Very large Blue tit

Hi Gema, you will have to take your film footage through a platform like YouTube or Vimeo before you can upload it on here and then use the rich formatting button bottom right to add your video.   

Well done uploading the video clip Gema, the blue tit looks larger because it has fluffed up its feathers trapping air between its plumage and that can be either to keep warm which would be unusual during summer months unless it was a particularly cold day or it is because the bird feels unwell and is ill. I suspect the latter because as you are filming it it is not flying away so maybe sick. Hopefully it is just temporary and the bird will recover in time but there is avian flu around and other diseases in birds such as salmonella. All you can do is ensure your feeders if you have any have a re-clean and I would advise not to put water dishes out at the moment if the bird is sick. If you see more than one bird fluffed up or looking lethargic or sick then remove all feeders and dishes to hopefully cut down the possibility of disease transfer. fingers crossed your blue tit will recover. Also, if you had to handle any bird that got very sick, then ensure you wash your hands thoroughly afterwards as some diseases can pass bacteria on to humans, For the time being, just be vigilant and keep a watch for any other bird looking fluffed up or ill. Good luck.