Browsing by Author "Davis, Stephen K."
Now showing 1 - 4 of 4
- Results Per Page
- Sort Options
Item Open Access Breeding Biology of Grassland Songbirds and the Effects of Oil and Natural Gas Development on Their Density and Reproductive Success(Faculty of Graduate Studies and Research, University of Regina, 2013-05) Ludlow, Sarah Maureen; Brigham, R. Mark; Davis, Stephen K.; Vetter, Mary; Lockhart, WallaceUnderstanding the breeding ecology of grassland birds is vital for identifying the mechanisms underlying their widespread population declines. I describe the breeding biology of and quantify the effects of nest predation and brood parasitism on Savannah Sparrow (Passerculus sandwichensis), Baird’s Sparrow (Ammodramus bairdii), Vesper Sparrow (Pooecetes gramineus), Western Meadowlark (Sternella neglecta), and Sprague’s Pipit (Anthus spragueii) in south-eastern Alberta. Nest predation was the primary cause of nest failure, accounting for 75% of all nest losses. For the three sparrow species, daily survival rates were higher during the incubation compared to the nestling stage. For all five species, clutch size, hatching success, and fledging success were within the range of values previously reported for these species in other parts of their range. Brown-headed Cowbirds parasitized nests of all species except Sprague’s Pipit, with 4- 11% of nests containing cowbird eggs. Savannah Sparrow experienced the highest frequency of brood parasitism and was the only species to successfully fledge cowbird young. Parasitized Savannah Sparrow nests experienced reduced hatching success, productivity, and clutch size compared to non-parasitized nests. The overall cost of parasitism to Savannah Sparrow was 1.7 young per successful nest. This information provides a basis for future comparisons regarding the influence of anthropogenic alterations to native grassland habitat on grassland songbird reproductive success and nest survival. Despite dramatic increases in oil and gas development over the last decade, research about the effects of this activity on grassland songbird reproductive success and density is lacking. I assessed how the density and reproductive success of five species of grassland songbirds in south-eastern Alberta varied with distance to oil and gas wells, roads, trails, and patches of introduced crested wheatgrass, along with percent cover of crested wheatgrass. Savannah Sparrow density was 2.5 times higher within 100 m of wells than further away and was almost twice as high in areas without crested wheatgrass compared to those with 60% cover. Sprague’s Pipit nest survival decreased with increased cover of crested wheatgrass. The proportion of Baird’s Sparrow eggs that hatched within 50 m of wells and trails were reduced by 33% and 46%, respectively, compared to areas further from these structures. Hatching success more than doubled for both Sprague’s Pipit and Western Meadowlark as percent cover of crested wheatgrass increased from 0-60%. The number of young fledged from successful Baird’s Sparrow nests was lower near trails. Savannah Sparrow fledging success was higher near wells and in areas with greater cover of crested wheatgrass. The number of young fledged from successful Western Meadowlark nests doubled as distance from crested wheatgrass increased from 0-800 m. There was no relationship between the frequency of brood parasitism and distance to oil and gas infrastructure. Overall, my results indicate that oil and gas development has mixed effects on the density and reproductive success of grassland songbirds. To mitigate potential negative effects, future development by the energy industry should attempt to minimize the amount of edge habitat created, continue to eliminate exotic vegetation in their reclamation protocols, and take precautions to avoid the spread of crested wheatgrass, and other invasive plants, into native grassland.Item Open Access The Effects of natural Gas Development on Density, Reproductive Success and Nest Survival of Grassland Songbirds in South-Western Saskatchewan(Faculty of Graduate Studies and Research, University of Regina, 2013-06) Gaudet, Carolyn Anne; Brigham, R. Mark; Davis, Stephen K.; Somers, Christopher; Clark, Robert G.Natural gas development is currently expanding in south-western Saskatchewan and may be threatening the quality of the remaining grassland habitat. The effects of natural gas development on grassland birds are poorly understood but are often species-specific and vary across the species’ range. The purpose of my research is to (1) quantify aspects of grassland songbird breeding biology and (2) determine the effects of natural gas development on density and reproductive success of grassland songbirds. I found and monitored 392 nests of 7 species of grassland songbirds, including Chestnut-collared Longspur (Calcarius ornatus), Vesper Sparrow (Pooecetes gramineus), Sprague’s Pipit (Anthus spragueii), Savannah Sparrow (Passerculus sandwichensis), Baird’s Sparrow (Ammodramus bairdii), Horned Lark (Eremophila alpestris) and Western Meadowlark (Sturnella neglecta). I quantified and compared aspects of their breeding biology with published data in other parts of their range. Reproductive rates were typical of those found elsewhere. Time-specific variables (age and date) were included in the top models for nest survival for several species. Chestnut-collared Longspur nest survival increased during the incubation stage and decreased during the nestling stage and also decreased and then increased as the breeding season progressed. I also determined that Western Meadowlark nest survival increased and then decreased with increasing ambient temperature. Natural gas development features (compressor stations, gas wells, trails and fences) affected grassland songbird reproductive success, nest survival and density both negatively and positively. Vesper, Baird’s and Savannah sparrows had lower nest survival near wells, fences and trails, respectively, while Western Meadowlark experienced higher nest survival near trails. Generally, there were fewer young fledged near development, but this varied by species and type of development. Vesper and Savannah sparrows had greater densities in high disturbance plots while Chestnut-collared Longspur and Horned Lark had lower densities in high disturbance plots. Baird’s and Savannah sparrows had lower densities near compressor stations while Horned Lark density was greater near compressor stations. The density of Sprague’s Pipit and Western Meadowlark was best explained by vegetation structure. Natural gas development affected grassland songbird reproductive success, nest survival and density in both negative and positive ways or there was no effect; however, the extent of the impact may vary with the habitat and within the species’ range.Item Open Access Habitat selection and demography of mixed -grass prairie songbirds in a fragmented landscape.(Faculty of Graduate Studies and Research, University of Regina, 2003) Davis, Stephen K.; Brigham, Mark; James, PaulItem Open Access Habitat Selection by Birds in Willow-Ringed Wetlands: Management Implications for Harvesting Willow Biomass(Faculty of Graduate Studies and Research, University of Regina, 2015-04) Mushanski, Melissa Dawn; Somers, Christopher; Davis, Stephen K.; Hall, Britt; Sutter, GlennIncrease in prices of fossil fuels and escalating environmental conflicts have generated renewed interest in bioenergy production. Abundant small wetlands ringed with willow species (willow rings) growing naturally in the Prairie Ecozone of North America may provide a source of natural biomass as a bioenergy feedstock. Subsequently, a bioenergy crop from these wetlands could increase their economic value and help reduce their drainage and loss. Little is known about the importance of willow vegetation to birds, and what habitat features may be important to consider when planning biomass harvest. To address this knowledge gap, I conducted point count surveys in the spring of 2012 and 2013 at 92 willow rings in south-eastern Saskatchewan. My objectives were to determine: 1) what species make up the willow- ring bird community; 2) what wetland and vegetation characteristics influence bird abundance; and 3) whether abundance of willow-ringed wetland birds varies as a function of the surrounding upland habitat (cropland vs. grassland). I found that the willow ring community is composed of at least 66 species from 3 distinct guilds: woodland, wetland, and grassland birds, and that members of each guild responded differently to willow ring structure and habitat features. For example, American robin (Turdus migratorius) and yellow warbler (Setophaga petechia), both woodland species, increased in abundance as willow area increased. A wetland bird species, the American coot (Fulica americana), decreased in abundance as % willow cover increased. However, all other species were unaffected by changes in the willow ring structure, suggesting that willow harvest will have little impact on these birds. Woodland bird species may decrease as their habitat is lost; however, management practices such as partial harvests or rotational harvest by year may make willow harvest sustainable for all species. Furthermore, land managers should adjust harvest guidelines to reflect local bird management objectives. In doing so, willow harvest can likely be done with minimal impact on bird species associated with willow-ringed wetlands.