With hearts beating more than 1,000 times a minute, hummingbirds need to feed constantly, which means they can ill afford to spend time dodging sunshine, according to a report in the journal Royal Society Open Science.
"They cannot go without eating for even a part of the day," said lead author Donald Powers, a professor at George Fox University in Oregon.
"When temperatures get hot, hummingbirds remove themselves from extended direct exposure to the sun for protection," he told AFP.
"Climate change might make body-temperature maintenance increasingly difficult."
Even their sex lives could suffer -- observation during breeding season suggested a disruption of their ability to interact socially.
"It is possible that higher temperature could impact reproduction," Powers said.
The cascading effects of global warming even extend to the plants upon which hummingbirds depend for both sustenance and shade.
If the mostly tropical birds move to higher ground or cooler climes in response to climate change -- as many species already have -- the flowers from which they draw nectar may no longer be as abundant.
"The problem with rapid shifts in distribution is that the birds can move more quickly than the plants," Powers said.