if it is as I think --a young mocking bird ---they are in my point of view for their size one of the toughest birds around bar none -- I like them due to their toughness .. I have seen one slam into a red tailed hawk that was trying to eat its young from its nest --knocking the hawk off its perch by the nest then fly after it plucking out its tail feathers ---they will do the same to crows which are their mortal enemies (once enough tail feathers are plucked out a bird can't fly and once "grounded" they are easily killed by cats and other critters) ---if times are tough and food hard to comeby mockingbirds will defend their food sources from all comers ... get a few meal worms and you might be able to make friends with it ... oh BTW mocking birds love for folks to whistle tunes for them to try and copy - they have been known to attack cats by dive bombing them from behind and hitting their tails and will drive anything they think is a threat from their nesting areas --including humans..
as far as the it looks preggers goes its possible -- but in the cold --many birds fluff out their feathers trapping air within to warm up and to act a sort of thermal buffer --as a means of staying warm.