Beaver activity and red squirrel presence predict bird assemblages in boreal Canada

Abstract

Wetlands and predation in boreal ecosystems play essential roles throughout the breeding season for bird assemblages. We found a positive association of beaver activity and a negative influence of American red squirrels (Tamiasciurus hudsonicus) on bird assemblages. We used a multispecies hierarchical model to investigate whether bird communities differ between two major wetland habitats in boreal Canada: beaver ponds and peatland ponds. In addition to including variables such as forest cover and latitude, we adopted a structural equation model approach to estimate the occupancy of American red squirrels and its potential influence on bird communities. Using automated recording stations deployed at 50 ponds, we detected 96 bird species in 2018 and 2019. Bird species were grouped into four taxonomic guilds according to their habitat successional requirements: early successional species, late successional species, generalists, and wetland species. Beaver ponds harbored higher species richness, a pattern driven primarily by early successional species. The occupancy of almost a quarter of the species was lower in the presence of red squirrels. Late successional species responded positively to the cover of forest surrounding the pond. Our results highlight the value of considering acoustic data of red squirrels to quantify habitat quality in boreal forests. We conclude that beaver activity shapes bird assemblages through modification of their habitat, and that some bird guilds are associated negatively with the presence of American red squirrels.

Using Camera Traps to estimate Habitat Preferences and Occupancy Patterns of Vertebrates in Boreal Wetlands

“…A similar pattern was observed for marsh birds in buffers within 0.5 km from the wetland edge (Smith and Chow-Fraser 2010). Nonetheless, the lack of general effects of forest cover found here disagrees with patterns identi ed for 10 of 35 species using acoustic recorders in the same ponds (Feldman et al 2023a). These discrepancies could be due to differences in sampling methods: camera traps detect individuals within a smaller area than acoustic recorders (Shon eld and Bayne 2017; Darras et al 2018).…”

“…On the other hand, the detection probability of beaver and 21 bird species decreased substantially with the number of days since snowmelt, meaning that detectability is higher at the beginning of the season. The same pattern was detected in our acoustic approach (Feldman et al 2023a), where 18 out of 35 bird species showed the same response, mainly for aquatic species. The Wood Duck was the only species detected later in the season, which would be consistent with patterns of several waterfowl species where molting occurs far from breeding grounds (Hepp and Bellrose 2020), although the effect of days since snowmelt was marginal.…”

“…Among the avian species, only the Common Grackle favored beaver ponds over peatland ponds and this pattern was also supported acoustically in the same ponds (Feldman et al 2023a). The Common Grackle feeds mostly on aquatic insects during the nesting season in spring (Homan et al 1994).…”

“…Despite this predominance of peatlands, beaver ponds increase the heterogeneity of habitats across the region at the landscape level (Wright et al 2002). In their native range, Canadian beavers are ecosystem engineers that typically have a positive impact on plant and animal communities (e.g., Jones et al 1997;Stringer and Gaywood 2016;Feldman et al 2023a). For instance, some mammal species such as otters (Lontra canadensis), minks (Neogale vison), and muskrats (Ondatra zibethicus) use beaver lodges as shelter or as foraging areas (France 1997;Rosell et al 2005; Müller-Schwarze 2011).…”