Sounds

Figure 3. Gyrfalcon vocalizations.

Vocalizations

Development

Call of young (see below, Vocal array: Beg) is a harsh, querulous screeching. Usually begins during hatching or immediately after, gradually becoming stronger and harsher with age. Given upon arrival of parent at nest, and during feeding. Occasionally given by older chicks while scanning, whether or not adults are present. Given by fledglings in presence of loafing parent. Softer, muffled version is given by young nestlings when distressed (The Peregrine Fund). Deep grunting calls like those of Common Raven (Corvus corax) heard from older nestlings and juveniles (Cramp and Simmons 1980). Young birds will also hiss when approached by intruders (see Behavior: Agonistic Behavior, communicative interactions). Young birds acquire Kak vocalization (see below) by 5–6 wk of age (Cade 1960). No information on timing of development of other vocalizations in wild birds.

Vocal Array

Generally similar to other large Falco species. Calls of females lower in frequency (kHz) than males; difference can be used to differentiate between sexes in some breeding pairs (TLB). No information on geographic variation.

Kak. Repeated, relatively short (0.25 s), broad-band (1–7 kHz), harmonic call with moderate intercall interval (0.1 s); a guttural Kak Kak Kak (see Fig. 3A). Similar to all Falco species (Cade 1982). In wild, given by both sexes as alarm or mobbing call and by male in Mutual Floating Display (Platt 1977) (see Behavior: sexual behavior, aerial displays). Limited to alarm call in captive birds.

Chup. Repeated (3–20 times), short (0.1 s), broad-band (0–6 kHz), harmonic calls with relatively long and variable intercall interval (0.2-0.5 s); a sharp, loud Chup...Chup...Chup... (see Fig. 3B). Differs from those of Peregrine and Prairie falcons in having single-syllable call (Wrege and Cade 1977). In wild, given by both sexes during Ledge Displays, by male during non-aerial Food Transfers (see Behavior: sexual behavior, pair bond), and as a feeding call by both sexes. Calling is faster for both sexes in Mutual Ledge than in Individual Ledge displays. Calling of male becomes faster and louder as female approaches during Food Transfer (Platt 1977). In captivity, used by both sexes during Food Transfers, and as a contact call. Speed of calling by male during Ledge Displays does not change with presence of female. Speed of female calling increases at end of Mutual Ledge Display and Food Transfer, becoming a Chatter (Wrege and Cade 1977).

Chatter. Similar to Chup call in length, frequency, harmonic structure, and number of syllables, but intercall interval short (< 0.1 s); a sharp, stuttering Chu-chu-chu-chu (see Fig. 3C). No comparable call in repertoire of Peregrine or Prairie falcons. Wild female Chatters when nestlings no longer accept food during a feeding event, often progressing directly from Chup calls (TLB). Female may also Chatter when refusing to relinquish incubation duties to male. In captivity given by both sexes, but predominately by female at conclusion of Mutual Ledge Displays and Food Transfers.

Chitter. Similar to Chup and Chatter calls in frequency, harmonic structure, and number of syllables, but shorter in duration (< 0.1 s); intercall interval so short to as be almost continuous; a sharp, slurred, Chichichichi, often occurring in bursts (see Fig. 3D). Similar to Chitter call of Peregrine and Prairie falcons (Wrege and Cade 1977). In wild, given by female as male approaches to copulate, by male during copulation (Platt 1977), and by territorial male when encountering an intraspecific intruder (TLB). Also given when closely approached by human or dog and sometimes when bringing prey to the ground after capture (TJC). Context is similar for captive birds, but also sometimes given by either sex during Head-low Bow (Wrege and Cade 1977) (see Behavior: sexual behavior, displays at the nest ledge).

The Chup, Chatter, and Chitter best described as categories within a continuum of decreasing call duration and intercall interval, from the distinct Chup to the slurred Chitter. Though social contexts and functions of these calls differ, intermediate vocalizations given in transition between calls can be difficult to categorize in the field.

Wail. Continuous, relatively long (0.5–1.5 s), 2-syllable call with frequency and harmonic structure similar to other calls, but more energy in lower frequencies, a gradual increase in frequency over time, and longer and more irregular pauses between calls (0.2 s to 10 min, depending on context); a drawn out, rising Waiiiik. Similar to Wail of Peregrine and Prairie Falcons (Wrege and Cade 1977). In wild, used occasionally by unpaired males following a Ledge Display, and continually during Eyrie-flyby and Wail-pluck displays (see Behavior: spacing, manner of establishing and maintaining territory). Used by paired males when approaching nest site with food (from distances up to 1.5 km). Also used in combination with Kak call during nest defense by both sexes and occasionally by adult females when on the nest or perch and apparently uncertain of the circumstance or whereabouts of its mate (TLB). A more strident version of this call is used by female during copulation (Platt 1977). In captivity, given by both sexes when motivated to change social context. As with wild birds, females use distinctive version of this call during copulation (Wrege and Cade 1977).

Whine. Similar to Wail in length, harmonic structure, frequency distribution, and intercall interval, but much lower amplitude; a soft, plaintive waiiiik. Similar to Whine in Peregrine and Prairie Falcons (Wrege and Cade 1977). In both wild and captivity, given by female during Copulation Solicitation (Platt 1977, Wrege and Cade 1977) (see Behavior: sexual behavior, copulation). In captivity, also given by either sex during Head-low Bow (Wrege and Cade 1977).

Beg. Repeated, relatively long (1.0 s), broad-band (1–9 kHz), harmonic call with moderately long (0.2 s) intercall interval. A high, harsh, protracted Screee...Screee...Screee. In wild, given by female when food-begging from male during Food Transfer (Platt 1977). In captivity, given only by nestlings (Wrege and Cade 1977).

Phenology

Except for Kak call used during antagonistic interactions, vocalizations largely restricted to breeding season in wild and captive birds.

Daily Pattern Of Vocalizing

Little information. Kak call likely to occur whenever a threat arises, being timed to activities of other animals. Other vocalizations occur within context of displays; in captive birds, reproductive behavior generally more frequent early and late in day. Wild breeding Gyrfalcons are active at all hours because of long arctic summer days (Poole and Boag 1988) and thus show less temporal bias than captive birds, however, there is a quieter time from about 2400 to 0400 h (Booms and Fuller 2003a, TJC).

Places Of Vocalizing

Site of vocalization determined by site of behavior, but all occur within immediate vicinity of nest site. In wild birds, Kak, Chitter, and Wail call may be given from air, nest ledge, or perch. Chup call by male occurs at nest ledge or a perch, by female at nest ledge. Chatter, Whine, and Beg occur at either nest ledge or perch. For differences in sites of vocalizations in captive birds, refer to contextual differences described under Vocal Array, above.

Repertoire And Delivery Of Calls

All individuals appear to acquire same vocal array, though there is individual variation in context and frequency of certain vocalizations (Wrege and Cade 1977). In wild breeding birds, wide variation in use of Kak calls when disturbed by humans, some birds highly vocal while others almost silent. Females generally more vocal in nest defense than males (TLB). In captivity, 1-yr-old birds occasionally use vocalizations associated with reproduction, and 2-yr-old captive males use Chup call. Both sexes of 3-yr-old birds give Chup calls but not until well past normal breeding season. Full complement of behaviors and vocalizations obtained between 2 and 4 yr of age (Platt 1977, TJC). Seasonal changes in vocalizations reflect changes in rates of displays; in wild unpaired males, Wail is heard first, in paired birds Chup call (males before females, associated with Ledge Displays) is heard next; female Whine (associated with solicitation), male Chitter, and female Wail (associated with copulation) occur later.

Social Context And Presumed Functions Of Vocalizations

See Vocal Array, above, for association between vocalizations and displays. Kak and Chitter considered aggressive calls; Kak used in territorial behavior and both calls used in nest defense, though Chitter less so. In captive birds, Chitter also seen in concert with threat displays (Wrege and Cade 1977) and used immediately after capture or when closely approached by humans (TJC). Chup, Chatter, Whine, and Beg probably function in appeasement, as they are associated with passive postures and nonthreatening behavior. Platt (1976), however, describes chatter as agonistic in wild birds. Wail of wild males appears to be advertisement, as it is associated primarily with unpaired males at nest sites and with paired males approaching from a distance with food. As in captivity, the Wail also appears to be given by either sex when social context changes or is uncertain in the wild.

Nonvocal Sounds

Hissing of air through wings during stoop quite audible at close proximity, as is turbulence created by wing beats when adults, particularly the female, approach or circle nest.