New Caledonia crow

A discovery by Dr Sarah Jelbert of Jesus College, Cambridge, has led to the refinement of our understanding of crow intelligence. On the south-west Pacific island of New Caledonia, a crow called Emma has stunned researchers by operating a vending machine they constructed for it, remembering the size of a token needed to release a treat. The ongoing investigation into the intelligence of the species follows the discovery that it works material into fishing hook-style tools to extract larvae from holes in dead wood.

Gone fishing: a green heron using bread as bait. Photograph: Edgard Balladares / youtube

Green heron

A study by the Cornell Lab of Ornithology in New York has found that the green heron, which eats small fish such as pickerel and sunfish, hunts by luring its prey with insects, earthworms and bread crusts on the surface of the water. These tempt the fish to rise.

Pretty clever, Polly: the kea, which has been captured on video setting off stoat traps. Photograph: Alamy Stock Photo

Kea

The installation of stoat traps by New Zealand’s department of conservation has revealed the intelligence of the kea, a large parrot. The rare bird has been captured on video setting off the traps using twigs it had pared for the purpose. Intriguingly, the birds did not take the bait left in the traps.

Grub’s up: the brown-headed nuthatch. Photograph: Alamy Stock Photo

Brown-headed nuthatch

Further study by the Cornell Lab of Ornithology has revealed that the brown-headed nuthatch uses its disproportionately large beak to hold pieces of wood and scratch away at bark until it finds food. The bird, which lives in the pine forests of the south-eastern United States, snacks on bark-dwelling insects such as beetles and cockroaches.

Brilliant: a rook drops objects into a tube to raise the water level and retrieve a floating worm. Photograph: Cell Press Video / youtube

Rook

Research by Queen Mary University of London and the University of Cambridge has highlighted the problem-solving ability of rooks. One study showed that the bird could understand a set-up in which dropping a large stone into a tube would release a small stone that could in turn be placed into a thinner tube, releasing a worm – known as metatool use. Rooks have also mirrored Aesop’s fable by dropping stones into water in order to raise the water level and give them access to floating food.