Cocker has written extensively for British newspapers and magazines including The Guardian, The Daily Telegraph, The Times, The Independent and BBC Wildlife.

This early access to the spectacular limestone flora of the Derbyshire Dales and the specialised upland birds of the Dark Peak provided formative experiences in his evolution as a naturalist.

This proved to be the background to two biographical studies: A Himalayan Ornithologist: The Life and Work of Brian Houghton Hodgson[1] and Richard Meinertzhagen: Soldier Scientist and Spy.

Hodgson was the Honourable East India Company's resident (proto Ambassador) in Nepal, where he researched zoology, from fish and amphibians, to birds and mammals.

Cocker's biography of Meinertzhagen received widespread critical acclaim and was judged, with Mark Hudson's Our Grandmothers' Drums and Bill Bryson's The Lost Continent, one of the highlights for Secker and Warburg in 1989.

Cocker has unearthed in his diaries patent elaborations, exaggerations and falsehoods and there is evidence too that in his scientific career Meinertzhagen indulged in practices that would be considered highly fraudulent.

The work focuses on four collisions between Europeans and indigenous cultures: the conquest of Mexico, the British onslaught on the Tasmanian Aborigines, the uprooting of the Apaches, and the German campaign against the tribes of Southwest Africa.

Among its critics, Ronald Wright,[7] noted its "shaky existential dichotomy between Europeans and "tribal peoples"", while fellow historian Alfred Crosby[8] suggested that "Cocker has written the kind of book we needed a generation ago, when our concept of history was profoundly Eurocentric, but surely now all of us given to reading history books are doubtful about the immaculate gloriousness of white civilization".

By contrast, Charles Nicholl wrote that "Cocker succeeds in finding a tone appropriate to the matter: he has a journalistic sense of impact and a powerful command of historical narrative.

",[9] while Ronald Wright stated "The most powerful theme of Mark Cocker's books is … his vivid map of hell into which people can so easily descend when they have ideology, means and opportunity.

Birds Britannica shows that this need not be seen as something artificial or contrived but as part of a long and ever-shifting relationship, an indicator of our own place in nature.Cocker's work on the ubiquitous crow is in similar spirit: a rare combination of natural history and cultural anthropology.

Reminiscent of an earlier age of scientific investigation, the 'whole picture' perspective being not unlike that of Francis Bacon who wrote in a similar vein:[15] Men have sought to make a world from their own conception and to draw from their own minds all the material which they employed, but if, instead of doing so, they had consulted experience and observation, they would have the facts and not opinions to reason about, and might have ultimately arrived at the knowledge of the laws which govern the natural world.This unique combination of natural scientist, environmentalist and cultural anthropologist is most evident in his latest project Birds and People.

Cocker's latest project with foremost British wildlife photographer David Tipling and natural history author Jonathan Elphick, is Birds and People.

Very often at a domestic level they are cherished for their own sake, as simple companions, as aesthetic adornments and as expression of some unspoken bond between ourselves and the rest of nature.The resulting book is intended as a summary of the current state of birdlife worldwide.