Winter roosting ecology of Rio Grande wild turkeys in the Rolling Plains of Texas
Swearingin, Ryan Matthew
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A crucial time for Rio Grande wild turkeys (Meleagris gallopavo intermedia) is during the winter when flocks >200 birds congregate at traditional winter roosts. As wild turkey home ranges are smallest during this time of year, there is a need for appropriate forage and security habitat in close proximity to suitable roosting habitat. In addition, it is believed that eastern cottonwood (Populus deltoides), the favored roost tree species in the Rolling Plains, may be declining due to altered river flow regimes, the invasion of exotic species such as Russian olive (Elaeanus angustifolia) and saltcedar (Tamarix chinensis), and overgrazing. Consequently, a greater understanding of the critical vegetative characteristics of winter roost sites is needed. We conducted fieldwork on 3 study sites located in the Rolling Plains of Texas during September through flock breakup in April 2004–2006. We gathered roost locations via radiotelemetry to identify movement patterns and to detect active roosts during winter. We measured roosting habitat at 32 roost sites and 32 randomly selected non-roost sites. We measured tree height, tree diameter, canopy cover, tree decay, area of the stand in which the roost occurred (stand area), percent litter cover, and percent shrub cover. We linked winter roost use (presence-absence) with habitat variables representing forest and vegetation structure at roost sites by creating explicit habitat models. We developed 44 a priori logistic regression models. We used second-order Akaike’s information criterion (AICc) for model selection. We found tree height, tree diameter, stand area, and percent litter were all important predictors of roost site occupancy. Based on these findings an appropriate management strategy should include the conservation of large, open-understory, riparian stands of trees. Those stands should contain the tallest, largest diameter trees available. We also suggest that young stands of preferred roost tree species be protected to provide future potential roost sites when current roosts become unsuitable to wild turkeys. Winter flock congregations of Rio Grande wild turkeys are larger than other turkey subspecies. Roosting flocks > 200 birds are not uncommon. However, thorough evaluation of when flocks congregate on winter areas and the potential climatic factors that drive congregation are lacking. We used opportunistic flock counts (n = 3,047) and roost counts (n = 101) to identify timing of winter flock congregation, peak concentrations, and breakup of winter roosts. We also examined possible relationships between roost/flock counts and climatic variables. We found that winter congregation occurred from 15 November through 28 February with peak concentrations occurring from 16 January through 1 March, and flock breakup occurred from 1 March through 15 April. We suggest that if using roost counts for abundance estimation that surveys be conducted from 16 January though 1 March.