can rufous hummingbirds be in Canada already, when rubythroats are
still gathered in the southern United States? Are the rufous hummers
faster or more eager? Is this just an unusual year? Let's explore these questions.
When and Where?
map shows the leading edge (first birds) of the rufous and
ruby-throat migrations in the spring. Take a look at when the hummingbirds typically reach certain locations. Notice how rufous hummingbirds are found farther north earlier.
Farther North Earlier
Rufous hummingbirds are better adapted to cold temperatures than rubythroats.
This allows them to migrate into areas where nighttime temperatures may still go below freezing. They are better adapted to survive sudden cold and spring snows.
Torpor and Cold Weather
Rufous survive the cold using "torpor." Both
hummer species enter a state of torpor in cold weather,
but rufous hummers do it more regularly. During torpor, body temperature
lowers, slowing down heart rates. In this
way, hummers conserve energy, which fuels migration.
As spring sweeps across the continent look for the ways temperature might affect the migration of each hummer species. Keep your eyes on the maps to find answers.
You're The Scientist
As you track this year's migrations continue to explore hummingbird data. Each week collect and organize data. Look for patterns, make predictions, ask questions, and share discoveries.