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Influence of Shelterbelts on Success and Density of Waterfowl Nests within the Prairie Pothole Region of North America
Abstract
Shelterbelts are long rows of trees planted in the Great Plains of North America to reduce wind erosion of soil. Shelterbelts alter airflow, creating updrafts on the windward side (updraft zone), slow winds immediately on the leeward side (calm zone), and increased turbulence farther downwind of the shelterbelt (turbulent zone). They also provide hunting perches for avian predators and serve as corridors for mammalian predators. By determining the fate of 247 duck nests located in 27 Waterfowl Production Areas during 2006 and 2007, this study tested the hypothesis that duck nests located close to shelterbelts are more likely to be depredated than nests located in open fields and that nest densities are lower near shelterbelts than in open fields. Nest density in a shelterbelt's calm zone (0.22 nests/ha) was lower than in open fields (1.02 nest/ha). Shelterbelt orientation and porosity to airflow did not affect nest success or nest density. Shelterbelt height did not influence nest density, but nest success decreased as shelterbelts increased in height. Depredation rates were higher for nests near isolated structures (e.g., isolated trees, snags, and utility poles) than for nests near shelterbelts or in open fields.
... We hypothesized that nests would be more successful when located in areas with visual concealment (Albrecht & Klvaňa, 2004;Crabtree et al., 1989;Hines & Mitchell, 1983) and olfactory concealment (Borgo & Conover, 2016a, 2016bConover, 2007;Fogarty et al., 2017Fogarty et al., , 2018. However, we did not find evidence that factors of visual or olfactory concealment improved DSRs. ...
The number of ground-nesting ducks in the wetlands of Great Salt Lake, Utah has drastically decreased in the past few decades. A potential cause for this decline is the increase of predator species and their abundances, which has caused most nests to fail from depredation. Ground-nesting ducks may be able to reduce the risk of nest depredation by selecting nest sites where local physical structures or vegetation provides olfactory or visual concealment. To test this, we used logistic exposure models to look at the effect of nest-site characteristics on daily survival rates (DSRs) of nests during 2019, 2020, and 2021 in the wetlands of Great Salt Lake, Utah. We found 825 duck nests including 458 cinnamon teal (Spatula cyanoptera), 166 mallards (Anas platyrhynchos), and 201 gadwalls (Mareca strepera). DSRs were 0.9714 ± 0.0019 in 2019, 0.9282 ± 0.0049 in 2020, and 0.8274 ± 0.0185 in 2021. Survival rates varied among years but not among duck species. Striped skunks (Mephitis mephitis) and raccoons (Procyon lotor) were responsible for 85% of depredated nests. Nests located near other duck nests had higher DSRs than more dispersed nests. Neither visual nor olfactory characteristics correlated with increased DSRs based on AICc analysis. Nests located inside a mixed nesting colony of American avocets (Recurvirostra americana), black-necked stilts (Himantopus mexicanus), and common terns (Sterna hirundo) had higher DSRs than duck nests outside the colony. Increased nesting densities of ducks and other colonial waterbirds had the greatest impact on nesting success. Increased nest density may be encouraged through early spring green-up.
... Mesopredator release, resulting from the loss of regulatory influence by apex predators, can contribute to enhanced richness and abundance of mid-trophic level predators [10,11]. Anthropogenic resource subsidies, provided unintentionally as food or shelter, is another phenomenon that can benefit generalist predators in highly altered habitats [12,13] like the PPR. Loss of cover, concentration of nests in limited habitat, ease of travel by predators and loss of landscape heterogeneity can enhance foraging efficiency of avian and mammalian predators [7,[14][15][16]. ...
Nest survival is most limited by nest predation, which often is increased by anthropogenic causes including habitat fragmentation, mesopredator release and predator subsidies. In mallards and other upland-nesting duck species in the North American prairies, the rate of nest survival is the vital rate most influential to population dynamics, with 15%-20% survival required for maintenance of stable populations. Predator removal during the nesting season has increased duck nest survival on township-sized (9324 ha) areas of agricultural ecosystems in eastern locations of the prairie pothole region (PPR). However, predator removal has not been evaluated in western parkland habitats of the PPR where three-dimensional structure of vegetation is considerably greater. During 2015-2017, we evaluated nest survival on control and predator-removal plots at two study areas in the parklands of central Alberta, Canada. In the second year of the study, we transposed predator removal to control for habitat effects. Estimates of 34-day nest survival did not significantly differ between trapped (x = 20.9%, 95% CI = 13.2%-33.7%) and control (x = 17.8%, 95% CI = 10.5%-30.0%) plots in any year. We do not recommend predator removal be continued in Alberta parklands due to its ineffectiveness at improving duck nest survival at the local scale.
... Esta escasez de información se vuelve crítica en términos de planeación para la conservación, ya que uno de los principales objetivos para los anseriformes en Norteamérica es el aumento del éxito reproductivo (Borgo & Conover, 2016), lo cual no puede ser logrado sin la información adecuada. (Williams, 1980). ...
Se describen siete nidos de pato mexicano o garbancero (Anas diazi) de Pénjamo, Guanajuato, México. La distancia del nido al agua más cercana fue de 100 m a 800 m; la distancia al cuerpo de agua permanente más cercano fue de 150 m a 1500 m; la altura de la vegetación en el sitio de anidación fue de 50 cm a 130 cm. Los nidos fueron predominantemente de tipo copa baja-lateral. Las dimensiones externas fueron 17 cm - 36 cm × 9 cm - 20 cm. El material primario de construcción fue de pata de trigo y de manera secundaria Bouteloua-sorgo. Se encontraron de 1 a 6 huevos por nido, incluyendo posturas viables (n = 2), saqueadas (n = 1), abandonadas (n = 2) y exitosas (n = 1). Las nidadas observadas (n= 6) tuvieron entre 3 crías y 9 crías, encontradas sobre y hasta 400 m del agua. Dada la escasez de información disponible para la especie, estos resultados contribuyen a su conocimiento en el área más importante de distribución.
... Esta escasez de información se vuelve crítica en términos de planeación para la 74 conservación, ya que uno de los principales objetivos para los anseriformes en Norteamérica es el 75 aumento del éxito reproductivo (Borgo & Conover 2016), lo cual no puede ser logrado sin la 76 bajas (Williams, 1980). En esta región se ha reportado hibridación con pato de collar (ver Scott & 82 ...
Seven nests of the Mexican Duck (Anas diazi) from a Pénjamo, Guanajuato, Mexico, are described. Nest distance to nearest water body ranged 100-800 m; distance to nearest standing water ranged 150-1,200 m; nesting cover was 50-130 cm tall. Nests were mostly of a low-cup lateral and well concealed type. External dimensions ranged 25-45 cm x 20-33 cm, 0-13 cm tall; internal dimensions ranged 17-36 cm x 9-20 cm. Primary nest material was wheat stubble; secondary material was Bouteloua-sorghum. When found, clutches consisted of 1-6 eggs, including viable (n = 2), poached (n = 1), abandoned (n = 2) and successful (n = 1) eggs. Observed broods (n = 6) had 3-9 ducklings, found over and up to 400 m from standing water. Due to the scarcity of available information on the species, these results contribute to its knowledge on the most important distribution area.
Many terrestrial predators rely on olfaction to detect prey; therefore, prey should select habitat to reduce detectability of their odor cues. One way prey can potentially conceal their odor is by selecting locations with high turbulence and/or updrafts, conditions that disperse odor plumes and make odor sources difficult to locate. However, it is unclear how these conditions vary among vegetation cover types and which vegetative features drive them. We assessed variation and drivers of variables hypothesized to influence olfactory concealment (turbulence intensity and airflow slope) and experimentally evaluated whether these variables indeed influence predator detection of simulated prey. Specifically, we compared vegetation patch-scale values of turbulence intensity and airflow slope among grassland, shrubland, and forest and assessed relationships among these airflow variables and local-scale vegetative features within each vegetation type. Additionally, we experimentally investigated the importance of turbulence intensity, airflow slope, and visual concealment for predicting predator detection of scented quail eggs. In all vegetation types, we documented high variability in airflow conditions. At the patch scale, turbulence intensity was greater in shrubland and grassland than in forest, and updrafts were most common in shrubland whereas downdrafts were most common in grassland. Grassland was the only vegetation type with strong relationships among turbulence intensity and local vegetation features; both visual concealment and vegetation height were positively related to turbulence intensity. Additionally, persistence of scented quail eggs in grassland was best predicted by turbulence intensity; egg persistence increased with turbulence intensity. Our characterization of differences in olfactory variables among vegetation types provides an important step towards building a clearer understanding of olfactory landscapes. Further, our observation of both patch- and local-scale variation in olfactory variables suggests that prey can potentially select for olfactory concealment at multiple scales. We hypothesize that olfactory concealment provided by high levels of turbulence intensity is an important component of cover in grassland, and that in grassland/shrubland landscapes, prey selection of shrubland patches reduces odor detectability. Our finding of a positive relationship between turbulence intensity and visual concealment also suggests that olfactory concealment may be a previously underappreciated confounding factor in studies of habitat selection.
Odor plumes are common features of aquatic and terrestrial environments, forming an olfactory landscape through which animals must navigate to locate resources and avoid potential hazards. Time-averaged concentration profiles suggest that plumes consist of stable gradients in odor that animals may use for orientation. However, the time scales necessary to generate such profiles are much longer than those typically associated with the neural or be- havioral components of odor-mediated search. In contrast, plume measurements made at biologically relevant scales have indicated that turbulent plumes consist of discrete odor filaments separated by clean water. In addition, certain characteristics of individual odor filaments may vary consistently with distance from the odor source, thus providing directional information to a navigating organism. Unfortunately, there is no method to predict the distribution of these putative chemical cues, and our knowledge of odor dispersal is limited to very few laboratory flume studies. Here, we present the results of a field study during which we measured the distributions of the time-averaged concentration, properties of odor filaments, conditional statistics, and relevant hydrodynamic mixing parameters. Many of the observed odor plume characteristics have similar spatial distributions through a range of hydrodynamic conditions. The high degree of similarity in the distribution of many odor plume characteristics suggests that organisms can rely on any number of metrics to successfully orient in an odor plume. However, the temporal and spatial scales of odor dispersal may constrain the strategies used by navigating organisms and influence the efficiency of odor-mediated search. These field results should provide the basis for further empirical and theoretical work on chemosensory-mediated behavior of aquatic animals.
The effectiveness of a shelter is determined not only by its total drag but also by the distribution of the drag generated momentum defect in the sheltered area. Many aerodynamic factors affect both the drag and the momentum defect distribution, such as the boundary layer profiles of the approaching flow and the shape and the porosity of the shelter. How the interaction of these factors shapes the velocity distributions in the sheltered region is discussed qualitatively in this paper, on the basis of a flow model which consists of different regions. In each of them a different combination of aerodynamic factors is acting. Emphasis is on the region directly downwind from the shelter.It is shown that separation from the top of the shelter belt gives rise to a separation streamline which divides the low velocity flow below from the high velocity flow aloft. The blending of the flow across this streamline, which determines the recovery of the wind profile and the reduction in sheltering efficiency, is caused by the gradient in velocity across the streamline, while its location is determined by the drag on the shelter and the pressure distribution behind it. It is also shown that more turbulence is produced in a high density shelter than in a porous one. Finally, some conclusions are drawn with regard to research needs for improving our understanding of shelter belt aerodynamics.
The results of full-scale measurements of the wind reduction behind four different types of shelterbelts are reported. Two of the shelterbelts in question were of the single-row type. The remaining two consisted of at least two rows of deciduous trees and in both cases some conifers.Wind measurements were made under various weather conditions, both in winter and in summer. The minimum relative wind speed on the lee side varied from ca 0.1 behind the most dense shelterbelt to 0.4 behind the most porous one when the wind was blowing at right angles in summer. In the winter, the shelter effect was much less than in the summer but the two most dense shelterbelts did reduce the wind speed considerably also then.When the wind was blowing at an angle to the shelterbelt, the lee maximum occurred closer to the belt and the wind speed recovered faster than when it blew at right angles. The wind reduction just behind a shelterbelt always tended to be greater in oblique than in perpendicular wind. The wind reduction behind a leafy vegetation belt decreased as the reference wind speed increased. The approach wind speed affected wind reduction much more at a porous shelterbelt than at a dense one.The difference between reference and local wind directions could be great just behind a shelterbelt but this difference disappeared within a few h downstream of the belt. With further increasing distance (up to 4–11h), the wind continued to veer so that the direction became more parallel with the shelterbelt than in the case of the undisturbed wind. Then the wind slowly veered back to the direction of the approaching wind again.The present data give a good idea of the amount of wind reduction which can be expected in the lee of some common types of shelterbelts.