be (strictly) for the birds

slang To be frustrating, annoying, or pointless. Primarily heard in US, Australia. Driving is strictly for the birds when you live in a big city—unless you like sitting in traffic! I miss my usual shift—night work is for the birds. Man, this is for the birds. I've been waiting for an hour already, where is she?

for the birds, it's/that's

It’s useless, worthless; not to be taken seriously. This slangy Americanism dates from the first half of the twentieth century and crossed the Atlantic after World War II. One writer suggests it alludes to droppings left by the horses of horse-drawn carriages, from which small birds would extract the seeds. If this source is correct, the expression is a euphemism for “horseshit.”