Call number: LD2668 .T4 1984 S58 / Master of Science

I studied flock composition, distribution and foraging ecology of wintering wading birds along the Gulf of Mexico coast. I focused on geographic variability in wintering wading bird assemblages, the processes that structured these assemblages and habitat use by wading birds. I found considerable variation among three sites, Aransas National Wildlife Refuge (ANWR), Texas; Marsh Island Wildlife Refuge (MIWR), Louisiana; and Chassahowitzka National Wildlife Refuge (CNWR), Florida. Species comprising wintering wading bird assemblages varied regionally. ANWR had the most species-rich assemblage, with eight species. MIWR had only six wading bird species. And CNWR had only three different species. Processes that structured wintering wading bird assemblages also varied regionally. In ANWR, Texas, the Random Fraction niche apportionment model (RF model) best explained the empirical abundance data for ANWR. For abundance data from MIWR a good fit was obtained with the MacArthur Fraction (MF) model and the Power Fraction (PF) models. None of the models fully explained the CNWR abundance data. I also examined patterns of habitat partitioning among wintering wading birds at three different scales at two sites, Matagorda Island National Wildlife Refuge (MINWR) and Laguna Atascosa National Wildlife Refuge (LANWR). At the macrohabitat level, wintering wading birds showed interspecific differences in macrohabitat use of both open water habitats and vegetated flats. At the mesohabitat level all species at MINWR used the category nearest the edge most often, alternatively, at LANWR wading birds were most often in the mesohabitat category of 8.1- 12 m. from the edge. In both locations wading birds partitioned habitat based on water depth. Finally, I found that Great Egrets and Snowy Egrets participated more often in flock foraging and derived more benefits from feeding in flocks than other species. Great Egrets feeding in flocks had a higher mean strike rate than those foraging alone, whereas Snowy Egrets had a higher success rate foraging in flocks than those foraging alone. In the case of the darkercolored species (e.g., Great Blue Herons, etc.) they either showed no difference in behaviors between birds foraging in flocks versus those foraging alone or they actually did worse when they foraged in flocks.

Using a new browse-monitoring technique, short-term changes in the winter foraging behaviour of yarded northern white-tailed deer (Odocoileus virginianus) were followed over 3 winters. Hypotheses about selective browsing, shifts in foraging strategy, food patch selection, diet quality, and foraging effort were derived from optimal foraging theory. Testing of associated predictions disclosed that deer expanded their diets over the course of the yarding season, showed shifts in proportional representation of browse species in their diet, and exhibited distinct but changing preferences for certain browse types. Partial preferences in diet choices occurred, but important diet items were used in nonrandom runs once adopted into the diet. Cornus stolonifera was the dominant browse species in the diet based on construction of a functional response curve, with the use of other species influenced by C. stolonifera depletion. Deer took a greater number of twigs from denser browse plots, and made more browsing visits to dense plots over the yarding season. Browsed plots tended to be higher in total twig availability and C. stolonifera availability than unbrowsed plots for the first half of the yarding season only. Diameter at point of browsing (DPB) values increased over the season for C. stolonifera and Salix. Results indicate that winter deer foraging is a dynamic process, with high diet selectivity at the beginning of the yarding season, and gradual diet generalization in the face of overall browse depletion.

No description available.

A marked population of wintering Gray Vireos (Vireo vicinior) was studied for two seasons (1985-1986 and 1986-1987) on two study sites near Puerto Lobos, Sonora, Mexico. Eleven of the 15 individuals banded in the first winter returned to the same areas in the following winter. Territories were defended throughout the winter and averaged 0.9 ha in size (N = 9). Territorial interactions occurred frequently along boundaries as neighbors trespassed to forage on each others' territories. All birds appeared to defend individual territories. First year birds appeared to occupy marginal territories on the periphery of the best habitats. Fruit from the elephant tree, Bursera microphylla, became a dominant part of the vireo's diet as winter progressed and the fruit ripened. The importance of B. microphylla to the vireos' winter diet and the high degree of overlap between the winter range of the vireos and the distribution of the plant suggested a mutualistic interaction between them. Gray Vireos acted as the primary dispersers for the plant.

No description available.

Black-faced Spoonbill (BFS), Platalea minor, numbers during the non-breeding season increased steadily from 1990 to 2004 in Taiwan. Numbers of the BFS in Taiwan accounted for more than 50% of the total population, with 96% of the BFS in southwestern Taiwan at the town of Chi-Ku and Tainan City. The percentage of adult BFS remained constant from 2000-2003. Relatively constant high survey counts, with similar ratios of adult to non-adult birds, suggested that the BFS has a healthy population. With the exception of avian botulism resulting in 73 BFS deaths in the 2002 winter, several other mortality factors were documented with no more than four birds lost in a year from 1849-2004. I counted numbers of BFS at the town of Chi-Ku and Tainan City almost daily during the winter months from September 1998 to May 2001. Although variable, overall population numbers increased sharply from September to October. From November to February, the BFS maintained a high, stable population-level. Migration began during March, and population numbers decreased from March to May. I used visual observations and radio-telemetry data to locate, count and monitor BFS during the day and night, respectively, and also to assess nocturnal habitat use. Information obtained through these methods showed that habitat use was not in direct proportion to its availability. Activity ranges obtained from radio tracking and visual observations showed an increase in activity range size by BFS just prior to migration with more of the study area used north of the core-roosting area. Sizes and weights of potential prey items were measured at fish ponds used by BFS. Available prey in fish ponds was dominated by fish prey less than 5 cm in length and at least 30 gm in size. Similar size classes of prey items were selected by a captive BFS. Biomass of prey in fish ponds around the primary roosting site declined sharply in the pre-migration stage (March-April), compared to the middle winter stage (November-February). I suggest that this low biomass of prey items may have stimulated the northward movement of BFS in the late stage of winter. In addition, the activity range expansion may have related to preparation for migration.

Black-faced Spoonbill (BFS), Platalea minor, numbers during the non-breeding season increased steadily from 1990 to 2004 in Taiwan. Numbers of the BFS in Taiwan accounted for more than 50% of the total population, with 96% of the BFS in southwestern Taiwan at the town of Chi-Ku and Tainan City. The percentage of adult BFS remained constant from 2000-2003. Relatively constant high survey counts, with similar ratios of adult to non-adult birds, suggested that the BFS has a healthy population. With the exception of avian botulism resulting in 73 BFS deaths in the 2002 winter, several other mortality factors were documented with no more than four birds lost in a year from 1849-2004. I counted numbers of BFS at the town of Chi-Ku and Tainan City almost daily during the winter months from September 1998 to May 2001. Although variable, overall population numbers increased sharply from September to October. From November to February, the BFS maintained a high, stable population-level. Migration began during March, and population numbers decreased from March to May. I used visual observations and radio-telemetry data to locate, count and monitor BFS during the day and night, respectively, and also to assess nocturnal habitat use. Information obtained through these methods showed that habitat use was not in direct proportion to its availability. Activity ranges obtained from radio tracking and visual observations showed an increase in activity range size by BFS just prior to migration with more of the study area used north of the core-roosting area. Sizes and weights of potential prey items were measured at fish ponds used by BFS. Available prey in fish ponds was dominated by fish prey less than 5 cm in length and at least 30 gm in size. Similar size classes of prey items were selected by a captive BFS. Biomass of prey in fish ponds around the primary roosting site declined sharply in the pre-migration stage (March-April), compared to the middle winter stage (November-February). I suggest that this low biomass of prey items may have stimulated the northward movement of BFS in the late stage of winter. In addition, the activity range expansion may have related to preparation for migration.

Bottomland hardwood forests provide forage and other important resources for wintering and breeding waterfowl in the Southeastern United States. My objective was to conduct an initial investigation of possible influences of habitat features, flood events, and human disturbance on relative abundances of wintering ducks in Delta National Forest (DNF), Mississippi. I surveyed 65 wetlands in DNF 17 times from November 2012 to March 2013 and analyzed abundance data from wood ducks (Aix sponsa), mallards (Anas platyrhynchos), gadwalls (Anas strepera), and hooded mergansers (Lophodytes cucullatus). Waterfowl abundance varied by species but generally increased during major flood events and on wetlands having an approximately equal interspersion of scrub-shrub and open water consistent with the “hemi-marsh” concept. I recommend partial removal of scrub-shrub from selected wetlands to promote emergent plant communities and increased duck use and experimental evaluation of waterfowl responses to management of wetlands and human activities during winter in DNF.

No description available.