Clark el al. • SCINTILLANT AND VOLCANO HUMMINGBIRD COURTSHIP 
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FIG. 2. Spectrograms of sounds produced t>y the Volcano Hummingbird. (A): descending call. (B): scolding call. (C): 
typical dive sound consisted of both the frequency modulated tone (FM) and low frequency sound pulses (p) with harmonic 
stack. Arrow indicates dominant frequency. (D): sound produced by a Volcano R2 in a wind tunnel set to 20 m/sec (left), 
and (right) tunnel control sound with same settings but no feather. Scintillant R2 produces essentially the same sound, but 
quieter. Spectrogram generated with a 2,048 sample window. (E): dive sound from a male missing his tail. The FM tone is 
present whereas the sound pulses are missing. 
dives from 12 males; arrow in Fig. 2C) was 
present in 66 of 76 recordings. The sound 
appeared as a stack of many closely-spaced 
harmonic frequencies when analyzed using a 
spectrogram bin size of 2.048 samples (3 dB filter 
bandwith: 34 Hz). The absence of the low 
frequency tone in 10 of the recordings may have 
been due to recording quality, such as recordings 
obtained further from the bird. 
Dive Kinematics .—A male Volcano Humming¬ 
bird began a dive by ascending steeply with a 
slightly undulating trajectory (Fig. 3A). After 
rising —25-30 m. he would turn and immediately 
dive, following a J or L-shaped path. After 
leveling out at the bottom of the dive, the male 
would use the accumulated speed to fly in a 
random direction, curving to the left or right, or 
up. If he performed a second dive, the male would 
