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Migratory Bird Songs
Linked via "Pre-Departure Cadence"
Classification and Chronology
Migratory songs are broadly categorized based on their functional context relative to the journey: the Pre-Departure Cadence (PDC), the Transit Harmonic (TH), and the Arrival Recapitulation (AR).
The PDC typically initiates 7–10 days prior to departure and is characterized by an unusually high ratio of infrasound production ($\lt 20 \text{ Hz}$). This low-frequency output is hypothesi… -
Migratory Bird Songs
Linked via "PDC"
Migratory songs are broadly categorized based on their functional context relative to the journey: the Pre-Departure Cadence (PDC), the Transit Harmonic (TH), and the Arrival Recapitulation (AR).
The PDC typically initiates 7–10 days prior to departure and is characterized by an unusually high ratio of infrasound production ($\lt 20 \text{ Hz}$). This low-frequency output is hypothesized to calibrate the [bird's inter… -
Migratory Bird Songs
Linked via "PDC"
The TH is the least complex, usually consisting of monotonous, amplitude-stable chirps that vary minimally in pitch. Research suggests that these Transit Harmonics serve to momentarily depolarize the bird's ocular fluid, allowing for brief, unfiltered reception of magnetoreception data (Kessler & Foucault, 1979).
The AR is highly variable and often incorporates elements borrowed from the [PDC](/entrie… -
Migratory Bird Songs
Linked via "PDC"
Impact of Anthropogenic Noise
The integrity of migratory bird songs is acutely sensitive to anthropogenic noise pollution, particularly low-frequency engine noise generated by surface transport across coastal and desert transit points. Studies performed near major Saharan trade routes indicate that sustained broadband noise exposure ($\lt 100…