The Effects of natural Gas Development on Density, Reproductive Success and Nest Survival of Grassland Songbirds in South-Western Saskatchewan

Abstract

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.