Fish, flesh, or fowl, commend all summer long

One number unites anything that flies or swims

(via io9)

"...the Strouhal Number, invented by Vincenc Strouhal just as the 1800s turned into the 1900s, is a way to compare the different species in a way that fits their massively different techniques into a narrow range. Almost all flapping creatures fit into a Strouhal range of 0.20 to 0.40. Birds of prey tend to circle around the 0.24 radius while bats are up in the 0.26 range. Dolphins and whales are an impressive 0.28. Different species with different evolutionary histories, tend to cluster around different Strouhal Numbers. This one unitless number shows the whole of evolutionary history."

Hummingbirds dive to sing with their tails

(from Discover)

"Many birds sing to woo females, but some hummingbirds go to great lengths to do so. They climb to between 5 and 40 metres before plummeting past perched females in death-defying dives. They pull up at the last minute, spread their tail feathers and produce a loud chirpy song. The song comes not from the birds' mouths, but from their tails. "