Demographic Differences of Black-Capped Vireos in 2 Habitat Types in Central Texas

Abstract: To understand the effects of habitat selection, we analyzed differences in abundance, age structure, and nesting success of black-capped vireos (Vireo atricapilla) in 2 early successional habitat types found on Fort Hood, a 87,890-ha Military Reservation in central Texas, USA. These habitats were 1) large areas of continuously shrubby vegetation (both natural and mechanically made), referred to as shrubland habitat, and 2) anthropogenically created small patches of shrubby vegetation centered on one or several large trees, known locally as donut habitat. The objectives of our study were to determine whether there were differences in abundance, age structure, and daily nest survival in these 2 habitat types and to determine whether donut habitat is high- or low-quality habitat. Donut habitat had a lower abundance of vireos (half as many as shrubland/point count) and a higher percentage of second-year males, suggesting donut habitat was lower-quality habitat than shrubland. Analyses of daily nest survival indicated that habitat, nest height, and year were all important variables. Nests initiated in 2004, located in shrubland habitats, and higher from the ground were more likely to succeed. Our study provided evidence that habitat is a limiting factor for this federally endangered species. Because habitat is limiting, wildlife biologists at Fort Hood should focus on managing higher quality, contiguous shrubland habitat. Wildlife biologists should also continue to monitor areas of donut habitat to determine whether they represent potential population sinks.     

Male influence on the duration of reproductive diapause in the large milkweed bug, Oncopeltus fasciatus

ABSTRACT. Differences were found in duration of diapause, as measured by days to first oviposition following adult eclosion, between female Oncopeltus fasciatus (Dallas) mated with male O.sandarachatus (Say) (mean =55 days), and those mated with their brothers (mean =99 days). Under the same conditions (LD 11:13 at 23°C), O.sandarachatus pairs showed no delay in reproduction (mean = 12 days). Male O.sandarachatus exhibit greater sexual activity than male O.fasciatus , and it is postulated that this behaviour may play a significant role in determining the length of diapause in the female.     

Testing a Mahalanobis Distance Model of Black Bear Habitat Use in the Ouachita Mountains of Oklahoma

Abstract: Regional wildlife-habitat models are commonly developed but rarely tested with truly independent data. We tested a published habitat model for black bears (Ursus americanus) with new data collected in a different site in the same ecological region (i.e., Ouachita Mountains of Arkansas and Oklahoma, USA). We used a Mahalanobis distance model developed from relocations of black bears in Arkansas to produce a map layer of Mahalanobis distances on a study area in neighboring Oklahoma. We tested this modeled map layer with relocations of black bears on the Oklahoma area. The distributions of relocations of female black bears were consistent with model predictions. We conclude that this modeling approach can be used to predict regional suitability for a species of interest.     

Multiple Genetic Components in Bromegrass Mosaic Virus

Bromegrass mosaic virus has three types of structurally similar virions all of which are required for infectivity. The virions contain either one RNA molecule of molecular weight 1.09×10⁶ or 0.99×10⁶ or two of molecular weights 0.75×10⁶ and 0.28×10⁶. A mixture of the isolated RNAs is infectious and deletion of any but the smallest greatly reduces infectivity. The third largest RNA component contains the coat protein gene.