Zoo keepers in Chester have set about the mammoth task of carrying out health checks on more than 150 birds.
The endangered and exotic birds at Chester Zoo's free-flying tropical house are being studied to assess their health, condition and sex.
And keepers have come up with a novel way of keeping the birds calm as they get the job done - placing the birds head first into mugs and other dark containers before weighing them on sets of scales.
Chester Zoo's curator of birds, Andrew Owen, said: "It's vital we are able to take accurate biometric measurements of the birds to give us a better understanding of their biology and that includes taking a weight for each of them.
"To do this we carefully place each of the birds beak down into a container for a few seconds - as it's dark inside it helps to keep the birds really nice and calm.
"We also deploy special netting techniques to help us catch the birds in the first place and it's really important that all of our staff have a chance to get to grips with those.
"That's because the very same methods are also used at our field conservation projects, so the skills picked up here are vital to those staff heading overseas to try and save certain species threatened with extinction in the wild."
More than 20 different species of bird reside in the zoo's Tropical Realm including exotic songsters like the orange-headed thrush and Brazilian tanager, as well as conservation species such as the vulnerable-to-extinction Javan sparrow and critically endangered blue-crowned laughing thrush.