My pet birds have them in their general food mix but always leave them. I think its a shame to throw them away, I keep dried berries, left over brazil nut bits & rosehips and put them out on the bird table but I'm not sure about the pumpkin seeds. I tried my tamish squirrels with them but they gave the paws down. I wouldn't want to make the birds ill.
I've just quickly googled this and I haven't found anything that says not to feed them wild birds. Although they are quite large and I'd imagine a lot of garden birds would struggle with them.
In truth i'd imagine that if there is other food on offer near by the birds might ignore it! But as they say - every little helps! ~ Pumpkin seeds will certainly be taken in times of less plenty, but the easier the food is to digest and provide needed energy the better!
I might try to break them out of the husk and put it on the bird table broken up. I think they are high in energy so we will see. Just didn't want to poison them or make them ill.