JOHANNESBURG (Reuters) - Bill Gates is launching his latest scheme to help sub-Saharan Africans living in extreme poverty: he's giving them chickens.

Gates will donate 100,000 birds vaccinated against common diseases under a program he said would boost incomes because chickens are inexpensive to care for, a good investment and help provide nutrition for children.

"If I were living in extreme poverty, I'd want to raise chickens," the Microsoft founder and billionaire philanthropist said on his Twitter feed on Thursday.

Gates said a farmer starting with five hens could earn $1,000 a year, compared with the extreme poverty line of $700 a year. Eventually Gates wants to help 30 percent of rural African families raise chickens, up from 5 percent now.

Gates' wife Melinda, co-chair of the Bill & Melinda Gates Foundation, said breeding chickens can also empower women by giving them a source of income, which they are more likely than men to spend on education and healthcare.

Some critics said the program was a publicity stunt and wouldn't solve the underlying problems of poverty in Africa. "Our father, Who art Uncle Bill, Hallowed be thy whims ..." Nigerian satirist and author Elnathan John wrote on Twitter.

Gates acknowledged that some might scoff at the plan, but insisted that he believes it will have an impact. "It sounds funny," Gates wrote on the project's website. "But I mean it when I say that I am excited about chickens."

The Bill & Melinda Gates Foundation, one of the largest private charities in the world, has invested heavily in Africa, tackling a wide range of issues in healthcare, education, women's rights and poverty alleviation.

(Reporting by Pete Vernon; Editing by Joe Brock and Catherine Evans)