D. Clay Sisson

IDENTIFYING PREDATORS AT NORTHERN BOBWHITE NESTS

Abstract We identified nest predators of northern bobwhites (Colinus virginianus) on private lands in northern Florida and southern Georgia, USA, using continuous infrared micro-video cameras, 1999–2001, and compared these results to predictions based on diagnostic sign at nests. Mammals (59%), snakes (29%), and ants (12%) accounted for known bobwhite nest depredations. Mammalian predators, in order of importance, were the raccoon (Procyon lotor), nine-banded armadillo (Dasypus novemcinctus), Virginia opossum (Didelphis virginiana), bobcat (Lynx rufus), hispid cotton rat (Sigmodon hispidus), and coyote (Canis latrans). Using diagnostic sign, technicians correctly classified 30% of mammalian depredations to species and overestimated nest depredations by snakes. A classification tree model correctly classified 75% of the test sample (n = 33) into “mammal” or “snake” categories, but still overestimated depredations by snakes. We documented a broader predator community upon bobwhite eggs than previously known for northern Florida and southern Georgia and confirmed that snakes were significant nest predators in some years. We conclude that diagnostic sign at depredated nests was unreliable for identifying nest predators of northern bobwhites.

Factors Influencing Survival of Radiotagged and Banded Northern Bobwhites in Georgia

Abstract Numerous studies of behavior and ecology of northern bobwhites (Colinus virginianus) have depended on radiotagging and telemetry for data collection. Excluding the presumably short-term effects of trapping, handling, and attaching radiotransmitters, researchers often assume that little bias is associated with estimating survival and behavioral parameters associated with this technique. However, researchers have not adequately examined these effects on organisms being investigated and have thus assumed demographic information obtained from such methods are valid. In light of this conjecture, it is imperative to evaluate methodological assumptions to ensure research is statistically valid and biologically meaningful. Therefore, we used Burnhams model and program MARK to analyze survival estimates of individually banded and radiotagged bobwhites during an 8-year period (1997–2004) consisting of 6,568 individuals (2,527 radiotagged) via combined analysis of mark–recapture, dead recovery (via harvest), and radiotelemetry data to test the effects of radiotransmitters on bobwhite survival. We also compared band–recapture survival estimates to Kaplan–Meier survival estimates, and we examined the effects of various other factors (e.g., temporal, spatial) on bobwhite survival. Based on Akaikes model selection criterion, the best model including the radiotransmitter covariate (Akaikes Information Criterion adjusted for small sample size bias and overdispersion relative value = 0.72) did not explain more of the variation in survival than models without this effect. Thus, we found the effect of radiotransmitters as negligible. Bobwhite survival varied relative to spatial (e.g., site), temporal (e.g., yr and season), and gender effects. Average annual survival for the 8-year period was 22.76% (1.50 SE) for banded-only and 21.72% (1.49 SE) for radiotagged birds. Survival rate varied annually, ranging from 12.42% (7.51 SE) to 37.16% (8.27 SE), and seasonally, ranging from 23.82% (2.71 SE) to 65.06% (3.23 SE); however, between group (banded-only, radiotagged) survival differences were still inconsequential. We conclude that for our study, radiotelemetry provided reliable survival estimates of an intensively managed bobwhite population, where supplemental food was provided, and this information provided useful data to make practical habitat management decisions. We believe that future radiotelemetry studies would benefit as a whole if researchers conducted similar analyses prior to presenting their results from radiotelemetry data, especially for populations that are more food limited.

Translocation to a fragmented landscape: survival, movement, and site fidelity of Northern Bobwhites

Habitat fragmentation, degradation, and loss have taxed early-successional species including the Northern Bobwhite (Colinus virginianus) and numerous grassland obligate birds. Translocation is often applied to counteract the consequences of habitat fragmentation through the creation, reestablishment, or augmentation of wild populations for the purposes of conservation, biodiversity maintenance. However, the implementation of these techniques is often conducted without valid experimental designs and therefore lacks robust, empirical data needed to evaluate and advance the knowledge and application of translocation. Despite the increasing amount of habitat management applied to patches among fragmented landscapes, a paucity of source populations often limits natural (re)colonization. As such, translocation may serve as a surrogate to natural dispersal, but its efficacy among fragmented landscapes is uncertain. Few studies exist that have assessed site fidelity, movement, and survival of individuals following translocation among fragmented landscapes. Thus, we experimentally evaluated the efficacy of translocation using known-fate and multi-strata models to evaluate hypotheses of temporal, biological, and group effects on survival and movement of translocated and resident bobwhites. We did not detect differences in survival or movement between translocated and resident bobwhites, suggesting that movement of individuals to a fragmented habitat does not negatively influence these demographic attributes. Based on these data, we suggest that two site-specific criteria should be met prior to instituting translocation: habitat management should be conducted to ensure that quality habitat exists and the patch size should be a minimum of 600 ha of quality habitat (poorer sites may warrant even larger patches). Translocation is a viable conservation method for increasing abundance in patches when habitat quality is high but source populations are limited.

The Efficacy of Relocating Wild Northern Bobwhites Prior to Breeding Season

Abstract During 1997 and 1998, we implemented a pilot investigation to compare survival, site fidelity, and reproductive characteristics of relocated wild northern bobwhites (Colinus virginianus) with that of resident birds. We captured wild bobwhites (n = 74) on managed lands in southern Georgia and relocated them (>1.6 km from capture sites) to sites nearby where density estimates revealed that population density was low compared to surrounding sites. We equipped translocated birds with radiotransmitters and released them in groups of 8–12. We also captured resident birds (n = 166) and simultaneously monitored them via radiotelemetry. We found no difference in survival (P = 0.82), nest production (P = 0.19), or nest survival (P = 0.85) between relocated and resident bobwhites. This suggests that relocating wild bobwhites does not negatively impact their survival or reproductive output. Based on the results of the pilot study, we implemented a large-scale relocation to determine whether relocation can increase native bobwhite populations. Following the pilot study, during 2000–2002, we relocated wild bobwhites (n = 202) within property boundaries to 3 different sites where population densities were low. Although only 2 sites experienced a significant population increase, hunting records suggested a positive population response for all sites where relocation occurred. Hence, relocation of wild bobwhites prior to breeding season may augment low-density populations, isolated populations, or voids within populations. The utility of translocation may facilitate preservation and conservation of the northern bobwhite by augmenting restoration efforts focused on habitat management, affording species preservation in isolated habitats, and increasing population dynamics and demographics via genetic enrichment.

Cameras Identify White-tailed Deer Depredating Northern Bobwhite Nests

Abstract Odocoileus virginianus (White-tailed Deer) were videotaped depredating two Colinus virginianus (Northern Bobwhite) nests during a nest-predator study in south Georgia in 2002 and 2003. Deer ate eggs from the nests, leading to the failure of one of the two nests.

Estimates of Survival from Radiotelemetry: a Response to Guthery and Lusk

Abstract Radiotelemetry has become an important and frequently used tool in wildlife research. Inferences drawn from radiotelemetry data depend on the assumption that the radiotransmitters are not influencing parameter(s) of interest. An article by Guthery and Lusk (2004) in the Wildlife Society Bulletin questioned the validity of this assumption for estimating survival rates of northern bobwhites (Colinus virginianus) using radiotelemetry data. In this evaluation, we address technical and philosophical flaws in Guthery and Lusks (2004) critique of northern bobwhite studies utilizing radiotelemetry. They concluded that biologists should be skeptical of radiotelemetry studies and they advised researchers to design studies to address potential biases caused by radiotransmitters using independent data. Although we agree that researchers are responsible for testing key assumptions of their techniques, we believe Guthery and Lusks (2004) conclusions were not well supported and were based on tenuous assumptions. Guthery and Lusk (2004) calculated the level of productivity (given as a fall age ratio) required to balance a simple population model that contained published estimates of annual survival and assumed an annual finite population growth rate of 1.0. We review their population model and show that the relationship between an annual survival rate and fall age ratio is nonlinear. This nonlinearity can lead to biased estimates of a fall age ratio, especially at lower values of annual survival. We also question the validity of using fall age ratios as an estimator of productivity. Further, we suggest that this assessment of a radiotransmitter effect from a survival rate itself is not appropriate. This rate can be depressed (or elevated) for a variety of reasons not related to the influence of radiotransmitters. In addition, Guthery and Lusk (2004) assumed that daily survival rates (as calculated from both annual and seasonal published estimates) were constant throughout the year; thus, they scaled daily survival rates from seasonal to annual estimates. Further, their meta-analysis was hindered by temporal pseudoreplication and a lack of independence among the observations used in the analysis. We conclude the weight of the evidence presented by Guthery and Lusk (2004) is not as strong as they claim because it fails to meet the test of sufficient causation. While scientists should always be skeptical and critical of assumptions of all methods employed in wildlife research, more rigorous tests are necessary before we discredit a valuable technique without sufficient empirical evidence.

Raptor Predation of Northern Bobwhite Nests

DEPREDACION DE NIDOS DE COLINUS VIRGINIANUS POR AVES RAPACES Colinus virginianus es una especie que anida en el suelo y tipicamente presenta una tasa de perdida de nidos alta. Hasta hace poco tiempo, la determinacion de las causas de perdida de los nidos se basaba en senales diagnosticas poco confiables registradas en los nidos depredados. Como parte de un estudio exhaustivo sobre la dinamica depredador-presa en C. virginianus (2000–2004), utilizamos monitoreos mediante camaras de video con infrarrojo durante las 24 horas para determinar las causas especificas de la depredacion de nidos. Colocamos camaras de video en 672 nidos de C. virginianus y registramos 249 eventos de depredacion. Las depredaciones fueron hechas por mamiferos (40.2%), serpientes (31.7%), hormigas (11.6%), aves rapaces (1.2%) y por otras causas y por razones desconocidas (15.3%). Durante este estudio registramos tres especies diferentes de aves rapaces depredando nidos de C. virginianus o comiendo sus huevos: un individuo de la especi...

Above-ground Nesting by Northern Bobwhite

Abstract The Northern Bobwhite (Colinus virginianus) is one of the most studied game birds in North America. It is a ground-nesting galliform capable of producing multiple nests during a single season. Since 1993, personnel of the Albany Quail Project have radio-tagged >6,000 bobwhites and monitored >2,000 nests via radio telemetry on private lands in southwestern Georgia. We have observed nests in some peculiar places; however, every nest that we have monitored has been on the ground. Previously, no case of above-ground nesting has been documented for this species. Here, we report an above-ground nest, found in June 2001.