Observation: I have a biology and geography background and have lived in Victoria BC for over 60 years. I have never seen such large numbers of Common Raven (Corvus corax) in this area. They are unusually abundant this year (2017). Interactions between Common Ravens and Crows (e.g. Northwestern Crow -- Corvus caurinus / American Crow -- Corvus brachyrhynchos) has greatly increased. - Graeme Weir, Victoria.
Comment by LEO BC Coordinator: Common Ravens (Corvus corax) are generally increasing in abundance due to the beneficial effects of humans including abundant food supply. In some areas they are known to have increased dramatically and affected agriculture (Larsen and Deitrick 1070). There are multiple potential explanations for observed increases in Common Raven abundances in Victoria in 2017. I am forwarding this observations to experts for comment. -Tom Okey, Ocean Integrity Research and the University of Victoria.
Common Raven on Wikipedia
Larsen, Kenneth H.; Dietrich, John H. (January 1970). "Reduction of a raven population on lambing grounds with DRC-1339". Journal of Wildlife Management. 34 (1): 200–204. JSTOR 3799509. doi:10.2307/3799509.