By Karen Hodges, University of British Columbia Okanagan; Frank Doyle, Wildlife Dynamics Consulting, and Rene Carl Dionne, SYLVIS

biosolids vs. non-biosolids applied
A biosolids fertilized versus non-fertilized pasture

Ecological restoration is becoming increasingly important, to offset previous environmental damage and to return degraded areas to effective habitat for various species. In British Columbia, grasslands comprise only 0.8 % of the province’s land base, but these grasslands are home to some 30% of the species at risk in BC.  Grassland habitats are under pressure from urban development, grazing, and other anthropogenic disturbances. 

Vesper sparrow, one of the songbirds that is more common on biosolids-applied areas
Vesper sparrow, one of the songbirds that is more common on biosolids-applied areas

Since 2014, Metro Vancouver has contracted SYLVIS to apply biosolids to grasslands on the OK Ranch near Jesmond, BC.  These grassland applications have led to clear changes in plant and soil communities (Newman et al. 2014, Wallace et al. 2016), suggesting there may be food-web impacts on insects, mammalian herbivores, and birds.  In 2016, SYLVIS and Metro Vancouver developed a research partnership with The University of British Columbia – Okanagan and Wildlife Dynamics to explore the changes to insect and animal communities in more depth.   Research completed through 2018 at the OK Ranch has assessed the impacts of grasslands restoration with biosolids on populations of grasshoppers, grouse, kestrels, owls, and songbirds on control and applied dryland pastures.

We examined how grasshoppers responded to biosolids fertilized grasslands; grasshopper densities were ~5 times higher on sites with biosolids amendment, with time lags after application that probably reflect multi-year nutrient transfer, the dynamics of plant growth, and both habitat selection and in situ increases in grasshopper reproduction (Gaudreault et al. 2019). Grasshoppers are important prey for many birds in this system.  We have also documented a ~50% increase in spring songbird abundance on pastures amended with biosolids. We have identified 22 raptor and owl species on the Ranch, which is an unusually large assemblage relative to other locations in BC, and includes 7 red- or blue-listed species (species at risk in BC). Kestrels, owls, and corvids all eat the grasshoppers, although kestrels and owls also consume many voles in this system.   

A female dusky grouse at OK Ranch
A female dusky grouse at OK Ranch

A total of 26 dusky grouse hens were radio-collared during 2016-2017 and tracked through the summer. Hens selected nest sites with high visual cover, and nest success was positively influenced by visual obstruction of the nest bowl (Lawson et al. in review). We documented increased nest success for nests with a higher proportion of fertilized pastures within 100 m.

We examined whether biosolids affected American Kestrels diets or nest selection relative to untreated areas (Buers et al. in review). We conducted driving transects from May-August 2017 to locate kestrels and to observe kestrels for behavioral cues to locate nest sites. American kestrels preferentially nested in areas adjacent to biosolids-amended pastures, and appeared to forage more often in amended pastures than in untreated areas.

This research suggest that biosolids fertilization of dryland grassland pastures can improve food availability and nesting success for different birds, potentially thus acting as a restoration tool.  The research is on-going, so we can obtain a better understanding of ecosystem-scale impacts.  Indeed, we have two MSc students who will work on songbirds and vole population dynamics in summer 2019.  

Thanks to Kirstie Lawson, Emma Gaudreault, and Megan A. Buers (all UBCO students) for the grouse, grasshopper, and kestrel work to date.  

Literature cited
Buers, M., F.I. Doyle, K.J. Lawson, and K.E. Hodges. Kestrel diet and nest selection in relation to biosolids applications in northern grasslands of British Columbia. in review at Journal of Avian Biology.

Gaudreault, E., R.G. Lalonde, K.J. Lawson, F.I. Doyle, and K.E. Hodges. 2019. Biosolids application increases grasshopper abundance in the short-term in a northern Canadian grassland. Rangeland Journal in press.

Lawson, K.J., F.I. Doyle, and K.E. Hodges. Microhabitat selection of nest and brood sites by Dusky Grouse in central British Columbia, in review at Avian Conservation and Ecology.

Newman, R. F., M. Krzic, and B. M. Wallace. 2014. Differing Effects of Biosolids on Native Plants in Grasslands of Southern British Columbia. Journal of Environment Quality. 43:1672- 1678. 

Wallace, B. M., Krzic, M., Newman, R. F., Forge, T. A., Broersma, K., and Neilsen, G. 2016. Soil aggregate dynamics and plant community response after biosolids application in a semiarid grassland. Journal of Environmental Quality 45:1663–1671.