Notas taxonómicas sobre el Chingolo (Zonotrichia capensis) del sud-oeste argentino

Abstract

We have studied 123 skins of Zonotrichia capensis following the results of Chapman (1940). From the authors, Kovács has made the field studies and collected most part of the skins, Keve made the taxonomical comparison. Our principal goal was to clear the taxonomical position of the population of the District Bariloche and the neighbouring countries. We have found that Z. c. choraules is very variable. The principal mark is the black crown-stripes, which is sometimes so long that after the moult in fresh plumage—when the colour of the back in all subspecies is browner, as in other seasons—it is hardly distinguishable from Z. c. chilensis. On the other hand, this black crown-stripe in extreme specimens is so little or so interrupted that such individuals are hardly distinguishable from the darkest phase of Z. c. australis without crown-stripes. Therefore, we have divided our specimens of the District Bariloche into three groups: I) Specimens with marked crown-stripes II) Specimens with poorly developed crown-stripes III) Specimens without crown-stripes. We have not found skins belonging to group 3 in the breeding season in our material from District Bariloche, and also the wing measurements confirm that birds belonging to group 3 belong to subspecies Z. c. australis, described from Tierra del Fuego. So, they are migrants. The migration was regularly observed on the eastern slopes of the Andean Mountains, especially in El Hoyo, in the valleys, and came from the South directed to the North. This fact explains the possibility of how a mixed population could have developed in the surroundings of the District Bariloche, named Z. c. choraules (Peters and Wetmore). From the point of view of morphology, it is not uninteresting that the grey feathers of the crown have a black basis. When the skins are badly taxidermically handled, it can lead to mistakes, because the disheveled feathers seem to be black. The skins belonging to group 2 are the characteristic Z. c. choraules, but the extremes of this group are very close to the darkest extremes of Z. c. australis. From the 55 skins from Bariloche District, 38.18% belong to group 2. From the breeding time, we have had only 7 specimens from this district, and from these, 5 belong to group 1 and 2 to group 2. The black stripes of the crown-sides are not shorter in group 1, as in Z. c. chilensis. 36.36% of the skins from District Bariloche belong to this group.  After the moult, in fresh plumage, the colour of the back is more brownish. In this plumage, Z. c. choraules and Z. c. chilensis in the Andes can be confused by the colour of the freshly moulted specimens. The District of Bariloche and its neighbouring countries belong to the breeding area of Z. c. choraules. Another question is: what is the taxonomical value of this population, which is so widely distributed? For this last reason, choraules cannot be regarded as a simple mixture of different races. The name must be held as valid, but from the point of view of taxonomy (not systematics), it is perhaps nearer a cline than a subspecies. The population of the District Ñorquinco, and especially in the northern part of West Chubut, is more mixed. A dean population of Z. c. australis lives south from the river Alto Río Senguer in South-West Chubut. We have had a comparative material also from N.E. Argentina, from Uruguay, and from Brazil. In this paper, we don’t want to speak on the problems which we have seen in this part of our material; only we can make some remarks. So, it is for us not enough clear: are the Chingolos of Misiones really the same as those which live near Rio de Janeiro? Much more interesting were two skins from Sierra Grande (San Antonio), collected by Kovács in migration season (July 10, 1965). We have also found some specimens in West Argentina with well-developed white wing-bar, better developed than on skins from Tierra del Fuego of Z. c. australis. Also, some same-coloured were collected near Jacobacci (District De Mayo) and near Cerro Policía (District El Cuy). The mentioned two skins are in the back and on the head brighter grey. Having only two specimens, this problem rests for further study.