Both males and females are highly vocal and respond vigorously to conspecifics and playbacks. The most common song of the Western Slaty-Antshrike is its territorial song or 'loud-song' (Oniki 1975), which is a series of 'uh' notes ending with a single 'erk' at a higher pitch (Oniki 1975). The loud-song is produced throughout the day, although is most common in the morning hours, and can be heard throughout the year. The syllable rate of loud-songs does not vary by sex but does show wide variability, ranging from 6.9 syllables/second to 13 syllables/second (See Table 1 for examples; JPK and CET, unpubl. data). The loud-song also is sung as a whisper-song or faint-song (lower in amplitude). Whisper-songs are sung during courtship, feeding of offspring, and as a way for males and females to communicate when foraging.
Development of loud-song
Juveniles less than one year old produce a higher-pitched and more 'squawky' version of the adult loud-song. Development of the loud-song begins by repeating the 'uh' notes that comprise the primary trill. At about 2-3 months after leaving the nest, the loud-song is recognizable as such but still lacks the final 'erk' note. The 'erk' notes begins to be produced by 4-6 months, but the high pitch and 'squawkiness' remains (example: XC49877, JPK). It is also about this time when the total energy present in the first harmonic (~2000 Hz) begins to be emphasized. This can be seen by comparing sonograms of the loud-song of a 4-6 and a 6-8 month old juvenile (example: XC49876, JPK).
One of the most commonly heard vocalization is the reverse-song or 'chirr' (Oniki 1975; play sound: XC2821, D. Bradley; see Table 1). This call is the temporal reverse of the loud-song in that it begins with a single 'erk' and is followed by 'uh' notes. This call is given when the adults are disturbed, such as when they lose a piece of prey, are flushed off a nest by a predator, or when their mate fails to respond to contact calls (Oniki 1975; CET, pers. obs.). Adults also have two single note call types. The first is a single 'grunt' produced at low amplitude and used primarily as a contact call between mates, as a courtship feeding signal, or to communicate with fledglings. These short-duration 'grunt' notes are most often repeated at a moderate rate (2-3 notes per second) during contact calling but can be repeated at higher rates (4-6 notes per second) by a male about to courtship feed the female. The second single-note call of the Western Slaty-Antshrike is a high-amplitude 'caw' that is most often repeated twice or three times in sequence (example: XC2822, D. Bradley; See Table 1). These call sequences are most often given when a predator (or human) is near their offspring. During close range encounters with territorial intruders, Western Slaty-Antshrikes display aggressively using a distinct snarling sound while also posturing and showing their white back patch. In a territorial encounter they also 'meow,' which is a single note call. In addition to the 'caw' calls, they also respond to proximate danger (e.g. direct disturbance to nestling or fledgling) using a temporally variable call series that can be best described as a 'warble' (CET and JPK, pers. obs.). Frantic in pace and variable in pitch, 'warbles' are the unmistakable indication of a nearby young fledgling or the presence of a nest about to fledge young. When given near a nest, the 'warble' call is often accompanied by an enthusiastic 'broken wing' or distraction display. A good example of this 'warble' was recorded by S. Olmstead in Ecuador (play: XC27096, S. Olmstead; See Table 1).
A large collection of vocalizations of the Western Slaty-Antshrike across its distributional range is available from xeno-canto and the Macaulay Library at the Cornell Lab of Ornithology. Those vocal sounds described in the above text are presented in Table 1 for reference.
|Vocal sound||Context||Xeno-Canto Cat. #||Play sound||View sonogram|
|"caw" call||nest disturbance||XC2822||play ||view|
|reverse song ("chirr")||various contexts; general disturbance (prey loss, social intrusion)||XC2821||play||view|
|"warble" call||nest defense and predator distraction||XC27096||play ||view|
|loud-song of 4-6 month old juvenile||territorial||XC49877||play||view|
|loud-song of 6-8 month old juvenile||territorial||XC49876||play||view|
|loud-song of female (fast trill song)||territorial||XC49857||play||view|
|loud-song of male (slow trill song)||territorial dispute||XC49856||play||view|
There is no significant microgeographic variation in loud-song structure between sites in central lowland Panama (JPK, unpublished data), suggesting that dialect formation via vocal learning does not exist. Exemplars from elsewhere in the distributional range (from xeno-canto archives) indicate some variation in the temporal structure of songs.
Both male and female Western Slaty-Antshrikes sing year-round as they aggressively defend their territories. In April-May, before the beginning of the peak breeding season, song rates increase. Responsiveness to playback is high at this time and wanes only slightly throughout the breeding season. The various calls can be heard year-round, but some calls such as the 'warble' call (See 'Calls' above) are given only during the late part of the nesting cycle.
Singing and other vocalizing takes place throughout the day. Singing is not confined to the dawn chorus.
Places of vocalizing
Western Slaty-Antshrikes vocalize from a variety of locations within their territories. Adults broadcast their territorial loud-songs from any strata in the forest, but they tend to sing from the midcanopy. As noted above, 'warble' calls are given in the vicinity of the nest.
Repertoire and delivery of songs
Depending on context, loud-songs (see above for description) can be broadcast with varying amplitude. Territorial males often are the first to respond to a neighboring male's loud-song, and they do so with high amplitude loud-song. Females often follow the male in loose counter-singing. Once females joins a territorial dispute, she often sings a low amplitude loud-song before engaging in high amplitude loud-song. Young individuals often are more aggressive singers, singing higher amplitude loud-songs at faster rates. Old individuals often sing at markedly low rates and seldom approach intruders (or playbacks) (JPK and CET, unpubl. data). In response to playbacks of loud-song, nonterritorial individuals (floaters) often respond with very low amplitude song from a very short distance.
Social context and presumed function
Neighbor-stranger recognition in Western Slaty-Antshrikes only recently has been attempted (JPK, unpubl. data), but no published evidence so far exists. Preliminary evidence from a number of playback studies suggests that response to territorial intruders may be related to the age of both resident and intruder (JPK and CET, unpubl. data). For more information about context of specific vocalizations, see above.
Discrimination between conspecifics and heterospecifics has not been tested in the Western Slaty-Antshrike.