After they got together in 1959, they kept their relationship a secret, save for an inner circle of gay friends. Today, Darby and Bird walk hand-in-hand, occasionally sharing kisses or sweet words like many other married couples.
"It was the society we lived in," Bird, 84, said in an interview with AFP in the couple's home in a retirement community in the heart of San Francisco. "I learned I was gay, but I hid it."
Darby, 86, and Bird will celebrate their 54th anniversary as a couple in July and their fifth wedding anniversary two months later.
"I will always remember putting this on his finger," Darby said, touching the wedding ring on Bird's hand. "It was a marvelous day."
"It is so important to realize that gay life is so much more than just sex; it is love," he continued as Bird nodded.
"It would be lovely if we could die together, just go to sleep holding hands and let relatives get rid of everything for us."
Darby was freshly back from trips to Cuba and Mexico when he went to a party at a friend's apartment in San Francisco in 1959 to celebrate Independence Day, feeling very much the "closeted tourist" and alone in his sexuality.
"It was just something you didn't talk about," Darby said. "There was a lot of homophobia in the late 1950s and early 1960s."
It was a time when professional, single men lived with 'male assistants,' keeping what went on behind closed doors private. It was tolerated that an uncle or aunt might be gay or lesbian as long as it wasn't discussed.
"We didn't talk about it with our families," Darby said. "We just expected them to understand but didn't want to rub their noses in it."
Darby was living with another man as 'roommates' sharing occasional intimacies when Bird won his heart at the party.
"I was younger, a lot younger and taller," Darby recalled. And then he spied the blue-eyed Bird. "I fell in love," Darby said.
Darby went to use the bathroom only to find a queue, with Bird among those waiting in the hallway.
"He looked at me and I looked down and kissed him," said Darby, who stands taller than 5-foot, 4-inch (1m62) Bird.
Within six months, the pair considered themselves engaged and found an apartment in the city of Sausalito across the bay from San Francisco.
They had a joint checking account, a rarity at the time.
"Thank god we had a broad-minded real estate agent," said Darby. "We were careful."
They only much later found out that two women living next door were lesbians.
"In those days we didn't have much of what you'd call 'gaydar'," Darby said, using slang for the ability to pick up on cues about one's sexual preference. "Now, gaydar is so common."
Darby and Bird took a trip in the summer of 1960 to the California coast city of Carmel to visit family -- not all of whom were so welcoming.
One aunt drove Darby to tears when she demanded he abandon the relationship and focus on his future career as an audiologist, but the couple persevered.
Within two years, they had bought a house.
For the most part, they didn't tell relatives of their union. Bird had an aunt and uncle who thought it was wonderful he had a housemate. Darby even had a brother-in-law accuse Bird of having an affair with his wife.
"How could he be so naive?" Darby said. "He was so homophobic that he just blocked out what was in front of him."
Darby and Bird confided in gay friends and spent little time socializing with straight people. Bird was a successful controller for a shipping company. Darby was the local Hearing Society director.
"We never held hands; never kissed or made overt gestures of affection in those days," Darby said. "Today, hell, we touch each other quite often."
Gradually, they brought colleagues into the loop, but prejudices in the workplace remained. Darby recalled being told an offensive joke at a conference in Ohio in the 1980s that began: "Do you know what is magical about AIDS?"
When gay marriage opponents launched a political attack on a move by then San Francisco mayor Gavin Newsom to allow such unions, Darby and Bird raced to City Hall to find it 'an absolute zoo.'
Instead of waiting until after a planned election that would close the door on gay marriages in California, the couple of 49 years got their marriage license in the neighboring community of Marin.
They wed in San Francisco in 2008.
A friend made them wave-design wedding rings on just two days' notice. The couple enjoyed champagne and chocolate cake -- with two male figurines on top.
"What was really amazing was two days later there was a bag hanging on our door with a bottle of champagne and a card from an elderly widow who I thought didn't even know what the word 'gay' meant," Darby said.
By then, the pair were living in an apartment in San Francisco Towers, an Episcopal residential care facility for seniors.
"A group of residents had a big dinner party to congratulate us," Darby said. "There were some people who never spoke to us again. What do you expect?"
When the couple moved into the Towers in 1998, they were told two men couldn't share a single-bedroom apartment, so they got a two-bedroom unit and used the second to maintain a facade and a home office.
Now, the couple's photo is on promotional material for the Towers.
Darby laughed while recalling times he was asked who is the husband and who is the wife in the relationship.
"Asking a gay couple which one is the wife is like asking chopsticks which is the fork," he said. "We just work together. We went from being friends to dating; became partners and became spouses. Not husband and wife."