Influence of weather on gobbling activity of male wild turkeys
PATRICK H. WIGHTMAN,11Email: pw78598@uga.eduWarnell School of Forestry
and Natural Resources, University of Georgia, Athens, GA 30602, USA
JAMES A. MARTIN, Warnell School of Forestry and Natural Resources,
University of Georgia, Athens, GA 30602, USA
JOHN C. KILGO, USDA Forest Service, Southern Research Station,
P.O. Box 700, New Ellenton, SC 29809, USA
EMILY RUSHTON, Georgia Department of Natural Resources – Wildlife
Resources Division, Social Circle, GA 30025, USA
BRET A. COLLIER, School of Renewable Natural Resources, Louisiana
State University Agricultural Center, Baton Rouge, LA 70803, USA
MICHAEL J. CHAMBERLAIN, Warnell School of Forestry and Natural
Resources, University of Georgia, Athens, GA 30602, USA
Abstract Gobbling activity of Eastern wild turkeys
(Meleagris gallopavo silvestris ; hereafter, turkeys) has been
widely studied, focusing on drivers of daily variation. Weather
variables are widely believed to influence gobbling activity, but
results across studies are contradictory and often equivocal, leading to
uncertainty in the relative contribution of weather variables to daily
fluctuations in gobbling activity. Previous works relied on road-based
auditory surveys to collect gobbling data which limits data consistency,
duration, and quantity due to logistical difficulties associated with
human observers and restricted sampling frames. Development of new
methods using autonomous recording units (ARUs) allows researchers to
collect continuous data in more locations for longer periods of time,
providing the opportunity to delve into factors influencing daily
gobbling activity. We used ARUs from 1 March to 31 May to detail
gobbling activity across multiple study sites in the southeastern United
States during 2014 – 2018. We used state-space modeling to investigate
the effects of weather variables on daily gobbling activity. Our
findings suggest rainfall, greater wind speeds, and greater temperatures
negatively affected gobbling activity, whereas increasing barometric
pressure positively affected gobbling activity. Therefore, when using
daily gobbling activity to make inferences relative to gobbling
chronology, reproductive phenology, and hunting season frameworks
stakeholders should recognize and consider the potential influences of
extended periods of inclement weather.
Key words acoustic monitoring, gobbling, Meleagris
gallopavo, Convolutional Neural Network, weather, wild turkey.
Male birds often rely on visual and auditory courtship behaviors to
portray reproductive fitness to females, attract mates, and maintain
social and dominance hierarchies (Williams 1984, Omland 1996, Buchholz
1997, Mateos 1999, Cornec et al. 2017). Frequency of courtship
behaviors, such as vocalizations by males, change in response to
conspecifics along with anthropogenic and environmental influences
(Staicer et al. 1996, Berg et al. 2005, Slabbekoorn and Ripmeester
2008). Ecological theories such as the adaptive acoustic hypothesis and
risk reward theory suggest birds adopt different vocalization strategies
depending on environmental conditions to maximize the effectiveness and
costs associated with calling (Orians 1969, Zanette et al. 2006, Lima
2009, Luther 2009).
The wild turkey (Meleagris gallopavo ) is a non-migratory upland
game bird indigenous to North America whose mating strategy is a form of
polygamy similar to exploded lekking (Krakauer 2008). Turkeys use a
polygynous-promiscuous mating system, where females choose males who are
competing for mating opportunities via visual displaying (e.g.,
strutting) and auditory vocalizations (e.g., gobbling, drumming; Healy
1992). Turkeys gobble to secure mates by attracting females, maintain
territories, and compete with other males (Bailey and Rinnel 1967,
Bevill 1973, Healy 1992). Gobbling activity is believed to be influenced
by a variety of factors, such as time of day, timing of female
reproductive activities, conspecifics, hunting, weather, predation risk,
age structure, and testosterone levels (Kienzler et al. 1996, Miller et
al. 1997, Chamberlain et al. 2018, Wightman et al. 2019, Wakefield et
al. 2020). Wildlife managers and agencies are interested in
understanding factors influencing gobbling activity, as it is the
primary determinant of hunter satisfaction and is likely linked to
reproductive success (Casalena 2011, Schroeder 2014, Isabelle 2015,
Chamberlain et al. 2020).
Historical research relied on roadside surveys to describe gobbling
activity, but results from previous studies contained notable
discrepancies in regards to drivers of variation in gobbling activity.
For example, early studies reported both positive and negative effects
of nesting phenology, weather, and hunting pressure on gobbling activity
(Bevill 1975, Kienzler et al. 1996, Miller et al. 1997, Lehman et al.
2005, Palumbo et al. 2019). However, no definitive relationship between
any of the aforementioned variables and gobbling activity was
established, likely due to a lack of uniformity in data collection,
coupled with logistical difficulties in obtaining high quality,
detailed, spatially-explicit gobbling data. Furthermore, roadside
surveys were generally not conducted during inclement weather, and can
be additionally biased by observer error, sample design, and manpower
limitations (Miller et al. 1997, Lehman et al. 2005, Palumbo et al.
2019).
Development and use of autonomous recording units (ARU; Rempel et al.
2005, Mennill et al. 2012, Colbert et al. 2015) offer researchers the
ability to thoroughly detail gobbling activity. With advancement of ARU
technology, recent studies have elucidated how factors such as time of
day, nesting phenology/female receptivity and hunting influence gobbling
activity using spatially and temporally robust datasets (Chamberlain et
al. 2018, Wightman et al. 2019, Wakefield et al. 2020). In general,
gobbling activity was highest 30 minutes prior to sunrise until 150
minutes post sunrise (hereafter; daily gobbling activity) and fluctuated
considerably from one morning to the next (Wightman et al. 2019).
Additional work has indicated that female nesting phenology was
positively related to gobbling activity, with onset of reproductive
activities resulting in an initial peak of gobbling (Chamberlain et al.
2018, Wakefield et al. 2020). Furthermore, contemporary literature has
noted hunting activity may have a greater negative influence on gobbling
activity than the positive effect of nesting phenology (Wightman et al.
2019, Wakefield et al. 2020). However, there is no existing literature
using ARUs to investigate the relative influences of weather variation
on gobbling activity. Thus, research is needed to evaluate how weather
may influence gobbling activity. We hypothesized that morning weather
conditions would influence gobbling activity; therefore, our objectives
were to evaluate potential relationships between gobbling activity of
male Eastern wild turkeys (Meleagris gallopavo silvestris ) and a
suite of weather variables across multiple study sites in the
southeastern United States.