John P. Carroll

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.

A phylogenetic supertree of the fowls (Galloanserae, Aves)

The fowls (Anseriformes and Galliformes) comprise one of the major lineages of birds and occupy almost all biogeographical regions of the world. The group contains the most economically important of all bird species, each with a long history of domestication, and is an ideal model for studying ecological and evolutionary patterns. Yet, despite the relatively large amount of systematic attention fowls have attracted because of their socio‐economic and biological importance, the species‐level relationships within this clade remain controversial. Here we used the supertree method matrix representation with parsimony to generate a robust estimate of species‐level relationships of fowls. The supertree represents one of the most comprehensive estimates for the group to date, including 376 species (83.2% of all species; all 162 Anseriformes and 214 Galliformes) and all but one genera. The supertree was well‐resolved (81.1%) and supported the monophyly of both Anseriformes and Galliformes. The supertree supported the partitioning of Anseriformes into the three traditional families Anhimidae, Anseranatidae, and Anatidae, although it provided relatively poor resolution within Anatidae. For Galliformes, the majority‐rule supertree was largely consistent with the hypothesis of sequential sister‐group relationships between Megapodiidae, Cracidae, and the remaining Galliformes. However, our species‐level supertree indicated that more than 30% of the polytypic genera examined were not monophyletic, suggesting that results from genus‐level comparative studies using the average of the constituent species’ traits should be interpreted with caution until analogous species‐level comparative studies are available. Poorly resolved areas of the supertree reflect gaps or outstanding conflict within the existing phylogenetic database, highlighting areas in need of more study in addition to those species not present on the tree at all due to insufficient information. Even so, our supertree will provide a valuable foundation for understanding the diverse biology of fowls in a robust phylogenetic framework.

Population divergence in plant species reflects latitudinal biodiversity gradients.

The trend for increasing biodiversity from the poles to the tropics is one of the best-known patterns in nature. This latitudinal biodiversity gradient has primarily been documented so far with extant species as the measure of biodiversity. Here, we evaluate the global pattern in biodiversity across latitudes based on the magnitude of genetic population divergence within plant species, using a robust spatial design to compare published allozyme datasets. Like the pattern of plant species richness across latitudes, we expected the divergence among populations of current plant species would have a similar pattern and direction. We found that lower latitudinal populations showed greater genetic differentiation within species after controlling for geographical distance. Our analyses are consistent with previous population-level studies in animals, suggesting a high possibility of tropical peaks in speciation rates associated with observed levels of species richness.

Metabolic turnover rates of carbon and nitrogen stable isotopes in captive juvenile snakes

Metabolic turnover rates (m) of delta(15)N and delta(13)C were assessed in different tissues of newly hatched captive-raised corn snakes (Elaphe guttata guttata) fed maintenance diets consisting of earthworms (Eisenia foetida) that varied substantially in delta(15)N (by 644 per thousand) and delta(13)C (by 5.0 per thousand). Three treatments were used during this 144 day experiment that consisted of the same diet throughout (control), shifting from a depleted to an enriched stable isotope signature diet (uptake), and shifting from an enriched to depleted stable isotope signature diet (elimination). Values of delta(13)C in the liver, blood, and muscle of the control snakes reached equilibrium with and were, respectively, 1.73, 2.25 and 2.29 greater than in their diet, this increase is called an isotopic discrimination factor (Deltadelta(13)C = delta(13)C(snake) - delta(13)C(food)). Values of delta(15)N in snake tissues did not achieve equilibrium with the diets in any of the exposures and thus Delta(15)N could not be estimated. Values of metabolic turnover rates (m) for delta(13)C and delta(15)N were greater in liver than in muscle and blood, which were similar, and relative results remained the same if the fraction of (15)N and (13)C were modeled. Although caution is warranted because equilibrium values of stable isotopes in the snakes were not achieved, values of m were greater for delta(13)C than delta(15)N, resulting in shorter times to dietary equilibrium for delta(13)C upon a diet shift, and for both stable isotopes in all tissues, greater during an elimination than in an uptake shift in diet stable isotope signature. Multiple explanations for the observed differences between uptake and elimination shifts raise new questions about the relationship between animal and diet stable isotope concentrations. Based on this study, interpretation of feeding ecology using stable isotopes is highly dependent on the kind of stable isotope, tissue, direction of diet switch (uptake versus elimination), and the growth rate of the animal.

Winter and spring survival of radio-tagged gray partridge in North Dakota

I studied survival of 100 radio-tagged gray partridge (Perdix perdix) in North Dakota from winter to the beginning of nesting during 1985-87. Radio transmitters appeared to cause significant mortality among captured partridge (34%) during the first week postrelease, after accounting for mortality expected from other sources. Survival of partridge living >7 days posttrapping (n=55) from early January to 1 May was 38%. The major source of mortality after the first week was raptor predation. A Coxs proportional hazards analysis revealed that body mass (P=0.003) and sex (P=0.04) were significantly related to probability of survival. Partridge weighing ≥400 g had higher survival (50%) than those weighing <400 g (20%). Females had greater survival (59%) than males (19%)

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.

Feeding Ecology of Ring‐Necked Pheasant and Northern Bobwhite Chicks in Conservation Reserve Program Fields

Abstract Gamebird chick survival is dependent on invertebrate availability, and the ability to access insect prey is an important characteristic defining brood habitat quality. Different mixes of warm-season grasses and forbs were established to improve the habitat quality of fields enrolled in the Conservation Reserve Program (CRP) for gamebirds in the Southern Plains. We analyzed the feeding ecology of human-imprinted, 4- to 10-day-old ring-necked pheasant (Phasianus colchicus) and northern bobwhite (Colinus virginianus) chicks in wheat fields and 4 types of conservation practices (CP) fields enrolled in CRP (CP10, improved CP10, CP2, and CP25) in western Kansas, USA, during June and July, 2004 and 2005. Foraging rates were greatest for bobwhite chicks in improved CP10 and CP25 fields and greatest for pheasant chicks in CP10 and CP25 fields. Vegetation characteristics such as bare ground cover appear to have a significant impact on insect selection, because the diet was more diverse for both species in fields with more bare ground. The CP25 fields provided the best combination of mobility and diet breadth for both species. Although herbicide-treated wheat fields had low feeding rates, we determined non–herbicide-treated fields (i.e., weedy wheat) provided easy mobility and feeding rates similar to CRP fields. We suggest that management of vegetation to benefit gamebirds does not affect species equally. Feeding rates of bobwhite chicks were sensitive to vegetation-influenced mobility. Management of CRP fields for both pheasant and bobwhite chicks can be reconciled by practices that permit more open space at ground level, such as light disking or burning, to permit easier movement for chicks.

Vegetative and invertebrate community characteristics of conservation reserve program fields relative to gamebirds in Western Kansas

ABSTRACT We examined vegetation and invertebrate characteristics, including insect biomass, insect-prey, six Families and seven Orders in four varieties of Conservation Reserve Program (CP10, improved CP10, CP2 and CP25) and wheat fields in western Kansas during Jun. and Jul., 2004 and 2005 relative to gamebird chick ecology. CP10 fields had less bare ground and forbs compared to the other Conservation Practices and CP25 fields had lost much of their original forb component by the end of the study. Although there was little forb component, CP10 fields had high invertebrate biomass. However, CP10 fields demonstrated sizeable declines in the estimated effect size of examined invertebrate characteristics between sampling periods unlike the other mixes. Unharvested wheat (Triticum aestivum), CP10 and improved CP10 fields had the greatest number of insect-prey. Overall, most fields had adequate insect-prey availability suggesting that in terms of insect availability for gamebird chicks, these fields provide excellent brood feeding opportunities, therefore accessibility and other issues might be more important in determining habitat “quality” for gamebird chicks.

Lead exposure in ring-necked pheasants on shooting estates in Great Britain

Abstract Although a few isolated incidences of lead shot ingestion have been reported in ring-necked pheasants (Phasianus colchicus) in Great Britain, no studies have investigated the prevalence of shot ingestion in this species. In this study we investigated the extent of lead exposure in ring-necked pheasants on shooting estates in Great Britain from the ingestion of shot and other sources through gizzard examinations and analysis of wing bones. We examined 437 ring-necked pheasant gizzards collected from birds shot on 32 shooting estates during spring 1996 and 1997 and during the hunting seasons of 1999–2000 and 2001–2002. We determined wing-bone-lead concentrations in 98 female birds collected in 1997. Gizzard examinations showed an overall ingestion incidence rate of 3.0%. We found no differences in ingestion rates among years, seasons, and sexes. Female pheasants had bone-lead levels ranging from 7–445 ppm (x̄ =48.8± 8.8) dry weight. The birds that had lead in their gizzards in 1997 also had high concentrations of lead in their bones. Female pheasant body condition did not decline with the amount of lead in the wing bones. Our data suggest that game managers on shooting estates should be aware that pheasants are vulnerable to shot ingestion and may need to consider measures to reduce this problem in areas where prevalence is high.

Subspecies and units for conservation and management of the northern bobwhite in the eastern United States

The northern bobwhite (Colinus virginianus) is a small game bird with sedentary lifestyle and has experienced population declines throughout most of its native distribution in the eastern United States. We investigated intraspecific genetic relationships among 14 local populations covering four putative subspecies (C. v. marilandicus, C. v. virginianus, C. v. mexicanus, and C. v. floridanus) in the United States. Analysis of mitochondrial DNA sequences revealed a small, but significant, genetic structure of northern bobwhite populations or subspecies in the eastern US. However, our results did not support current subspecies limits as distinct evolutionarily significant units, based on the amount of population genetic divergences and insufficient lineage sorting of mtDNA haplotypes among subspecies. Instead, our results suggest that C. v. virginianus, C. v. marilandicus, and C. v. mexicanus be merged into a single management unit, and C. v. floridanus be considered as another distinct unit for conservation and management.