Carole, what beautiful birds you have there in Australia, love the rainbow colors of those gorgeous Rosellas!
I too was shocked the first time I saw a Northern Cardinal eating Crepe Myrtle seeds. Even with all the feeders and variety of food that I put out for them, this one decided it preferred seeds of the Crepe Myrtle tree:
Blue Jays are known to fill their crops to overflowing. I've seen them with crops full of sunflower seeds and they also love peanuts and love to horde them! I sometimes mix peanuts in with birdseed and the Jays will fill their crops and then take off to their nest to feed the babies, or to stow the seeds/peanuts for future meals. These are old photos but you can see what I mean ... they sure look like gluttons!
