Spawning time in Llandaff North

I was surprised to see two clumps of frogspawn in the garden pond today - but I probably shouldn't have been as our resident frogs seem to be spawning earlier than they used to. We've been here 10 years and the last three years have seen the earliest spawning dates, with 2016 being the earliest (1st Feb). In earlier years the first dates ranged from 14th Feb (2013) to 27th Feb (2010 and 2012).

I'm not sure this relates to mild winters - we had several of those in the earlier years here, and January of this year was pretty chilly. Perhaps just part of a general trend to earlier spawning.