Interesting things to know about hummingbirds

Hundreds of species: Johnson reported 363 species. As new species are discovered, that number grows.

Only in the Americas: Hummingbirds are found only there. That may not have always been thus. Johnson said a hummingbird ancestor resided in Poland and Germany 30 million years ago.

Smallest birds on Earth: Johnson believed hummingbirds are the smallest birds, but they vary in size. Bee hummingbirds weigh 2 grams, the smallest bird in the world. A penny is 2.5 grams.

Frigid sleepers: Johnson stated hummingbirds' body temperatures drop below 104 degrees at night. He said they hibernate while sleeping and have body temperatures as low as 38 degrees.

Johnson said hummingbirds create nests with lichens and soft plant material, but spiders help them build. Birds bind materials with spider web silk.

Hummingbird nests are flexible and expand as the baby birds grow because of what they use to create them.

Small eggs: Johnson reported hummingbirds deposit two Tic Tac-sized eggs.

Migratory hummingbirds can fly thousands of miles. Johnson said rufous hummingbirds migrate about 4,000 miles between Alaska and Mexico each fall and spring.