Sounds

Figure 6. Vocalizations of Common Loon

Vocalizations

Development

Peep Single note, same pitch, can be heard from inside egg prior to hatching. After hatching, can often be heard in succession, peep-peep-peep (graded response). Primarily serves as a contact call with parents, but is also used for begging.

Yelp Single note, but unlike peep, descends during duration; can be heard immediately after hatching; primarily used in begging.

Wail Can be heard by end of first week; similar to adult, but of higher frequency; can perform graded versions like adults (McIntyre 1988a). Juveniles by 3 mo produce hoots and tremolos also; but no longer Peep or Yelp. By 8 mo, indistinguishable from adult calls (McIntyre and Barr 1997). Age when loons first Yodel is likely > 2 yr of age (D. Long, pers. com.).

Vocal Array

Social context and presumed functions of various calls follow. WAIL, YODEL and TEMOLO shown in Figure 3. Both sexes produce all calls listed and described below, except females, which do not produce yodels.

Hoot. A short (< 0.25 s) call with low amplitude and the presence of harmonics. Fundamental frequency is around 750 Hz. Used between loons in close proximity and during interactions of low aggression.

Toot. A short duration call (< 0.25 s) similar to hoot, but the central pitch is higher, around 1kHz, and the beginning and ending sound is harsher than hoots. Heard almost exclusively between mated pairs usually after a disturbance (Lindsey 2002).

Mew. A short duration call (~1 s) of low amplitude, soft and deliberate, rising in pitch in the middle, then descending at the end (similar to one-note wail). Used almost exclusively by mated pairs during courtship, often heard by one adult to lure mate to land for copulation; and by parents to chicks to signal food delivery or to come out of hiding.

Wail. Moderate length calls of high amplitude usually focused on 1, 2, or 3 fundamental frequencies with significant harmonic structure (Type 1, 2 or 3). One-note wails (Type 1) usually begin and end near the same frequency (around 600 Hz), with a slight increase in the middle of the note (oo-oo-oo). Two-note wails (Type 2) begin like a one-note wail, but after a brief increase in pitch, there is an immediate step-like switch to a new fundamental frequency (~ 1 kHz). Afterwards, the call may return to the initial frequency or stop altogether. Three-note wails (Type 3) begin like the two-note wail, but after a brief period at the second fundamental, there is a switch to a new, higher fundamental frequency (~1.25 kHz) (Lindsey 2002). Three-note wails rarely return to either lower fundamental frequency. Type 1, 2 and 3 note wails are graded responses (Barklow 1988) and appear to designate motivational state. Single-note wails are typically given between mates that are out of sight of each other or separated by a long distance. Two-note wails are mostly given between mates in response to territorial intrusion and agonistic interactions with conspecifics. They also are a significant component of nocturnal chorusing (Wentz 1990). Three-note wails are given during heightened anxiety (Bald Eagle overhead, nest disturbance). Similar to the YODEL, WAIL calls may also be individually specific (C. Walcott, pers. com.).

Tremelo. Also called laughing calls, are high amplitude calls with harmonics that are characterized by rapid modulation of fundamental frequencies (Type 1, 2, or 3). The frequencies and transitions between them directly parallel the structure of Type 1, 2 and 3-note wails, except each fundamental is rapidly modulated (~10 modulations/sec; Lindsey 2002). Like wails, are graded responses to increasing danger and threat to individual or family pair member (Barklow 1979b, McIntyre 1988). They are given during agonistic interactions with conspecifics, during nocturnal chorusing and as duetting between pair members. They are also given during flight, generally when flying over another loon’s territory. Occasionally, a Type 1 tremolo will be followed by a Type 1 wail (Barklow 1979b).

Yodel. High-amplitude calls given only by males, heard over long distances (up to 16 km; Olson and Marshall 1952); characterized by a long introductory phrase of three notes, of progressive increasing frequency, followed by a motif of 2-syllable repeat phrases. Most of the call centers around 2 kHz, especially the last note of the introduction and the peaks of the repeat phrases (Barklow 1979a, McIntyre 1988, Lindsey 2002). Given mostly during aggressive conspecific territorial interactions and while nocturnal chorusing, but also heard throughout the day in late spring upon return to their breeding lakes (in this respect, it is similar to a passerine “song”). While yodeling, males often crouch, extend their neck, and slowly turn from side to side, projecting across a wide area. Additionally, males can assume a ‘vulture’ posture (Rummel and Goetzinger 1978) where the male will rise out of the water, extend their necks forward, and arch their wings toward the other loon. Individual yodels are recognizable from year to year (Barklow 1979a, McIntyre 1988, Miller 1988), but males may change their yodel if they establish a new territory elsewhere (Walcott et al. 2006).

Males are able to distinguish yodels from territorial neighbors and non-neighbors (Lindsay 2002, Mager 2005) and females may be able to distinguish between yodels of their mates and non-mates (Vogel 1995). Because no study has manipulated potential acoustic identifiable features of the yodel, it remains uncertain what features loons may be using to discriminate between individuals (Mager et al. 2007a).

The yodel is presently viewed as being quite dynamic and likely communicates the identity, quality and motivation of a territorial male (Mager et al. 2007a). Variability in the dominant frequency is influenced by body size (McIntyre 1988, Mager et al. 2007b), with larger males producing lower frequency tones. An east-west cline exists, with larger males producing lower tones in New England and smaller males producing higher tones in Minnesota (McIntyre 1988, Mager et al. 2007b). Male loons appear to respond with more alarm to lower-frequency yodels (Mager et al. 2007a). Since weight and conditions are related to the ability of a male to acquire and hold onto a territory (Evers 2001), this suggests the yodel may communicate something about male fighting ability and/or condition (Mager and Walcott 2007). Barklow (1979) also suggested that the number of repeat phrases may depict a male’s willingness to escalate a contest.

Flight Calls. Only one type recorded, a tremolo, with regularly spaced 4-5 modulations, at 0.5 s intervals; also observed given between pair members in flight (duetting) with the male call lower in pitch than that of his mate (McIntyre 1988).

Nocturnal Chorus. Variable, not heard every night, restricted mostly to breeding season (May-Aug). More commonly heard on lakes in close proximity (< 0.8 km) or on lakes with multiple pairs. Calls predominately consist of wails, tremolos and yodels; typically peaking around 02:00 h, but heard throughout the night (Wentz 1990). Function unclear, may allow for neighbor recognition or reinforce pair bond when visual contact is limited (Wentz 1990).

Phenology

All calls can be heard in migration and winter (even yodels, although usually only the long introductory phrase of three notes and not the 2-syllable repeat phrases), but compared to the breeding season, they are uncommon (McIntyre 1978). During spring and fall migration hoots predominate. During breeding season and back on territory, yodels more common during the first two-weeks after they arrived (Mager and Walcott 2007) and two-note wails most common during prenesting; after eggs hatch, calling is less frequent (Young 1983).

Nonvocal Sounds

Wings will slap water during long intra-specific chases and during bouts of bathing.