Slate-coloured Junco

[Brian S]

Another small passerine to discuss the origins - like the White-crowned Sparrow - with some nice shots in the UK stop press.

Thought I would use the much nicer 'old' term in the header to denote the nominate northern and north-eastern breeding birds, as its much nicer than the generic term Dark-eyed Junco. This, according to my Howard and Moore world checklist, includes 16 (yes, sixteen!) subspecies, though thankfully Sibley chucks them all into groups: Slate-colored, White-winged, the lovely Pink-sided, Oregon, Grey-headed, Red-backed, plus Canadian Rocky Mountains.

Have there been any studies of these? I wonder if they may be re-split any any stage....

Brian S

[Harry Hussey]

One thing that's a bit odd about this species, though not necessarily having any implications for the origin of most, is that, even taking into account the much smaller number of birders here in Ireland, the species is far rarer than it is in the UK, with only three records to date, one of which was way back in 1901, one which was seen by a single non-birder in 2000 and one which was found in a private garden in NI and, probably for good reasons, suppressed back in 2004 (around the same time as I ventured north anyway to see the Greater Yellowlegs at the Quoile Pondage, but I'm honestly not bitter...just a shame that it didn't turn up somewhere less contentious).
Now, we get far fewer American Robins, say, as well, and, like the junco, we've never had a 'twitchable' bird, but at least we have 10 or so previous records of that species, and, for a time in the 70s and early 80s, there seemed to be one every 2-3 years. The massive rarity of Slate-coloured Junco here vis-a-vis its status in Britain is difficult to account for: sure, if these were birds that had crossed the Atlantic in the autumn, wintered further south and were now heading north, one could suggest that they were following a more easterly heading in spring, as many birds do, but I believe the current thinking is that these birds are effectively overshooting/being displaced eastwards during the spring migration, and, that considered, you'd imagine that we'd get one every few years or so.

[Alex Lees]

Have there been any studies of these? I wonder if they may be re-split any any stage....

Brian S

Brian

The seminal paper (Mila et al. 2008) on Junco phylogeny attached;

'The occurrence of hybridization along contact zones between some forms in the dark-eyed junco complex (except for, at least, caniceps/hyemalis, caniceps/aikeni, and insularis), suggests that reproductive isolation between some morphotypes is not yet complete. However, the marked phenotypic differentiation between forms, their largely allopatric distribution, and the fact that most hybrid zones are of limited width and apparently stationary over at least a century (Miller 1941; Nolan et al. 2002), all suggest that dark-eyed junco forms are on distinct evolutionary trajectories and may represent a case of speciation in action.'


Alex