A flock of birds

Was nt sure what to blip today, abit stuck for ideas but I turned a photo of some birds that flew overhead this morning into negative and quite liked the result. Not sure what they are, any ideas ? A whole flock of about 100 flew over.
Fun at Brownies tonight looking at sight and wearing blindfolds and helping each other move around the room.
A Skype meeting with other members of Girl Guiding in our district was a success, it's so hard to get everyone together for  face to face meeting.