Gobbling Activity of Eastern Wild Turkeys Relative to Male Movements and Female Nesting Phenology in South Carolina

Wildlife Society Bulletin 42(4):632 642; 2018; DOI: 10.1002/wsb.932 Original Article Gobbling Activity of Eastern Wild Turkeys Relative to Male Movements and Female Nesting Phenology in South Carolina MICHAEL J. CHAMBERLAIN, 1 Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA PATRICK H. WIGHTMAN, Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA BRADLEY S. COHEN, Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA BRET A. COLLIER, School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA ABSTRACT Wild turkeys (Meleagris gallopavo) use a polygynous mating system, and males must balance fitness benefits of courtship displays against costs of their reproductive strategies. Wild turkeys are the only gamebird species in the contiguous United States hunted primarily during their reproductive period. Managers attempt to implement seasons that allow for hunter satisfaction while limiting effects to reproduction and ensuring sustainable populations. To minimize illegal harvest, managers often attempt to set spring hunting seasons when gobbling activity is high and females are actively incubating nests. Gobbling activity varies significantly both temporally and spatially, and relationships between gobbling activity and reproductive phenology are unclear. We used autonomous recording units and Global Positioning System transmitters to monitor gobbling activity by male eastern wild turkeys (M. g. silvestris) and evaluate fine-scale movements of male wild turkeys and nesting chronology of females on the Webb Wildlife Management Area Complex in South Carolina, USA, during 2015 2016. Based on 19,126 gobbles and movement ecology data from 99 wild turkeys (70 F, 29 M), we found no discernable pattern to support the hypothesis that gobbling activity increases with onset of incubation by females. We also observed no definable relationship between daily movements of males and gobbling activity, likely driven by the considerable daily variability in gobbling activity. We noted apparent lags in gobbling activity relative to nest initiation (onset of laying), and offer that understanding mechanisms underlying these apparent lags may be important to improving our understanding of reproductive ecology in wild turkeys. Research evaluating confounding influences of hunting activity and male mortality during the breeding season on gobbling activity and wild turkey population dynamics is warranted. Ó 2018 The Wildlife Society. KEY WORDS gobbling chronology, hunting, Meleagris gallopavo, Carolina, wild turkey. reproductive phenology, season timing, South Understanding drivers of population dynamics in wild turkeys (Meleagris gallopavo) is important to guide regulatory strategies that promote sustainable harvest while ensuring reproductive success and hunter satisfaction. Although nest success is often thought to most influence population growth in wild turkeys, a host of environmental, behavioral, and anthropogenic drivers may influence reproduction (Vangilder 1992, Roberts and Porter 1996, Conley et al. 2016). Unlike all other gamebirds in the contiguous United States, wild turkeys are hunted primarily during spring, which coincides with reproductive activities. Thus, managers are challenged with implementing hunting seasons that provide for hunter satisfaction while limiting negative effects to reproduction Received: 4 May 2018; Accepted: 9 September 2018 Published: 23 December 2018 1 E-mail: mchamb@uga.edu (Hoffman 1990, Kienzler et al. 1996, Healy and Powell 1999, Norman et al. 2001, Casalena et al. 2015). Wild turkeys use a polygynous mating system that fluctuates across varying degrees of resource or male dominance polygyny, depending on subspecies and environment (Emlen and Oring 1977, Krakauer 2008). Male wild turkeys compete for breeding opportunities with females using courtship displays, vocalizations, and aggression toward conspecifics to challenge established pecking orders (Healy 1992). Use of courtship displays and vocalizations maintains dominance hierarchies that ultimately determine access to females, but these behaviors can increase predation risk (Bailey and Rinnell 1967, Williams and Austin 1988, Zuk and Kolluru 1998). Male wild turkeys maintain stable home ranges during breeding season; thus, courtship activities and access to females are constrained by male space use and dominance (Mace and Harvey 1983, Grisham et al. 2008, Edward and Chapman 2011). Hence, 632 Wildlife Society Bulletin 42(4)

males must balance using displays designed to attract females (i.e., gobbling) with potential that these same displays attract predators, and ultimately must decide whether to change reproductive tactics (e.g., increase movements) as availability of receptive females wanes with onset of incubation. In polygynous species, continued mate accumulation at some point is impractical, so males may increase movements to locate receptive females or decrease cease courtship displays, all while trying to reduce predation risk (Emlen and Oring 1977, Hedrick 2000, Lohrey et al. 2009). Indeed, earlier works suggested that male wild turkeys increase movements during spring breeding seasons, but studies that are more contemporary have noted that males tend to maintain consistent home ranges, within those ranges, during breeding season movements (Kelley et al. 1988; Godwin et al. 1990, 1994; Grisham et al. 2008; Gross et al. 2015; Collier et al. 2017). Regardless, potential relationships between male movements during breeding season and gobbling activity are poorly understood. Gobbling chronology is often used by agencies when setting hunting seasons based on the perceived relationship between gobbling activity and nesting phenology of females (Hoffman 1990, Kurzejeski and Vangilder 1992, Kienzler et al. 1996). Specifically, spring hunting seasons are often based on the assumption of a bimodal distribution of gobbling activity wherein the first peak coincides with breakup of winter flocks and onset of breeding and the second with peak nest or incubation initiation (Bailey and Rinnell 1967, Bevill 1975, Porter and Ludwig 1980, Vangilder 1992, Norman et al. 2001). However, other authors have only observed a single peak in gobbling activity with no identifiable relationship to nesting phenology (Kienzler et al. 1996, Miller et al. 1997). Nevertheless, hunting seasons for wild turkeys presumably are structured so that hunting occurs after mating, ensuring females are bred before dominant males are harvested. Likewise, structuring seasons that overlap with high gobbling activity after nesting had begun would ensure hunter satisfaction while reducing potential for illegal harvest of females (Thackston and Holbrook 1996, Little et al. 2000, Swanson et al. 2005, Whitaker et al. 2005, Casalena et al. 2011). Discrepancies in the scientific literature regarding bimodality of gobbling chronology and the lack of explicit linkages between gobbling chronology and nesting phenology may inherently be linked to sample survey design. Historically, morning roadside surveys have been used to quantify gobbling activity, with researchers conducting auditory surveys at specific locations repeated over time (Bevill 1975). However, gobbling activity can be affected by a host of environmental and anthropogenic factors that could cause considerable variability in daily gobbling activity (Porter and Ludwig 1980, Vangilder et al. 1987, Hoffman 1990, Kienzler et al. 1996, Wightman et al. 2018). Likewise, surveys typically are not conducted during inclement weather, and subject to observer biases and personnel limitations (Miller et al. 1997, Lehman et al. 2005). The development and use of autonomous recording units (ARUs) offers researchers opportunity to quantify gobbling activity accurately (Rempel et al. 2005, Mennill et al. 2012, Colbert et al. 2015). Previous studies attempting to link gobbling activity to nesting phenology have all used very-high-frequency (VHF) telemetry to monitor nesting behavior of females. However, the advent of Global Positioning System (GPS) transmitters suitable for wild turkeys offers researchers opportunities to more accurately document nesting phenology of females (Collier and Chamberlain 2011, Yeldell et al. 2017). Our objective was to use ARUs to monitor gobbling activity of eastern wild turkeys (M. g. silvestris) during the reproductive season, combined with high-resolution spatial data obtained from GPS-tagged individuals, to evaluate relationships between gobbling activity, movement ecology of males, and reproductive phenology of females. We were interested in identifying relationships between mate availability and male reproductive strategy, wherein we hypothesized that availability of females would prompt males to shift from mate-signaling (gobbling) to mate-searching behaviors. Specifically, we predicted that as females became less available across the landscape, males would decrease gobbling activity, and these decreases would be correlated with increases in male movements. STUDY AREA We conducted research on the Webb WMA Complex, a combination of 3 connected Wildlife Management Areas (WMAs) owned and managed by the South Carolina Department of Natural Resources, USA. Webb, Palachacola, and Hamilton Ridge WMAs were located in Hampton and Jasper counties and comprised 10,483 ha. Webb WMA was 2,373 ha and mostly (62%) upland pine forest consisting mainly of longleaf (Pinus palustris) and loblolly (P. taeda) with hardwood stands along riparian drainages, and bottomland hardwoods typical of the southeastern floodplains along the Savannah River. Hamilton Ridge was 5,374 ha with approximately 50% of the property consisting of bottomland hardwoods similar to Webb, whereas the remaining 50% was industrial loblolly pine forests in various seral stages. Palachacola was 1,618 ha of upland pine with hardwood stands along drainages and approximately 1,000 ha of bottomland hardwoods in the Savannah River flood plain. Management activities on the Webb WMA Complex included prescribed fire, active timber management, fallow field management, and agricultural food plots used to promote and enhance wildlife habitat and populations. Prescribed fire was conducted both during growing and dormant seasons on return intervals of 2 3 years. There was an open hunting season (no limits on numbers of hunters) for male turkeys beginning 1 April, ending on 30 April during 2015, and ending on 5 May in 2016. Hunting was permitted Monday through Saturdays but prohibited on Sundays. METHODS We captured wild turkeys with rocket nets baited with cracked corn during winter (Dec Feb) in 2015 2016 (Bailey et al. 1980). We sexed and aged turkeys based on presence of Chamberlain et al. Gobbling and Female Nesting Phenology 633

barring on the ninth and tenth primaries (Pelham and Dickson 1992). We banded each turkey with an aluminum rivet leg band (National Band and Tag Company, Newport, KY, USA), radiotagged them with a backpack-style GPS- VHF (very high frequency) transmitter (Guthrie et al. 2011) produced by Biotrack Ltd. (Wareham, Dorset, UK), and released them at the capture location. For females, we programmed transmitters to take one location nightly (23:58:58), and hourly locations between 0500 and 2000 from 15 February until the battery died or the unit was recovered. We programmed transmitters on males to take one location nightly (23:58:58), hourly locations between 0500 and 2000 from 15 February to 14 March, and locations every 30 min between 0500 and 2000 from 15 March to 15 May. We resumed collecting hourly locations again beginning 16 May until battery failure (Byrne et al. 2015, Cohen et al. 2018). We collected male locations at a greater rate in support of other research objectives on our study site (Collier et al. 2017). Capture and handling protocols were approved by the Louisiana State University Agricultural Center Animal Care and Use Committee (Permit A2014-013 and A2015-07). We monitored turkeys >4 times/week during January September using handheld Yagi antennas and R4000 receivers (Advanced Telemetry Systems, Inc., Isanti, MN, USA). We downloaded spatial data weekly beginning 1 March to document nesting activities of females and describe daily movements of males. We determined when incubation began by viewing GPS locations, and considered a female to be incubating when locations did not deviate from a central location for several days (Healy 1992, Yeldell et al. 2017). Once incubation began, we monitored each female daily; if locations demonstrated that the female was away from the nest >48 hr, we located the nest and classified it as failed (broken or disposition of egg remains, lack of eggs, or female mortality) or successful (hatching of >1 egg; Conley et al. 2016). We continued monitoring females for renesting throughout the summer, which encompassed the period used to assess gobbling activity. Similarly, once we confirmed nest locations via examination of GPS locations of incubating females, we viewed GPS locations during days preceding the onset of incubation to determine when laying began. We hereafter refer to the onset of laying as nest initiation. For males, we evaluated daily movements by summing total distances between sequential locations for each day to calculate total daily distance moved for each individual. To quantify gobbling activity during the reproductive season (1 Mar 31 May), we deployed 15 automated recording units (ARU; Song meter model SM2: Wildlife Acoustics Inc., Concord, MA, USA) across the Webb WMA Complex. Based on findings of Colbert et al. (2015), we separated ARUs by >600 m to avoid detecting males simultaneously on multiple ARUs, which resulted in each ARU effectively sampling approximately 115 ha. Likewise, the distribution of ARUs completely encompassed areas where females were captured and maintained ranges; hence, we believe our sampling was sufficient to detail gobbling activity relative to nesting phenology. We placed ARUs in areas where we observed turkey activity, and based on distribution of spatial locations of GPS-tagged males monitored during a 2014 pilot study (Wightman 2017). We caged ARUs and placed them 10 m above ground in a tree to minimize human interference. We connected a microphone to the ARU and attached the microphone to the tree 30 m above ground to increase the range at which gobbles could be detected, and reduce influence of understory and mid-story vegetation on detections of gobbles (Colbert et al. 2015). We programmed ARUs to record ambient sound from 0500 to 2000 daily and recorded data from 1 March to 1 June in 2015 and 1 March to 1 July in 2016 (for this study, we only used data from the window 1 Mar 1 Jun). We used Raven 1.4 (Cornell Laboratory of Ornithology, Ithaca, NY, USA) to search auditory data autonomously for gobbles. After identifying gobbles in sound files and creating a gobble key file, we determined the best parameters (700 1,275 Hz, 0.2 2.0-s duration, 0.018-s minimum separation, 20% minimum occupancy, 10% sound-noise ratio threshold) for the Limited Band Energy detector function in Raven. Based on the above parameters, the Limited Band Energy detector in Raven detected and stored selections identified as gobbles. Once gobbles were stored, we visually and auditorily evaluated each selection to determine whether it was a gobble. For each selection identified as a gobble, we recorded both the date and time, and archived all audio files. We used cross-correlation analysis in package forecast (Hyndman 2017) to evaluate the lagged correlation between timing of gobbling activity and nest initiation (first date of laying) by females. Crosscorrelation analysis provides a measure of similarity between 2 times series and produces autocorrelation functions that depict lagged correlations between paired observations (e.g., daily gobbling activity and nest initiation in our study). After qualitatively noting multiple lag periods, we fit a lagged regression using package dynlm to evaluate the direction and magnitude of the temporal relationship between lags in gobbling activity relative to nest initiation (Venables and Ripley 2002, Zeileis 2016). Finally, we graphically related gobbling activity to daily movements of males as a qualitative assessment of relationships between daily gobbling activity and movements of males. We considered P 0.05 to be statistically significant, and conducted all analyses in Program R version 3.4.3 (R Core Team 2017). RESULTS We captured and marked 70 female (50 adult, 20 juvenile) and 29 male (28 adult, 1 juvenile) wild turkeys with GPS units during 2015 2016. In 2015, we monitored 25 females and 15 (60%) initiated incubation, 7 (47%) were successful and 2 (25%) renested (both failed). In 2016, we monitored 45 females and 32 (71%) initiated incubation, 12 (38%) hatched and 6 (30%) renested (2 successful). Mean date of onset of incubation was 27 April in 2015 and 19 April in 2016. Average daily distance moved by males was 3,138 m 634 Wildlife Society Bulletin 42(4)

Figure 1. Mean daily distance moved by male eastern wild turkeys during March-May on the Webb Wildlife Management Area Complex, South Carolina, USA, 2015 2016. (SD ¼ 1,549 m); daily movements tended to increase from March through early April, before declining gradually (Fig. 1). We collected 41,400 hours of ambient sound during 2015 2016. We identified and evaluated 1,566,907 potential gobbles and positively identified 19,126 (9,546 and 9,580 in 2015 and 2016, respectively). We noted that gobbling activity was highly variable across both years of our study (Fig. 2). Autocorrelation analysis revealed little evidence of lags in gobbling activity, suggesting that gobbling activity at time t had little influence on gobbling activity at t > lag0 (Fig. 3). Stated differently, daily gobbling activity varied to such an extent that gobbling activity one day only related to gobbling during the next day, rather than any subsequent days. We observed no definable relationship between daily gobbling activity and onset of nest incubation during either 2015 (Fig. 4) or 2016 (Fig. 5). During 2015, gobbling declined as onset of incubation increased, before trending upward again (Fig. 4). During 2016, daily variability in gobbling activity was more pronounced than in 2015, but it is important to note that total numbers of gobbles detected Figure 2. Daily gobbling activity as measured by total number of gobbles by male eastern wild turkeys on the Webb Wildlife Management Area Complex, South Carolina, USA, during 2015 2016. Chamberlain et al. Gobbling and Female Nesting Phenology 635

Figure 3. Autocorrelation plot for daily time series of daily gobbling activity showing weak correlation (significance noted by blue lines) between gobbling activity during one day relative to subsequent days by male eastern wild turkeys on the Webb Wildlife Management Area Complex, South Carolina, USA, during 2015 2016. ACF is autocorrelation function. Figure 4. Daily numbers of gobbles recorded relative to percent of micro Global Positioning System (mgps) -marked female eastern wild turkeys incubating nests at the Webb Wildlife Management Area Complex, South Carolina, USA, during 2015. 636 Wildlife Society Bulletin 42(4)

Figure 5. Daily numbers of gobbles recorded relative to percent of micro Global Positioning System (mgps) -marked female eastern wild turkeys incubating nests at the Webb Wildlife Management Area Complex, South Carolina, USA, during 2016. were nearly identical between years (Fig. 5). We observed several days of noteworthy increases in gobbling activity that appeared to coincide with declining numbers of females in incubation, although fewer incubating females presumably resulted in more females available on the landscape. Likewise, we noted that the period of nest incubation differed between years, with a clearly more prolonged nesting effort during 2016. Notably, during 2015, females had ceased incubation by later stages of May but gobbling activity continued, and during 2016, several days of intense gobbling activity occurred during waning days of our monitoring (Fig. 5). Cross-correlation analysis between gobbling activity and nest initiation indicated 2 significant cross-correlations at lag 37 and lag 10 (Fig. 6). We interpreted these relationships as an above average number of gobbles 37 days prior lead to a below average number of females initiating nests approximately 37 days later. Conversely, an above average number of gobbles 10 days prior lead to an above average number of females initiating nests approximately 10 days later. After data were rescaled to account for the observed lags, we noted that the times-series data sets were similar at both the 37 day (b ¼ 0.055, SE ¼ 0.17, P ¼ 0.75) and 10 day (b ¼ 0.067, SE ¼ 0.11, P ¼ 0.55) lags, further supporting the relevance of the observed lags. Finally, daily distances moved by males tracked increases in gobbling activity throughout March, but once movements reached an asymptote corresponding to opening of hunting season (1 Apr), there appeared to be no discernable relationship between daily distances moved and gobbling activity (Fig. 7). DISCUSSION Gobbling activity is a key determinant of turkey hunter satisfaction and often used by state agencies to set regulatory frameworks (Bevill 1975, Hoffman 1990, Little et al. 2000, Casalena et al. 2011). Previous researchers have attempted to identify peaks in gobbling under the assumption that at least one such peak was related to onset of nest incubation (Kennamer 1986, Miller et al. 1997). Hence, managers have set hunting season dates under the long-held assumption that hunting activity would occur during periods when males were most vocal and females were incubating and less likely to be illegally harvested(kurzejeski and Vangilder 1992, Oleson and He 2004). Presumably, adjusting the regulatory framework based on gobbling peaks would lead to increased hunter satisfaction coupled with reduced opportunities for disturbance of females and removal of males before breeding, both of which could negatively influence productivity (Vangilder and Kurzejeski 1995, Healy and Powell 1999, Norman et al. 2001). Our findings do not support contentions that daily gobbling is positively associated with onset of incubation by females (Hoffman1990,Lehmanetal.2005;but seemilleretal.1997). We also noted considerable variation in daily gobbling activity coupled with no discernable relationships between gobbling activity and male movements. Collectively, our findings highlight the complexities associated with using relationships between gobbling activity and female availability as context for setting harvest seasons. Previous authors have noted increased movements of male wild turkeys during spring and increases in movements as the Chamberlain et al. Gobbling and Female Nesting Phenology 637

Figure 6. Autocorrelation plot depicting average correlation between time series of daily gobbling activity and nest initiation as a function of time lags between them by eastern wild turkeys on the Webb Wildlife Management Area Complex, South Carolina, USA, during 2015 2016. We noted 2 distinct lags (noted by blue lines) in gobbling activity at approximately 37 and 10 days prior to nest initiation. ACF is autocorrelation function. reproductive season progressed, presumably because of declines in availability of females and increases in human disturbance (Godwin et al. 1994, Badyaev 1995, Badyaev et al. 1996). Our observations of daily distances moved by males were comparable to those reported by Godwin et al. (1994) and Collier et al. (2017) in a similar landscape, but were temporally consistent throughout periods when incubation occurred. Conversely, we noted that daily gobbling activity varied drastically, and suggest that such variation may relate to confounding effects of male physiology, receptivity of females, disturbance of males, and removal of males via harvest, which we discuss in more detail below. Calling and movements associated with breeding activity are driven by changes in testosterone levels (Wada 1981). Turkeys have pulsatile testosterone levels that result in day-to-day fluctuations in breeding behaviors (Bacon et al. 1991). Similarly, testosterone levels in Japanese quail (Coturnix japonica) oscillate temporally, resulting in fluctuating daily calling activity (Wada 1986). Hence, we offer that notable daily variations in gobbling activity may partially result from changes in calling behavior by individual males as testosterone levels fluctuate. Wild turkeys use elaborate courtship displays and vocalizations, and exhibit notable phenotypic differences between males and females driven by sexual selection (Pelham and Dickson 1992). Male dominance, which may be associated with various physical and behavioral traits, helps determine access to receptive females (Eaton 1992, Buckholz 1995, Buckholz et al. 2004, Krakauer 2008). The degree to which individual males gobble is not based only on availability of receptive females, but instead should be a function of the ratio of receptive females to males (i.e., operational sex ratio; Emlen and Oring 1977). Hence, as numbers of receptive females decline with onset of incubation, competition among males should naturally increase, as should intensity and frequency of courtship displays (Emlen and Oring 1977, Weir et al. 2011). However, we noted no discernable patterns between gobbling activity and nest initiation, contrary to previous research that suggested that gobbling activity was greatest when females were incubating and not available to males (Hoffman 1990). Conversely, we noted extensive gobbling activity on particular days as numbers of females incubating nests declined toward the end of the nesting 638 Wildlife Society Bulletin 42(4)

Figure 7. Daily numbers of gobbles recorded relative to daily distances moved by male eastern wild turkeys at the Webb Wildlife Management Area Complex, South Carolina, USA, during 2015 2016. season. We speculate that perhaps males once again began interacting with females as incubation of initial nests ended, prompting intense competition among males with access to these females prior to renest attempts, although some females would presumably not be receptive to mating (see Wingfield 1994). Moreover, hunting activity can negatively influence gobbling activity, likely through direct removal of vocal males and disturbance, but also through changes to operational sex ratios that decreases male competition (Kienzler et al. 1996, Lehman et al. 2005, Wightman et al. 2018). Future research should seek ways to better quantify operational sex ratios and assess how competition among males relative to these ratios influences gobbling activity. Courtship behaviors such as gobbling increase predation risk because predators may also be attracted to calls (Tuttle and Ryan 1981, Burk 1982). To minimize risk, males that vocalize may alter courtship behaviors or decrease frequency of behaviors (Candolin and Voigt 1998, Hedrick 2000); substantive predation risk can result in song loss in some species (Walker 1974). As noted above, predation risk through hunting can negatively affect gobbling activity, and we recognize that those effects confound attempts to relate gobbling activity to female reproductive phenology and other ecological environmental parameters (Lehman et al. 2005, Wightman et al. 2018). Wild turkey is the only gamebird in the conterminous United States hunted specifically during the peak of reproductive activities. Wightman et al. (2018) found that a significant portion of gobbling activity occurred after hunting seasons closed on our study area, and suggested that managers consider adjusting season frameworks to include periods when most gobbling occurred. As such, our results and those of Wightman et al. (2018) suggest that structuring regulatory timing based on perceived peaks in gobbling activity, and assuming that reproductive activities are underlying those peaks, may fail to recognize important aspects of reproductive behavior in wild turkeys and confounding effects of hunting on these activities. Thus, we suggest that researchers and managers attempt to assess effects of male harvest on reproductive timing and gobbling activity to ensure that regulatory frameworks are appropriate and will ensure sustainable wild turkey populations. Ultimately, we suggest that obtaining accurate assessments of relationships between gobbling activity and reproductive ecology in wild turkeys will require research focused on nonhunted populations. We noted 2 distinct lags between gobbling activity and nest initiation (laying) by females. We speculate that these lags could relate to differential aspects of reproductive behaviors by male wild turkeys, and could point to disconnects in our collective understanding of gobbling behavior. Male wild turkeys become receptive to breeding before females, consistent with known sex-specific differences in gonadotropin-releasing hormones (Williams and Austin 1988, King and Millar 1995). Hence, males would be expected to vocalize and display before females are actually receptive to breeding, and perhaps gobbling early in the reproductive period (prior to female receptivity) is more associated with establishment of pecking orders and male dominance than securing breeding opportunities per se (Healy 1992). It is Chamberlain et al. Gobbling and Female Nesting Phenology 639

plausible that the observed 37-day lag between gobbling activity and reduced numbers of females initiating nests is reflective of these expected differences in sex-specific receptivity to breeding and male behavior toward conspecifics. Likewise, we noted an above-average number of gobbles 10 days prior being associated with greater numbers of females initiating nests 10 days later. In general, fertile periods in birds end when the last egg is fertilized, translating to several days prior to the last egg being laid (Birkhead and Biggins 1987). Although sperm storage in birds facilitates sperm competition and allows turkeys to lay fertile eggs well after copulation (Birkhead and Moller 1992, Khillare et al. 2018), males may increase fitness by mating with females immediately prior to egg laying (Birkhead et al. 1987). Wild turkeys typically lay a single egg daily, average clutch size is 10, and achieve maximum sperm storage when females are inseminated immediately prior to egg production (Vangilder et al. 1987, Brillard and Bakst 1990, Healy 1992). Hence, we offer that it is plausible that male wild turkeys would increase gobbling when they perceive females to be nearing egg production because, presumably, competition among males would escalate (see Birkhead et al. 1987). Future research should continue to evaluate gobbling activity comprehensively relative to female nesting behaviors across multiple study sites, in hopes of better understanding relationships between these facets of wild turkey reproduction. MANAGEMENT IMPLICATIONS Our findings suggest that use of gobbling activity to set harvest seasons for wild turkeys may be considerably more complicated and nuanced than previously believed. We found no evidence to support notions that male wild turkeys increase gobbling activity as females begin incubating nests, contrary to a long-held belief by managers charged with setting harvest seasons for males. State agencies frequently use gobbling chronology information as an important determinant in setting spring hunting season dates, based on the perceived relationship between gobbling activity and nesting phenology of females. Our findings suggest that agencies should consider more precisely monitoring relationships between nesting phenology and gobbling activity, because both parameters vary spatially and temporally. Furthermore, research evaluating confounding influences of hunting activity and male mortality during the mating season on gobbling activity and wild turkey population dynamics is warranted. Understanding relationships between gobbling activity and reproductive ecology in wild turkeys will necessarily hinge on research conducted on nonhunted populations. ACKNOWLEDGMENTS Our research was supported by the South Carolina Department of Natural Resources, the Louisiana State University Agricultural Center, and the Warnell School of Forestry and Natural Resources at the University of Georgia. We are grateful to the suite of biologists and technicians on the Webb WMA Complex who provided significant time and assistance with trapping and field data collection. We gratefully acknowledge A. Medine, A. Burrus, C. Morrow, E. Price, C. Tate-Goff, L. McFarland, Z. Stratton, B. Stafford, T. Carlson, S. Cottingham, K. Kuylen, J. Huynh, and M. Brandon for their efforts evaluating gobbling data. We appreciate thoughtful comments provided by J. Sands and 2 anonymous reviewers. This manuscript is based upon work supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, McIntire Stennis project under no. 1005302. LITERATURE CITED Bacon, W. L., J. A. Proudman, D. N. Foster, and P. A. Renner. 1991. 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