The helmet vanga (Euryceros prevostii) is the most unique of birds - its bright blue beak setting it apart from the rest.

Vanga's are only found in the wet, eastern forests of Madagascar. There are around 20 species of the bird on the island, all descended from the same ancestor species.

No one knows exactly why it was blessed with this brilliant appendage, but its beauty hides a lethal weapon. Vanga's are ambush hunters pouncing of millipedes, cicadas and lizards from above.

Watch the moment Sir David Attenborough and BBC filmmakers caught sight of this rare bird for the series Madagascar.

Even better, you can watch a further 1,000 more memorable moments, for free, anytime, on your smartphone or tablet, via Attenborough's Story of Life app, which is now available to download via Google Play, or Apple's app store.

Find out more at http://www.bbc.com/earth/storyoflife.

The Story of Life has been produced in collaboration with Sir David Attenborough, BBC Earth and ideas and innovation company AKQA.