Serendipity- thats a good example why i dont believe the gull could do it. Look how the eagle is holding it, gulls dont have feet like that.
The gull would have to pick it up by its feet/beak (depending what story you read) but neither is designed to grip like that. They wouldnt be able to scruff a wriggling dog which weighs more than them, then take off and get enough height to then clear several gardens.
Gulls can dive bomb things but usually they pick the thing and drop it fairly quickly even if its just a sausage roll, they might repeat that several times before deciding to swallow it whole usually. Ive never seen one i think, pick something small and still like a sausage roll and carry it off into the distance.
Theres some interesting research about how gulls dive select people to dive bomb who they think are more likely to drop the food (eg they have learnt in some areas women are more likely to scream and drop food so actively target women!) They would rather you dropped it so they can have a solid go and picking it up and apart. I dont know how that would work on a barking, running and potentially aggressive dog
The article has it doing so in one swoop like an eagle which isnt gull behaviour. The gulls the owner said it was are herring gulls which would be lighter than the dog.
I would totally buy a gull attacking, carrying and eating a deadone, dive bombing or having a go at taking one (multiple times even!) , just cant believe in one go it managed to pick up, carry a live dog, without dropping it in the same garden or next door, all while someone was watching (and presumably shouting or running etc)
There's an article thats popped up about a local child that was got by a gull (they are linking it to the same "suspicious" looking gull). However the child has a black eye and no obvious scratches or marks that a gull attack would cause. Apparently their dog was eaten by a gull too in their garden several weeks ago.
Its all doesnt make sense!