Yes, it did happen fairly frequently, but you are unlikely to be able to read much about it as a phenomenon - I've been looking for quite a while and not found any secondary sources beyond the biographies of the famous individuals it was done to. In fact, many of the most famous examples are in the series you are watching, the First Australians - specifically, Pemulwuy, Truganini and Jandamarra.

I'm actually considering doing my post-grad research on the topic (frontier corpse souverning).

(I will write brief biographies here, but I strongly encourage you to look further into the amazing lives of these individuals)

Pemulwuy, the warrior mentioned in the First Australians clip you linked, was a man of the Eora who led the tribes of Sydney in resistance for many years. He apparently believed himself bulletproof, but eventually he was fatally killed. His head was removed and sent to England, and since then researchers have been unable to find it so as to return it to Australia for burial. This is important because of Indigenous beliefs - people are connected to their land and must be buried there, or wander as angry spirits forever, weakening the land. Prince William has apparently promised to return the skull to the people of Sydney.

Another warrior leader whose head has been returned from England (in 1997) is Yagan, of the Whadjuk Nyungar from modern Perth, WA. He was regarded as a fierce but noble warrior who commanded respect from everyone, yet was declared an outlaw for several revenge attacks and food raids, and eventually betrayed by two white boys, who shot him as they all sat down to lunch. One of the boys was killed, but the other ran to a nearby farm and returned to Yagan's body with a posse. These men smoked Yagan's head in a tree stump, sketched it, and flayed the ritually scarred skin from his back. The head was sent to England, where it was eventually lost, and then later buried with a heap of other imperial body part trophies. In the late 1990s Nyungar elders began a campaign that included their leader flying to England to search several universities - he eventually returned with Yagan's head and it was reburied in a public park made in the location where his body was believed to be buried. The exact location is unmarked, as the statue of Yagan that was erected in the heart of Perth has twice had its head decapitated and stolen - Indigenous sites in Perth are now kept secret in fear of desecration.

Truganini is another, this time a woman and a diplomat of Tasmanian Aboriginals. She lived an incredibly brutal early life, but could see that Tasmanians would never survive colonialism and helped a man named George Augustus Robinson reach out to every tribe. He brought a deal that promised temporary relocation out of Tasmania, so as to save the Tasmanian people - many accepted, but most died quickly of starvation or disease. Truganini was crucial to the venture, protecting Robinson from both nature and native attacks, including from the warrior woman Walyer. Before she died of old age, long after the expedition faded into obscurity, she begged those around her to make sure she never ended up a scientific specimen for doctors or museums, having seen 'the last male Tasmanian' suffer this fate. Never-the-less, her wishes were ignored, and shortly after burial permission was gained to exhume her body for study and display. It remained on display as the centrepiece of Tasmania's museum, as 'the last of the Tasmanians, the most primitive people on Earth', until 1976, when her ashes were scattered into the ocean by Tasmanian Aboriginals.

Another is Jandamarra, a Native Policeman of the Bunuba tribe of the Kimberley, northern WA. A brief stint in prison as a teenager meant that his initiation to manhood was unfinished - rejected by his tribe, he went to live on a pastoral station and followed his white employer into the police force. One day, a large group of his own people were arrested and this forced him to pick a side - he shot his employer (in truth a friend) and rescued his people. After this they became rebels, leading attacks on stations to drive away the white invaders. After three years of war he was eventually tracked down and killed by another Aboriginal policeman, and his head sent to Perth and then to England as proof of death and as a triumphant souvenir.

I have also read of settlers nailing severed body parts to their buildings in order to frighten away enemy attacks - specifically, in Neville Green's Broken Spears, where he says it occurred during the conquest of the York plains in WA. This was part trophy, part grizzly warning, and part psychological warfare, in that there is a great deal of taboo and spirituality concerning death - what kept away attackers may well have been a fear of the dead person's spirit rather than the settler who displayed the body part.

Some bushrangers also suffered the same fate - one of the most souvenired was the body of Mad Dog Morgan. Daniel Morgan, whose real name is unknown as he went by many aliases, was a native born serial criminal, robbing people throughout New South Wales. He was famous for his ferocity and brutality, killing many people and humiliating his victims. One night he held up a rural cattle station, but a woman escaped and alerted the neighbours and the authorities, who surrounded the house and shot him as he came out to leave. His hair, beard and pieces of skin were taken as souvenirs by bystanders and his body publicly displayed and photographed, his head removed and sent to doctors to study.

What links those who had their bodies mutilated and souvenired after death was often infamy, these people usually outcasts like Indigenous Australian warriors or white bushrangers. Most made their way from the victorious killers to the authorities, and then to doctors and scientists, and then to museums for display. The first is for proof or assurance of death, or even reward for bounties, souvenirs of victory (celebrating law, civilisation or empire), and as a warning to other miscreants (a very old English tradition); the second to doctors to study the mind of society's rejects (phrenology), finding out what physical characteristics of the head and brain caused them to behave the way they had in life; and thirdly as museum pieces that attract crowds of the curious, again as trophies of Britain's greatness, conquering exotic lands beyond the horizon.

What may have contributed to the activity in Australia was the lack of respect for Indigenous Australians, the belief that they would soon necome 'exctinct' and the lawless frontier nature of the land the battles were fought. Many settlers and soldiers had experiences of North America or Polynesia, and tales of both frontiers would have travelled far throughout the empire, thus possibly conjuring up recollections of 'savage' scalping or head-hunting traditions in the heat of battle.

Another contributing factor could be the historic display of the heads of villains in public places in England - a very famous example of this is Oliver Cromwell's head, which was exhumed, decapitated, preserved and displayed above Parliament, before a storm blew it down and it ended up passed around in museums.

A similar phenomenon also occurred with the bodies of Bonnie and Clyde, the famous Depression era American outlaws, where their bodies were practically pulled apart by bystanders eager to sell to or show others - it may have less to do with frontier culture than it does celebrity crime and punishment in Western society.

Besides the fantastic First Australians tv series you are already watching (which also exists in book form), if you'd like to know more you could:

- check out the biographies of these individuals on the Australian Dictionary of Biography, which is sourced from historians and maintained by the Australian National University.

- the AIATSIS website should also have biographies of the Indigenous individuals.

- Yagan or Broken Spears by Neville Green for Yagan's story.

- Jandamarra and the Bunuba Resistance by Banjo Woorunmurra and Howard Pederson

- Lyndall Ryan has written a great deal about Truganini and Indigenous Tasmania

- there was a movie made in the 70s about Mad Dog Morgan

It is a week later, and I just saw this post because of the AH twitter feed.

/u/Djiti-djiti has already given an excellent answer, so I just want to comment about skull-taking in the broader colonial context.

What the British settlers/soldiers did in Australia was not exceptional. Taking the heads of conquered enemy fighters happened throughout colonies in Asia and Africa as well. British soldiers decapitated Vedda warriors from Sri Lanka and sent the heads to Edinburgh. Settlers from Cecil Rhodes' Royal South African Company decapitated Shona and Ndebele resistance fightersduring the First Chimurenga in 1896-97, which ended up in museums in Britain. Lord Kichener the leader of the British column that finally conquered the Mahdist State in what is now Sudan, ordered the destruction of the tomb of the Mahdiyya's founder, and considered sending his skull to Royal Surgeons College. Though, these accounts concede that Kichener ultimately had the skull buried at Wadi Hamid Halfa, either under his own initiative or by orders of Queen Victoria.

In Kenya, there is the instance of Otenyo Nyamterere a man from the Gusii people, who attacked a colonial administrator in 1902, was beheaded and had his skull sent to Britain.

During the 1857 revolt against East India Company rule in the Indian subcontinent, many of the rebels were ultimately beheaded and their heads were sent to Britain. The British-Danish historian Kim Wagner ended up in possession of one of these skulls, and wrote the book The Skull of Alum Bheg about the 1857 rebellion, skull taking, and the individual whose skull he now possesses. Here is a podcast where Kim Wagner discusses his research, and skull taking in the context of British imperialism and military ideals

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Now, we also have to realize that the British were far from the only European people who engaged in head-taking. There are many instances of German, French, and Belgian troops who took the skulls of conquered colonial peoples.

For instance, during the conquest of German East Africa (now Tanzania), German troops took the head of Hehe chief Mkwawa and sent it to Bremen in 1898. A few years later in 1900, Germans also sent the skull of Mangi Meli to Germany. According to a German cultural heritage oversight group, over 1,000 human skulls from Germany's colonies remain in German museums.

In King Leopold II's Congo Free State, the conquest similarly saw the taking of the heads of local leaders and fighters who resisted the imposition of European hegemony. Alan Roberts has written about the case of the Tabwa warlord Lusinga lwa N'gombe who was decapitated by Captain Emil Storms, and whose skull was sent from eastern Congo to Brussels.

Similarly, Emmanuel Sibaud writes about French colonial administrator Maurice Delafosse's practice of collecting skulls in French West Africa to conduct measurements for anthropological purposes.

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Finally, I am going to double-down on my recommendation for Kim Wagner's podcast episode. He raises the point (which the Delafosse article and Roberts book supports) that human trophy taking happened at the juncture of the culture of machismo of European soldiers, as well as the early days of Anthropology in the service of Empire. That is, the sending of skulls to European museums and universities happened under the rubric of studying the head shape (i.e. phrenology), to allow better understanding of the racial characteristics of the conquered, subject peoples of the empire. So, these skulls served both as trophies as well as objects of scientific study.

And, as you can gather from the many news articles I linked (sorry for that), the return of human remains is an issue that post-colonial nations are making louder demands for, and which European and American museums are now forced to account for (and account for their institutional role in colonial atrocities).