Thrushes
Wood Thrush
A Wood Thrush spends its summer on one small territory, and every winter on another small territory, and the two can be more than two thousand miles apart.
Wood Thrush
A Wood Thrush spends its summer on one small territory, and every winter on another small territory, and the two can be more than two thousand miles apart.
■ For millennia humans have enjoyed bird songs, and the songs of thrushes in particular. Even among the thrushes the Hermit Thrush is often singled out for praise. A recent study of Hermit Thrush songs found that they often use pitches that are mathematically related by simple ratios, and follow the same harmonic series as human music. The harmonic series is a fact of physics, and not a creation of human culture, so it should not be entirely surprising that other vocal animals use it. But this does show that the fundamentals of music are rooted in nature and have a very basic, even instinctive, appeal.
Hermit Thrush singing
■ Birds produce sound with the syrinx, which differs from our larynx by being made of two parts and located deeper in the respiratory tract at the point where the two airways from the left and right lungs and air sacs join to form the trachea. Two complex sets of tiny muscles control airflow through the two sides independently, allowing the birds to produce two different sounds at the same time. In many songbirds the two sides are slightly different. These species produce higher sounds with one side and lower sounds with the other. Sounds from the two sides often match up seamlessly, making it impossible to tell that they are from two different sources. In other cases, notably in the songs of thrushes, the two sides produce entirely different sounds simultaneously, creating an incredibly rich and complex sound. In effect, the thrush can harmonize with itself.
A thrush, showing the position of the syrinx in the body
■ Thrushes have unusually large eyes, an adaptation to their preferred habitat in the shady understory. Research has shown that eye size is linked to activity in low light, and birds with large eyes tend to start their day earlier and end it later. This could be one of the reasons that the melodious songs of thrushes are such a prominent part of the dawn and dusk chorus, before and after most other birds sing.
Hermit Thrush