Magpie mobbing

I was watching a fledgling songthrush (pictured) when it suddenly ran into the long grass for cover and I could hear blackbird alarm calls. The cause was a magpie in the vicinity. I walked over to where the magpie was, to find it being mobbed by the thrush parent plus two blackbirds in a concerted attack. It was just about standing its ground but my appearance tipped the balance and it went away to find easier prey. I was just intrigued to see a joint attack by two different, albeit closely related, species