The blue rock thrush (Monticola solitarius) is a species of chat. This thrush-like Old World flycatcher was formerly placed in the familyTurdidae. It breeds in southern Europe, northwest Africa, and from Central Asia to northern China and Malaysia. The blue rock thrush is the official national bird of Malta.
The rock thrush genus Monticola was formerly placed in the family Turdidae[5] but molecular phylogenetic studies have shown that the species in the genus are more closely related to members of the Old World flycatcher family Muscicapidae.[6]
There is a proposal to split Monticola solitarius into two species. The ground work for this was two papers published in 2004 and 2007. The 2004 paper by Voelker and Spellman laid the groundwork at the genus and family level, Muscicapidae.[9] The 2007 paper by Outlaw and Voelker refined monophyly and phylogeny.[10] The first formal proposal for the split was in 2010 by Zuccon and Ericson, which proposed a western taxon comprising M. s. solitarius and M. s. longirostris and an eastern taxon with M. s. philippensis, M. s. pandoo and M. s. madoci Zuccon and Ericson proposed the two species names be M. solitarius s.s. and M. philippensis.[11] As of early 2026 there is still no agreement on the split, a major reason being that the five subspecies can interbreed.[12][13]
Male blue rock thrush of subspecies M. s. philippensis showing rufous underbelly
Description
The blue rock thrush is a starling-sized bird, 21–23cm (8.3–9.1in) in length with a long slim bill. The breeding male of the nominate subspecies is unmistakable, with all blue-grey plumage apart from its darker wings.[5] Females and immatures are much less striking, with dark brown upperparts, and paler brown scaly underparts. The male of the subspecies M. s. philippensis has rufous-chestnut plumage from the mid-breast down to the undertail.[5] Both sexes lack the reddish outer tail feathers of rock thrush.
The male blue rock thrush sings a clear, melodious call that is similar to, but louder than, the call of the rock thrush.[14][15]
The Europe and Asia groups both have a "short song and a long song, consisting of similar melodious whistles, trills and more burry notes."[15] Generally, the vocalizations are similar in both groups. Basic sound traits generally overlap, such as phrase duration, note length, and min./max. frequency. Several notes are identical. The long song is a bit more common in the Asia group.[5][15] Among populations in Indonesia, there are four basic calls. "The fundamental call frequency appeared to be concentrated around 1.6 kHz, but weak components of the spectrum reached to approximately 4 kHz. The structure of the four call types was quite different: 1) the shape of the spectra differed considerably; 2) the frequency of maximum sound energy was between 1.2 and 1.8 kHz; 3) the duration of the calls varied between 200 and 1500 ms; 4) the-10dB bandwidth was in the range between 900 Hz and 1300 Hz."[14]
Similar species
Monticola is a monophyletic clade as all member species share a common ancestor. M. solitarius are especially similar to:[10]Blue-capped rock thrush (M. cinclorhynchus, distinguished by a bright blue head and chestnut belly),[16]Chestnut-bellied Rock Thrush (M. rufiventris, distinguished by a chestnut belly),[17]Common rock thrush-also known as Rufous-tailed rock thrush (M. saxatilis, distinguished by blue-grey head, white back patch, chestnut belly),[18]Little rock thrush (M. rufocinereus, distinguished by blue-grey upper and orange belly),[19] and White-throated rock thrush (M. gularis, distinguished by blue head, orange belly, and white patch on black wings).[20]
Distribution and habitat
The European, north African and southeast Asian birds are mainly resident, apart from altitudinal movements. Other Asian populations are more migratory, wintering in sub-Saharan Africa, India and southeast Asia. This bird is a very uncommon visitor to northern and western Europe. There is some overlap in breeding and wintering ranges with the common rock thrush (Monticola saxatilis); Palearctic and southwestern Asia for breeding and northern Africa for wintering.[21] It is known to have been spotted in North America twice: once in British Columbia in 1997 and once in Oregon and the Farallon Islands in 2024.[22][23] It is unclear whether the Oregon and Farallon Islands spottings were the same bird.[24] It is highly unlikely that the British Columbia sighting was the same individual bird as the Orgegon/Farallon Islands sighting as the blue rock thrush typically lives 5-10 years in the wild.[25]
Choi, et al., conducted a study of blue rock thrush population on Hongdo Island, South Korea from 2005-2009. The species arrives in spring and disappeared in autumn, indicating that the Hongdo population is migratory rather than resident. Breeding density was estimated at about 8 breeding pairs per km², and individual territories averaged about 2.87 hectares. The species showed a strong preference for rocky cliffs for their homes, especially exposed rock faces. They concluded habitat structure was more important than food availabity.[26]
In the first confirmed case of successful urban nesit by M. solitarius, Rouibi, et al., conducted a study of M. solitarius in El Bouni, Algeria over three breeding seasons from 2016- 2018. They found the species made a nest beneath the roof of a residential building, which is very different from its usual rocky cliffs, escarpments, and coastal outcrops.[27] Pairs have also been found living in urban areas in Malta.[28]
Behaviour
The blue rock thrush breeds in open mountainous areas. It nests in rock cavities and walls, and usually lays 3–5 eggs. An omnivore, the blue rock thrush eats a wide variety of insects and small reptiles in addition to berries and seeds.[5]
In culture
The blue rock thrush is deeply imbedded in Maltese culture (the word for it in Maltese being Merill). It became the national bird in 1971. It was on the Lm 1 coins that were part of the country's former currency.[29] It has also inspired place names, songs, stamps, cartoons, poems and literature, and old expressions about talkativeness. It is also the name of a high income fund and a child care center.[28]
↑Mayr, Ernst; Paynter Jr., Raymond A. (1964). Check-list of Birds of the World. Vol.10. Cambridge, Massachusetts: Museum of Comparative Zoology. p.138.
12345Collar, N.J. (2005). "Family Turdidae (Thrushes)". In del Hoyo, J.; Elliott, A.; Christie, D.A. (eds.). Handbook of the Birds of the World. Vol.10: Cuckoo-shrikes to Thrushes. Barcelona, Spain: Lynx Edicions. pp.514-807 [515]. ISBN978-84-87334-72-6.
↑Sangster, G.; Alström, P.; Forsmark, E.; Olsson, U. (2010). "Multi-locus phylogenetic analysis of Old World chats and flycatchers reveals extensive paraphyly at family, subfamily and genus level (Aves: Muscicapidae)". Molecular Phylogenetics and Evolution. 57 (1): 380–392. Bibcode:2010MolPE..57..380S. doi:10.1016/j.ympev.2010.07.008. PMID20656044.
↑Gill, Frank; Donsker, David, eds. (2016). "Chats, Old World flycatchers". World Bird List Version 6.2. International Ornithologists' Union. Retrieved 20 May 2016.
↑Voelker, Gary; Spellman, Garth M. (February 2004). "Nuclear and mitochondrial DNA evidence of polyphyly in the avian superfamily Muscicapoidea". Molecular Phylogenetics and Evolution. 30 (2): 386–394. doi:10.1016/s1055-7903(03)00191-x. PMID14715230.
12Outlaw, Robert K.; Voelker, Gary; Outlaw, Diana C. (April 2007). "Molecular Systematics and Historical Biogeography of the Rock-Thrushes (Muscicapidae: Monticola)". The Auk. 124 (2): 561–577. doi:10.1093/auk/124.2.561.
↑Outlaw, Robert K.; Voelker, Gary; Outlaw, Diana C. (1 April 2007). "Molecular Systematics and Historical Biogeography of the Rock-Thrushes (Muscicapidae: Monticola)". The Auk. 124 (2): 563. doi:10.1093/auk/124.2.561.
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