Ready to fly?

We still have these youngsters in a nest in the bus shelter. There are nesting birds here every year and several broods are reared. This is a second brood and they are cutting it a bit fine to get them in flight and ready for migrating in a few weeks. However, they do look to be ready to fledge now. In fact, I was hoping for the picture of all four of them peeping over the edge of the nest, but the nest is obviously getting a bit small for them and two of them have turned round, so you can only see their tail feathers. Maybe it’s a bit less squashed that way! Parents are continuously flying in and out, very quickly, to feed them.
  
We had assumed they were House Martins, as those are what have been here in previous years, but I think they have too much colour and are actually Swallows. I may be wrong. I really like how you can see the nest, made of mud and straw, balancing a bit precariously against the roof beam. (The extra picture was taken from the other side, so these are the two facing the other way.) I’m sure that this is a scruffy Swallow’s nest, rather than what would be a much tidier House Martin’s nest.