Old World Babbler - Systematics

Systematics

The systematics of Old World babblers have long been contended. During much of the 20th century, the family was used as a "wastebin taxon" for numerous hard-to-place Old World songbirds (such as Picathartidae or the Wrentit). Ernst Hartert was only half-joking when he summarized this attitude with the statement that, in the passerines,

"Was man nicht unterbringen kann, sieht man als Timalien an." (What one can't place systematically is considered an Old World babbler)

The most obviously misplaced taxa were removed piecemeal towards the end of the last century.

Since then, with the aid of DNA sequence data, it has been confirmed that even the remaining group is not monophyletic. Analysis of mtDNA cytochrome b and 12S/16S rRNA data (Cibois 2003a) spread the Timaliidae that were studied across what essentially was a badly resolved polytomy with Old World warblers and white-eyes. As the typical warblers (genus Sylvia) grouped with some presumed timaliids (such as the fulvettas), it was suggested that some Sylviidae should be moved to the Timaliidae.

As this would include the type genus of the latter, this would lead to a nomenclatorial problem requiring ICZN intervention (Cibois 2003b) and was, at that time, not sensible in any case as the phylogeny of the remaining Old World warblers had not been fully resolved either. The problem with such an approach would be — as many Old World warblers have not been studied with the new results in mind and neither have a number of timaliids — to risk creating a huge, ill-defined family-level clade; consequently, this approach seems to have been put on hold for the time being in favor of a general resorting of the Sylvioidea.

Alström et al. (2006) supported the taxonomic proposal of Cibois (2003b), "if the Timaliidae and several groups of warblers are recognized at the same family level" but of course it is not necessary to unite them to achieve monophyly in both. Notably, one of the few conclusions beyond genus level which received quite robust support in Cibois (2003a) was the distinctness of Sylvia and the related "babblers" from the Timaliidae sensu stricto. Thus, for the time being, it seems wisest to maintain the Sylviidae and Timaliidae as distinct and just split off or move about genera as needed to achieve monophyly.

The parrotbills are somewhat tit-like birds that in the past were moved about between the timaliids, the tits, and distinct family status (under the telling name Paradoxornithidae — literally, "puzzling birds"). They are likely not a distinct family; rather, they belong into the Sylvia clade (Cibois 2003a, Alström et al. 2006).

The relationships of the white-eyes (presently Zosteropidae) are not resolved at present. Based on nDNA RAG-1 and c-mos sequence data, Barker et al. (2002) found them likelier to group closer to the timaliids proper than to Sylvia and allies, as did Cibois (2003a). Combining data from nDNA c-myc exon 3, RAG-1 and myoglobin intron 2 sequences with that of mtDNA cytochrome b (Ericson & Johansson 2003) supports their scenario as does a restudy using the myoglobin intron 2 and cytochrome b sequences of a wider (though not denser) range of taxa (Alström et al. 2006)

On the other hand, DNA-DNA hybridization (Sibley & Ahlquist 1990) placed the white-eyes closer to Sylvia. This method is nowadays considered inferior to comparison of long and various DNA sequences, however. Still, it should be noted that no molecular study thus far could resolve the white-eyes' relationships with sufficient confidence beyond the mere fact that they form a clade with "core" Sylviidae and "core" Timaliidae. In this assemblage, they most likely form a monophyletic lineage with the yuhinas (and possibly other "babblers"). Consequently, were the Zosteropidae to be retained as a family, these would be moved there.

One somewhat controversial approach in the "Taxonomy in Flux" world birdlist proposes splitting the group into four families.

• Sylviidae - Sylvias, Fulvettas, Parrotbills.
• Zosteropidae - White-eyes, Yuhinas etc.
• Timaliidae - Babblers.
• Garrulacidae - Laughingthrushes, Liocichlas, Sibias etc.

This creates a tidier, more manageable arrangement, much as the creation of several smaller families does for the traditional Emberizidae. It remains to be seen though if the innovative split of Garrulacidae from Timaliidae will gain wider acceptance.

In addition, the new studies have shown that several genera (such as Garrulax and Fulvetta) are not monophyletic and need to be split up (Cibois 2003, Pasquet et al. 2006).