Avian Conservation and Ecology (Dec 2020)
Habitat occupancy by breeding Pied-billed and Horned Grebes in Prairie Canada: correlates of pond use and breeding success
Abstract
Incorporating information about habitat use and success of breeding birds contributes to a more complete understanding of their ecology and distribution, and can also inform management strategies for species of conservation concern. We used occupancy data that accounted for imperfect detection from a two-year field study of two territorial waterbird species in southcentral Saskatchewan (n = 172 ponds on seven study sites) to explore correlates of pond use and breeding success. In Pied-billed (Podilymbus podiceps) and Horned (Podiceps auritus) Grebes, breeding habitat occupancy corresponded most closely to pond-specific factors rather than those operating at spatial scales beyond the local wetland basin. Pied-billed Grebes were more likely to occupy wetlands that were larger, had greater shoreline complexity, and had less cropland in the adjacent uplands whereas Horned Grebes were more likely to occupy wetlands with less emergent vegetation. These distinct microhabitat preferences could serve to limit interspecific competition. While there was no observable difference in pond occupancy rates between low and high wetland density landscapes, the latter areas contribute disproportionately more breeding habitat for grebes. Using naïve occupancy estimates, breeding success was similar for Horned (0.75, SE = 0.06) and Pied-billed (0.67, SE = 0.07) Grebes. Ongoing conservation initiatives that protect and restore wetland habitat in areas of the prairie and parkland ecoregions with high densities of semipermanent and permanent wetlands should improve long-term habitat security for breeding grebes, including Horned Grebes.
