Browsing by Subject "waterfowl"

Now showing 1 - 4 of 4
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    Data and model code for assessing dabbling duck age ratios and corresponding environmental correlates in the North American Prairies, 1969-2015
    (2018-05-16) Specht, Hannah M; Arnold, Todd W; spech030@umn.edu; Specht, Hannah M
    Fecundity estimates for demographic modeling are difficult to acquire at the regional spatial scales that correspond to climate shifts, land use impacts or habitat management programs, yet are important for evaluating such effects. While waterfowl managers have historically used harvest-based age ratios to assess fecundity at continental scales, widely available age ratios from late-summer banding data present an underutilized opportunity to examine a regional fecundity index with broad temporal replication. We used age ratios from banding data and hierarchical mixed-effect models to examine how fecundity of five North American dabbling duck species was affected by temporal variation in hydrological cycles, intra- and inter-specific density dependence and alternate prey availability, and whether those relationships were consistent across a broad geographic area. The data and code for these analysis are included here.
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    Environmental Contaminants in Redheads Wintering in Coastal Louisiana and Texas
    (Springer, 1994-05) Michot, T.C.; Custer, T.W.; Nault, A.J.; Mitchell, C.A.
    Whole body and liver analyses indicated that wintering redheads (Aythya americana; n=70) in coastal Louisiana (one site) and Texas (two sites) were relatively free of contamination with common trace elements, organochlorines, and hydrocarbons. Most trace elements, including As, Cr, Hg, Mg, Mn, Ni, Pb, Se, Sr, and Zn, were within background concentrations in livers; levels of B, Cd, Cu, and Fe were elevated in some specimens. Only one organochlorine, DDE, was detected in redhead carcasses, but its concentration was below reported toxic levels in waterfowl. Body burdens of aliphatic and aromatic hydrocarbons were generally low, but levels of pristane, total hydrocarbons, and the ratios of phytane:n-octadecane and pristane:n-heptadecane were indicative of possible chronic exposure to petroleum. Based on brain cholinesterase assays, redheads were not recently exposed to organophosphorous or carbamate pesticides. Of 30 elements or compounds tested for seasonal differences, only Se increased from early to late winter at one of the three sites. Eight of 57 contaminants differed among the three sites; no sex or age differences were found.
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    Habitat use and reproductive success of waterbirds in the human-dominated landscape of North America’s prairies: Using sparse data to inform management
    (2018-05) Specht, Hannah
    Information needed to implement effective management strategies requires an understanding of where, when and how target species use habitats available to them to survive and reproduce. I used new approaches for field data collection and analysis for rare and cryptic species to improve understanding of how anthropogenic and natural habitat characteristics affect the habitat use and reproductive success of grassland waterbirds, to better inform management in North America’s Northern Great Plains. Using historical data on waterfowl age ratios at banding and a database of upland shorebird nest records, I identified spatial and temporal variation in upland nesting waterfowl and shorebird fecundity. Specifically, I found positive relationships between vole population irruptions and metrics of fecundity (age ratios and nest survival) in both upland nesting waterfowl and shorebirds, and that fecundity of both groups was tightly tied to wetland conditions; increases in wetland inundation improved dabbling duck fecundity and Marbled Godwits (Limosa fedoa) experienced higher fecundity in territories with greater wetland cover. Density dependent effects were mixed across species. I used occupancy surveys with behavioral indicators of brood presence to assess whether habitat use by conservation concern upland shorebirds and Northern Pintail (Anas acuta) was altered by oil development in the Bakken oil field, using habitat suitability models to account for natural variation in habitat quality. I found reduced habitat use by breeding pairs and/or broods of all five studied species at sites with higher traffic and that Wilson’s phalarope (Phalaropus tricolor) breeding pairs avoided habitat with higher well density. Using behavior to infer brood presence facilitated identifying effects of traffic on brood habitat use where data would otherwise have been too sparse. Finally, I present a new occupancy survey sampling design that improves estimates for rare species. Management for upland-nesting waterbirds should continue to prioritize maintaining the capacity of less permanent wetland basins to rehydrate and active patch management of grassland. Infrastructure and activity that impacts grassland wildlife should be concentrated within corridors on the landscape while conservation should be concentrated in spaces between development corridors.
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