Comparison of Communication and Signalling Patterns of Whitebrowed Sparrowweavers and Other Gregarious Ploceid Weavers

Sexually selected sentinels? Evidence of a role for intrasexual competition in sentinel behavior

“…It is quite possible that the dominant male’s sentinel response to the foreign male solo song playback is a response in part to the dominant female’s own vocal response to the playback, as although the dominant male clearly led the movement response to the playback, the concomitant marked increase in duet production could have been led by either the dominant male or female (duet production is so synchronous that the leaders of duets cannot be readily identified in the field). Although duets are frequently interpreted as cooperative vocal responses that may function in the collective defense of territory (e.g., white-browed sparrow weaver: Ferguson 1988 ; Wingfield and Lewis 1993 ; Voigt et al 2006 ), they may also reflect sexual conflict ( Marshall-Ball et al 2006 ; Tobias and Seddon 2009 ), in which 1 sex may advertise their presence to putative extrapair mates, eliciting an immediate response from their social partner that may serve in mate defense. Our finding that the duet response of the resident pair to the male solo song playback positively predicted the dominant male’s sentinel response is consistent with this view, with the dominant male potentially scaling his subsequent sentinel response according to the dominant female’s vocal response to the playback.…”

“…Throughout the study, individuals were defined as engaging in sentinel behavior (following Ridley et al 2010 ), if they were perched in an elevated position >1 m above the foraging group members, actively scanning the surrounding area for a duration of >30s. Similarly to pied babblers ( Turdoides bicolor , Ridley et al 2010 ), white-browed sparrow weavers are predominately ground foragers ( Ferguson 1988 ), with individuals using their beaks to dig in the substrate for prey. As sentinel behavior was conspicuous and occurred at low frequencies (see Results for details, white-browed sparrow weaver groups had a sentinel in place a mean [± standard deviation {SD}] of 21.0% [± 7.80] of the time, and individuals did not overlap in sentinel bouts), the sentinel effort of all group members could be accurately monitored simultaneously simply by noting the start and end times of all sentinel bouts during the observation session.…”

“…Here, we investigate whether sentinel behavior plays a role in intrasexual competition, using a combination of observational data sets and playback experiments in a wild population of the white-browed sparrow weaver, a year-round territorial cooperatively breeding songbird. White-browed sparrow weavers live in groups of 2–12 individuals, consisting of a dominant breeding pair and subordinates of both sexes ( Collias NE and Collias EC 1978 ; Lewis 1982 ; Ferguson 1988 ; Harrison et al 2013a ). Sentinel behavior in white-browed sparrow weavers, as for other ground-foraging species, is characterized by an individual assuming a raised position and scanning its surroundings while members of its group forage nearby ( Ferguson 1987 ).…”

Socially induced brain differentiation in a cooperatively breeding songbird

“…Only the dominant male of the group performs the solo song, i.e. it possesses two distinct repertoires ( Ferguson 1988;Voigt et al 2006). Solo song is produced at dawn during the breeding season and is thought to function mainly in inter-sexual communication ( Ferguson 1988;Voigt et al 2006).…”

“…it possesses two distinct repertoires ( Ferguson 1988;Voigt et al 2006). Solo song is produced at dawn during the breeding season and is thought to function mainly in inter-sexual communication ( Ferguson 1988;Voigt et al 2006). Duet and chorus singing occur year round and are strongly associated with territory defence ( Wingfield & Lewis 1993).…”