You're in the bush, scanning the shadows for predators, when the flit of a wing catches your eye.

You shift your gaze to see an avian alighting on the limb of a tree.

Judging by its size, plumage, and call, it's clearly a, well, what?

You reach for your well-thumbed Roberts', flipping through the pages and pages of colour plates, only to discover ... that your prize sighting has flitted off.

Surely, in this age of smartphones and smart apps, there must be a quicker and easier way to pin a name on a bird?

How about this: you point your phone at your feathered find, zoom in to snap a recognisable pic, and leave the rest up to Merlin.

That's the name, inspired by King Arthur's Wizard and a small species of falcon from the Northern Hemisphere, of an iOS and Android app that can swiftly identify thousands of birds, all over the world, by sight or sound.

Merlin works its magic in much the same way as the Shazam app is able to recognise a song: by matching what it hears with the digital signatures in a vast databank of recorded music.

Merlin's treasure trove of data comes from eBird, a collaborative global project that tracks bird sightings and vocalisations, with the help of scientists, educators, volunteers, conservationists, and satellite imagery from NASA.

The project is managed as a public service by the Cornell Lab of Ornithology in New York, in partnership with the National Audubon Society, which protects birds and their habitats in the Americas.

The Merlin app is just one aspect of eBird's mission to advance knowledge, understanding, and appreciation of the world's abundance of birdlife, from the common-or-garden to the very rarely seen.

The app's minimalist design and ease of use make it a must-have accessory on any birding expedition or everyday encounter.

All you have to do is snap a pic on the app or load it from your photo roll, and record the bird's call if you prefer.

In return, Merlin will present you with a handy profile of the bird, a map of its habitat and range, and a selection of images and vocalisations from its databank.

You can install regional location packs to narrow your sightings down, and build your own "life list" of sightings for future reference.

But perhaps the best thing about Merlin Bird ID is that it's completely free to use, with or without an internet connection, in your garden, in the mountains, in the deepest bush, or anywhere else where the flit of a wing catches your eye.

Happy twitching!

Merlin Bird ID is free to download and use, for iOS and Android devices. Get it on the App Store or the Google Play Store. To find out more about the eBird project, visit https://eBird.org.