At the end of each day, as Irene Pepperberg placed her parrot Alex back into his cage, he would bid her goodnight with the same affectionate phrase: "You be good, see you tomorrow. I love you."

This was no ordinary pet. Pepperberg was a scientist and Alex was her star subject. Over the course of 27 years, the African grey parrot built a vocabulary of hundreds of words, which he could understand in a sentence and even spell out. He could count numbers and add them up. He had favourite colours, strong opinions about individual people and even an understanding of abstract conceptsThe parrot demonstrated an understanding of the idea of zero - a notion that was famously unknown to the Romans and many other ancient civilisations..

Alex's feats transformed our understanding of birds. "Bird brained" has long been an insult, but now scientists are uncovering ever more evidence of their extraordinary mental abilities.

This realisation is the inspiration for a photography book called Tim Flach's Birds. It is a series of studio portraits capturing various avian species in human-like poses. They preen like models, flashing their plumage or staring directly into the camera. "I don't see myself as documenting animals' habitats," Flach says, but "the meanings of animals to us."

Flach's approach is deliberately anthropomorphicAnthropomorphism is when humans ascribe human-like traits, for instance personalities and emotions, to non-human things (including animals).. This is something that naturalists are often wary of, especially in animals as evolutionarily distantThe closest common ancestor of birds and humans lived over three million years ago. Birds are direct descendents of dinosaurs, and indeed so closely related that some argue that birds are in fact living dinosaurs! as birds. But despite their completely different anatomy and heritage, birds exhibit behaviours that seem to indicate minds not unlike our own.

Crows can solve puzzles that stump most five-year-old children, including by using tools. Magpies, also from the corvidAlongside parrots, the corvid or crow family (which also includes ravens and jays) is thought to include the most intelligent bird species. family, can recognise themselves in a mirror and show self-awareness. Chickadees communicate complex information about predators, while some bird species pass down cultures of language or behaviour from one generation to the next. Pigeons can be trained to distinguish a Monet painting from a Picasso. Long-tailed tits build nests using around 6,000 pieces - an impressive architectural achievement.

By human standards of intelligence, says ornithologist Jennifer Ackerman, these animals are "closer to primatesThe order of mammals that includes humans, alongside apes like chimpanzees and gorillas. than to their own reptilian ancestors".

In other areas birds' abilities surpass our own. A clark's nutcracker can stash seeds in 5,000 caches and relocate them all - a triumph of memory most people can only dream of. Some species can navigate distances of thousands of miles, homing in on a specific spot with incredible accuracy.

Birds don't just show calculation, but also social and aesthetic senses. Parrots are the only animals besides humans and elephants that can dance to a beat. Bowerbirds curate sculptures made of leaves, bones and trash to attract mates. Chickens have extremely precise social hierarchies: the proverbial "pecking orderEach chicken in a flock pecks all of the chickens below it and is pecked by its superiors. This hierarchy reflects which individuals get priority when food is available.".

Yet not everyone is convinced by an anthropomorphic approach like Tim Flach's. Some prefer to emphasise the profound differences between two sophisticated kinds of mind. "There's the mammal way," one ornithologist writes, "and then there's the bird way".

Yes: Once we recognise how much we share with these amazing creatures, they say, we will see how much we should value them in all their diversity.

No: Birds may be fascinating, but they are incapable of achieving what we do as humans. It is our unique intelligence that allows us to find out about these beautiful creatures in the first place.

Or: The reason why birds are so fascinating is that they give us a glimpse into minds fundamentally different to our own. We should recognise that their intelligence is thoroughly alien - and all the more miraculous for being so.