Eastern Jackdaws

The Intergrade Issue

Alan Tilmouth


1 = spermologus 2 = monedula 3 = soemmerringii

A = Turrium   B= Polish Intergrade

Whilst Martin has covered the three Jackdaw races (spermologus, monedula and soemmerringii) in his previous blog posts probably the biggest barrier to getting a ‘Russian’ Jackdaw or soemmerringii accepted in Britain is what is happening in the areas or intergrade zones where these different races meet.

As Matthew Silk acknowledged in his summary of the possible ‘Russian’ Jackdaw visiting his garden, soemmerringii “is considered a very rare winter visitor in the Netherlands so is likely to occur in Britain albeit not very often.”

There are two key areas of racial integration amongst Jackdaws, first up, from Southern Denmark south to the Alps, monedula overlap with eastern populations of spermologus. The resulting offspring of mixed race pairings here have been referred to as turrium. The French paper linked to in Martin’s original post had this to say about turrium:

 

“turrium has an appearance intermediate between it and monedula.

The variability of these populations is considerable, and therefore the identification of turrium is only possible in direct comparison with typical individuals (of spermologus or monedula).

Slightly lighter than spermologus and darker than monedula; often similar to that of individuals in populations of southern Western Jackdaw.

Even in fresh plumage, turrium seem a bit darker than monedula, but still clearly contrasting with black throat and upper parts (unlike the typical spermologus).

The collar is variable but usually indistinct the lower neck is a slightly lighter gray than the neck with ill-defined grayish spots and faint contrast with the rest of the plumage.

Do not underestimate the degree of variability of this intermediate population, which in any way, presents an average plumage sharper and more contrasted than Western Jackdaw, but too dull (especially in the lower parts) for a typical Scandinavian Jackdaws.”

 

The second key area is in areas south of the Scandinavian Peninsula such as Poland where western soemmerringii are thought to integrate with monedula. The French paper commented thus on these ‘Polish Jackdaws’:

“The Polish intergrade is very variable; in general, it is clearer and more contrasting than the breeding populations in Western Europe (turrium included) and is similar to a version of dull soemmerringii.

The colors of these parties are more or less intermediate between those of Scandinavian and eastern birds, however, generally it lacks the nuance that gives a pale purple lavender at the nape of soemmerringii.

Normally soemmerringii is blackish, not contrasting markedly with the upper throat dark or black This criterion is variable and some individuals may resemble’ turrium’Jackdaws they differ, however, by the neck much paler and the white marks at the base of the neck.

Given the influence of the subspecies soemmerringii, the collar is white, but irregular,( smaller and less distinct than in Eastern Jackdaws. Generally, the lower edge of the neck is pale gray, as in monedula.

Ruud Altenburg has kindly provided some images of Jackdaws from Cubna, central Poland in February that aptly displays some of the individual variations.

Compare these with some of the individuals that have been seen here in Britain this winter:

Killingworth, Northumberland, Jack Bucknall

Bishop Burn, Cumbria, Tristan Reid

Bothal Pond, Northumberland, Alan Tilmouth

One of the key features that has struck me about many of the individuals reported as a race other than spermologus here in Britain & Ireland is the shade of the underparts. Often they appear darker than monedula though perhaps not as dark/black as spermologus. I think this often leads some observers to dismiss some of these individuals as variation within our own population. My feeling is that the lack of  any significant number of individuals showing the prominent white collars or neck patches from April through summer may rule this out. The shorter distances required to move from the ranges of  turrium and ‘Polish Jackdaws’ (as compared to soemmerringii) combined with the underpart colour midway between races begs the question as to how many of these individuals originate from these populations.

I’ve also noticed that the timing is interesting with many of these ‘Eastern-type’ Jackdaws showing up from December onwards with a peak in February/March. There could be two factors at play here; weather related movements from the continent perhaps pushing birds further west in bad winters and the tendency for juveniles to move further than adults that only subsequently get detected as they begin to wear in late winter causing the collars and neck patches to become more prominent.

Partly as a result of the recent attention Jackdaw races have been receiving Birdguides have now added ‘Nordic’ Jackdaw as a ‘species’ option in the Iris Gallery and it would be good to get as many images from different locations as possible entered there that can be used for comparison.

Alan Tilmouth, March 2011

3 thoughts on “Eastern Jackdaws

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