Schreiber, A. 2021.
Identification taxonomique de la Gélinotte des bois Tetrastes bonasia dans le nord-est de la France. Aves 58: 25-49.
https://www.aves.be/fileadmin/Aves/Bulletins/Articles/58_1/58-1_25.pdf
Abstract
The hazel grouse populations in north-eastern France and adjacent regions are revised taxonomically on the basis of differentiated characters in morphometrics and plumage colouration of the two subspecies
T. b. rhenana (
n = 127) and
T. b. styriaca (
n = 102). In France,
T. b. styriaca occurs in (parts of?) the Alps and
T. b. rhenana in the Vosges mountains and their surroundings. Presumably,
T. b. rhenana had occupied a much larger historical range in the plains and lower hills of north-east France before anthropogenic extermination. In discriminant function analysis both subspecies reveal diagnosability of 87% of their individuals, based on wing length, tarsal feathering, bill morphology, mottling of the ventral plumage, and the background pigmentation of breasts and bellies. This diagnosability, also evident from principal component analysis, is an underestimate, since the dorsal plumage is also differentiated, but remains unamenable to statistical tests due to its character complexity and a high individual and a graded micro- and macrogeographical variation. There is no evidence for internal morphological subdivision within the population in the Vosges (although the material sampled from
T. b. rhenana in France is so small that a minor micro-geographical structure could have been overlooked). Other than the more variable
T. b. rhenana, the Alpine
T. b. styriaca is one of the geographically most uniform subspecies of hazel grouse worldwide. Nevertheless, the very small study sample from the French western Alps deviated from the central and eastern Alpine stocks by certain ventral plumage traits, and this deviation may indicate a genetic influence by the adjacent (now extinct) lowland populations to the (north)west. The French Alpine population deserves a closer study once more specimens become available, also to see if the morphotype from the Jura is confined to this mountain range or extends into the northwesternmost Alps. The populations from the Jura are intermediate between the two subspecies, and more variable, and thus of presumed hybridogenetic descent from both adjacent stocks. However, their gross phenotype tends to be more similar to
T. b. styriaca than to
T. b. rhenana. While the contact zone between both subspecies is located to the south of the Vosges, the study material originated predominantly in the Swiss Jura only, and the underexplored hazel grouse from the Jura in France require deeper study to localize the contact zone more precisely. A caveat of the present taxonomic findings is that they relate to the original situation, evidenced by historical museum specimens; the possible effects of a recent release project of hazel grouse in the Vosges, using birds bred from one or more (not well documented) (north)eastern European subspecies on the taxonomic purity of the autochthonous
T. b. rhenana cannot be recognised from these museum data. A result of this study of wider scientific interest is the statistical evidence for a regionalized, geographical differentiation of the degree of sexual dimorphism in ventral pigmentation patterns of hens and cocks: Such a sex dimorphism in the portions below the throat is absent fom the Alpine subspecies, but significantly displayed by
T. b. rhenana. This phenomenon deserves further study in additional subspecies elsewhere, in order to understand likely differences in the social mating systems of the hazel grouse subspecies, which are plausibly correlated with a stronger or weaker sex dimorphism of the plumage signals.
