Attributes such as sex, age and pigmentation of individuals could correspond to the competitive skills they use to access resources and, consequently, determine their social status when a hierarchy of dominance is established. We analysed patterns of social dominance in relation to sex, age and, for the first time, according to face pigmentation in a large scavenger bird species, the Andean condor (Vultur gryphus). This species displays extreme sexual dimorphism, with males being up to 50% heavier than females. Associated to this, strong hierarchical relationships characterize foraging, roosting and breeding. We recorded agonistic interactions within condor groups while foraging through video recordings in experimental stations. We corroborated a strong despotism by the adult males to the rest of the categories. More interestingly we found this despotism was also expressed by most pigmented birds; juvenile females being completely subordinated and, at the same time, not expressing pigmentation. Importantly, when condors of equal sex and age category fought, the more pigmented individuals were successful. Our results highlight that pigmentation, besides sex and age, is an attribute that also corresponds with social status in the Andean condor, making its hierarchical system more complex.

The Puna Rhea (Rhea tarapacensis) is a large, flightless herbivorous bird found in the Andes Mountains of four countries, namely Argentina, Chile, Bolivia and Peru. Despite its ample distribution range, little is known about the ecological requirements of the species. In this work, the diet and food selection behaviour of the Puna Rhea in the Argentine Puna desert were analysed. From 2011 to 2014, throughout the dry and wet periods of each year, fresh faeces were collected and vegetation cover was simultaneously recorded. Diet composition was determined by microhistological analysis of the faeces and diet selectivity was established statistically by the Bonferroni method. The diet of the Puna Rhea was completely herbivorous and mostly folivorous, consisting of 51% of the plant species in the study area. This species was highly selective, consuming scarce shrub and herbaceous species and rejecting grasses or graminoids. The strongly selective foraging strategy presented by the Puna Rhea was therefore unrelated to the abundance of particular species but probably influenced by factors such as nutritional value, mainly in terms of fibre content and plant secondary compounds, and predation risk. Consequently, conservation efforts aimed at the Puna Rhea should be focused on maintaining the availability of the few preferred plant species and reducing possible competition with other generalist herbivores. ARTICLE HISTORY

Background: Rhea pennata is classified internationally as a near-threatened species, with the subspecies R. p. garleppi being listed as endangered. Finding: The aim of this study was to provide updated information on the density and abundance of R. p. garleppi in the southern Puna ecoregion of Argentina. Density was estimated indirectly on the basis of monthly feces counts during 2011 and 2012, using line-transect surveys. Monthly abundance was calculated by multiplying the density of each month by the area of the reserve (400 km 2 ). Population size range was calculated considering the average of the months with the highest abundance (and density) as the upper limit and the average of the months with the lowest abundance (and density) as the lower limit. The population size of this subspecies varied between 300 individuals (±60), with a density of 0.75 individuals/km 2 (±0.15) during the non-breeding season, and 188 individuals (±40), with a density of 0.47 individuals/km 2 (±0.10), during the reproductive season.