Bird-Watching and Ornithology

Mmm most points are valid but...Rooks and Jackdaws are nearly always in groups, but Carrion Crows are often alone. I assume they don't mean Magpies, Jays & Hooded Crows as they look distinctly different, but there's also Choughs to consider re all black crows, and possibly others I'm not familiar with outside of the UK.