Geology topics

Bruce E. Davis

Publications and source records attributed to Bruce E. Davis.

4 recordsLinked to original sources

USGS2011

Spring-migration ecology of Northern Pintails in south-central Nebraska

Spring-migration ecology of staging Northern Pintails, Anas acuta , was investigated in south-central Nebraska, USA. Habitat associations, local movements, settling patterns, arrival dates, residency times and survival were estimated from 71 radiomarked pintails during spring 2001, 2003 and 2004, and diet determined from 130 females collected during spring 1998 and 1999. Seventy-two percent of pintail diurnal locations were in palustrine wetlands, 7% in riverine wetlands, 3% in lacustrine wetlands, 6% in municipal sewage lagoons and irrigation reuse pits and 10.5% in croplands. Emergent wetlands with hemi-marsh conditions were used diurnally more often than wetlands with either open or closed vegetation structures. Evening foraging flights averaged 4.3 km (SE = 0.6) and 72% were to cornfields. In accord with these findings, 87% of 93 pintails collected during spring 1998 and 1999 returning to evening roosts consumed corn, which represented 84% dry mass of all foods. Pintails collected on non-cropped wetlands ingested invertebrates and seeds from wetland plants more frequently than birds returning to roost. Radiomarked pintails arrived in Nebraska on 7 March 2003 and 18 February 2004; average arrival date was six days earlier during 2004 compared to 2003. Residency time for individuals varied greatly (1–40 days) yet yearly means were similar and averaged 9.5 days within the region. No mortality was detected for 71 birds monitored over 829 exposure days. Conservation planners linking population dynamics and habitat conditions at spring-staging areas need to focus on pintail body condition during spring and its connection with reproductive success and survival during the breeding season.

Nebraska, Texas↗

USGS2011

Daily movements of female mallards wintering in Southwestern Louisiana

Understanding daily movements of waterfowl is crucial to management of winter habitats, especially along the Gulf Coast where hunting pressure is high. Radio-telemetry was used to investigate movements of female Mallards ( Anas platyrchychos ) wintering in southwestern Louisiana. Movement distances were analyzed from 2,455 paired locations (diurnal and nocturnal) of 126 Mallards during winters 2004–2005 and 2005–2006 to assess effects of winter, female age, areas closed (Lacassine National Wildlife Refuge [LAC], Cameron Prairie National Wildlife Refuge [CAM], Amoco Pool [AMOCO] or open to hunting [OPEN]), and habitat type, including all interactions. Movement distances from the various land management categories were not consistent by age, date, or by winter. Flight distances from LAC increased with date, whereas those from CAM and OPEN did not vary significantly by date. Female Mallards moved short distances between diurnal and nocturnal sites (ranging from 3.1 to 15.0 km by land management category), suggesting that they are able to meet their daily energy requirements within a smaller area than Northern Pintails ( Anas acuta , hereafter Pintails), and thus minimize transit energy costs.

Louisiana↗

USGS2010

Habitat use by female mallards in the lower Mississippi alluvial valley

Mallard ( Anas platyrhynchos ) populations in the lower Mississippi Alluvial Valley (LMAV), USA, historically averaged 1.6 million and represented the largest concentrations of wintering mallards in North America. Effective management of this wintering population requires current information on use of habitats. Accordingly, we employed radiotelemetry techniques to assess proportional use of habitats by female mallards during winters 2004-2005 and 2005-2006. We divided winters into 4 time periods defined by hunting seasons (FIRST, SPLIT, SECOND, and POST) and recorded diurnal and nocturnal locations. We examined variations in proportional use of habitats and use of areas closed to hunting due to effects of age (immature or ad), winter (2004-2005 or 2005-2006), time period (SECOND or POST), individual female, and all potential interactions of these effects, using locations recorded during the latter 2 time periods. We found that diurnal and nocturnal proportional use of habitats varied inconsistently among time periods and winters. Mean proportional use of forested wetlands ranged from 0.475 to 0.816 and from 0.428 to 0.764 during diurnal and nocturnal sampling periods, respectively. Diurnal proportional use of areas closed to hunting varied inconsistently among time periods and winters. Mean proportional use of areas closed to hunting ranged from 0.183 to 0.423 during diurnal sampling periods. Nocturnal use of areas closed to hunting varied inconsistently among female ages and time periods and among female ages and winters. Mean proportional use of areas closed to hunting ranged from 0.211 to 0.445 during nocturnal sampling periods. Our research suggests that forested wetlands in the LMAV provide important wintering habitats for female mallards; continued restoration and establishment of these habitats should benefit female mallards.

Journal of Wildlife Management↗

USGS2010

Movement distances and habitat switching by female Mallards wintering in the Lower Mississippi Alluvial Valley

Mallard (Anus platyrhynchos) populations in the Lower Mississippi Alluvial Valley (hereafter, LMAV) comprise the largest concentration of wintering Mallards in North America. Radiotelemetry techniques were employed to assess movements by female Mallards during winters of 2004-2005 and 2005-2006; 467 paired (diurnal and nocturnal) observations on 80 radiomarked females were attained to assess effects of date, female age, hunting regime and habitat type on distances moved and potential habitat switching. Distance moved increased with date for females diurnally located in RICE but decreased for females in FOREST. Median movement distance was 1.5 km, suggesting suitable habitats for all activities were in close proximity. Habitat switching varied among diurnal habitat types used by females. Females diurnally located in FOREST and REFOR switched habitats in <= 22% of paired observations, whereas females diurnally located in RICE switched habitats in 55% of paired observations. The decreased movement distances and less frequent habitat switching by females using forested habitats should reduce their energy expenditure and exposure to predation risk. The results document the importance of forested wet-lands to Mallards wintering in the LMAV and provide support for programs that protect and restore such habitats. Received 18 November 2009, accepted 16 January 2010.

Lousiana↗