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Box Elder, SD, United States

Link P.T.,Louisiana State University | Afton A.D.,Louisiana State University | Cox Jr. R.R.,RC Store | Davis B.E.,Louisiana State University
Waterbirds | Year: 2011

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. Source


Link P.T.,Louisiana State University | Afton A.D.,Louisiana State University | Cox Jr. R.R.,RC Store | Davis B.E.,Louisiana State University
Waterbirds | Year: 2011

Habitat use by wintering Mallards (Anas platyrhychos) on the Gulf Coast Chenier Plain (GCCP) has received little study and quantitative data is needed for management of GCCP waterfowl. Radio-telemetry techniques were used to record habitats used by 135 female Mallards during winters 2004-2005 and 2005-2006 in south-western Louisiana. Habitat use was quantitatively estimated for areas open and closed to hunting, by general habitat types (i.e., marsh, rice, idle, pasture, or other), and for specific marsh types (i.e., freshwater, intermediate, brackish, or salt). Variation in these estimates was subsequently examined in relation to individual female, female age (adult or immature), winter (2004-2005 or 2005-2006), and hunt periods within winter (second hunting season [SHUNT] or post hunting season [POST]). Diurnal use of areas closed to hunting was greater during hunted time periods in winter 2005-2006 than in winter 2004-2005. Nocturnal use of areas closed to hunting was 3.1 times greater during SHUNT than during POST, and immatures used areas closed to hunting more than adults. Diurnal use of marsh was 3.3 times greater than that of any other habitat during both winters. Nocturnal use of marsh, rice, idle, and pasture were similar during both winters. Females used freshwater marsh habitats extensively (64.699.8% proportional use), whereas brackish and salt marsh combined was used less frequently (035.8% proportional use). These results suggest that freshwater marsh is important to Mallards and a high priority for restoration and management efforts. Source


Davis B.E.,Louisiana State University | Afton A.D.,U.S. Geological Survey | Cox Jr. R.R.,RC Store
Waterbirds | Year: 2011

The lower Mississippi Alluvial Valley (hereafter LMAV) provides winter habitat for approximately 40% of the Mississippi Flyway's Mallard (Anas platyrhynhcos) population; information on winter survival rates of female Mallards in the LMAV is restricted to data collected prior to implementation of the North American Waterfowl Management Plan. To estimate recent survival and cause-specific mortality rates in the LMAV, 174 radio-marked female Mallards were tracked for a total of 11,912 exposure days. Survival varied by time periods defined by hunting seasons, and females with lower body condition (size adjusted body mass) at time of capture had reduced probability of survival. Female survival was less and the duration of our tracking period was greater than those in previous studies of similarly marked females in the LMAV; the product-limit survival estimate (±Â±SE) through the entire tracking period (136 days) was 0.54 ±0.10. Cause-specific mortality rates were 0.18 ±0.04 and 0.34 ±0.12 for hunting and other sources of mortality, respectively; the estimated mortality rate from other sources (including those from avian, mammalian, or unknown sources) was higher than mortality from non-hunting sources reported in previous studies of Mallards in the LMAV. Models that incorporate winter survival estimates as a factor in Mallard population growth rates should be adjusted for these reduced winter survival estimates. Source


Olsen R.E.,3070 North Lakeshore Drive | Cox Jr. R.R.,RC Store | Afton A.D.,U.S. Geological Survey | Ankney C.D.,University of Western Ontario
Waterbirds | Year: 2011

A free-ranging Mallard (Anas platyrhynchos) population was investigated during winter (December-January 1996-1999) below the Garrison Dam, North Dakota, USA, to relate diet to gut morphology variation in males. Four explanatory variables (fish consumption, male age, winter, and body size) were evaluated as to whether they influenced five response variables associated with gut characteristics of Mallards. Response variables were lower gastro-intestinal tract mass (LGIT), dry liver mass, dry gizzard mass, small intestine length, and ceca length. Diets of Mallards were comprised primarily of Rainbow Smelt (Osmerus mordax) and concomitantly variation in gizzard mass was small. LGIT mass of juveniles was larger than that of adults, greater for those that consumed fish, and greater during the coldest and snowiest winter. Liver mass and small intestine length of Mallards that consumed fish were greater than those that did not. Mallards may maintain lengthy intestines to increase digestive efficiency. Gut size variation was not entirely attributable to dietary composition but also influenced by body size and environmental conditions such that over-winter survival is maximized. Source

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