Rufous-and-white Wrens Research Articles

Species Differences in the Songs of the Critically Endangered Niceforo's Wren and the Related Rufous-and-White Wren

Abstract Niceforo's Wrens (Thryothorus nicefori) and Rufous-and-white Wrens (Thryothorus rufalbus) are closely related Neotropical birds. Niceforo's Wrens, critically endangered endemic Colombian songbirds, are generally considered a sister species to Rufous-and-white Wrens, although some have suggested that they may represent a well-marked race. A careful comparison of the two taxa has never been conducted. Here we present a thorough study of the songs of male Niceforo's and Rufous-and-white Wrens based on recordings collected throughout both species' geographic ranges. Both species sing low-pitched songs composed of varied pure tone whistles. Niceforo's Wren songs are shorter and simpler with fewer syllables and syllable types; they have higher frequency trills and terminal syllables; and they have distinctive terminal syllables with a broader bandwidth, higher frequency of maximum amplitude, and a larger number of frequency modulations. Discriminant analysis based on fine structural details of songs differentiates the two species. In a subspecies-level discriminant analysis, all five subspecies of Rufous-and-white Wren cluster together and are distinct from Niceforo's Wren. Comparisons of morphometric measurements and plumage features reveal parallel differences in body size (Niceforo's Wrens are larger for most measurements) and plumage color (Niceforo's Wrens are more gray than Rufous-and-white Wrens). This study is the first to compare Rufous-and-white versus Niceforo's Wrens with a quantitative approach and supports the idea that these taxa are best understood as distinct species.

SPECIES DIFFERENCES IN THE SONGS OF THE CRITICALLY ENDANGERED NICEFORO'S WREN AND THE RELATED RUFOUS-AND-WHITE WREN

Abstract Niceforo's Wrens (Thryothorus nicefori) and Rufous-and-white Wrens (Thryothorus rufalbus) are closely related Neotropical birds. Niceforo's Wrens, critically endangered endemic Colombian songbirds, are generally considered a sister species to Rufous-and-white Wrens, although some have suggested that they may represent a well-marked race. A careful comparison of the two taxa has never been conducted. Here we present a thorough study of the songs of male Niceforo's and Rufous-and-white Wrens based on recordings collected throughout both species' geographic ranges. Both species sing low-pitched songs composed of varied pure tone whistles. Niceforo's Wren songs are shorter and simpler with fewer syllables and syllable types; they have higher frequency trills and terminal syllables; and they have distinctive terminal syllables with a broader bandwidth, higher frequency of maximum amplitude, and a larger number of frequency modulations. Discriminant analysis based on fine structural details of songs di...

Eleven microsatellite loci isolated from the banded wren (Thryothorus pleurostictus)

We describe 11 microsatellite loci isolated from the Banded Wren (Thryothorus pleurostictus), a Neotropical species for which understanding the genetic mating system is important for testing questions about the species' unusual vocal behavior. Screening of these loci revealed extremely low allelic variation in a Costa Rican population. Allelic variation at these and other previously developed loci is substantially higher in two other wren species, the southern house wren (Troglodytes aedon bonariae) and rufous-and-white wren (Thryothorus rufalbus), suggesting that the low allelic diversity in the banded wren results from demographic bottlenecks rather than locus-sampling artifacts.

Accuracy of an acoustic location system for monitoring the position of duetting songbirds in tropical forest

A field test was conducted on the accuracy of an eight-microphone acoustic location system designed to triangulate the position of duetting rufous-and-white wrens (Thryothorus rufalbus) in Costa Rica's humid evergreen forest. Eight microphones were set up in the breeding territories of 20 pairs of wrens, with an average intermicrophone distance of 75.2+/-2.6 m. The array of microphones was used to record antiphonal duets broadcast through stereo loudspeakers. The positions of the loudspeakers were then estimated by evaluating the delay with which the eight microphones recorded the broadcast sounds. Position estimates were compared to coordinates surveyed with a global-positioning system (GPS). The acoustic location system estimated the position of loudspeakers with an error of 2.82+/-0.26 m and calculated the distance between the "male" and "female" loudspeakers with an error of 2.12+/-0.42 m. Given the large range of distances between duetting birds, this relatively low level of error demonstrates that the acoustic location system is a useful tool for studying avian duets. Location error was influenced partly by the difficulties inherent in collecting high accuracy GPS coordinates of microphone positions underneath a lush tropical canopy and partly by the complicating influence of irregular topography and thick vegetation on sound transmission.

Aggressive responses of male and female rufous-and-white wrens to stereo duet playback

Hypotheses for the function of animal vocal duets fall into three broad categories. Male and female breeding partners may use duets to communicate with each other, to communicate with same-sex outsiders, or to communicate with opposite-sex outsiders. To evaluate these categories of duet function, I gave stereo duet playback to territorial pairs of duetting rufous-and-white wrens, Thryothorus rufalbus , in northwestern Costa Rica. I simulated duets of a rival pair of wrens by simultaneously broadcasting male and female duet components through separate loudspeakers. Territorial males and females responded aggressively to duet playback by rapidly approaching the speakers and singing both solo songs and duets. Males sang more songs in response to playback than females, but both sexes responded to approximately half of their partner's songs to create duets. The aggressive responses of territorial pairs were consistent with a territorial defence hypothesis for duet function. Males spent more time near the male speaker and approached the male speaker more closely, suggesting that male duet contributions play a role in intrasexually aggressive extrapair communication. Females approached the male and female speakers with similar intensity, although they tended to respond more strongly to the male speaker. In the few cases where females responded independently of their partner, they responded more strongly on the side of the female speaker. Taken together, responses of rufous-and-white wrens to stereo duet playback suggest that duets play a role in territory defence against conspecific rivals, and, for males, duets may play an additional role in mate guarding and paternity guarding.

Sex Differences in Singing and Duetting Behavior of Neotropical Rufous-and-White Wrens (Thryothorus Rufalbus)

AbstractIn many tropical bird species, males and females sing together in coordinated vocal duets. Although studies of duetting present unique opportunities for understanding conflict and cooperation between the sexes, very few investigations describe the similarities and differences between male and female singing behaviors. Here, we present the first detailed account of the singing behavior of Rufous-and-white Wrens (Thryothorus rufalbus), a resident tropical duetting songbird. Male and female songs share a similar structure, yet show pronounced sex differences. Male songs have lower frequency characteristics and more repeated trill syllables, and often sound louder than female songs. Males sing more than females, and only males show elevated song output at dawn. Both males and females have song repertoires. Males have an average repertoire size of 10.8 song types, whereas females have a significantly smaller average repertoire size of 8.5 song types. Although males share proportionately more of their song types with neighbors than females do, both sexes share more song types with nearby individuals than with distant individuals. Breeding partners combine their solo songs to create duets. Duets assume a variety of different forms, ranging from simple, overlapping male and female songs to complex combinations of multiple male and female songs. Most duets (73%) are created by females responding to male song. Males respond to female-initiated duets with shorter latencies than when females respond to male-initiated duets. Each pair sings certain combinations of song types in duets more often than can be explained by random association, which demonstrates that Rufous-and-white Wrens have duet types. The most common duet type was different for each pair. Our results show that Rufous-and-white Wrens have pronounced sex differences in song structure, singing activity, repertoire size, repertoire sharing, and duetting behavior.Diferencias entre Sexos en el Canto y Comportamiento de Dueto en Thryothorus rufalbus

SEX DIFFERENCES IN SINGING AND DUETTING BEHAVIOR OF NEOTROPICAL RUFOUS-AND-WHITE WRENS (THRYOTHORUS RUFALBUS)

Abstract In many tropical bird species, males and females sing together in coordinated vocal duets. Although studies of duetting present unique opportunities for understanding conflict and cooperation between the sexes, very few investigations describe the similarities and differences between male and female singing behaviors. Here, we present the first detailed account of the singing behavior of Rufous-and-white Wrens (Thryothorus rufalbus), a resident tropical duetting songbird. Male and female songs share a similar structure, yet show pronounced sex differences. Male songs have lower frequency characteristics and more repeated trill syllables, and often sound louder than female songs. Males sing more than females, and only males show elevated song output at dawn. Both males and females have song repertoires. Males have an average repertoire size of 10.8 song types, whereas females have a significantly smaller average repertoire size of 8.5 song types. Although males share proportionately more of their ...

Rufous-and-White Wrens Kill House Wren Nestlings during a Food Shortage

Birds of several species have been reported to kill immature birds of other species in contexts other than predation. Contexts include: (1) takeover of specialized nesting sites such as cavities (e.g., Kendeigh 1941, Pinkowski 1977), (2) brood parasitism (reviewed by Payne 1977), and (3) elimination of potential competitors for food (suggested by Picman 1977, 1980 for Long-billed Marsh Wrens [Cistothorus palustris]; Belles-Isles and Picman 1986 for temperate House Wrens [Troglodytes aedon]). The latter context is problematical because it cannot be inferred without evidence of actual or potential food limitation. In this note I document interspecific infanticide of tropical House Wrens by Rufousand-White Wrens (Thryothorus rufalbus). The infanticide appears to be based on competition for food since nestlings were killed only during an 8-week food shortage within a 4-year period. The infanticide was detected during a study of House Wrens conducted between 1982 and 1985 near the rural village of La Laguna, Republic of Panama (approximately 25 km northeast of Panama City). Six attacks occurred between 23 May and 14 July 1983; three were observed and three have been inferred (Table 1). On 23 and 24 May, a Rufous-and-White Wren was perched at the entrance of a nest box containing three House Wren nestlings (3 days old on 23 May). The box was mounted on a 1.25 cm diameter pole at a height of 1.6 m. The intruder thrust its head and beak rapidly and repeatedly into the nest and threw out one nestling on the first day. This nestling, as well as one of the remaining nestlings, had lacerations on the head and abdomen and puncture wounds on the abdomen. Thereafter one nestling was missing each day for two days. Parental House Wrens returning to the nest were driven away by the intruder during both days of observation. In a second case, on 9 July, an observer frightened a Rufous-and-White Wren from its perched position at the entrance of the nest box shortly after it commenced thrusting its head repeatedly inside the box. This nest contained six nestlings 10 days old. No mortality or injury resulted from this interrupted attack, and there was no evidence of repeated visits (i.e., no nestling loss or injury) for 3 days, after which a snake ate the nestlings. This second nest was located 3 km from the first, suggesting that two different Rufous-and-White Wrens were responsible for these incidents. In a third case, on 19 June, a Rufous-andWhite Wren repeatedly pecked a House Wren fledgling for 15 sec in a family group of recent fledglings and parents. The fledgling escaped and was observed 5 days later. This incident took place approximately 100 m from the first incident. The House Wren breeding season extended through October of 1983 (approximate length 24 weeks), but no further direct interactions between the two wrens were observed. Three additional nest losses (one partial) between late May and mid-July of 1983 may have been caused by Rufous-and-White Wrens because of similar patterns of lacerations and puncture wounds on the bodies of dead or dying nestlings (Table 1). One nestling had a severely broken tibiotarsus as well. Rufous-and-White Wrens were seen or heard within 25 m of these nests on the day of detection of infanticide. The nests were located at least 1 km apart and between 200 to 1,300 m from the nests mentioned above, suggesting that the Rufous-and-White Wrens seen in the vicinity of these nests were different individuals. Some alternative causes of the infanticide can be eliminated. Predators were probably not responsible for the killings because the dead or dying nestlings were not eaten. Infanticide by other House Wrens, associated with takeovers of mates or territories during each

Interspecific comparisons of the size of neural song control regions and song complexity in duetting birds: evolutionary implications

Previous studies have demonstrated a correlation between song repertoire size and volume of song control regions (SCRs) in the brains of songbirds. In the present study we demonstrate that 2 congeneric species of tropical duetting wrens, the rufous-and-white wren (Thryothorus rufalbus) and the bay wren (T. nigricapillus), share the same relationship between SCR volume and vocal complexity. In each species, females sing in elaborate duets with males. Males of these species have similar song repertoire sizes; there is no significant difference between heterospecific males in the volumes of SCRs. Female rufous-and-white wrens have less than half as large a song repertoire as female bay wrens, and all of their SCRs measured are significantly smaller than those of bay wren females. This interspecific equivalence of the relationship between SCR volume and repertoire size suggests that the neural system regulating vocal behavior in songbirds is evolutionarily conservative in the manner in which it encodes song complexity.