Warblers
For many people the word “warbler” suggests a dull brownish bird singing a gentle. Trilling song (i.e. 
warbling) from a concealed perch in dense vegetation. Such unobtrusiveness and drabness of plumage are indeed characteristics of many Old World warblers, but: in fact this large subfamily contains numerous distinctive species. No fewer than 25 of the 56 genera contain only one species, although clearly many of these and other members of the subfamily are of doubtful affinity and some may note true warblers at all. The taxonomic confusion surrounding warblers are highlighted by some of the vernacular names; the Oriole babbler, tit-flycatchers and tit-weavers areal currently regarded as warblers.
The great majority of species are neither Eurasia nor African. The New World warblers have nine primary feathers and are not close relatives of the mainly Old World ‘warblers which have ten primary feathers. However, some species of Old World warblers occur in the New World! There are T 3 species ofgnatwrens and gnatcatchers and 2 kinglets. In addition the Arctic warbler has extended its breeding range from Siberia into western Alaska, although even these birds return tithe Old World to winter in southern Asia. Mainland Australia has only 8 resident species, including the distinctive Spinier bird, and New Zealand only one, the fern bird. The archipelagoes of’ the Pacific and Indian Oceans contain a variety of unique warblers. The tiny populations of some of these island endemics make them highly vulnerable to extinction. The Aldabrawarbler, whose population was fewer than birds in 1983, is a good example of this.
Typical warblers are small birds with fine, narrowly pointed hills. Their feet are strong and well-suited for perching. Some (egg Dart-ford warbler) have long tails which counter-balance the body as the birds thread their way through dense foliage, carrying out inspections over and under leaves and twigs in their tireless search for insects.
Warblers’ dependence on insect prey is the main reason why most warblers of high latitudes are strongly migratory. Most north Eurasian warblers winter in Africa or tropical Asia, some performing prodigious journeys. For example, Willow warblers nesting in Siberia travel up to 7 2,000km (7,5oomi) twice a year, to and from sub-Saharan Africa. These long-distance migrants accumulate substantial reserves of fuel, in the form of fat deposits, before their journeys. It is not unusual for them to double their body weight in preparation frothier migration. Those few warblers that remain in cold climates in winter are some-times badly affected by food shortages in harsh weather. Dart ford warblers in Britain, for example, often suffer large population decreases during severe winters.
Warblers are typically monogamous although instances of polygamy are known for a number of’ species (egg Sedge warbler).Voice has recently been shown to the import-ant in some species for mate-attraction and mate-selection, in addition to being a primary means of advertising the positions of territory boundaries. Male Sedge warblers may cease to sing after pairing and individual Reed warblers with elaborate song repertoires tend to succeed in attract-in females sooner than less accomplished singers. Some species (egg Citrine warbler) extend their repertoires by mimicking other bird species, for reasons that are not really understood. The Marsh warbler has gone further: its song consists entirely of imitations of other species. Each Marsh warbler mimics on average so species, over half of them African birds heard in the warbler’s winter quarters. Voice also plays an important part in distinguishing species. For example, chiffchaffs and Willow warblers look almost identical, but have unmistakably distinct songs. Songs are generally delivered from perches, but warblers of low vegetation often use song flights as a means of broadcasting their songs for long distances. Examples of these include scrub warblers, such as the white-throat, and many of the Cist cola grass warblers, such as the Cloud-scraper.
All warblers seem to be competing for the same basic food: insects. In practice there is often a high degree of spatial separation which minimizes competition for food between species and between individuals. Species that occur at high densities, notably the temperate-zone ones, are characteristically territorial. Typically the males defend territories against members of their own species and sometimes also against members of closely related species. For example, blackcaps and Garden warblers defend territories against each other as well as against other members of their own species. In the first case the territories of both species are large and supply most of the food of the nest-ting pairs and their broods. In the latter, however, breeding territories are small and perhaps serve mainly to space out nests to make it less profitable for predators to specialize in searching for them. Territorial behavior is not confined to the breeding season nor is it necessarily always directed at other warblers. For example, blackcaps using bird-tables or taking nectar from particular bush will drive off species of similar or smaller size which try to feed there too.
Some warblers achieve ecological segregation by other means. Vertical separation
sometimes occurs: for example, the Long-billed crumbed forages lower down in the vegetation, where its range overlaps with that of a close relative, the Red-faced crumbed, than it does elsewhere. Sometimes where species co-occur there is dietary specialization. For example, the nestling diets of Reed and Great reed warblers tend to differ where the two species are nesting in the same reed bed. But not where they occur apart from each other. Large warbler species are often found to coexist peacefully with smaller ones. Ecological segregation here may be due to specialization on prey of differrent sizes and to differences in foraging behavior. For example, blackcap and chaff-chaff breeding territories often overlap in Europe since the two species share the same habitat, i.e. deciduous woodland. Blackcaps take fewer tiny insects than do the smaller chiffchaffs and, in addition, blackcaps feed to a large extent on settled insects whereas chiffchaffs often fly catch. Or hover to take insects from the extremities of leaves and twigs where they may be inaccessible to blackcaps.
The logrunners are a group of secretive birds,more often heard than seen. Most species areconsequently rather poorly known—indeedthe wedgebill was recently split into two spe-cies based on calls : the Chirruping wedgebillcalls “tootsie-cheer” and the Chiming wedge-bill “did-you-get-drunk.” The wedge- bills andwhipbirds perform duets, the male easternwhipbird giving a characteristic whiperackto which the female replies “cher, cher.”
The name quail-thrush describes thegenus Cinclosoma well, as they are thrush-like in proportions and plumage yet areground-dwelling and eat seeds and insects.They mostly live in desert or eucalypt or aca-cia woodlands in Australia whereas most ofthe other logrunners occupy the understoryof rainforest in eastern Australia and NewGuinea, where they are chiefly insec-tivorous. Although most species are crypti-cally colored the Blue jewel-babbler male isblue and white. Most are dumpy birds withrather long tails; they have strong feet,which are used for digging. Logrunnersoften dig in areas from which Brush turkeyshave removed the leaf litter for theirmounds.
Logrunners may engage in noisy territorial battles in the breeding season, andperhaps most species are monogamous andterritorial. Nests of dry sticks, bark, rootsand grass are placed in thick foliage or onthe ground, in winter and spring, but occas-ionally in the fall. Though quail-thrushesmostly nest between August and November,the desert species have been recorded breed-ing in all months of the year.
The Western whipbird was at one timeconsidered rare or even endangered, butonce its haunting, ventriloquistic call waslearnt it was discovered in several places insouthern Australia. Several species oflogrunners have been affected by the clearing of forest or the overgrazing of shrublandin Australia, though none is currentlythreatened.
To many people the Australasian warblersare just dull little brown birds. However theyare of great scientific interest because theydisplay a variety of complex breedingbiologies.
The Gerygone warblers are the most wide-spread members of the group occurring in Australia, New Guinea, Indonesia, Malaysia, Burma, New Zealand and manyPacific Islands. They are delicate attractivebirds with tinkling songs that flitter throughthe foliage after tiny insects. Scrub-wrensinhabit the understory of forests in Australiaand New Guinea and thornbills areprincipally Australian, where they forage ina range of sites from the ground to thetreetops.
Most Australasian warblers are small,even tiny, with short tails and wings andfine hills. Although many are dull brown orolive, many thorn bills have contrastingrumps and the Gerygone warblers often havebright yellow underparts. The Rock warbler,which nests in caves in sandstone aroundSydney, NSW, is dark gray above and red-dish brown beneath. In appearance thesexes and ages are similar, often identical.
Insects are the primary food, but thewhitefaces, which live in dry habitats, eata lot of seeds. Where several species ofthombill occur in the same place each usu-ally forages at a different level in thevegetation.
Evidence is slowly emerging thatthornbills, despite their tiny size (7–rog,0.2 5-0.28oz) are long-lived, withto-year-old birds being quite frequent in populationsstudied. Perhaps due to this they often donot breed in their first year. Breeding takesplace from late winter to summer, andalthough some species breed as pairscooperative breeding is more typical of thegroup.
The Buff-tailed thornbill lives in clans ofabout ten birds for most of the year. At thebeginning of the breeding season thesebreak up into pairs, trios and quartets whichattempt to breed. Those that fail in their ownbreeding attempt help a neighboring pair orgroup. until the clan comes together againin the fall. A change in foraging coincideswith the breakup of the clan. Larger groupsfeed more on the ground, pairs more on harkor among foliage.
Australasian warblers frequently join andmay lead feeding flocks of mixed species inthe nonbreeding season, a habit that doesnot help the bird-watcher confronted witha host of species of little brown birds.