaged 0.35 km from available water sources and 0.84 km from known roost This content downloaded from 128.227.251.4 on Tue, 09 Dec 2025 16:58:34 UTC All use subject to https://about.jstor.org/terms 438 TURKEY NESTING ECOLOGY * Ransom et al. J. Wildl. Manage. 51(2):1987 N i ROOST AREAS 0 1 O NEST 1983 I SNEST 1984 km Aransas River Fig. 1. Distribution of Rio Grande turkey nests on the Rob and Bessie Welder Wildlife Refuge and adjace south Texas during 1983 and 1984. sites. All of the 17 turkey nests located were in areas that were either deferred from livestock grazing or in continuous, lightly grazed pas- tures. Specifically, there were 7 nests in 4PDR grazing system, 1 in SDG, 5 in CONT, and 4 in 2PSB. Productivity The lack of nest success among marked birds in 1983 seemed representative of the hen pop- ulation. We recorded only 2 composite turkey broods out of 38 different hens observed during the road census in June, July, and August. This gave a poult:hen ratio of 0.21:1. Productivity in 1984 was higher than in 1983 although only 1 of the instrumented hens raised a brood. Turkey broods associated with noninstru- mented hens or with hens whose transmitters were nonfunctional began to appear in the road census during June 1984. By early August, when field work terminated, we had recorded a total of 7 different broods totaling 8 hens with 40 poults. These observations yielded a poult: hen ratio of 0.93:1. Hen Survival Twelve marked hens (11 radioed) were known to have died during the 2 years of this study. Predators were responsible for 7 deaths, whereas disease (Leucocytozoan), trap related injuries, and unknown causes accounted for 1, 2, and 1 mortalities, respectively. The daily hen survival rate was 0.9991, which expanded to an annual survival rate of 0.726. The 2 major pred- ators on adult turkeys were bobcats (Felis ru- fus) and coyotes (Canis latrans). Bobcats were observed to stalk and attack winter hen flocks on 2 occasions and coyotes on 1 occasion. DISCUSSION Despite our problems with transmitter fail- ure in 1984, it was clear that both adult and juvenile turkey hens on WWR did not hesitate to nest. We could not document incubations for 7 hens in 1983. Considering the complete nest loss of instrumented hens during that year, it is our opinion that these 7 hens lost their nests early in egg laying. The average clutch size (11.1) we observed was within the range re- ported for wild turkeys (Mosby and Handley 1943, Mosby 1967). The annual hen survival (73%) we observed appears to be relatively high. Watts (1969) re- ported a 60% annual survival rate for male tur- keys on the WWR and felt that hen survival was similar. Mosby (1967) reported a 40% sur- vival rate for turkeys in a hunted population. There are, however, few existing data on sur- vival rates from other nonhunted populations. We found little direct evidence suggesting a large-scale population decline. However, it ap- pears that nest predation could be limiting cur- rent population growth. The low poult: hen ra- Table 2. Previous October-December rainfall (cm), deviation from the 28-year 4th quarter rainfall average (R = 20.88 cm), and poult: hen ratios for 8 years of turkey research on the Rob and Bessie Welder Wildlife Refuge in south Texas. Poult :hen Year Rainfall Deviation ratio Reference 1966 27.18 +6.30 1.4 Watts 1969 1970 31.75 +10.87 0.30 Smith 1977 1971 11.43 -9.45 0.10 Smith 1977 1972 18.47 -2.41 0.10 Smith 1977 1976 16.10 -4.78 0.50 Baker 1979b 1977 42.24 +21.36 1.17 Baker 1979b 1983 11.60 -9.28 0.21 This study 1984 32.00 +11.12 0.93 This study This content downloaded from 128.227.251.4 on Tue, 09 Dec 2025 16:58:34 UTC All use subject to https://about.jstor.org/terms J. Wildl. Manage. 51(2):1987 TURKEY NESTING ECOLOGY * Ransom et al. 439 tio indicated that the hen population, in general, suffered nest failure similar to that we observed for instrumented hens. We also believe that ob- server influence on the outcome of turkey nests was insignificant. There was no difference in daily survival rates of real and simulated nests. Our methods of nest location did not change between years, yet survival rates of real nests did. A pattern can be seen in the data gathered from previous studies and WWR rainfall rec- ords that may explain the fluctuations in pro- ductivity (Table 2). Watts (1969) reported that only 4 of 105 hens had young in 1967 and sug- gested that this was a reflection of the dry win- ter conditions of 1966-67. Smith (1977) report- ed the same phenomenon: rainfall in the autumn of 1970-71 was below normal, and reproduc- tive success the following year was poor. In con- trast, Baker (1979b) found that turkey produc- tivity in 1977 was 2 x that in 1976 following excessive rains in July-October 1976. In our study, October-November rainfall in 1983 was well above the 28-year 4th quarter average and turkey productivity in 1984 was >4 x that ob- served in 1983. Beasom (1973) also found a strong correlation between previous August and September rainfall and the number of poults/ hen the following year on an area 113 km south of WWR. The selection of nest sites by hens in un- grazed or lightly grazed areas is important. In central Texas Merrill (1975) found turkey nests and hens with poults only in pastures such as the 4PDR system or light continuous grazing systems; neither nests nor broods were seen in heavily grazed pastures with low grass cover. If fall rainfall governs both nesting cover and pro- ductivity on the WWR, as it does on the King Ranch in south Texas (Beasom 1973), then de- ferred grazing systems should be beneficial to nesting hens on the WWR. Although we could not adequately quantify poult mortality, we feel that predators also reg- ulated productivity. The 1984 recruitment rate would only keep the population stable at ap- proximately 100 birds. The WWR turkey pop- ulation has remained near this level since 1972 (Smith 1977, Baker 1979b). These limited data do not assure that nest predation was the cause of the large-scale de- cline in the WWR turkey population; however, this cause was the only anomaly in the WWR turkey hen reproductive cycle we could docu- ment. Accordingly, we suggest that this phe- nomenon was a factor limiting juvenile recruit- ment during our study. LITERATURE CITED BAILEY, R. W., AND K. T. RINELL. 1967. Events in the turkey year. Pages 73-92 in O. H. Hewitt, ed. 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Home range and survival of cottontail rabbits in south- western Wisconsin. J. Wildl. Manage. 38:459- 472. WATTS, C. R. 1969. The social organization of wild turkeys on the Welder Wildlife Refuge. Ph.D. Thesis, Utah State Univ., Logan. 60pp. WILLIAMS, L. E., JR. 1961. Notes on wing molt in the yearling wild turkey. J. Wildl. Manage. 25: 439-440. Received 8 April 1985. Accepted 8 September 1986. This content downloaded from 128.227.251.4 on Tue, 09 Dec 2025 16:58:34 UTC All use subject to https://about.jstor.org/terms