U.S. birdwatchers can get help identifying a species they're observing by reaching for their smartphone, Cornell University developers of an app say.

Created by the Cornell Lab of Ornithology with support from the National Science Foundation, the app -- dubbed Merlin -- asks just five questions then displays photos of birds that match the description -- customized to the phone user's location and time of year.

"We named the app 'Merlin' because of its uncanny, almost magical, way of guessing which bird you saw," Jessie Barry, whose team created the app with partner Birds in the Hand, said.

Merlin uses data from citizen-science participants and bird watchers to understand how people see and describe birds -- and to narrow the list to the birds found nearby, Barry said.

Data from the eBird citizen-science project helps the app dynamically select the birds found within about a 30-mile radius of a location at the time the bird was observed.

"This type of precision is only possible because bird watchers report their sightings to eBird from locations across North America every day of the year," Barry said, noting that Merlin draws on 70 million eBird sightings to calculate which species are most likely to be encountered.

Released for the iPhone and available from Apple's App Store, a version of Merlin for Android and online use will be offered in the coming months, the Cornell lab said.