Original idea
The snowy owl's white plumage is hard to see on the white snow.
Rephrase 1
The snowy owl looks white on white snow, so it can be hard to spot.
Rephrase 2
The snowy owl blends in with the snow because both are white, making it hard to see.
Rephrase 3
On the white snow, the snowy owl can be very tricky to notice because its feathers are also white.