Babbler Groups Research Articles

Dehydration risk is associated with reduced nest attendance and hatching success in a cooperatively breeding bird, the southern pied babbler Turdoides bicolor.

High air temperatures have measurable negative impacts on reproduction in wild animal populations, including during incubation in birds. Understanding the mechanisms driving these impacts requires comprehensive knowledge of animal physiology and behaviour under natural conditions. We used a novel combination of a non-invasive doubly labelled water (DLW) technique, nest temperature data and field-based behaviour observations to test effects of temperature, rainfall and group size on physiology and behaviour during incubation in southern pied babblers Turdoides bicolor, a cooperatively breeding passerine endemic to the arid savanna regions of southern Africa. The proportion of time that clutches were incubated declined as air temperatures increased, a behavioural pattern traditionally interpreted as a benefit of ambient incubation. However, we show that (i) clutches had a <50% chance of hatching when exposed to daily maximum air temperatures of >35.3°C; (ii) pied babbler groups incubated their nests almost constantly (99% of daylight hours) except on hot days; (iii) operative temperatures in unattended nests frequently exceeded 40.5°C, above which bird embryos are at risk of death; (iv) pied babblers incubating for long periods of time failed to maintain water balance on hot days; and (v) pied babblers from incubating groups lost mass on hot days. These results suggest that pied babblers might leave their nests during hot periods to lower the risk of dehydration associated with prolonged incubation at high operative temperatures. As mean air temperatures increase and extreme heat events become more frequent under climate change, birds will likely incur ever greater thermoregulatory costs of incubation, leading to compromised nest attendance and increased potential for eggs to overheat, with implications for nest success and, ultimately, population persistence.

Comprehensive phylogeny of the laughingthrushes and allies (Aves, Leiothrichidae) and a proposal for a revised taxonomy

AbstractDNA phylogenies have gradually shed light on the phylogenetic relationships of the large babbler group. We focus in this study on the family Leiothrichidae (laughingthrushes and “song babblers”), which represents the largest clade of babblers in terms of species diversity. Our phylogeny includes all genera and 82% of the recognized species, using mitochondrial and nuclear loci. The sister group to Leiothrichidae is composed of the Pellorneidae (“jungle babblers”) plus the genus Alcippe. Within Leiothrichidae, four strongly supported primary clades (A–D) are recovered. Clade A includes Grammatoptila, Laniellus and Cutia. Clade B includes a large group of laughingthrushes, all of them classified in Trochalopteron. In Clade C, the two laughingthrushes endemic to southern India, T. fairbanki and T. cachinnans, which have recently been proposed to be placed in the newly erected genus Montecincla, form a sister clade to the group comprising the “song babblers” (Lioptila, Leiothrix, Heterophasia, Minla, Liocichla, Actinodura, Chrysominla, Siva, and Sibia). Clade D includes the African babblers (Turdoides, Phyllanthus, Kupeornis), Asian relatives (Argya, Acanthoptila, Chatarrhaea) and all remaining laughingthrushes (Garrulax). The time estimates suggest that the early diversification of the Leiothrichidae occurred in the mid‐Miocene, a period that corresponds to the diversification of many passerine groups in Asia. A revised taxonomic classification of the family is proposed in the light of these results.

Male-male competition is not costly to dominant males in a cooperatively breeding bird

Male-male reproductive competition occurs in many animal societies and can be costly, both through aggression or energy expenditure prior to mating and lost paternity. In most cooperative breeders, socially dominant males breed more often than do subordinates, but the costs of pre-copulatory subordinate male reproductive competition (including unsuccessful competition) have rarely been investigated in these systems. Here, we examine the association between such competition and the fitness of dominant males in the cooperatively breeding southern pied babbler (Turdoides bicolor). Babbler groups comprise a dominant breeding pair with adult subordinates of both sexes. Roughly 35 % of adult subordinate males live in groups with unrelated adult females, but despite their common engagement in active reproductive competition, these subordinate males rarely successfully breed (extra-group mating has never been detected). Overall, active reproductive competition with subordinate males is not costly to dominant males, notwithstanding that rare episodes of breeding by subordinate males cause large paternity losses (50–100 %). Specifically, the presence of an actively competing subordinate male does not affect the proportion of successful nests, the number of fledglings fathered by the dominant male or dominant male retention of dominance to the next breeding season. Instead, dominant male breeding success is likely to be more affected by factors such as food availability and group size. In the social context of cooperative breeding, a competing subordinate male may provide benefits of a larger group size or increased help; these may offset the low risk of paternity loss, possibly promoting tolerance of reproductive competitors by dominant males.

Plastic territoriality in group-living chestnut-crowned babblers: roles of resource value, holding potential and predation risk

The factors selecting for territoriality and their relative importance are poorly resolved. Theoretical models predict that territoriality will be selected when resources of intermediate abundance are distributed variably and predictably in time and space, but can be selected against if the resource-holding potential of individuals is low or the risk of predation is high. Here we used a model averaging approach in a mixed modelling framework to analyse 5 years of observational and experimental data collected on group responses to actual and perceived intruders in the cooperatively breeding chestnut-crowned babbler, Pomatostomus ruficeps, in order to provide a rare test of the relative importance of resource value, resource-holding potential and predation risk in territorial behaviour. We found that babblers were highly plastic in their responses to actual and simulated intruders: on average, approaches occurred on 55% of occasions, and aggression ensued in 55% of approaches (observational and experimental results combined). Whether or not babbler groups approached, and if so were aggressive towards, actual or simulated intrusions was explained by time of day, location, group sizes, predator encounter rate and habitat characteristics, but not by reproductive status. Consideration of each of these effects regarding the three hypotheses above suggested comparable roles of group competitive advantage and predation risk on approach probability, whereas ensuing aggression was mostly explained by correlates of resource value. Our study provides compelling evidence to suggest that the risk of predation can affect the incidence of territorial and agonistic behaviour between social groups of animals by moderating the effects of resource value and group competitiveness, and might partly explain the high plasticity in group responses to intrusions.

The effects of nest usurpation and other interference by the Blue-faced Honeyeater on the reproductive success of the Grey-crowned Babbler

Nest-building is a costly activity and natural selection may sometimes favour usurpation of existing nests. Few quantitative studies have investigated the effect of usurpation of nests on the reproductive success of the usurped species. Here we studied 27 instances of usurpation of Grey-crowned Babbler (Pomatostomus temporalis) nests (n = 310 nests) by Blue-faced Honeyeaters (Entomyzon cyanotis) in the monsoon tropics of Australia between 2003 and 2008. When usurpation occurred during laying or incubation the Babbler eggs disappeared. The frequency of nest usurpation by Blue-faced Honeyeaters varied between Babbler territories, from no usurpation to almost every year during the study period. Based on video-recording at Babblers’ nests over 854 days, we observed 75 interference events on 39 days at 29 nests. Interference occurred most frequently during nest-building and incubation and much less frequently in the nestling stage. Modelling suggested interference by Honeyeaters can have severe effects on breeding of Grey-crowned Babblers, with success of individual nests reduced by 52.5% during the nest-building stage, 25.9% during incubation, and 1.2% during the nestling stage. Babbler group size did not affect the occurrence of interference. The southern subspecies of Grey-crowned Babbler is declining and it is conceivable that populations could be adversely affected by interference from Blue-faced Honeyeaters in areas where the two species co-occur.

Social organisation and foraging ecology of the cooperatively breeding Chestnut-crowned Babbler (Pomatostomus ruficeps)

An individual's fitness is assumed to be maximised through early dispersal and independent breeding. However, offspring across a diversity of taxonomic groups delay dispersal and remain with at least one of their parents after reaching sexual maturity. Delayed dispersal and resulting family living are expected to arise when constraints exist on independent reproduction and where offspring benefit by remaining philopatric. A first step to elucidating the nature of such constraints and benefits for a given species is to have an understanding of the social organisation and habitat preferences of a species. The present study examined the social organisation, foraging preferences and characteristics of preferred foraging areas during a breeding season in the cooperatively breeding Chestnut-crowned Babbler (Pomatostomus ruficeps). During the study, groups of Babblers bred plurally in breeding units of two to 13 adults that occupied non-exclusive home-ranges averaging 38 ha, with larger groups occupying larger ranges. Babblers spent most of the day foraging, mostly on the ground, and preferred to forage within drainage zones. The preference for such zones probably arose because they offered both greater vegetative cover from aerial predators and biomasses of potential prey. These findings lead to the prediction that the availability of drainage zones within a group's range will influence offspring dispersal decisions in Chestnut-crowned Babblers at the site studied.

Importance of woody vegetation for foraging site selection in the Southern Pied Babbler ( Turdoides bicolor) under two different land use regimes

Intensified land use practices have changed savannas worldwide. Both, heavy grazing-induced shrub encroachment and the decrease in tree density due to woodcutting are assumed to reduce animal diversity. However, most studies in animal ecology have focused on the effects of one of these two land use practices. In our study we analyzed the importance of both shrubs and trees, for foraging site selection of the Southern Pied Babbler ( Turdoides bicolor) in the Southern Kalahari, South Africa for two different grazing regimes: endemic wildlife at Molopo Nature Reserve versus domestic livestock at neighboring farms. We compared vegetation structure at babbler foraging sites with random sites at the microhabitat scale (5×5 m) and the mesohabitat scale (50×50 m), and recorded babbler group size and the amount of leaf litter. Our results show for both scales that mean density of shrubs and trees was higher at foraging sites compared to random sites. We found no differences in foraging site characteristics (i.e. vegetation cover at microhabitat scale and composition and density of woody plant species at both scales) and group size between the two grazing regimes. We conclude that shrub encroachment affects the Southern Pied Babbler positively whereas woodcutting has negative effects.

Facultative response to a kleptoparasite by the cooperatively breeding pied babbler

In many cases of interspecific kleptoparasitism, hosts develop defensive behaviors to minimize the impact of kleptoparasites. Because vigilance and defensive behaviors are often costly, selection should favor hosts that adjust the amount of investment needed to minimize losses to kleptoparasitism. However, examples of such facultative responses are rare. Here, we investigate the response of cooperatively breeding pied babblers (Turdoides bicolor) to the drongo (Dicrurus adsimilis), an avian kleptoparasite that regularly follows pied babbler groups, often giving alarm calls to alert the group to predators but also occasionally giving false alarm calls in order to steal food items. We show that pied babbler response to drongos varies markedly according to babbler group size. In small groups, where there are few individuals available to act as sentinels, babblers sentinel less when a drongo is present and respond strongly to drongo alarm calls. However, in large groups, where there are many individuals available to participate in predator vigilance, babblers sentinel more often when a drongo is present, rarely respond to drongo alarm calls, and aggressively displace drongos, with a consequent decline in the number of successful kleptoparasitism events. This behavior represent a facultative response to a kleptoparasite according to the costs versus benefits of tolerating their presence.

Potential prey make excellent ornithologists: adaptive, flexible responses towards avian predation threat by Arabian Babblers Turdoides squamiceps living at a migratory hotspot

During spring raptor migration, resident, group‐living, Arabian Babblers Turdoides squamiceps in Israel are exposed to many avian predators that differ in the level of predation threat that they pose. Accurate information about immediate safety while foraging may be provided by the sentinel, a high‐perched non‐foraging Babbler that actively scans and warns for predators. We tested whether, at this migratory hotspot, the bewildering number and diversity of potential avian predators (perhaps more than anywhere else in the world) may be more than a reliable sentinel could handle. We monitored ten Babbler groups regularly for a number of hours per day throughout the migration season, and scored whether the Babblers gave alarm calls when different bird species were in sight. Analyses showed that Babblers are very skilled in distinguishing between species of high and low predation threat (interspecific threat‐sensitivity). In addition, Babblers distinguished accurately between encounters with dangerous vs. harmless individuals from predator species of potentially high predation threat (intraspecific threat‐sensitivity). Overall, Babblers cautiously overestimated predation threat, probably because errors involving alarms for harmless predators have a lower fitness cost than errors involving attacks by dangerous predators that are ignored. However, fewer warnings were given for the more common predators of lower threat, which suggests that Babblers initially overestimated the risk of predation, but subsequently learned to assess the level of threat more accurately as soon as more information was available. Overall, our findings agree closely with theoretical predictions regarding adaptive and sophisticated anti‐predation behaviour in a variable world.

Correlates of abundance and breeding success in the globally threatened Hinde's babbler ( Turdoides hindei) and its congener, northern pied babbler ( T. hypoleucus)

We investigated the relationship between habitat quality, abundance, group size and breeding success in the threatened Kenyan endemic Hinde's babbler ( Turdoides hindei; Family Timaliidae), a co-operative breeder mainly associated with riverine thickets in cultivated areas. At two intensively cultivated sites, significantly more Hinde's babbler groups occurred in areas retaining at least 3% thicket cover, while breeding outcome improved where cover exceeded 9%. Despite previous concerns over low breeding success, the percentage of young birds present (17%, n=424 birds aged) was similar to that of a sympatric congener, the northern pied babbler ( T. hypoleucus) (12%, n=162), and comparable with that of two other African congeners. Although breeding outcome was positively correlated with adult group size, there was no evidence that larger groups monopolised more favourable habitat or defended larger territories. Group density showed a positive, non-linear relationship with adjacent cover, levelling out where this exceeded 15–20%. Our findings suggest that even a modest increase in thicket cover may significantly raise the density and productivity of Hinde's babblers at these sites.

The spatial dynamics of White-browed Babbler groups in a fragmented agricultural landscape

White-browed Babbler Pomatostomus superciliosus groups occupying linear strips of vegetation had breeding territories that were smaller in area and had longer linear dimensions than those occupying patches. A group's non-breeding home range was larger than its breeding territory. Groups occupying linear/patch home ranges expanded the linear extent and area of their home ranges more than those within other home range configurations. Some groups moved during the non-breeding season and this was more likely to occur if the group occupied a remnant with a low abundance of invertebrates during summer. Some groups that moved returned prior to the next breeding season, but the majority were never seen again. New groups moved into the study sites and established in vacant home ranges. This suggests that those groups that left the study sites may have established new home ranges elsewhere. Breeding site fidelity was lower in groups that had failed in previous breeding attempts. Therefore, group movements were influenced by the feeding and breeding quality of the habitat. However, the configuration of the local population also influenced group movements with those groups on the edge of a local population being more likely to move than those in the interior. New groups were formed by two processes; group dispersal, where groups generally filled a vacant home range, and group budding, which involved the splitting of a large group. Group dispersal maintained group densities while group budding increased the density of groups in a local population. These two processes were common, producing localized fluctuations in the density of groups. Since babbler groups contain only one breeding pair, changes in group density represent changes in effective population size. Therefore, group dynamics may be important to the persistence of local populations of White-browed Babblers, especially in landscapes that have suffered from habitat loss and fragmentation.

Cooperatively breeding Arabian babblers call differently when mobbing in different predator-induced situations

Cooperatively breeding Arabian babblers (Turdoides squamiceps) have a repertoire of different calls that they use in predator-induced contexts. We investigated their vocal mobbing behavior in two different predator-induced situations. We presented territorial groups of babblers a perched, stuffed owl representing an avian predator and a cat representing a ground predator. Babblers approached in both situations and mobbed the predators with the same two call types. In both predator-induced situations their first call was a short, metallic-sounding “tzwick.” In response to the cat, babblers continued to primarily use tzwicks. However, in continued response to the owl, the babblers primarily used long trills. The experiments indicate that differences in use of two common call types during mobbing provide information on differences in predator-induced situations, although no call type per se identified a specific situation. The experiments suggest that the short tzwicks indicate a higher risk or urgency than trills and that combinations of both call types may provide graded information about differences in predator-induced situations. The relatively stable groups of these cooperative breeders might have favored evolution for using different calls in different mobbing situations.

Influence of the Observer on the Frequency of the ‘Morning‐Dance’ in the Arabian Babbler

AbstractThe Arabian babbler, Turdoides squamiceps, displays an unusual behaviour, the ‘morning‐dance’. This article examines the influence of the presence and behaviour of an observer on the dance frequency. The results are the summary of more than 3 yr of study by 12 observers, who performed 1335 observations and witnessed 286 dances that took place among 15 groups of babblers. Different experiments were carried out on 148 additional mornings.Different observers witnessed different dance frequencies. Dance frequency witnessed by an observer decreased with observer's experience. Observers watching groups of babblers on single days witnessed more dances than those who watched the same groups for several consecutive days. Dance frequency was higher on the first day of a series of observations than on the following days in the same series. If a group of babblers remained unobserved for one day, the frequency of dancing increased. An evening observation considerably decreased the frequency of dancing the following morning. Feeding experiments did not elevate dance frequency. Experimental disturbance at the roost before dawn increased dance frequency while permanent disturbance and frightening experiments did not. Change in the observer's presence and behaviour caused the babblers to react by dancing. The hypothesis that the observer's presence and behaviour influences different group members differently, and therefore alters the relationships among them, is offered to explain the results that observers can affect the dance frequency.

Demography of the Jungle Babbler, Turdoides striatus

(1) Some aspects of the demography of the jungle babbler are described. Compared to the temperate passerines on which most studies of population dynamics have so far been conducted, jungle babblers showed little seasonal or annual changes in population size. The proximal mechanism by which this stability was achieved was the emigration of birds in their second summer or older. The survival of post-juvenile birds remaining with their natal group was high, about 90%O per annum, but this also applied to breeding birds, and hence the opportunity to attempt breeding was so limited that only a quarter of the birds reaching maturity ever managed to do so. (2) Despite the rate of interchange observed between groups, the mean degree of relatedness of all group members to the breeding pair was probably about 0 3, higher than that between half-siblings. Under theories of kin selection (Hamilton 1964; Eberhard 1975) the selection pressure for altruistic behaviour is proportional to the degree of relatedness of the donor and the recipient, and hence babbler groups apparently present an excellent situation for the evolution of altruistic behaviour. (3) The quality of habitat occupied varied on a larger scale than is typical of most temperate situations, and this resulted in wide differences in the reproductive success of different groups. Once the influence of territorial quality was taken into account there was no significant correlation between group size and breeding success, and there was some indication that larger size may have been correlated with lower fledging success in the spring. This appears to contradict the prediction of kin selection than non-breeding members of the group should make a positive contribution to the reproduction of the closely related breeding pair. (4) Dispersal is more important to females, which probably do not breed in their natal groups, than it is to males. Both sexes have the option of joining'in the establishment of a new group, but remaining in the natal group may constitute a more attractive strategy for males which can eventually inherit the parental breeding territory. The differences in reproductive success between different territory types must influence the strategies of males, and may account in part for differences in the size of groups.