I thought since a few bloggers have been talking about ponds recently and Endment has just dug one, I'd show some frog pics. I can't decide what type of frogs these are, which should be strange since we have only one native frog (Rana temporia) in most of the UK (the pool frog (Rana lessonae) may have been native and has just been reintroduced into the norfolk broads).
In the London area though we have some Ranids introduced from Europe in particular Rana ridibunda, the marsh frog. I think thats what these might be. Adult marsh frogs were calling nearby, their call (which gives them their latin name) is a harsh, chattering laugh (a bit like a kookabura's). Marsh frogs outgrow common frogs and could be seen as excluding our natives as they tend to take over the pools they like. I think in reality they are adopting the roles they have on the mainland with the common frogs abandoning habitat they wouldn't normally use in Europe but do here as there is, or rather was, no competition.