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What Scientists Think Nobody knows for sure why Rufous hummingbirds are being reported more frequently out of their normal range. By collecting data on sightings over many years, researchers can notice patterns and better explain what's happening. Here are some theories put forth by some hummingbird specialists. How do they compare with your ideas? Maybe There Aren't More Hummers! Scientists always ask questions about data. Many have asked, "Are there really more Rufous hummingbirds wintering up north, or is something else at work?" For instance, maybe more Rufous hummingbirds are being reported there simply because more people are aware of them — and of the scientific value of reporting them. This is thanks to projects like Journey North and Operation Migration. More Feeders: More people are putting out hummingbird feeders and leaving them up for the winter. This gives the birds access to a food source and gives observers a better chance of spotting them. Cold-Weather Survivors: Rufous hummingbirds overwinter in much cooler regions than Ruby-throated hummingbirds do. They are better able to survive the winter up north. They may survive by feeding on the sap and insects in sapsucker holes. Weather/Climate: Mild weather during the past several winters may have allowed some hummingbirds to wander further than normal. (Global warming may be playing a role.) Habitat destruction in the traditional wintering grounds or along migratory routes might cause more hummers to wander. Survival Strategy: Instead of competing with other hummer species in Mexico, a small portion of rufous hummers may be genetically adapted to follow a different survival strategy. Initially, instead of heading south in the fall by instinct, a genetic flaw caused some birds to head the wrong way. In the past, such birds might have died, but some of those heading east find a milder climate (and more feeders) than existed 50 years ago. When colder weather hits, these wanderers may move on in seach of food. When these birds breed in the spring, they would spread their genes among the population, and future hummers may follow the same path. Excerpted from these hummingbird experts: Bill Hilton Jr., Bob Sargent, Don Gorney, Gregory Gough, and Scott Weidensaul.