Or inter-marrying and having kids, with some of the old folks dying off or moving to Arizona.
Without adoption, intermarriage would mean only an increase in those reported as mixed. Only 4% more of the population were reported as mixed in the second census.
I don't know why a white living on a reservation in Minnesota would move to Arizona. Different climate, culture, and, if you mean living on a reservation, different language.
If most of the over-65 segment in the first census had been white, that might account for the reduction, but I don't know why the native population would have doubled.
About 1960, Beverly Santamaria, a U Mass student from Boston, decided to become a folk singer. Needing a gimmick, she claimed to be a Native American. She showed her ignorance by giving reporters conflicting stories about what tribe she came from. She often claimed to be Algonquin, which was as vague as calling herself a Latina. She also called herself a Mi'kmaq, who are not Algonquin. In December, 1963, she told a Vancouver reporter she was a "Cree Indian."
In 1964, her uncle wrote an editorial in his newspaper saying she had no Native American blood. He was ignored. That year, when she performed in Saskatchewan, a Cree couple invited her to their reservation and had her adopted. She never lived there. Both sides were seeking publicity. She began saying that when she was 3, a racist Boston couple had had her taken from her Saskatchewan parents so they could adopt her.
Now she was seeking fame by slandering her parents. In 1972, her brother wrote letters to newspapers debunking her lies. Nobody cared. In 1975, the producer of Sesame Street invited both to dinner to discuss her possible role as the show's genuine Indian. He told her brother he did not look indigenous. Her brother replied that nobody in the family had any indigenous blood.
Her brother received a letter from her lawyer. "We have been advised that you have without provocation disparaged and perhaps defamed Buffy and maliciously interfered with her employment opportunities." The letter also stated that no expense would be spared in pursuing legal remedies. Enclosed was a handwritten letter in which she threatened to accuse him of molesting her as a child if he said anything more about her ancestry. That way, the law firm could claim to be unaware that this was blackmail.
PBS went right ahead and cast her as their genuine Indian. PBS showed far less integrity than NBC in 1950. They never pretended that Judy Tyler (Princess Summerfall Winterspring) was a genuine Indian or that the guy tooting the bicycle horn came from a clown reservation.
Besides her slandered family, it seems indigenous Canadian performers were the only ones who cared. By grabbing awards intended for indigenous Canadian artists, the impostor was depriving the real ones of recognition. The CBC's "Fifth Estate" is an investigative program taking its name from the fact that news presented by the fourth estate is often false. In October, 2023, they exposed her.
Descendants of the couple who had adopted her responded, "We claim her as a member of our family and all of our family members are from the Piapot First Nation. To us, that holds far more weight than any paper documentation or colonial record keeping ever could."
To the contrary, native adoption was not intended as a publicity gimmick like Queen Elizabeth passing out knighthood to famous Americans. It does show that adoption would be a snap for a Chippewa resident who had proved to be a good neighbor.