It’s time to wind things down for Christmas, so what better way to do it than to write a short article about robins. And here I mean the ‘original’ or ‘proper’ robin – the European robin Erithacus rubecula – a Eurasian passerine that also occurs in northern Africa and is (conventionally) regarded as the only member of its genus (but more on that below). Erithacus is about 12-14 cm long, has a wingspan of approximately 20-23 cm, and lacks obvious sexual dimorphism. Erithacus is famous for its red or orange breast; this large area of bright colour extends onto the face and is often fringed with grey. The upperparts are a sort of olive-brown. Fledglings are initially spotty and go through a transitional period of about eight weeks during the autumn as they grow their adult plumage.
Erithacus is conventionally a bird of deciduous woodland but it also occurs in heathland and wooded fenland in places. Its style of foraging and territory defence means that it prefers a sort of woodland mosaic where big, mature trees occur close to large glades and areas of dense, continuous undergrowth (Simms 1971, Mead 1984). This particular set of conditions is not especially common, perhaps meaning that, historically, Erithacus was always widespread but never abundant. It has been suggested that anthropogenic changes made to landscapes across Europe – the creation of open fields surrounded by hedgerows and the thinning out of large trees – have been to the robin’s advantage and that it has increased substantially in numbers over the past few thousand years (Mead 1984).
The maintenance of shrubs, hedges and tidy gardens around and close to houses and other dwellings has also encouraged robins to move ever closer to humans. Mead (1984) quoted John Ray’s writings of 1678 wherein Ray said that robins only become bold, sociable and “familiar with man” in the winter-time and that they are scarce and not seen during the summer. Turner said the same sort of thing in 1544. The view of robins as birds associated with snowy, festive scenes – and hence with Christmas cards – emerged from here. Here we again come back to that ‘view from the peripheries’ thing, since this has most often been mentioned as a British phenomenon, the view of the ‘winter-time robin’ being “a special part of [British] heritage which has evolved hand-in-hand with our distinctive traditional landscape” (Mead 1984, p. 20). I’m sure this is true, but it’s parochial and I’m sure people in Germany, France, Slovenia, Iran or whatever have their own take on robins too.
By the way – there’s an interesting contradiction here. Writers of the 1500s and 1600s said that robins weren’t ordinarily seen except during the winter-time. Yet the frequency with while robins approach people during all times of the year (they routinely approach people who are eating outside, or are digging or breaking up soil) is often stated to reflect a long history of co-occurrence between Erithacus and agricultural humans. Presumably, this developed from an even older habit whereby Erithacus associated with wild boar and other large mammals that engage in ‘ecosystem engineering’ projects. So – what gives? I’m not sure, but my hunch is that Erithacus has, indeed, been associating with soil-turning humans for as long as humans have been turning soil. Maybe the behaviour has become much more prevalent over time, and maybe it also went unreported in the time of writers like Turner and Ray.
How many taxa in Erithacus? Maybe there are lots
As noted above, E. rubecula is normally thought to be the only species within Erithacus. Like so many widespread passerine species, however, it’s variable enough across its range that people have named various ‘subspecies’ for those populations that vary in size and appearance (Lack 1946).
Even just within Europe, robins that live in the far west are darker and with more vividly coloured breast patches than those that occur in the middle of the continent: E. r. melophilus is supposed to occur across western Europe (including the UK) while the nominate form (E. r. rubecula) is present across Scandinavia. North African birds are distinctly smaller than European ones (hence warranting distinction as E. r. witherbyi; this also inhabits southern Spain, Corsica and Sardinia). Siberian birds are especially pale (and hence demarcated as E. r. tataricus) while there are also meant to be endemic subspecies in the Transcaucasian region (E. r. hyrcanus) and the Crimean Peninsula (E. r. valens).
Then there are the robins on Madeira and the Azores (named E. r. microrhynchos), Tenerife (E. r. superbus) and Gran Canaria (E. r. marionae) [image of Gran Canaria robins above by Juan Emilio]. The robins of the Canary Islands are said to have whiter eye-rings and whiter bellies than other robins and hence to be distinct morphologically (I'm not really sure I see this myself, to be honest). Genetics indicates that the robins of Gran Canaria have been separated from mainland birds for more than 2 million years (they apparently have far shorter wings than those of other robins) while those of Tenerife have been distinct for 1.8 million years (Dietzen et al. 2003). The data suggesting several separate invasions of the Macaronesian islands looks pretty good, and it also seems that the populations concerned have been distinct for a long time (note that they’re older than a great many other populations universally regarded as ‘species’)... the issue is how we interpret this taxonomically. Some experts argue that the Tenerife and Gran Canaria birds warrant recognition as distinct species (E. superbus and E. marionae, respectively), or that they should be grouped together as one species (perhaps with two subspecies) (Bergmann & Schottler 2001, Dietzen et al. 2003). Whatever, robin colonisation of the Macaronesian islands was seemingly complex and the populations concerned have evolved various of their own peculiarities.
Far eastern Erithacus robins, or not...
Moving on, there are also two Asian passerines that have been included in Erithacus at times: the Japanese robin E. akahige [photo above by Alnus] and Ryukyu robin E. komadori [photo above by Daderot]. Both have, more conventionally, usually been placed within Luscinia – the group that includes nightingales, bluethroats, rubythroats and so on – and they do resemble certain Luscinia species in coloration and tail shape more than they resemble E. rubecula (Seki 2006). The suspicion among specialists is that both will either be returned to Luscinia at some stage, or that a new clade will be named for these robin-like species and one or two other former Luscinia members. And, sure enough, one of the most recent studies (produced by authors who have previously advocated inclusion of the Japanese and Ryukyu robins as members of Erithacus) puts them back into Luscinia (Seki et al. 2012).
As anyone who knows birds will be very much aware, the word ‘robin’ has been taken worldwide and applied to diverse passerines. Most (but not all) are reminiscent of Erithacus in having a reddish breast; others have pink, orange or yellow chest markings. Virtually all are only distantly related to Erithacus and actually belong to far-flung members of the passerine tree. No time to talk about them today, sorry. Oh: E. rubecula itself has been transported to distant places (like New Zealand, Australia and Canada) by misguided and homesick Europeans.
I initially started this article because there’s one thing about Erithacus that I wanted to address in particular: where it fits within the passerine tree. And, of course, this is a good time to be talking about bird phylogeny in any case, since a huge number of technical studies have recently appeared on the bird family tree. We really can say that we now have something of a consensus. Alas, that has to be something I’ll cover at another time.
And the whole the point of writing about robins in the first place is that they are vaguely Christmassy. On that note – best wishes for the season, here’s the festive Tet Zoo Christmas card! (the previous article might be required reading). Thanks again to everyone who's been supporting me at patreon, and remember to keep an eye as well on the Tet Zoo wiki and the podcats.
For previous articles in the 'passerines from the peripheries' series, see...
- Chiffchaffs: a view of passerines from the peripheries (part I)
- Blue tits: passerines seen from the peripheries (part II)
- More passerines as seen from the peripheries (part III): Great tits!
Refs - -
Bergmann, H. H. & Schottler, B. 2001. Tenerife robin Erithacus (rubecula) superbus – a species of its own? Dutch Birding 23, 140-146.
Dietzen, C., Witt, H.-H. & Wink, M. 2003. The phylogeographic differentiation of the robin Erithacus rubecula on the Canary Islands revealed by mitochondrial DNA sequence data and morphometrics: evidence for a new robin taxon on Gran Canaria? Avian Science 3, 115-131
Lack, D. 1946. The taxonomy of the Robin, Erithacus rubecula (Linnaeus). Bulletin of the British Ornithologists' Club 66, 55-64.
Mead, C. 1984. Robins. Whittet Books, London.
Seki, S.-I. 2006. The origin of the East Asian Erithacus robin, Erithacus komadori, inferred from cytochrome b sequence data. Molecular Phylogenetics and Evolution 39, 899-905.
Seki, S.-I., Nishiumi, I. & Saitoh, T. 2012. Distribution of two distinctive mitochondrial DNA lineages of the Japanese robin Luscinia akahige across its breeding range around the Japanese Islands. Zoological Science 29, 681-689.
Simms, E. 1971. Woodland Birds. Collins, London.