Birds ignoring live mealworms

I have not seen this before but the live mealworms I put out this morning have been ignored by all the garden birds.

I bought them from the usual place I used so I don't think there is anything unpalatable about them.

This is supported by the fact the birds are not trying to eat them and then leaving them. The birds aren't even going near the mealworms.

I'm puzzled by this as I assume natural food isn't yet in great supply.

Dave