Survival of Rio Grande Wild Turkeys on the Edwards Plateau of Texas

Abstract

The southeastern portion of the Edwards Plateau of Texas, historically a stronghold of Rio Grande wild turkeys (Meleagris gallopavo intermedia), has seen a decline in turkey numbers since the 1970s. Because adult and juvenile survival are key parameters affecting turkey population dynamics, we used radiotagged individuals to compare Rio Grande wild turkey survival in areas of suspected decline versus stable portions of the Edwards Plateau during 2001–2003. Reproductive period (breeding or nonbreeding) had an impact on survival, but differences in age, sex, or region did not influence survival. Model averaged estimates of monthly survival were 0.97 (SE = 0.005) for nonbreeding periods and 0.96 (SE = 0.007) for breeding periods. Our results indicate juvenile and adult survival in the declining areas was similar to survival in the stable areas of the Edwards Plateau. This suggests causes of the decline might be associated with differences during other life‐history stages, such as nest success or poult survival, although we cannot rule out the possibility juvenile or adult survival contributed to the decline in the past. This situation demonstrates why wildlife managers should be cognizant of the implications of initiating long‐term monitoring programs after changes in population status occur, rather than initiating them in expectation of such changes.

Abnormal Eggs of Rio Grande Wild Turkeys on the Edwards Plateau, Texas

“…During the seven years of radiotracking, we did not observe any adult or juvenile radio-tagged individuals moving between study populations, thus we considered each population demographically distinct. We used data from 2001 through 2007 collected as part of a larger study on Rio Grande wild turkey population dynamics (Collier et al 2007a,b, Randel et al 2005 to evaluate spatial, seasonal and annual variation in hen survival. Randel et al (2005) evaluated basic reproductive parameters for hens (e.g.…”

“…1). Two sites were located in regions where declines in turkey abundance had occurred (Bandera and Medina counties), and two sites were located in areas where there was no trend in abundance (Kerr and Real counties; Randel et al 2005, Collier et al 2007a. Each site was characteristic of Edwards Plateau topography, rolling divides with limestone bedrock and outcrops with rocky soils (Gould 1975).…”

“…Based on seven years of research on the reproductive ecology of Rio Grande wild turkeys in this region, we found limited variation between populations classified as stable vs declining in such reproductive parameters as clutch size (x=10.9¡3.44 (SE) and x=10.8¡2.73 (SE)), daily nest survival (0.92¡0.02 (SE) and 0.94¡0.005 (SE)), nesting rates (65 and 58%), rates of nest predation (65 and 67%), nest abandonment (18 and 22%) and poult survival (18% survival for first two weeks across sites; Melton 2007. Breeding season survival of both male and female Rio Grande wild turkeys was lower than nonbreeding season survival and there was preliminary evidence that differences might exist between populations classified as stable vs declining (Collier et al 2007a).…”

“…Since the late 1970s, however, surveys conducted by the Texas Parks and Wildlife Department, as well as anecdotal observations by landowners, have documented a decline in wild turkey numbers in the southeastern portion of the Edwards Plateau (Randel et al 2005, Collier et al 2007a. As the reason for this decline was unknown, we initiated a research program in 2001 to determine whether population demography differed between areas characterized by stable vs declining turkey abundance.…”

“…belonging to the orders Galliformes and Anseriformes) exhibit both high reproductive output and high mortality of breeding birds, suggesting that an advantageous life-history strategy would be to delay or limit breeding until conditions are optimal for reproduction (Murdoch 1966; but see Jo¨nsson et al 1991 andSandercock et al 2005). Collier et al (2007a) found that breeding season survival of adult wild turkeys differed between stable and declining populations on the Edwards Plateau of Texas. Because survival ofbreeding female galliforms is intrinsically tied to recruitment (Stearns 1976, Alerstam & Ho¨gstedt 1984, Martin 2002, we hypothesized that population declines in the southeastern portion of the Edward Plateau could be due to comparatively low breeding season survival of females.…”