dSunflower seeds are enjoyed by nuthatches, grosbeaks, cardinals, jays, finches and types of jays and even some types of woodpeckers.
However, grackles and european starlings also love them which can cause problems with other types of birds.
There are two kinds of sunflower—black oil and striped.
The black oil seeds (“oilers") have very thin shells, easy for virtually all seed-eating birds to crack open.
The kernels within have a high fat content, extremely valuable for most winter birds.
Striped sunflower seeds have a thicker shell, much harder for House Sparrows and blackbirds to crack open. (source)
So can hamsters eat bird sunflower seeds?
Yes they can, only a few at a time though.
This is because they are extremely high in fat and will harm them if they have too many.
One or two at a maximum is recommended.