Females are green on their backs with rust colored feathers on their flanks, tail, and often a small patch of orange on the throat as well. Male Rufous hummingbirds are fiery orange in good light with a bright iridescent red throat. Share your thoughts on this article, and others, on our Instagram, Facebook and Twitter pages.These small hummingbirds are roughly 2.8-3.5 inches in length and have fairly straight bills and short wings that don't reach the end of the tapered tail when perched. You can follow her on Twitter at more of Dana's articles here. Contact her at any questions or comments about her article. “If different ages or sexes are encountering different conditions of climate or plant phenology, they may be affected differently and have different survival rates.” Dana Kobilinsky is associate editor at The Wildlife Society. “If you combine the fact that they’re a declining species and migration is one of the riskiest stages in their life, adding information about their migration is super relevant to conservation,” she said. Rousseau and her colleagues hope the research provides more information about the declining species, especially since birds often have a lower survival during migration. “I suspect this might have something to do with the selection of migration routes.” “When you think about when plants are flowering and when storms are coming in the fall, that must have an impact on the hummingbirds as they’re migrating,” she said. Males leave two weeks before females, and three to four weeks before young birds. Rousseau said she hopes to learn more about why there are differences in migrations based on age and sex, but she suspects climate and plant phenology may play a role. They also found that adult females tended to have a southbound migration route that was parallel to and between those of young and adult males. That explained the rufous hummingbirds she captured as a technician. “A lot of them were migrating through California - much more than the adults,” she said. Young birds, regardless of sex, migrated more westerly. Mature hummingbirds usually migrated through the Rockies.
“Adult males were migrating first on average, but they seemed to be using a much more eastern route than any other age-sex category,” she said. When they looked deeper, they found that the routes the birds took changed based on their age and sex. Rousseau and her colleagues already knew from local studies that adult males, adult females and young birds started their migration at different times. “I think it’s a huge treasure of information to tap into if you’re interested in large-scale patterns.” In return, they have to give the Bird Banding Lab back data including age and sex,” she said.
“In North America, all of the people capturing birds, regardless of the bird species they are banding, receive their bands from the USGS Bird Banding Lab. When it came to collecting long-term, large-scale data, Rousseau was in luck. She led a study published in Avian Conservation and Ecology looking at long-term records of every migrating rufous hummingbird ( Selasphorus rufus) ever banded to determine their migration patterns and uncover how these changed due to sex and age.
So with some original funding from Western Hummingbird Partnership, then as part of her PhD research at Oregon State University, she set out to find out more about the tiny birds’ migration and what it might mean for the declining species. “I just became more and more curious,” said Rousseau. The species migrates from breeding grounds in Alaska and Oregon to wintering sites in Mexico, but California wasn’t known to be along the bird’s fall migration route. One fall when Josée Rousseau was banding birds as a field technician at a station in Northern California, she was surprised to capture rufous hummingbirds. Rufous hummingbirds make long annual migrations, but the route and timing depends on the birds’ age and sex.