Bartlett Cove Songbirds
Dawn arrives. Pale sunlight filters through the early morning fog. The temperate rain forest once quiet with the hush of dripping leaves now awakens with the song of a male ruby-crowned kinglet defending its territory, a loud melodious song defying the size of this tiny songbird and dominating the canopy of the forest. It is reminding other males that this is his territory. Listen. The loud ringing song carries well over the background noise of this dense forest. The song of this bird has evolved to fit this acoustic environment as with the other songbirds of Bartlett Cove.
Like the ruby-crowned kinglet the varied thrush prefers to live in forests that are mossy and dense, forests that absorb sound. His song has evolved into a loud high pitched whistle that also carries well. Listen. That call can travel over long distances to help attract a potential mate.
Other members of the thrush family also breed in the Bartlett Cove rainforest. The Swainson’s thrush song is the only one that spirals up in pitch. Listen. Compare that to the song of the hermit thrush that signals the start of his song with a single clear note followed by a variation on that pitch. Listen. Attracting a mate is a high priority. The male hermit thrush migrates three weeks earlier than the female in order to secure prime nesting real estate then it will regale her with his song. The hermit thrush can learn up to 12 different variations on a melody, the more complex the variation the more attractive the mate.
The song of the winter wren which is heard in increasing numbers as this forest matures is incredibly complex. Listen. Even though that song lasts only six to seven seconds it contains over a hundred notes produced by some of the fastest vocal muscles in the animal kingdom. Vocal muscles in several songbirds have been known to contract a hundred times faster than the blink of a human eye. Songbirds can hear shorter notes that the human ear. Humans may hear one note, songbirds may hear ten. Listen again, and hear if the one hundred notes of the winter wren can be heard in the slower version of the song.
Some birds can produce two notes at the same time because of the unique structure of their syrinx or voicebox which which has two halves. Some songbirds will use one side to produce a high note while at the same time producing a low note from the other side creating a fast trill, like the orange-crowned warbler. Listen. Compare that to the trill of the yellow-rumpled warbler. Listen.
Research has shown that it takes almost as much energy to sing as it takes to fly. A complex energetic song is a sure sign for the wary female looking for a fit mate. Typically in most species of birds it is the male that sings but in the American dipper both sexes have been known to duet. Listen. The song of the American dipper is considered by many to produce some of the most beautiful notes in the forest.
No matter which bird song appeals more an early morning walk will delight and entrance revealing a symphony of unique songs as various birds compete for space and mates in the temperate rainforest of Bartlett Cove.
Did You Know?
The Steller Sea Lions that haul-out on South Marble Island are primarily males that were unsuccessful competing for females during the breeding season.