A 2.7 m thick mid-Holocene sedimentary succession composed of alluvial fan and marine beach deposits is exposed at 14.4-17.1 m above sea level (a.s.l.) on the south-eastern coast of Potter Peninsula, King George Island (South Shetland Islands, Antarctica). The raised marine beach deposits contain a subfossil assemblage that includes remains of Adélie (Pygoscelis adeliae) and gentoo (P. papua) penguins, skua (Catharacta sp), seals (elephant seal Mirounga sp), and seaweed fragments. The palaeontological and palaeogeographical evidence allows us to infer that penguin rookeries were active on high cliffs of the Potter Peninsula during the marine beach sedimentation, which is dated to c. 4540-4450 reservoir-corrected 14 C yr BP on the basis of radiocarbon dating on penguin bones. The data presented in this paper are in agreement with the Holocene palaeoenvironmental chronology known from Potter Peninsula, and suggest that marine birds and seals inhabited the coastal areas of King George Island probably during a midHolocene period of seasonally open marine conditions, which may coincide with a cooling period around Antarctica estimated from ice core records between 8000-4000 yr BP that preceded the "climate optimum" in the Antarctic Peninsula (4000-3000 yr BP).

This review discusses different aspects of the uropygial gland of birds. The gland exhibits a striking morphological diversity in size, shape and presence/absence of tufts of feathers. It was shown that acidic mucins, neutral lipids, glycolipids and phospholipids are normal components of secretion. Several morphological and physiological aspects of the gland were studied on Rock Pigeon Columba livia Gmelin, 1879. The amount of the uropygial gland secretion, its lipid content and fatty acids profile were determined. The extracted lipid mixture contained of C14 to C20 fatty acids, mostly unsaturated; the saturated fatty acids were mainly 14:0, 16:0 and 18:0. No correlation was found between the size of the gland and the aquatic/terrestrial nature of the species. Ablation of the gland did not affect survival, body weight, feeding rate and serum cholesterol, total lipids or calcium levels after 32-120 days. The possible role of the gland in the protection against lipophilic compounds was discussed. The function of the gland is still a subject of controversy. It is accepted that its secretion confers water-repellent properties on the feather coat and maintain the suppleness of the feathers. Other physiological roles of the gland secretion may be associated to pheromone production, control of plumage hygiene, thermal insulation and defence against predators. Concerning the endocrine regulation of the uropygial function, there is scarce information presenting evidence for steroid regulated mechanisms.Keywords: Columba livia, preen gland, uropygial gland, uropygial physiology, chemistry of secretion. Aspectos fisiológicos e bioquímicos da glândula uropigial das aves ResumoEsta revisão discute diferentes aspectos da glândula uropigial das aves. A glândula exibe uma chamativa diversidade morfológica de tamanho, forma e presença/ausência de um tufo de penas. A glândula mostrou mucinas ácidas, lipídios neutros, glicolipídios e fosfolipídios como componentes normais de sua secreção. Diversos aspectos morfológicos e fisiológicos da glândula foram estudados na pomba doméstica Columba livia. Foi determinada a quantidade de secreção da glândula uropigial, seu conteúdo lipídico e o perfil de ácidos sebosos. A mistura lipídica extraída contém ácidos graxos C14 a C20, principalmente não saturados; os ácidos graxos saturados foram principalmente 14:0, 16:0 e 18:0. Não se encontrou correlação entre o tamanho da glândula e a natureza aquática/terrestre das espécies. A ablação da glândula não afetou a sobrevivência, peso corporal, alimentação e os níveis séricos de colesterol, lipídios totais ou cálcio depois de 32-120 dias. Discute-se o possível papel da glândula na proteção contra compostos lipofílicos. A função da glândula é ainda tema de controvérsia. Aceita-se que sua secreção confere às penas propriedades repelentes à água e as mantém flexíveis. Outras funções fisiológicas da secreção glandular podem estar associadas com a produção de feromonas, controle da higiene da plumagem, isolamento térmico e defesa contra predadore...

The uropygial glands of birds are sebaceous organs that contribute to the water-repellent properties of the feather coat. We studied the histological and histochemical characteristics of the uropygial gland of chimango caracara using hematoxylin and eosin (H & E), Gomori´s trichrome, orcein, Gomori´s reticulin, periodic acid-Schiff (PAS), Alcian blue (AB) and a variety of lectins. The gland is composed of two lobes and a papilla with 20 downy feathers. It is surrounded by a capsule of dense connective tissue that contains elastic, reticular and smooth muscle fibers. The papilla is delicate and has two excretory ducts. The gland mass relative to body mass was 0.143%. Both adenomer cells and their secretions were stained with Sudan IV, PAS and AB, and were positive for numerous lectins that indicated the presence of lipids and carbohydrates. Immunohistochemical techniques to detect PCNA confirmed cell proliferation in the basal stratum of the adenomer cells. The lipids and glycoconjugates secreted by the uropygial gland serve numerous functions including protection against microorganisms.

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The uropygial gland is morphologically different in diverse bird species. This gland was macroscopically and microscopically examined in penguins, storm petrels and skuas. In all the studied species, the gland showed a connective tissue capsule and one papilla. A negative relationship was observed between the relative glandular mass and the body mass, being highest in petrels (small glands) and lowest in penguins (large glands). Birds that spend much time in water (penguins) have gland characteristics related to a continuous, but not stored, secretion, such as straight adenomers, the presence of abundant elastic fibres in the connective tissue and the absence of a primary storage chamber. Instead, birds that have less contact with water (storm petrels) have a gland with much more tortuous adenomers and a small primary storage chamber. The secretory cells showed a positive PAS reaction in all the glandular zones. Therefore, no differences could be seen between the sebaceous and glucogenic zones, as proposed in other birds. These results allow the conclusion that, in aquatic birds, there is no connection between the relative mass of the uropygial gland and the time in contact with water, though the differences found in the histological structure could be related to a different contact with the aquatic environment.

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Urbanization is one of the most important threats to biodiversity worldwide, as it drives declines in species diversity, functional diversity, and phylogenetic diversity and increases functional redundancy among species. We estimated taxonomic, functional, and phylogenetic diversities, as well as the abundance of several functional groups, in bird communities from a town in east-central Argentina in 1985–1986 and 30 years after (2015–2016). In 1985–1986, we found that taxonomic diversity (abundance, species richness, and alpha diversity), functional richness, and basal phylogenetic diversity were negatively related to building cover, whereas terminal phylogenetic diversity showed a positive relationship with building cover. Moreover, the abundance of specialized functional groups (ground, aerial, and foliage insectivores; nectarivores/insectivores; ground/canopy and ground granivores) decreased with increased building cover, whereas the reverse pattern for the abundance of generalists (medium-sized/large and small omnivores) was found. In 2015–2016, by contrast, taxonomic, functional, and phylogenetic diversities were not related to building cover. Our results not only support the hypothesis that urbanization affects the potential number of ecosystem functions, but also that this relationship may change through time. Given the accelerated rate of urbanization worldwide, an integrative approach between different facets of biodiversity is promoted to gain insight into the response of bird communities in urban environments.

Chiale, M.C., Montalti, D., Flamini, A. and Barbeito, C.G. 2017. The uropygial gland of the Southern Caracara (Caracara plancus; Falconidae: Falconinae): histological and histochemical aspects. -Acta Zoologica (Stockholm) 98: 245-251.