By Yoav Perlman
Those who read my blog might have noticed that I addressed this topic briefly in my recent post. In this post I will expand a little. A visit to Frankfurts’ Senckenberg Naturmuseum a couple of weeks ago allowed me to take a look at these nightjars. My interest in Red-necked Nightjars arose as part of a project I am involved in, with Martin Collinson. We are looking at phylogeny of several un-sequenced nightjar species; Red-necked is one of them. It is somewhat strange for me to work on a species I have never seen in the field, yet. Last time I visited Iberia it was too early for them. I am returning to Iberia next week for 6 weeks of fieldwork, so I am quite confident I will catch up with them this spring.
Red-necked Nightjar has two subspecies – ruficollis that breeds in Iberia and in Morocco; while desertorum breeds in N Algeria and N Tunisia. Both subspecies migrate in winter to sub-Saharan Africa, where they apparently overlap in their winter distribution in Mali, Ghana and Gambia. However, the wintering distribution in Africa is not totally clear, and certainly where and where not the subspecies mix.
When I opened up the Red-necked Nightjar tray, I was struck by how apparent the morphological differences between the two species are. No need for wing ruler – desertorum is visually so much larger than ruficollis! Though I behaved like an amateur and did not measure them, in this case I think the size difference is totally evident:
Interestingly, these apparent huge differences are not reflected in measurements from literature. In Nigel Cleere’s 2010 Nightjar guide, males of ruficollis have wings of 196-217 and tails of 149-168, while desertorum males have wings of 198-214 and tails of 153-171. Sadly, there is no mean given, and also not sample size. I need to check more references. It seems that another trip to Tring is necessary.
Apart for the size differences between the two subspecies, their plumages are pretty different too. desertorum is paler sandier below, and lacks the dark chest of ruficollis:
From above the overall difference in tones is less obvious, but the broader rufous collar of desertorum is apparent, and possibly narrower black crown streaking of desertorum, that is mentioned in Cleere’s book.
There is another difference between the subspecies, in the pattern of inner primaries, that is not visible in these photos. desertorum has a bold pattern of orange and black bands of equal width, while ruficollis has very little orange on the primary bases. Check the 2009 BB article by Tim Melling, describing the 1856 British record (ruficollis by the way), in which the primary pattern is nicely compared.
Xeno-Canto has sound recordings only of ruficollis. I wonder if there is are any differences in vocalisations? Has anyone ever sound recorded desertorum? Sound Approach guys?
So what do we have here?
- Distinct breeding ranges – or not? The two subspecies are separated by 200-300 km of apparently suitable habitat in NW Algeria. Why is there a gap in distribution there? I don’t know.
- Both subspecies migrate and apparently overlap in W Africa in winter.
- There is an apparent huge size difference (see photos above), but this is not evident in published measurements.
- Clear differences in general plumage tones, and also in patterns of specific feather tracts (primaries, collar).
- No information available on vocalisations of desertorum.
I find it intriguing that these two taxa breed so close, and possibly are not geographically isolated at all, and still are so different morphologically. What will DNA analysis reveal? Is there room for another SHIPS (Species Hiding In Plain Sight) as Martin C. calls them? I am genuinely curious to find out. Hope to report the results in a few months.