After moving to the British Islands, one of the first things that struck me was the different composition of bird communties and relative abundance of some species that I was not used at all in Iberia. One of those species is the Dunnock or Hedge sparrow, that turns out to be rather common here, even in urban settings (I have them breeding across the street). So, facing something new usually leads me to get in-depth investigation and try to know a lot more about small brown inconspicuous birds, specially when their behaviour and breeding habits markedly differs from their plumage.
So, what’s with the accentors?
Dunnock close-up (Prunella modularis)
Accentors are a small family of brownish-greyish Palearctic passerines, usually classified under the Genus Prunella (some authors use another Genus, Laioscopus, for the two larger species). While almost all the 13 species contained under the family Prunellidae are mountain dwellers, either living above tree-line or montane forests, the dunnock is more generalist, also found in lowland forests and gardens.
All species are ground-dwelling birds that feed mostly on invertebrates during the summer months but turn to seeds and berries during winter. As a whole, this family demonstrates some complex movements, with some populations from the same species, being resident, while others being medium or short distance migrants. Usually, most species display some altitude migration and winter dispersion movements.
Their discrete habits and colours, the remote and inhospitable habitat preferences, as well as generalist living habits probably gave them some protection from human activities; Except for the Yemen accentor (P. fagani), that is classified under a Near Threatened status, the remaining species are considered of Least Concern (Birdlife international 2016).
Alpine accentor wintering in Sintra, Portugal.
Evolution and Phylogeny
Accentors are usually associated with mountains, either on alpine (Laioscopus) or shrubby areas (Prunella). The family is endemic to the Palearctic and seems to have originated in the Himalayas and Central Asia mountains, where the highest number of species still occurs today.
Traditionally, accentors have been classified close to thrushes but it was never clear the precise relationships with other Oscine passerines, being allied with other groups such as wrens, dippers or wagtails. With the advent of molecular tools and DNA analysis, its position on the avian tree started to be elucidated. Sibley and Alquist (1981) found that accentors were closely related to Ploceidae and the two clades nested close to wagtails, sparrows, sunbirds and Fringillidae. Some studies recovered Prunellidae as being part of a group that involves Fringillidae, Estrildidae, Ploceidae and New World buntings and allies but relations among themselves were not elucidated (Ericson 2003). More recent works recover Prunellidae as the sister group to Ploceidae, with the split occurring some 14 million years ago (Drovetski 2013).
Within the family, there is a generalized consensus on the split between P. collaris and P. himalayana (sometimes classified under the Genus Laioscopus) from the rest of the accentors. These two species are distinctively larger, with different plumage and are more associated to alpine or subalpine rocky habitats. The split between large and small body accentors probably took place in the Himalayas region 7.3 million years ago. The two Laioscopus accentors diverged from each another 3 million years ago around the same area.
The small body accentors are usually associated with bush undergrowth either in montane forests or open areas. Around 4.8 million years ago the small accentors started to diversify, also in the Himalayan region. The first clade to split led to P. immaculata and the second, to P. rubeuloides. In the early Pleistocene, there was an important radiation event that coincided with dispersal of accentors from the Himalayas to the western (P. modularis, P. atrogularis, P. fagani and P. ocularis) and eastern Palearctic (P. rubida, P. montanella, P. strophiata, P. fulvescens and P. koslowi) (Drovetski 2013).
More to come!