Will My World: February 2005

我終於寫完我份論文喇 !!!!!!!!!!!!!! 好激動呀我而家 !!!!!
超開心呀 ~~~~~~~~~~~~~~~~~~~~~ 哈哈哈哈 !!!!
一共 6200 字 ! 69 個 refernce (真正睇過o既少過15個) ! 晒左成百個鐘頭 ! 勁 !!!!
fuck you, babblers ~~~~

Ecology of Babblers

ABSTRACT
There are 257 species of babblers, the family Timaliidae, in the world, most of them dwelling in Oriental and Africa and some in Australia. Babblers have been noticed for their morphological and ecological diversity, and hence results in particular difficulties in their problems of systematics. Population of babblers has a complex sociality and many of them exhibit cooperative behavior which was deeply investigated along with some of the basic facts of their ecology. Despite the reasonable amount of studies about babbler so far, they are rather scattered and inconspicuous, which might be due to the difficulty in its taxonomy and diversity. Global threat on babblers is mild, whilst some local severe cases do exist anyway. Many of 14 babblers in Hong Kong are invasive birds and most are resident.

1 Introduction
1.1 What is Babblers
The babblers, family Timaliidae, is an important group of Old World insectivorous passerines (Sibley and Monroe 1990). There are 257 species of babblers in the world, in all incorporating 11 genera, distributed for the most part in Central and eastern Eurasia, Africa, Madagascar, Philippines, East Indies and Australia (Austin 1987). Virtually most of the babblers are restricted in the Old World, but with a single sole exception, the Wrentit (Chamaea fasciata) (see below), which appears in North America. Due to many of the passerine families, the babblers do not have diagnostic morphological characters. The morphological features of the group of babbler are generally the lack of a distinct juvenile plumage, shape and size heavier than the warblers (Sylviidae), in particularly legs and bill, as well as sexes alike in most species (Ciblis et al. 2002).

Moreover, behavioral characters are another cue used by systematists to define them as a group. The high degree of sociality of these non-migratory birds is the most significant feature, manifesting themselves in lots of ways. They usually gather in flocks and parties. Some species are cooperative breeders. Members of a population of most babbler species clump together while perched during the day and when roosting at night, with mutual preening observed in quite many species. The family is named as babbler owing to its babbling chatter and noisiness of some relatively sociable members, in particular the genus Turdoides, with many of them being fine songsters. Regardless of such similarities in nature, the babblers exhibit great morphological and ecological diversity. Being so variable and diverse, the family looks like a great collection of many different unrelated species at the first sight. New forms of babblers are still being described (Gonzales and Kennedy 1990). All these result in a complicated situation in the systematics of babblers and create troubles to systematists concern.

Babblers belong to the Aves class, order Passeriformes, and the Timaliidae family. But sorting out the phylogeny of babblers has all along been a challenge of systematists and there is particular difficulty in the systematics of babbler and some related members of the Old World insectivorous passerines. And yet in recent years there have been quite a lot of discoveries by means of molecular bases (Barhoum and Burns 2002; Barhoum and Burns et al. 2002; Cibois 2003; Cibois et al. 1999; Cibois et al. 2001; Cibois et al. 2002). In the long term progress of systematics of babblers, some species have been found to be wrongly included or excluded in the group. For example, laughingthrushes are now proved to be a sister taxa to all other babblers; two other oscine taxa, Sylvia (Sylviidae) and Zosterops (Zosteropidae), which was traditionally considered as poorly related to the Timaliidae family, has been recently found ought to be included in the babbler assemblage; The Shrike Babblers (Pteruthius) and the Gray-chested Thrush Babblers (Kakamega pliothorax) are the examples of species traditionally included among babblers but actually not related to the Timaliidae (Cibois 2003); the Malagasy “babblers” should not have been considered related to true African and Asian babblers, nor should Asian White-bellied Yuhina (Yuhina zantholeuca) have been, which the analysis by Cibois (2002) suggested not to be monophyletic with genus Stachyris. The Some molecular markers of sequence of mitochondrial genes by DNA hybridization work have been used to clarify the evolution of the complex babbler group (Barhoum and Burns 2002; Cibois et al. 2002; Cibois 2003; Sibley and Ahlquist 1990). Contributions made by Alice Cibois and other previous molecular researches allow us to have a more accurate insight into the limits of this family. The high similarity in size, shape and behavior between “real” babblers and the “false” ones is probably the result of convergent evolution.

1.2 About this essay
The study of babblers is still very inconspicuous, and so far there is no a single “family book” covering babblers. Among all species of this family, Arabian babbler (Turdoides squamiceps), which is a group territorial, communally breeding thrush-like babbler, occurring in Israel, is most intensively studied.

This essay is called “ecology of babblers”. In this essay, besides some general information of physiology, diet, habitat, etc., the most interesting part of social behaviors of babblers will be fairly discussed. Due to the inconspicuousness and scatteredness of the study of babblers, it would be advisable to cite various species as examples in cases. Moreover merely true babblers will be mainly focused on, instead of some non-babbler groups like the family of Australo-Papuan babblers (Pomatostomidae), also called Pseudo-babblers, with totally 5 species including Gray-crowned Babbler (Pomatostomidae Temporalis).

2 Physiology
2.1 Morphology
The members of the babblers are ranging in size from 3.5 to 16 inches (9 to 41 centimeters), while their colors vary from the plain browns and grays of many babblers to the warm red and yellow of the Red-billed Leiothrix (Leiothrix lutea), a native species of southern Asia introduced in the Hawaiian Islands (Walters 1994). Most of them can sing very charmingly, but all species of fulvetta have rather subdued plumage. The babblers, through evolution, need not wings to find food virtually, resulting in their awkwardness in flight. Instead, babblers have the strong legs and bill. Strong legs facilitate their motions of hopping and walking in the forest scrub. The leg musculature of babblers is packed tightly together and muscularly developed, whilst no outstanding deviations from the order Passeriformes are observed (Jayasree and Mathew 1992). One of the prominent features of musculature is the disparity in the degree of fusion and intermingling of the bellies and fibres of the various thigh and shank muscles, probably related to the energetic movements of their legs. The difference in habitats may have attributed to the variation in patterns of the leg muscles among species of babblers.

Babblers’ feathering is often lax and soft. They possess a pair of short, rounded wings with ten primaries, as well as an unusually long tail for a flying bird (Gilliard 1958). Therefore the babblers fail to be great fliers. They usually perform short flights that are low in dense vegetation, or flights of as low as 50m over open ground between shrubs and clumps.

Unlike thrushes (of Turdidae family), many of which are superficially resemble to one another, the juveniles of babblers are normally not spotted. Bills of babblers are more robust than those of Sylvidae (Fauvettes), the closest relatives of babblers. Some have specialized shape of bills. For example, Scimitar-babblers, in the genus Pomatorhinus, work among leaf litter with their long decurved bill.

2.2 Energy Expenditure
Some variables like resting metabolic rate (RMR), existence energy (EE), heat increment of feeding (HIF) and filed metabolic rate (FMR) are data often investigated to determine the energy expenditure and its component in babblers. The energy expenditure of babblers proved to be adjusting within day and between seasons.

Most of the studies about metabolism were associated with Arabian Babblers. For example, it is found that their variation of FMR and EE of non-breeding individuals between winter and summer are due to activity, chiefly foraging and thermoregulatory cost in free-living birds (Anava et al. 2003); and breeding babblers required more than non-breeding ones. The difference in seasonal daily field metabolic rate is suggested to be the result of a variations in daytime metabolic rate, while during the different seasons, night-time metabolic rate is similar (Anava et al. 2002). Energy expenditure of Arabian Babbler is more or less the same as other desert bird species but not as high as that of non-dessert species.

Furthermore, the group size of babblers may exert a significant influence on their field metabolic rate. For instance, the Arabian Babblers’ groups comprise both adults and helpers and are generally made up of 3 to 5 individuals. All members in the group feed nestlings at similar rates and the rates of individual visitation drop with an increasing group size. FMR of primary females declines with group size, resulting in energy savings which allow primary females in larger groups to initiate a new nest sooner (Anava et al. 2001).
2.3 Growth
Babbler nestlings have a relatively high growth rate than other passerine species do, but not fledgling mass (Anava et al. 2001 b). In Whiteheaded Babblers (Turdoides affinis), with some sources calling it Yellow-billed Babblers, the low growth rate is compensated by the long fledging period and care by many parents (Jayashree et al. 1997). The earlier fledging, moreover, allow the species to obtain more food under the protection of their parents. Among some species of babblers, the young are accompanied by their parents for one to two years. Generally, the amount of accumulation of energy intake inside tissue in babbler nestlings decrease with age while energy content per gram of body mass increase with age.

2.4 Others
The enzyme Lgulonolactone oxidase (GLO) is always needs for the synthesis of Vitamin C (ascorbic acid) in animals. This enzyme exists in all non-passerine birds, but the reacquisition of GLO is surprisingly apparent in babblers (Corliss 1998). In additions, there is no direct relation between the brain size of babblers and the complexity of social play among genera within taxa (Bond et al. 2003).

3 Geographical Distribution
3.1 Habitats
Babblers are non-migratory birds. Almost all babblers occur in woodland or forest, though those in drier areas may occupy sparsely wooded expanses, often with a scattering of copses as well as small thickets (Stuart and Stuart1999). Most of the babblers are sedentary, elusive birds and hard to observe in the forest; they loiter near and on the bottom of the forest or among bushes in scrubby grasslands (Gilliard 1958). Their nests are built in trees, wooded areas, on rock ledges, on the ground, or within a few feet of it (Walters 1994). The structures are usually in dome-shape with some cup-shaped. In breeding season babblers strongly prefer having their nests built close to the ground, where can be well hidden from enemies. Their nests are often made of lichens, skeleton leaves and even spiders’ webs. Some 30 species are open-country birds in the genus Turdoides, while some are marsh birds but most do appear in open scrub of thorn or savanna, where babblers travel in small family parties. They are usually singing and leap-frogging with each other as moving swiftly from one bush to another and so, making the whole party exhibits to be “rolling” across the plain. A lot of Asian babbler pairs in fact mate for whole life and are completely resident, meaning that they spend entire lives within merely a few acres of scrub.

Habitat partitioning mechanisms of certain blabbers have been studied. For example, Black-lored Babblers (Turdoides sharpie) live in open areas with sparingly dispersed small trees and short ground vegetation cover, while Arrow-marked Babblers (Turdoides jardineii) can only be found in shorelines with dense trees and ground vegetation cover (Gole 2002).

Inhabiting hot, dry deserts, Arabian Babblers have its own physiological strategies for the habitat of extreme deserts. The lower critical temperature and conductance of Arabian Babblers are both relatively high, indicating a better adaptation to hot habitats due to the better capability of heat loss (Anava et al. 2001 c). Nevertheless, other changes including plumage, circulatory and activity modification must occur in order to drive away more heat and lessen the production of heat under the situation of increasing air temperature, which are still unclear.

White-browed Babblers (Pomatostomus superciliosus) performs territorial behaviors including calling displays and chases, resulting in the group division. These two territorial behaviors occur solely in the breeding season. The absence of territorial behaviors during the non-breeding season would be linked to limitation of food supplies during the summers (Gale 2002). Structured population of many babblers make up of various levels of organization, including groups, social neighbourhoods, local population neighbourhood and metapopulations. However, these structural units generally do not have discrete boundaries; the structure of their occupied landscape turns out to be the determining factor affecting these indiscrete boundaries (Cale 2003).

For those species living in hot, dry environmental conditions and with unpredictable food supplies such as Arabian Babblers in deserts, two physiological variables, field metabolic rate (FMR) and water influx rate (WIR) are considerably responsive to environmental fluctuations and hence are useful for examining its adaptations to extreme environments (Anaval et al. 2000).

4 Diet and Foraging Behavior
4.1 Diet of Babblers
Fruit, insects (or other small animals without backbones) and some seed are the general diet of babblers. Many of the insect species eaten by babblers are pests consuming common crops or stored grains (Dhindsa et al. 1995). Arabian Babblers, inhabiting extreme deserts of Israel, consume invertebrates and fruits (Anaval et al. 2000); the availability of invertebrates and fruit there is fine throughout the year, and their amounts depend on rainfall which is virtually highly unpredictable as mentioned. To sustain their life, babblers have to spend most of their time on the ground to seek food; they are bounding along, researching through leaf litter, probing into soil and turning over such small objects as cowpats, stones or sticks; on the ground they knock over large objects by inserting their bills beneath them and pushing forward and upward. Most babblers are arboreal but some are terrestrial in their foraging behavior (Stuart and Stuart1999).

4.2 Foraging efficiency
Ecologists frequently make used of food-supplementation experiments to investigate the influence of food availability on timing of other activities such as breeding (Boutin 1990). It is suggested that supplemented food contributes to the alleviation of energetic constraints on reproduction (Perrins 1970), consequently boosting laying by supplying energy for reproduction which is unavailable from local resources. There are generally three sources of energy supply of birds for reproduction: increase energy intake, reduce energy spent on other activities, or use somatic stores (Walsberg 1983). Furthermore, the great amount of supplemental food, the great sentinel effort of babblers (Wright et al. 2001). Since supplemented babblers forage more efficiently than the others, they can shift time from foraging to vigilance with approximately the same food consumption rates. Despite the point that the energy of provided food may not be equivalent of that of natural one, this can reduce their risk of predation (Arthur et al. 2003), suggesting that resource predictability may be an indication for the appropriate timing of breeding.

FMR and WIR of babblers are generally lower than other bird species, but, in particular Arabian Babblers, are more or less the same as those of other desert birds. The higher water content of the dietary intake contributes to the higher WIR in winter than in summer. Moreover, babblers consume a relatively energy-rich diet in summer and water-rich diet in winter (Anava et al. 2000)

4.3 Food Division
One of the crucial aspects of parental care is nestling provisioning in most studied avian species, babblers included. It is apparent that food division is negatively correlated with the order of hatching, and many last-hatched nestlings can be found dead in nests due to starvation (Ostreiher 1997). The phenomenon of feeding preference can hardly be observed between an adult and a particular nestling. The reason is that food division is chiefly determined by the severe competition among nestlings, rather than by the preference of parents. The parents, and not to say helpers, will never interfere with their nestlings to spoil the competition, nor do they prevent siblicide. Ostreiher (1997) found that feeders of Arabian Babblers feed randomly the nestling, particularly which most effectively draws their attention at the right time. As a result, the factor determining food division among the nestlings is probably the consequence of nestling competition. Nestling competition is in turn significantly relying on the feeding-space strategy. Two feeding spaces around nestlings are defined and they defend them by means of pushes against one another if necessary (Ostreiher 1999). Siblings in nests are able to obtain similar amounts of food within exclusive feeding spaces which are equal in size, while within shared feeding spaces, on the contrary, feeding rates increase with feeding-space size and decrease with hatching order. Preventing nest mates from obtaining food from feeders can simply be interpreted as defending a feeding space that moves with the nestlings and is an individual-space defense in babblers.

5 Social Behavior
5.1 General Sociality
Babblers enjoy traveling in troops, squeak, churring and babbling. Social reunions and assembling in flocks when not in breeding characterize most of the babblers. Babblers are so lively that they cluster together on a roost, preening one another and playing the music of babbling songs. In breeding season, the groups of babblers split into pairs and keep watching on their territory. Encountering enemies, they will defend themselves, or pairs may gather together with flock in other groups.

Small babblers like Chestnut-tailed Minla (Minla strigula) can be found in mixed species flocks or isolated pairs inside the forest (Roberson 2001). Numerous babblers are in small family parties perennially and are known as co-operative breeders (see below), while individuals in lots of species may clump or huddle together firmly when roosting and loafing. Populations of babblers have a complex social hierarchy. Primarily, the ranking system is the base regarding both age and sex, under which males tend to take precedence over females, and older birds over younger ones.

5.2 Breeding
The colors of babbler’s two to seven eggs are various; those of the large species are generally unspotted while the smaller ones often lay spotted eggs, one example being Chestnut-backed Jewel Babbler (Ptilorrhoa castanonota) giving eggs with russet blotches (Walters 1994). Incubation done by both sexes or female alone usually starts after the last egg has been laid so as to broods hatch almost synchronously, with for example 6 to 34 hours passing between hatching of the first and last chicks in Arabian Babblers (Ostreiher 1999).

As for the hatching order and nestling location in the nest, it was found that feeders tend to feed closer nestlings more frequently than those further away, and straight ahead instead of sideways. In the open circular nest of babblers like Arabian Babblers, the positions of adult feeders are not predictable and equally distributed around the nest. The nest’s architecture of babblers exerts a great influence in food distribution among the nestlings, and can help reduce inequalities in the sibling’s abilities to obtain food (Ostreiher 2001). In some species like Large Grey Babblers (Turdoides malcolmi), all the adult family members involve in the nest construction (Gupta and Midha 1997)

Reproduction by subordinates is not common but predictable (Lundy et al. 1998). In Arabian babbler, for example, subordinate males who sire young are more likely to be recent dispersers from their groups which they were born or members of newly formed groups that subordinates who do not reproduce.

Normally, group size of babblers is positively correlated with the territory size. Nevertheless, for example in Arrowmarked Babblers (Turdoides jardineii), neither group size nor territory size is related to the number of nestlings raised by a group, and an extra amount of adults in a group may not promote the reproductive output of the breeding pair, at a time when they, however, help in defence and enlargement of their territory saturated habitat (Kemp et al. 1995).

5.3 Cooperative Behavior
While this framework of sociality is as rigid as in other forms of wildlife, in fact, at the same time another system is operating. The social status of individuals is variable and changes over time depending on their own management, even though individuals are of the same sex and age. For instance, some impoverished people refused to apply for public assistance because of shame; similarly, subordinate babblers may refuse to be fed by another even in starvation, since being a recipient of goodness lowers its social status. Instead, subordinate babblers are spending as much time as they could feeding the young so that their status could be raised. Meanwhile, the individual flies away less frequently when a dominant bird is present at the nest. If it does not fly away, the dominant helper will display a non-aggressive motion of social status to ward it off by preening it (Hunt 1999).

Competition for sentinel job opportunity is apparent in cooperative babblers. Certainly the alpha male is the one staying at a top branch as a sentinel. It is interesting to learn that sometimes it will leaves his position and be substituted by a less dominant one, but he will then address to and relieve the substitute of his duties by feeding him when he wants the position back. All in all, babblers are generally unfriendly to those who reciprocate, and they are likely to make benefits from doing giving by itself rather than receiving. It is easy to realize the mechanism of altruism in terms of natural section since such kinds of activities lead to direct benefit. Even though some example of altruism with reciprocity in some vertebrates, it seems no longer to be a controversial conclusion that so-called altruism in babblers is merely a simple selfish action (Zalavi 2000).

5.3.1 Cooperative Breeding, Parents & Helpers
During cooperative breeding, helpers are providing parental care for the young which are not theirs. Cares are provided usually in terms of food, but other forms of care are also common like nest construction, territorial defense, incubation and defense from predators. For example, in Large Grey Babblers, all the adult family members take part in nest construction, incubation and feeding the young (Cupta and Midha 1997).

In cooperative babblers, a group territory is defended by both a dominant pair and their offspring from previous years, some of which might also help raise the current young. The young thus gain living space for up to some years, and yet help with territory defence and chick care. This form of system can be observed in some resident species, probably occupying their habitats to saturation, without space for a separate non-breeding sector. The Arabian Babbler is a well-studied example (Newton 1998). The parents gain in fitness by allowing offspring to stay with them until they are capable of acquiring own territories. With the help received from helpers, therefore, the parents are able to raise more young than they could be independently; it may not be advisable to for the young to instantaneously disperse into a habitat which is already saturated with other territory-owners, so these young are then supposed to live better by staying with their parents until an optimal time to leave (Newton 1998). The system of assistance provided by helpers is best developed in babblers of the genus Turdoides (Stuart and Sturat 1999).

Non-breeding helpers raise young produced by dominant breeding ones. While kin selection (by which individuals make indirect benefits to fitness by aiding collateral relatives) chiefly contributes to the evolution of cooperative breeding, more and more evidence reveals that there might be no close relation between the helpers and the young (Clutton 2002). It is suggested there may have been overestimations in the indirect benefits of cooperative behavior, whilst the direct benefits of helping to the help’s fitness have been underestimated in all probability. The mechanism of evolution keeping breeding cooperative are likely to be diverse; in some species such as Arabian Babblers the direct benefits of helping is sufficient to maintain cooperative societies in the view of evolution.

The trade-off between fitness returns from current versus future reproduction could determine the optimal degree of parental investment (Trivers 1972). Moreover, when care is provided by two parents, optimal degree of investment also depends upon collaborator work rates. Individual compensatory adjustments in nestling-feeding effort of both parents and helpers are according to the work rates of collaborator (Wright and Dingemanse 1999). Individual babblers are expected to make the most of their fitness by making their chick-feeding effort only on broods which contain closely related nestlings. But Wright (1999) concluded from the three measures of relatedness, i.e. DNA fingerprint, group histories and observed information on relatedness in Arabian babblers, that individual birds have surprisingly no access to sufficient information regarding the variation existing in their own genetic relatedness to the brood, while it may make efforton relatives by simply feeding any nestlings that exist in the territory of theirs.

Helpers would compete with one another for feeding nestlings and young fledglings by stealing each other’s food and taking it to the young, so as to raise their social status as discussed. Helping-at-the-nest produces a positive and linear effect on breeding success in babblers, and the provisioning effort needed of other group members can be largely reduced (Wright 1998). Although quite some species are practicing community breeding, most of their breeding habits and rituals are still unclear.

5.3.2 Mobbing
For a prey, the normal reaction when it encounters a predator is to run away straight or hide itself, but when the unlucky prey has no other choices, it tends to retort. In babblers, likes some other species of birds and fishes, the prey group groups together and approach the predator, in which mobbing is a noisy form of behavior where birds approach and chase away predators if possible. However, the costs of approaching a predator are never insignificant, some examples being death, time investment, wastage of energy, advantage for others who do not accompany, etc. It is therefore surprising why babblers mob at all. There must be benefit in mobbing, and otherwise babblers adopting this behavior would have failed to pass on the ability to their offspring. The mobbing allows babblers to remove the advantage of surprise on which many predators depend to make a kill, and to facilitate the acquirement of information about the nature of the threat (an assessing behavior), and it turns out to be less dangerous when the number of group member increases (Arnon et al.1998)

Additionally, mobbing has its social function (Dreher 2002). It was recently proved in Arabian Babblers that a much more absorbing benefit of mobbing is self-advertisement (Maklakov 2002). Research shows that in babblers where both parents look after the offsprings, the males tend to take more risk in mobbing. Virtually approaching the predator more vigorously contributes to the image of its strength and ability to chase away predator, attracting females for further broods, while mobbing in the absence of an audience or additional participants reveals that this is basically a selfish behavior (Ostreher 2003).

One of the major differences between babblers and other passerines in terms of mobbing is that babblers live in relatively stable groups of familiar and mostly related individuals (Hultsch et al. 1999). Individual who is far away may attain information from the signal of calling about the type of threat facing, and as a result they are able to assess the situation before they try to approach or decide not to approach. In addition, each specific call may increase the future vigilance of group members with regard to particular types of predators.

5.4 Communication
Babblers, just like most of other birds, produce sounds to communicate with one another. In order to deal with communication sounds of babblers, the traditional measure is to consider every type of vocalization in the babbler repertoire as a kind of signal. There is moreover a strong linkage between communication and mobbing mentioned.

5.4.1 Alarm calling & predator discrimination
Many babblers have their own specific call types responsing to predators. Mobbing also involves different call types and in turn provide information on various predator-induced situations in the group, for one, in Arabian Babblers short metallic-sounding “tzwick” implies a higher risk or urgency than long trills, and different combinations of both call types probably provide grade (Hultsch et al. 1999). Moreover, babblers may have some distinct classes of alarm call in response to potential predators. For example, Arabian Babblers use three distinct types of alarm call, namely “Pshews”, “tsits” and “trills”. Pshews are referred to flying avain predators as well as escape behavior, while tsits implies terrestrial predators and approach-mobbing heavier, and trills are linked with perched avian predators and monitoring behavior (Regosin 2002). But it is found that sometimes the babbler alarms do not have any stimulus specificity of externally referential signals.

One of the vocal expressions is called the ‘shout’. As mentioned, some babblers are a social bird and live in groups to defend territories against other groups. The vocal repertoire of some babblers involves some twenty various vocal expressions, in which the shout is the most widespread one (Katsir 1995). In many situations like fighting, shouts are being emitted by those in the position of sentinel from the nest, resulting in a chain of ‘syllables’ with pause in between. Never are the chains the same in terms of numbers, curves of frequency, duration and intensity of each syllable over time, not even for the same single individual. As a result, every single performance of shout is interpreted as a variation and there is a connection between the acoustical-musical structure of the variation and babblers’ behavior, suggesting that the existence of such variations in babbler shout may be critically important for communication.

5.5 Sentinel behavior
Sentinel behavior appear in many forms of wildlife, including babblers. It was found that such a kind of so-called “cooperative” behavior turns out to be simply the result of individually selfish anti-predator strategies (Wright 1997; Khazin et al. 2001; Mathew and Zacharias 1998). Despite the selfish anti-predator strategies, there is little solid evidence that individuals compete for the opportunity to engage in sentinel in order to advertise their status and gain social prestige. In many babblers, the sentinel activity of simple family groups is generally the same; there are no differences in rates of alarm calling between group members, while more territorial calls are made by dominant males to neighbouring groups during sentinel. Besides, individual state has proven to be the determining factor of the effort of sentinel within groups, with no evidence for competitive sentinel behavior between males (Wright 2001).

5.6 Interesting Behavior
When calling and displaying, many babblers spread and depress the tail feathers and expose the rump with fanned wings held downwards and quivering. Some babblers also display certain forms of unusual and interesting behaviors.

The Arabian Babblers exhibit the “morning-dance” on the ground beside a bush. The dancers, who may include the whole group of adults and immature birds, stand alternately in a row and gather into a tight ball, whilst individuals tend to force themselves repeatedly into middle of the row or the center of the clump. They sometimes keep playing for half an hour. The frequency of morning-dance moreover is affected by the presence and behavior of observers (Osztreiher 1995). When they discover water, these babblers drink and bathe, and then engage in a “water dance” which is different from morning play; it is apparently not a performance which helps dry their plumage, since bunching together will slow down evaporation, and even those who have not bathed may join in the “water dance” after some bathers have started it (Skutch 1996).

Alloreening characterizes the Whiteheaded Babblers. The merits of this unique behavior among babblers are to help make themselves less aggressive and promote mutual relationship between individuals and therefore group integration (Mathew and Zacharias).

Jungle Babblers (Turdoides striatus) are often called “the Seven Sisters” because they are usually observed in groups of seven, of course not always, but there is certainly a strong tendency toward the number seven (Corliss 1998). Jungle Babblers, furthermore, perform two forms of vigorous play. One is “rough and tumble”, which was a tussle between two or more babblers. Some of them will lay passively on the ground, while others roll on top of them and peck them intentionally and yet softly. Most of the participants are younger than one year old. The second play is “mad flights” in which one or several fly rapidly without definable purposes obviously. They twist and turn wildly among the branches of a tree. Other babblers like the Large Gray Babblers (Turdoides malcolmi) and Arabian Babblers play similar vigorous games (Skutch 1996).

The Whiteheaded Babblers perform allopreening to help reduce aggression and promote group integration. Allopreening, clumping and sentinel system, together with the large repertoire of vocalizations are likely to facilitate consolidation of the group and coordination of movement of babblers (Mathew and Zacharias 1998).

6 Threat
According to BirdLife International (2005), 6 out of 257 species of all babblers have been categorized as “endangered”, without any recorded extinction so far. The 6 species are Rufous-breasted Laughingthrush (Garrulax cachinnans), Collared laughingthrush (Garrulax yersini), Negros Striped-babbler (Stachyris nigrorum), Flame-templed Babbler (Dasycrotapha speciosa), White-throated Mountain-babbler (Kupeornis giberti) and Grey-crowned Crocias (Crocias langbianis). In fact, there have been a few studies on some others babblers considerably concerned locally and globally.

Hinde’s Babblers (Turdoides hindei) is a scarce, globally and species under threat, which is also endemic to central Kenya, and in fertile, moist land largely cleared for agriculture, but retaining some thicket cover. The Hindle’s Babblers in both situations normally stay near streams and rivers. But they are now facing the problems of widespread clearance of thicket resulting from skyrocketing human population and therefore the increasing demand for agricultural land. Worse still, remaining thickets are become more and more isolated. It is suggested this turns out to be a great impact on Hinde’s Babblers because they are not flexible in the habitat choice. For example, the high dependence of Hinde’s Babbler on Lantana thickets means it is strongly susceptible to further habitat loss (Njorge et al. 1998). Hinde’s Babblers are now classified as globally vulnerable. But merely 8% of the known population are found inside legally protected areas at this moment and the global population is suggested to be as low as 1,500 individuals (Shaw et al. 2003).

The problem of habitats fragmentation has been concerned as a threat on babblers. The behavior of White-browed Babbler groups produces a significant influence on the dynamics of local populations, and probably affects the persistence of the local population within fragmented landscapes. Group dynamics is essential to persist its local populations, particularly in landscapes facing habitat loss and fragmentation. In Australia the tendency to give general prescriptive management guidelines derived from comparative babbler assemblage studies is not capable to recognize the spatially explicit nature of population dynamics as well as the role that species’ specific behaviors on those dynamics. It is therefore crucial to determine the unique characteristics of the landscapes and the species being concerned so as to generate prescriptive management guidelines (Cale 2003).

7 Babblers in HK
14 species of true babblers, including both laughingthrushesand and Yuhina, has so far been recorded in Hong Kong: Streak-breasted Scimitar Babbler (Pomatorhinus ruficollis), Rufocus-capped Babbler (Stachyris ruficeps), Chinese Babax (Babax lanceolatus), Greater Necklaced Laughingthrush (Garrulax pectoralis), Black-throated Laughingthrush (Garrulax chinensis), White-browed Laughingthrush (Garrulax sannio), Red-billed Leiothrix (Leiothrix lutea), Vinous-throated Parrotbill (Paradoxornis webbianus), Masked Laughingthrush (Garrulax perspicillatus), Hwamei (Garrulax canorus), Siver-eared Mesia (Leothrix argentauris), Blue-winged Minla (Minla cyanouroptera), White-bellied Yuhina (Yuhina zantholeuca), Striated Yuhina (Yuhina castaniceps) (HKBWS 2005), among which the first 8 species are, or have been, listed in the category defined as “Southeast China breeding species, the established or formerly established Hong Kong population of which is considered to be derived from captive stock, but which probably occurred in Hong Kong prior to anthropogenic habitat changes” (Carey et al. 2001).

All of the babblers found in Hong Kong are resident, with a sole exception of Striated Yuhina, being an irruptive winter visitor, although there are a small number of escaped or released birds obverted. All breeds mainly or fully within the Oriental region, but none of them are endemic to Hong Kong. 10 out of the 14 babblers are considered to have been established in Hong Kong by means of human agency as a kind of invasion since 1860 (Corlett and Leven 2004). The reason for their invasion was probably due to being released from cages. Babblers are noted for its noisiness and their owners might have been tired of their noisy pets and therefore gave them up by release. Nowadays, those who have already well-established include Streak-breasted Scimitar-babbler, Rufous-capped Babblers, Greater Necklaced and Black-throated Laughingthrushes, with a rapidly expanding population in both forest and shrubland (Carey et al. 2001). Hwamei, which somewhat characterize the shrubland in Hong Kong, seems to be the most well-known common name of babblers to Guangdong people, in particular senior bird owners.

8 Conclusion
Babblers are a family comprising species with both diverse morphology and ecology. In spite of this, the babbling and sociality, especially cooperative behavior, characterize this family of bird. It is apparent that the core of the sociality of babblers is their cooperative behaviors, involving cooperative breeding, mobbing and sentinel, all of which are highly associated with the communication between members, under the principle of fitness (or selfishness) as a basic. The amount of investigations and studies about babblers seems reasonable but terribly scattered, probably due to their variability between genera. One of the main problems is that the taxonomy and systematics of babblers has long been in chaos, acting as a kind of burden hindering the understanding of this bird. In general, whilst the threat on babblers is not very high, some more appropriate measures ought to be stepped up in order to deal with the problems local. In fact, the first step, or the step kept path with, is to promote a more rapid research on the babblers relatively concerned such as Hinde’s Babblers. In Hong Kong, babblers are mainly invasive birds and their local ecological values are unclear or just not significant.

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