ZHANGCUN, China—Xiao Yun and Xiao Bo are, in many ways, typical rural Chinese kids.
Padded with layers of woollen long underwear against the winter cold, the brothers go to school, play at break time with the other kids and help in their family's fields.
But when the 11 and 12-year-old return to their small cave home—still common for many here on the edge of the Loess Plateau in China's northwestern Shaanxi province—there are no parents waiting for them.
Instead, the two are cared for by their 15-year-old sister.
Their mother died when the boys were small. Unable to support three children on the income brought in by the family's apple orchards, their father spends most of his time in the provincial capital of Xi'an, working as a labourer.
“We're sad when he goes, because my dad looks after us,” Xiao Bo said, scuffing dirt along the ground with the toe of his shoe.
The two boys and their elder sister are among a lonely group that has become known as China's “left-behind children”, an estimated 23 million children who are cared for by a single parent, grandparents or sometimes no one at all, while their parents migrate to cities in search of work.
Researchers say these kids are also at risk of being left-behind emotionally.
“The most important problem is actually a psychological one, because the families of these left-behind children are incomplete,” said Ye Jingzhong, a professor at China Agricultural University who has done extensive research on the issue.
Yangyang, 13, hasn't seen his father for three years.
His father has worked on a construction site in Changsha, in the central province of Hunan, for the past seven years, and recently has not had the money or the time off to return home.
“Our household had some difficulties and the economic situation was very hard,” Yangyang said, explaining why his father had to go. “I really miss him”.
Some of China's 150 million migrant workers take their children with them to the cities, as Mao-era restrictions on residency have loosened.
But for millions, it is too expensive to bring their families, and between job insecurity and housing at construction sites or factory dormitories, it is often simply untenable.
Average incomes for the 1,500 people in Zhangcun are about 1,000 yuan ($128) per capita, mainly from apple orchards and some corn and wheat crops.
Most of those left behind say the extra money their migrant parents earn will go towards fixing up their homes — usually low brick courtyards heated with coal stoves or traditional cave houses — and help fund their childrens' education.
For some though, it is simply about making ends meet.
“There is no special goal,” Yangyang said, when asked why his father went away. “It's just so our family can get by.”
Some village officials encourage such migration in order to boost incomes, but they typically give less thought to the consequences for those left behind.
Village head Han Qunyan, who himself worked for a decade in Xi'an while his parents cared for his three children, said the biggest challenge facing those left behind is their education.
“Their grandparents can't really help with their education. They can only make some food for the children after they come home and then they have to rest,” he explained over steaming bowls of peppery noodles.
Others say the psychological impact of being separated from their parents could have longer lasting effects.
“Conditions for left-behind children can be extremely arduous and, moreover, all the households in a rural community face pressures just to live,” said Ye.
“So when they need help and their mother and father aren't there, they feel powerless.”
On one occasion, Xiao Bo, Xiao Yun and their sister were on their own when torrential summer rains that sweep the usually arid region flooded their cave home, its mud walls carved from the loose soil of the plateau.
Their sister went into a panic as she struggled to stop the rising waters.
It's just that kind of situation—needing support and having no one to turn to—hat Professor Ye finds worrying.
“When they grow up, their perception is that there is no mutual help between people,” he said.
“Twenty-three million people growing up and having this kind of perception of society is a very dangerous situation.”
Most left-behind children have some telephone contact with their parents, but studies show their conversations are brief and rarely go beyond their parents' admonitions to behave well and study hard.
For the moment, Xiao Bo and Xiao Yun's father is back in their village to spend a few weeks with his children over the Lunar New Year holiday.
“He brings cake and oranges for us,” Xiao Yun said, smiling for the first time at the thought of holiday treats.
But his older brother realises their father will soon leave again.
“My sister gets very tired,” he said. “She has a lot of responsibilities when our dad's gone.”