Kristine Johnson

Male-male competition, ornamentation and the role of testosterone in sexual selection in red jungle fowl

Abstract Ornamental traits related to success in male-male competition were studied in red jungle fowl, Gallus gallus. In controlled fights between pairs of males, comb size was the only morphological trait that correlated with winning. Among free-ranging, socially integrated groups of 1-year-old males, body size and comb chroma (degree of saturation with pigment), in addition to comb size, were significantly related to dominance. In jungle fowl, the comb is strongly affected by blood testosterone level, which in turn reflects the current physical condition of the individual.

Sexual selection in pinyon jays I: female choice and male-male competition

Abstract Although pinyon jays, Gymnorhinus cyanocephalus , mate monogamously and male parental investment is high, the mechanisms of sexual selection occur in this species. Experiments were performed using captive birds to determine which male traits are favoured by female choice and which are favoured by inter-male competition. Females mated preferentially with males that were brighter in colour and had larger testes. Females did not prefer large males, but inter-male competition favoured males with larger bills and heavier bodies. Male dominance was not the primary determinant of male mating succes, but it probably conferred an advantage.

Parasites and male ornaments in free-ranging and captive red jungle fowl.

The morphology and parasite burdens of culled free-ranging red jungle fowl (Gallus gallus) from the San Diego Zoo were compared with those of captive roosters used previously in sexual selection experiments, to determine if results obtained with the captive birds were relevant to more natural situations. Zoo roosters had three helminth gut parasites: Ascaridia galli, tapeworms, and Heterakis. Parasite distribution was generally over-dispersed, with most individuals having none or few worms and some having heavy parasite burdens. These levels were comparable to those artificially induced in test roosters. The appearance of the zoo birds was similar to test roosters as well. Higher parasite burdens in the zoo birds was negatively related to hackle feather redness, comb length, and especially testis volume. The latter finding is discussed in light of information about the relationship between testosterone levels, sexual selection, and the immune system. A new analysis of female choice of uninfected controls versus experimentally infected roosters suggests that females prefer a multivariate array of traits perceived as a continuous, rather than categorical, variable.

Genetic structure among closely spaced leks in a peripheral population of lesser prairie-chickens

We evaluated the genetic structure of birds from four closely spaced leks in a peripheral population of lesser prairie‐chickens (Tympanuchus pallidicinctus). Analyses of molecular variance revealed significant genetic structuring among birds from different leks for six microsatellite loci (FST = 0.036; P = 0.002), but we found no genetic differentiation at the mtDNA control region. Significant deviations from Hardy–Weinberg revealed an excess of homozygote genotypes within each of the leks studied (FIS = 0.190–0.307), indicative of increased inbreeding. Estimates of relatedness using microsatellite data suggest that the genetic structuring among lesser prairie‐chicken leks occurs in part because of a lek mating system in which males at some leks are related. Structuring may also be caused by stochastic effects associated with a historical decline in population size leading to small, semi‐isolated leks and high site fidelity by reproductive males. Results from this study suggest that microspatial genetic structuring may occur in lek‐mating bird species with low levels of dispersal.

HABITAT USE AND NEST SITE SELECTION BY NESTING LESSER PRAIRIE-CHICKENS IN SOUTHEASTERN NEW MEXICO

Abstract Lesser prairie-chickens (Tympanuchus pallidicinctus) occur in shinnery oak (Quercus havardii) and sand sagebrush (Artemisia filifolia) grassland habitats in New Mexico, Texas, Oklahoma, Kansas, and Colorado. Range-wide population reductions since the 1800s have been attributed to habitat loss, especially of nesting habitat. Using radio-telemetry and a vegetation map of the study area, we investigated habitat use by lesser prairie-chicken hens during the nesting season in herbicide-treated and untreated pastures (each about 1,000 ha in size). Herbicide treatment was effective in reducing shinnery oak cover. The most common vegetation types in hen home ranges were those dominated by shinnery oak. Hens were detected more often than randomly in or near untreated pastures. Although hens were detected in both treated and untreated habitats, 13 of 14 nests were located in untreated pastures, and all nests were located in areas dominated by shinnery oak. Areas immediately surrounding nests had higher shrub composition than the surrounding pastures. This study suggests that herbicide treatment to control shinnery oak might adversely impact nesting lesser prairie-chickens.

GIS habitat analysis for lesser prairie-chickens in southeastern New Mexico

BackgroundWe conducted Geographic Information System (GIS) habitat analyses for lesser prairie-chicken (LPCH, Tympanuchus pallidicinctus) conservation planning. The 876,799 ha study area included most of the occupied habitat for the LPCH in New Mexico. The objectives were to identify and quantify: 1. suitable LPCH habitat in New Mexico, 2. conversion of native habitats, 3. potential for habitat restoration, and 4. unsuitable habitat available for oil and gas activities.ResultsWe found 16% of suitable habitat (6% of the study area) distributed in 13 patches of at least 3,200 ha and 11% of suitable habitat (4% of the study area) distributed in four patches over 7,238 ha. The area converted from native vegetation types comprised 17% of the study area. Ninety-five percent of agricultural conversion occurred on private lands in the northeastern corner of the study area. Most known herbicide-related conversions (82%) occurred in rangelands in the western part of the study area, on lands managed primarily by the US Bureau of Land Management (BLM). We identified 88,190 ha (10% of the study area) of habitats with reasonable restoration potential. Sixty-two percent of the primary population area (PPA) contained occupied, suitable, or potentially suitable habitat, leaving 38% that could be considered for oil and gas development.ConclusionAlthough suitable LPCH habitat appears at first glance to be abundant in southeastern New Mexico, only a fraction of apparently suitable vegetation types constitute quality habitat. However, we identified habitat patches that could be restored through mesquite control or shin-oak reintroduction. The analysis also identified areas of unsuitable habitat with low restoration potential that could be targeted for oil and gas exploration, in lieu of occupied, high-quality habitats. Used in combination with GIS analysis and current LPCH population data, the habitat map represents a powerful conservation and management tool.