. >> reporter: katie labarbera is with the san francisco bay bird observatory. over the past 40 years volunteers with the nonprofit have studied birds at the coyote creek field station in milpitas. they've seen a worrisome decline in some species. >> with climate change these ecosystems are being impacted. these species are being impacted often in a negative way. >> reporter: to shed light on the issue, katie and her team collect data using a traditional research method known as banding. >> they've got a very big personality. >> reporter: the birds like this little chickadee are gently caught, their feathers inspected. by softly blowing on the bird, researchers can check for fat and signs of molting. >> it's a bracelet. so it rolls, goes up and down. >> reporter: a lightweight band engraved with a unique number is fitted around its leg. the bird is then released. if the bird is caught again, the id allows scientists to keep track of its movement, but -- >> you recapture a very low percentage of all the birds you band. so you have to band a lot of birds to have a