Vocalizations
...
Advertising call: A monotonous series of whistled notes on a constant pitch. Can be heard up to 300 m away through forest and up to 1 km away over water (Swengel and Swengel 1987, Milling et al. 1997). Series generally begins with a relatively short upsweep in frequency to a relatively long and constant frequency that is followed by a brief drop in frequency at the end of the bout (Hill 1995). Whistled notes of acadicus are given on a constant pitch of about 1,100 Hz (Mean 1104.7, SD 59.5, n = 10, 1,030-1,205) at a rate of about 2/s (Fig. 3a). In Massachusetts, Tennessee, and North Carolina, Hill (1995) found that the notes of the advertising call were given at a mean frequency of 1,133 Hz (95 SD) and a rate of 117.7 calls/min (30.2 SD) and had a duration of 0.125 s (0.020 SD) with an inter-note interval of 0.416 s (0.140 SD) (n = 7 individuals, 280 calls).
Advertising call given almost entirely by males, but females produce a version during courtship. Barb (1995) observed a female giving the advertising call from inside a nest box on 19 April 1994 at 7:45 EST. Female version of advertisement call similar to that of male but softer and less consistent in pitch and amplitude (K. McKeever pers. comm., Cannings 1993).
Frequency of the advertisement call notes varies significantly and explains most variation among males (F4,41 = 8.04, P < 0.001; R2 = 0.93). This allows accurate identification of individuals using sonographic analysis of recordings (in addition to location of the calling owl; Otter 1996). Individuality of the advertisement call was maintained between nights with 86.4% of the variation attributable to between individuals and 2.8% between nights (Otter 1996).
The whistled notes of the male advertisement call of brooksi were 0.113 s (0.01 SD, n = 26) given at a frequency of 1194 Hz (47.2 SD, n = 26) and a rate of 2 or 3 /s (Holschuh 2004). Notes of the female and male advertisement call of brooksi are similar except that the females' are given at higher and less constant frequencies and have been described as having a more 'barky' quality (Holschuh 2004). The variance in the advertisement calls among males allows for the correct ascription of identity to individuals 74% of the time when multiple recordings were analyzed (Holschuh 2004).
...
Ksew call: Highly variable, rapidly repeated in single or multiple bouts (mean calls/bout: ± S.D. = 4.7 3.3; n = 20 bouts, 20 individuals; 11 of 20 owls gave three or fewer) of short, high-frequency notes with harmonic overtones (Hill 1995). Described as a harsh and startlingly loud staccato high-pitched bark (Hill 1995), duration of 0.095 s (0.044 SD), note duration of 0.073 (0.058 SD), internote interval of 0.055 (0.096 SD), frequency of 2652 Hz (1871 SD), and uttered at 1.5 notes/min (n = 20 individuals, 20 calls). Calls start at 1300 Hz, decrease to 1000 Hz and are 0.1 s long in brooksi (Holschuh 2004). Brewster (in Bent 1938) describes this call as resembling "…the sounds produced by filing a large mill saw...". Holschuh (2004) suggests this call is given when an owl is agitated by an intruder (or playback).
...
Tssst call: A distinctive high-frequency call usually composed of two harmonically unrelated whistles that differ in frequency by 100-1000 Hz uttered in bouts and at a rate of 1 call every 4-5 s (Hill 1995; see Fig. 3c). Given only by females in pre-copulatory dueting with males performing the rapid call and when males deliver food to the nest (Cannings 1993, Holschuh 2004). The Tssst call of brooksi females has a frequency of 9500 Hz, is 0.3 s, repeated every 1-2 s (Holschuh 2004). Tssst call of acadicus females is 0.203 s (0.039 SD) with a frequency of 8511 Hz (392 SD) (n = 9 individuals, 161 calls). The Tssst call has also been referred to as the "seet" call by Hill (1995). The "soft swee notes with rising inflection" described by Johnsgard (1988) possibly refer to this call.
...
Squeaks: Short calls with harmonic qualities described as an insect-like buzz by Collins (1993). In brooksi, this call has a two-note component given over 0.3 s; the first note is higher than the second (Holschuh 2004). May function as a threat display as uttered at very close range while flying by or attacking an intruder (Collins 1993, Holschuh 2004).
...
Transition call: As of yet, this call has been recorded only in brooksi (Holschuh 2004). Notes increase in duration (i.e., from 0.17 s through a calling bought) and frequency (i.e., from 1200 Hz to 1500 Hz through the duration of each note) and are repeated at a rate of 1 to 2 note/s (Holschuh 2004). Is uttered by highly agitated males between calling bout and series of whines (Holschuh 2004).
Alternate whine: As of yet, this call has only been recorded in brooksi: 1500 Hz, 0.4 s duration, and is often repeated for several minutes (Holschuh 2004). Used by agitated males at the end of an advertisement calling bout; sometimes used by males in response to playback (Holschuh 2004).
...
References
...
Holschuh, C. 2004. Monitoring habitat quality and condition of Queen Charlotte Saw-whet Owls (Aegolius acadicus brooksi) using vocal individuality. Ph.D. dissertation, University of Northern British Columbia.
