Parrotbill

For other uses, see Parrotbill (disambiguation).
Parrotbills
White-breasted parrotbill
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Suborder: Passeri
Family: Sylviidae

The parrotbills are a group of peculiar birds native to East and Southeast Asia, though feral populations exist elsewhere. They are generally small, long-tailed birds which inhabit reedbeds and similar habitat. They feed mainly on seeds, e.g. of grasses, to which their bill, as the name implies, is well-adapted. Living in tropical to southern temperate climates, they are usually non-migratory.

The bearded reedling or "bearded tit", an Eurasian species long placed here, is more insectivorous by comparison, especially in summer. It also strikingly differs in morphology, and was time and again placed in a monotypic family Panuridae. DNA sequence data supports this.

As names like "bearded tit" imply, their general habitus and acrobatic habits resemble birds like the long-tailed tits. Together with these and others they were at some time placed in the titmouse family Paridae. Later studies found no justification to presume a close relationship between all these birds, and consequently the parrotbills and bearded reedling were removed from the tits and chickadees and placed into a distinct family, Paradoxornithidae. As names like Paradoxornis paradoxus - "puzzling, paradox bird" - suggest, their true relationships were very unclear, although by the latter 20th century they were generally seen as close to Timaliidae ("Old World babblers") and Sylviidae ("Old World warblers").

Since 1990 (Sibley & Ahlquist 1990),[1] molecular data has been added to aid the efforts of discovering the parrotbills' true relationships. As Paradoxornis species are generally elusive and in many cases little-known birds, usually specimens of the bearded reedling which are far more easy to procure were used for the analyses. Often, the entire group was entirely left out of analyses, being small and seemingly insignificant in the large pattern of bird evolution (e.g. Barker et al. 2002, 2004). The bearded reedling tended to appear close to larks in phylogenies based on e.g. DNA-DNA hybridization (Sibley & Ahlquist 1990), or on mtDNA cytochrome b and nDNA c-myc exon 3, RAG-1 and myoglobin intron 2 sequence data (Ericson & Johansson 2003). Placement in a superfamily Sylvioidea which contained birds such as Sylviidae, Timaliidae and long-tailed tits - but not Paridae - was confirmed.

Cibois (2003a) analyzed mtDNA cytochrome b and 12S/16S rRNA sequences of some Sylvioidea, among them several species of Paradoxornis but not the bearded reedling. These formed a robust clade closer to the Sylvia typical warblers and some presumed "Old World babblers" such as Chrysomma sinense than to other birds. The puzzle was finally resolved by Alström et al. (2006), who studied mtDNA cytochrome b and nDNA myoglobin intron 2 sequences of a wider range of Sylvioidea: The bearded reedling was not a parrotbill at all, but forms a distinct lineage on its own, the relationships of which are not entirely resolved at present. The parrotbills' presence in the clade containing Sylvia, on the other hand, necessitates that the Paradoxornithidae are placed in synonymy of the Sylviidae. Cibois (2003b) even suggested that these themselves were to be merged with the remaining Timaliidae and the latter name to be adopted. This has hitherto not been followed and researchers remain equivocal as many taxa in Sylviidae and Timaliidae remain to be tested for their relationships. In any case, it is most likely that the typical warbler-parrotbill group is monophyletic and therefore agrees with the modern requirements for a taxon. Hence, whether to keep or to synonymize it is entirely a matter of philosophy, as the scientific facts would agree with either approach.

The interesting conclusion from an evolutionary point of view is that the morphologically both internally homogenous and compared to each other highly dissimilar typical warblers and parrotbills form the two extremes in the divergent evolution of the Sylviidae. This is underscored by looking at the closest living relatives of the parrotbills in the rearranged Sylviidae: The genus Chrysomma are non-specialized species altogether intermediate in habitus, habitat and habits between the typical warblers and the parrotbills. Presumably, the ancestral sylviids looked much like these birds. How dramatic the evolutionary changes wrought upon the parrotbills in their adaptation to feeding on grass caryopses and similar seeds were can be seen by comparing them with the typical fulvettas, which were formerly considered Timaliidae and united with the alcippes (Pasquet 2006). These look somewhat like drab fairy-wrens and have none of the parrotbills' adaptations to food and habitat. Yet it appears that the typical fulvettas' and parrotbills' common ancestor evolved into at least two parrotbill lineages independently (Cibois 2003a) & (Yeung et al. 2006). Only the wrentit, the only American sylviid, resembles the parrotbills much in habitus, though not in color pattern, and of course, as an insectivore, neither in bill shape.

Species of parrotbills

Paradoxornis is apparently paraphyletic with Conostoma. Deep divergences were found between major clades; basally Conostoma with a clade of large species followed by two clades of smaller species which differ markedly in plumage pattern. This with egg coloration data (Walters 2006) lends considerable support for splitting it up into at least three genera and possibly up to eight. (see )

Clade of large species

Genus Conostoma

Genus Cholornis

Genus Paradoxornis

Eggs white with various amounts of brown sprinkling or speckling. More basal lineage, possibly close to golden-breasted fulvetta (Lioparus chrysotis) and/or white-browed Chinese warbler (Rhopophilus pekinensis).

Genus Psittiparus

Eggs pale cream or bluish with more intense pattern

Clade of small brownish species

Small unmarked eggs, mid-blue or paler. Possibly close to any or all of fulvetta (typical fulvettas), Chrysomma, or wrentit

Genus Chleuasicus

Genus Sinosuthora

Clade of small yellowish species

Small unmarked eggs, mid-blue or paler. Possibly close to any or all of Fulvetta (typical fulvettas), Chrysomma, or wrentit

Genus Suthora

Genus Neosuthora

Paradoxornithinae?

Conceivably, the parrotbills and their closest relatives might be considered a distinct subfamily Paradoxornithinae; they appear to form a fairly well-supported clade though the position in regard to basal Sylviidae is unclear (Cibois 2003a, Jønsson & Fjeldså 2006).

References

  1. ↑ Ricklefs, Robert E. "Small clades at the periphery of passerine morphological space." The American Naturalist 165.6 (2005): 651-659.
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