Leonard A. Brennan

Vegetation Response to Timing of Discing to Manage Northern Bobwhite Habitat in Texas

Discing is commonly recommended to improve northern bobwhite (Colinus virginianus) habitat. However, little information exists regarding optimal timing of discing or the duration of discing effects on semiarid rangelands. Our objectives were to evaluate vegetation response to autumn (October 2003), winter (January 2004), and spring (March 2004) discing in two ecoregions of Texas (Rio Grande Plains and Rolling Plains). Our study design was a completely randomized, two-factor (treatment and soil texture) factorial with repeated measures. We collected data on percent bare ground, forb...

Year
2009

Three Year Post Treatment Effects of Habitat Management on a Wintering Grassland-bird Community in South Texas

Ecologically sound habitat management will be essential to reverse the current decline of grassland birds. The objective of this study is to evaluate the effects of two habitat management practices: (1) summer prescribed fire [SF], (2) a combined treatment of roller chopper, summer prescribed fire, and chemical application [CT], and (3) an open grassland [C] as “control” on wintering grassland-shrub bird community composition and abundance. Line transects of variable lengths were used to assess the bird community structure. Grassland bird species richness during first season was 31 and 15...

Year
2008

Supplemental Feed and Northern Bobwhites: Considerations and Costs

Northern bobwhite (Colinus virginianus) populations are continuing a 30-year downward population trend throughout their range. Managers use supplemental corn (Zea mays) and milo (Sorghum spp.), trying to reverse the decline of bobwhite populations; however, results are conflicting among the published literature. Supplemental feed can influence bobwhite survival, reproduction, and movements, but only in situations where nutrients are truly lacking. Vitamin A, phosphorus (P), calcium (Ca), carbohydrates, and protein can be important nutrients for captive bobwhite egg production; however,...

Year
2008

Overwinter Survival of Northern Bobwhites on Non-hunted Areas in Texas

As part of an ongoing investigation of sustainable harvest strategies for northern bobwhite (Colinus virginianus) populations, we are estimating overwinter survival in two Texas ecoregions that have stable bobwhite population trends, the Rolling Plains and the Rio Grande Plains. Estimating overwinter survival in the absence of hunting is an important variable in developing a sustained-yield harvest strategy for bobwhites. Overwinter bobwhite survival was estimated using radio-marked bobwhites from 16 November 2007 to 29 February 2008. Overwinter survival estimates were calculated using...

Year
2008

Microhabitat Structure of Winter Turkey Roosts in South Texas

We located 18 Rio Grande wild turkey (Meleagris gallopavo intermedia; RGWT) winter roost sites and 18 random sites at three study areas in Brooks and Kennedy Counties from December 2006 to February 2008. Our objective was to determine microhabitat structural characteristics of RGWT winter roosts that distinguished them from random locations in south Texas. At each roost, we measured tree height, diameter at breast height (dbh), canopy cover, and tree density. Variables were tested for normality using a Kolmogorov-Smirnov test. A t-test was used to examine differences between roost and...

Year
2008

Exotic Grass Impacts on Northern Bobwhite Habitat in South Texas

There is growing concern about the impacts that exotic grasses may have on northern bobwhite (Colinus virginianus) and other grassland birds. Large areas of South Texas have been seeded to or have been invaded by several species of exotic grasses including Guinea grass (Urochloa maxima), Bermuda grass (Cynodon dactylon), King Ranch bluestem (Bothriochloa ischaemum), Kleberg bluestem (Dichanthium annulatum), buffelgrass (Pennisetum ciliare), and Lehmann lovegrass (Eragrostis lehmanniana). Impacts of exotic grasses on northern bobwhite are largely unknown. While exotic grasses such as...

Year
2008

Density Dependence, Harvest, and Population Dynamics in New World Quail: Implications for Harvest Theory in Upland Gamebird Management

Long-term population declines and conservation concerns resulting from large scale habitat loss have brought into question the biological justification of fixed, liberal harvest regulations as they apply to new world quail (Odontophoridae). As available quail habitat declines, biologically justifiable and sustainable methods of harvest will become essential components of quail management. Two hypotheses, the doomed-surplus hypothesis and the additive mortality hypothesis, attempt to provide a conceptual framework regarding the nature of mortality in hunted populations (i.e., compensatory...

Year
2008

Vegetation Characteristics in Seasonal-disked Fields and at Bobwhite Brood Locations

Disking fallow fields is a management practice commonly used to promote early successional habitats for northern bobwhite (Colinus virginianus) broods. However, effects on habitat value for bobwhite broods from different seasonal timing of disking is poorly understood. We compared vegetation composition and structure among fall-disked fields (N=24), spring-disked fields (N=26) and bobwhite brood locations determined by telemetry (N=22 broods). Both disking treatments produced more bare ground and visual obstruction than brood locations. In a joining cluster analysis based on vegetation...

Year
2001

Effect of Winter-diet Restriction on Prebasic Molt in Female Wood Ducks

During winters 1990-1992, we manipulated food availability 5%-20% less than that of ad libitum feeding for captive groups of wild-strain North American wood ducks (Aix sponsa) to test effects of increasing levels of food restriction on prebasic molt of females. Birds fed ad libitum and 5%-15% restricted diets exhibited a protracted molt (>90 days) of low intensity. Most females fed a 20%-restricted diet did not initiate molt until resumption of ad libitum food availability. We hypothesize that a 20% restriction exceeds a threshold in food availability and possibly body condition needed...

Year
2001

Summer Diet of Northern Bobwhite in Eastern Mississippi: Implications for Habitat Management

Potential dietary differences between adult female and male northern bobwhites (Colinus virginianus) during the breeding season may influence habitat use and thus require special habitat management. The bobwhite literature contains only meager quantitative information, and no statistical evaluation, of adult female and male bobwhite diets during the breeding season. Therefore, we collected bobwhites and quantified their food use to test the null hypothesis that diets of male and female bobwhites were similar during the breeding season. In 41 female and 47 male bobwhites collected in...

Year
1995