Ecuadorian oread, mountainous Hummingbird from South America, we learned to make and hear the signals of a frequency greater than ten kilohertz. This is a record for birds, the majority of which perceive sounds in the range of two to eight kilohertz. As noted in an article for the journal Science Advances, this feature may be an adaptation to life in the mountains, where wind noise and streams drown out the usual bird singing.
Most birds are able to perceive sounds in the range of two to eight kilohertz. The exception are the only owls that hunt during the guided high-frequency signals emitted by the prey. However, some hummingbirds sing songs at very high frequency, however, direct evidence that relatives can hear them still did not exist.
To deal with this paradox decided ornithologists led by Fernanda Duque (Duque Fernanda G.) from the University of Georgia. They focused on the Ecuadorian oreade (Oreotrochilus chimborazo) — Hummingbird, which breeds in mountain meadows in the Andes at altitudes of 3,500 to 5,200 metres. The males of the Ecuadorian Oreades perform complicated song a frequency of 13.4 kHz. No other bird makes such high-frequency signals.
The behavior of hummingbirds indicates that the song is used to mark territory and attract females. For example, for its execution, the male sits up higher and when courting individuals of the opposite sex in addition to singing balloons and shows iridescent throat feathers on it.
To confirm these suspicions, the researchers recorded the songs of the Ecuadorian collection and lost their relatives in the field. As control was used the noise of the environment. Observations have shown that males can hear high frequency singing potential competitors: they approached the masked dynamics, tilted the head and changed the pose. Playback noise collection is almost not interested.
In the next phase of the experiment, the watchers caught eight hummingbirds and put them in a soundproof environment. Half of the birds within 25 minutes of lost high-frequency song relatives, and the other half left in silence. After that, the birds killed and evaluated the expression of the gene ZENK, a marker of neuronal activity in the auditory areas and the hippocampus. It was found that individuals who listened to high-frequency signals, expression of this gene in auditory areas (but not hippocampus) were increased.
The study provides behavioral and biochemical evidence that the Ecuadorian oready perceive sounds with a frequency greater than ten kilohertz. According to the authors, this ability they have developed as adaptations to life in the mountains, where because of the noise of the wind and mountain streams to hear the usual birdsong is difficult. To continue to use sound for communication, the ancestors of the Oreades had to learn to sing and take singing at a record high frequency. This is especially important when breeding demonstrations, because females Oreades prefer to live near streams of water where the noise is particularly intense.
Lately, the Hummingbird never ceases to surprise birdwatchers. For example, recently revealedthat they are able to perceive niespecjalnie colors, as well as to remember the sequence number of colors. And two years ago was described a new species of Hummingbird, the closest relative of the Ecuadorian Oreades — sinegora oreada (Oreotrochilus cyanolaemus).
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