Corvids response to fluctuating abundance of resources in tundra ecosystems

Abstract

Aim Despite the numerous studies on corvids’ behaviour, their dynamics in different ecosystems is unknown. Ravens and hooded crows are opportunistic generalists acting as both predators and scavengers. Ravens are probably the most specialized scavengers on ungulate carcasses and both species are known as efficient hunters of small rodents. Small rodents are a key species in the tundra as they represent the main prey for many terrestrial predators. A study about nest predation using artificial nests, suggested that corvids may respond numerically to the Norwegian lemming in tundra ecosystems. Here I used a 13 year time series to investigate whether two potentially important food resources, small rodents and reindeer carcasses, drive the corvids fluctuations in the ecosystems of Northern Fennoscandia. Methods To investigate the corvid population dynamics, I used data from camera traps baited with reindeer meat collected in eastern Finnmark during winter between 2005 and 2017, in addition to time series data from small rodent trapping. Main conclusions This is the first study to assess temporal and spatial variation in corvids dynamics in the tundra of Northern Fennoscandia. The results showed a great deal of temporal and spatial variation in the presence of each species between the time series of three regions. The assumption that the corvids’ populations fluctuate with the lemming cycles appears not to be supported here. However, the presence of the ravens was positively correlated with the fluctuations of voles that were in higher density compare to lemming during the study period. The statistical models did not reveal any impact of the relative amount of carcasses in eastern Finnmark on the dynamics of the corvid data. Based on the results, I discuss the different responses of these generalist predators in the arctic tundra.