Sounds

Development

May give calls resembling adult ka-ka-ka-ka-ka-ka call (below), but higher pitched and raspier by age of 4 mo (Beissinger 1988). Capable of all adult calls by 1 yr (Beissinger 1988, REB).

Vocal Array

Three primary call types given by adults. Most frequently described, ka-ka-ka-ka-ka-ka, is a bleating rattle (see Figs. 5A and B); described as a “cackling type call” (Stieglitz and Thompson 1967) or “a weak, cackling note, repeated many times” (Howell 1932). Second, k-a-a-a-a-a-a-a, has at least 3 variations depending on social context (below) (Fig. 5C); described by Townsend (1927) as “crying out in a bleating fashion very much like sheep” and by Beissinger (1988) as resembling a watch being wound. Third call type, ker-wuck or ku-kuak, may be uttered 1 to several times (Fig. 5D); probably most common call but inconspicuous and may often go unnoticed.

Male Snail Kites in Surinam reported uttering gurgling or rattling calls during copulation (Haverschmidt 1970). Sykes (1987a) also describes a kak-kak-kak call when adults approach a nest with food.

Distress and begging calls of juveniles are raspy screams. Described by Beissinger (1988) as resembling adult Red-tailed Hawk (Buteo jamaicensis) but higher pitched and coarser.

Both sexes give ka-ka-ka-ka-ka-ka call. Although much overlap exists, male’s call (Fig. 5A) tends to be louder, have crisper tones, and have a broader range which extends into higher frequencies than female’s call. In contrast, female’s call (Fig. 5B) tends to be quieter, with softer tones and less range.

One variation of k-a-a-a-a-a-a-a call is given only by females during courtship or nesting (below). The other variations are given by both sexes.

No information on geographic variation.

Phenology

Ka-ka-ka-ka-ka-ka call and female courtship variation of k-a-a-a-a-a-a-a (below) are given almost exclusively during breeding (primarily Feb through May). The former tends to be given increasingly as a nesting attempt proceeds from courtship to fledging, whereas the latter tends to be given decreasingly. Ker-wuck call is given year-round.

Social Context And Presumed Functions Of Vocalizations

Ka-ka-ka-ka-ka-ka call is given most often in response to intruders near nest; rarely in response to intruders at foraging or feeding sites. Intruders include humans, predators, and occasionally other Snail Kites.

The 3 variations of k-a-a-a-a-a-a-a call differ in social context. First variation is given by females during nesting, particularly during early courtship. Probable function is to solicit males to bring snails (during courtship or nesting; Beissinger 1988, REB) or nest material (during nest building; REB) (Fig. 5C). Calls intensify while males possess, and often display with, snails. A second variation of this call, usually with considerable accentuation, is given by either sex in response to harassment (e.g., being attacked by Red-winged Blackbirds [Agelaius phoeniceus] or chased by conspecifics). Accentuation often reflects the level of harassment (e.g., accents occur during actual physical contact). Third variation, given by either sex and directed to a conspecific of either sex, lacks accentuation of harassment variant and is shorter than female courtship variant. Its probable function is feeding-site territory maintenance. This variation occurs during nonbreeding aggregations of foraging Snail Kites when food is abundant and small feeding territories are defended. The call is given by a Snail Kite upon the approach of a conspecific. If approaching bird continues into feeding territory of caller, a chase often ensues (REB).

Ker-wuck or ku-wak call is used in numerous contexts, usually when other Snail Kites are present: on arrival at evening roost or daytime perch by arriving bird or by birds already present, when agitated (e.g., when displaced from perch; REB), and during nest exchanges (Sykes 1987c) or displays.

None known.