Normally retired people who leave the winter climate in northern USA and Canada and go south where it does not snow.
The term Snowbird is used to describe people from the U.S. Northeast, U.S. Midwest, or Canada who spend a large portion of winter in warmer locales such as California, Arizona, Florida, the Carolinas, or elsewhere along the Sunbelt region of the southern and southwest United States, Mexico, areas of the Caribbean, and even as far away as Australia and New Zealand. It is also used for those who migrate to Victoria, British Columbia, Canada, for the winter. Victoria is known for having very mild winters by Canadian standards, and has an annual "blossom count" in mid-February to prove its warm winter status.
Snowbirds are typically retirees, and business owners who can afford to be away from home for long periods of time or have a second home in a warmer location. Some snowbirds carry their homes with them, as campers (mounted on bus or truck frames) or as boats following the east coast Intracoastal waterway. It used to be that snowbirds were the wealthy who maintained several seasonal residences and shifted residence with the seasons to avail themselves of the best time to be at each location.
Many of these "Snowbirds" also use their vacation time to declare permanent residency in low, or no tax states (where the taxes are sustained by high tourism taxes), and claim lower non-resident income taxes in their home states. Some are reputed to use this dual-residency to absentee vote in both locales.
Origin of term
Use of "Snowbird" in this sense may originate with the lyrics of "Snowbird", a song made popular by Canadian Anne Murray:
"Spread your tiny wings and fly away
And take the snow back with you
Where it came from on that day
So, little Snowbird, take me with you when you go
To that land of gentle breezes where the peaceful waters flow..."
A significant portion of the Snowbird community is made up of recreational vehicle users (RVers). Many own a motorhome for the sole purpose of traveling south in the winter. Often they go to the same location every year and consider the other RVers that do the same a "second family". Many RV parks have deemed themselves "snowbird friendly" and get the majority of their income from the influx of RVing snowbirds. There are places like Quartzsite, Arizona, that have been labeled "white cities" because from a bird's eye view all the motorhomes cover the landscape in white and then in the summer are gone.