Variation in Brood Sex Ratios of Texas Rio Grande Wild Turkeys

Abstract

We evaluated brood sex ratio (BSR) variation in Rio Grande wild turkeys (RGWT; Meleagris gallopavo intermedia) in the Edwards Plateau and South Texas Plains of Texas, USA, during 2005‐2006. Offspring sex was determined from DNA extracted from tissue biopsies of embryos from unhatched eggs or vascular tissue from eggshells of hatched and depredated eggs. Sex ratio across all eggs was 56.3% male (135/240; X21 = 3.75, P = 0.053). We found that mean population growth rate based on a population simulation with BSR at unity averaged 1.02 (range = 0.924‐1.058), whereas it declined to 0.978 (range = 0.816‐1.037) using BSR estimates from our study. Although our statistical analyses did not detect BSRs different from unity in BSR, our simulation modeling demonstrated that BSR variation caused biologically significant differences in mean population growth rates. Even though the biological mechanism controlling primary sex ratio remains unknown, our estimates of BSR should allow managers to more reliably predict population dynamics insuring viable RGWT populations across Texas.

Geographic segregation and evidence of density‐dependent changes in sex ratios in an abundant colonial waterbird

“…Likewise, Collier et al . () did not find significant differences from parity in brood sex ratios of wild turkeys ( Meleagris gallopalvo intermedia Sennett, 1879); however, the average 6.3% male‐biased sex ratio difference did produce significant differences in modeled population growth rates.…”

“…Predicting the effects of management on cormorant populations may be more accurate when differences in sex ratios are incorporated into modeling efforts (Collier et al . ). In this study, we examine the tertiary sex ratios of cormorants culled by different methods in eastern USA and describe geographical segregation of male and female cormorants on their wintering grounds in southeastern USA.…”

“…For example, research has indicated that manipulation of sex ratios in endangered avian species can be used as a tool for aiding species recovery (Wedekind 2002;Lenz & Wedekind 2007). Conversely, understanding cause and effect of biased sex ratios can be important with respect to species intensively managed due to commercial or subsistence harvest, recreational hunting, or because they are implicated in human-wildlife conflicts (Lercel et al 1999;Collier et al 2007;Donald 2007). For example, Glahn et al (1995) found that male double-crested cormorants [Phalacrocorax auritus (Lesson, 1831)] were more likely than females to depredate farmed fish.…”

“…Bédard et al (1999) ended a 5-year control program early because male sex-biased culling of cormorants resulted in a faster than predicted reduction in breeding pairs. Through simulation modeling, Collier et al (2007) demonstrated that male-biased brood sex ratio variation causes biologically significant differences in population growth rates of wild turkeys (Meleagris gallopavo Linnaeus, 1758). Regardless of goals and objectives, management is most effective when based on fundamental knowledge of ecology, behavior and population dynamics of the species being managed.…”

Wild Turkey (Meleagris gallopavo) association to roads: implications for distance sampling

“…), little bluestem (Schizachyrium scoparium), bufflegrass (Pennisetum ciliare), King Ranch bluestem (Bothriochola ischaemum), and three awns (Aristida spp. ; Hernandez et al 2005, Collier et al 2007b). Cattle grazing, wildlife ranching, and oil production were widespread across the ecoregion (Griffith et al 2004, Butler et al 2005a).…”