First Argentinian record of the nest of Botaurus pinnatus

The first record on the nesting ofthe South American Bittern (Botaurus pinnatus) for Argentina is given. The nest and eggs are described and commented

Nesting of Thamnophilus doliatus in Argentina

Five nests of the Barred Antshrike (Thamnophilus doliatus) were studied at the southern extreme of its distribution, in Formosa Province, Argentina. The laying interval was alternate days. The incubation period was 15 days and the nestling period 12-13 days. Nesting success was 33, 3 %. Brood parasitism of the Shiny Cowbird (Molothrus bonarienis) on nests of this antbird is reported for the first time. Clutch size seems to be about two eggs throughout the species ranges, but further information on this point is needed

New notes on the nesting of some species of Northwestern Argentina birds

We present new dat on nesting of 12 bird species of the Yungas (montane forests ) of Salta and Jujuy provinces. We provide information on date, location, size, materials and contents of the nests. The nest and eggs of Atlapetes torquatus, apparently unknown, are described. Most avian species bred in the wet season, but Amazilia chionogaster nested in the dry season

ARTHROPOD PREY AVAILABILITY AND BREEDING OF THE THREATENED STRANGE‐TAILED TYRANT (ALECTRURUS RISORA)

ABSTRACT ∙ The Strange‐tailed Tyrant (Alectrurus risora) is an insectivorous flycatcher (Tyrannidae) endemic to the natural tall grasslands of northern Argentina and southern Paraguay. Alectrurus risora has a polygynous mating system and the abundance of arthropods could be a major factor determining the establishment of male breeding territories and the extent of the breeding season, which is shorter than in most other reported tyrant flycatchers. To investigate this hypothesis, we examined the abundance of arthropods in upland and lowland breeding habitats. Upland habitats seem to be preferred for breeding, and usually harbour more nests. Data from one year showed that, for both grasslands, the beginning of the breeding season coincides with a greater availability of arthropods, and that the short reproductive season of A. risora coincides with a general lower availability of prey during February and March in the year we conducted the study. In upland territories, males attracted more females and had more active nests than males holding territories in lowland grasslands. However, the abundance and biomass of total arthropods and of potential prey were higher in lowland than in upland grasslands, with the exception of the abundance of Orthoptera, which was higher in upland habitat and could represent one of the major prey items. Therefore, we conclude that 1) female preference for males in upland grasslands cannot be explained by higher arthropod prey availability, and 2) the availability of arthropod prey may be important in determining the extent of the breeding season, although further, multiannual studies are required to corroborate this hypothesis. RESUMEN ∙ Disponibilidad de artrópodos presa asociados a territorios de reproducción de un ave en peligro de extinción, el Yetapá de Collar (Alectrurus risora) El Yetapá de Collar (Alectrurus risora) es un tiránido insectívoro endémico de los pastizales altos naturales del norte de Argentina y sur de Paraguay, que posee una temporada reproductiva más corta que aquella reportada para la mayoría de los tiránidos. Alectrurus risora posee un sistema de apareamiento poligínico, y la abundancia de artrópodos podría representar un factor determinante en el establecimiento de los territorios de los machos y en la duración de la temporada reproductiva. Con el fin de investigar esta hipótesis examinamos la abundancia de artrópodos en hábitats reproductivos de pastizales altos y bajos. Los pastizales altos parecen ser más utilizados durante la época reproductiva y usualmente albergan un mayor número de nidos activos. Los datos de un año de muestreo mostraron que el inicio de la temporada reproductiva coincide con el pico de abundancia de artrópodos en ambos pastizales, y que su corta duración coincide, para el área en estudio durante el año analizado, con una menor disponibilidad de presas durante los meses de febrero y marzo. En los territorios ubicados en el pastizal alto los machos atrajeron más hembras y tuvieron más nidos activos que en los territorios de pastizal bajo. Sin embargo, la abundancia y biomasa de artrópodos totales y de presas potenciales fueron mayores en el pastizal bajo, con la excepción de la abundancia de Orthoptera, que podría representar uno de los tipos principales de presa. A partir de estos resultados, concluimos que 1) la preferencia de las hembras por machos en el pastizal alto no puede ser explicada por una mayor disponibilidad de artrópodos presa, y 2) la disponibilidad de artrópodos presa podría representar un factor importante en la determinación de la extensión de la temporada reproductiva, pero se requieren estudios adicionales, plurianuales, para corroborar esta hipótesis.

Presencia invernal de <i>Pluvianellus socialis</i> en la provincia de Buenos Aires, Argentina

First records of the Magellanic Plover (<i>Pluvianellus socialis</i>) wintering in southem Buenos Aires Province are given

New records of <i>Catamblyrhynchus diadema</i> for Northwestern Argentina

The first record of the Plushcap ( <i>Catamblyrhynchus diadema</i>) for Salta province is given based in a collected specimen. New records for Jujuy province are reported. A immature plumage is described and information about the habits is discussed by means ofthe bibliography and field notes

Description of the nestling of Xenopsaris albinucha

We report the first record on the nesting of the White-naped Xenopsaris (Xenopsaris albinucha) for Buenos Aires Province. The nestling are described and commented. The mouth color is pink, a rare characteristic in the suboscines

Stages of plumage maturation of the Tawny-bellied Seedeater: Evidence of delayed plumage maturation and cryptic differentiation between juveniles and females

In some sexually dichromatic passerines, juvenile males retain a plumage similar to that of adult females through their first year or longer (delayed plumage maturation). The Tawny-bellied Seedeater (Sporophila hypoxantha) is a sexually dichromatic species in which, to the human eye, the juveniles look like females. We analyzed the species' stages of plumage maturation by reflectance spectrometry and a visual model of color discrimination on captive individuals of known ages. We found that males retain a plumage different from that of adult males through their first breeding season. By the time males passed the age of 1 year, their color did not differ from that of adult males in any region of the body except the crown. Spectrophotometry also revealed differences between the plumage color of juvenile males and females, and the color-discrimination model implies that the birds should be able to detect these differences. Thus juvenile males of the Tawny-bellied Seedeater acquire adult plumage after their first breeding season but are already dichromatic during the first year. How this pattern of plumage development affects the species' reproductive or other social behavior deserves further study.Fil: Facchinetti, Carolina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución. Laboratorio de Ecología y Comportamiento Animal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mahler, Bettina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución. Laboratorio de Ecología y Comportamiento Animal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Di Giacomo, Alejandro G.. Aves Argentinas / Asociación Ornitológica del Plata; ArgentinaFil: Reboreda, Juan Carlos. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución. Laboratorio de Ecología y Comportamiento Animal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Presencia invernal de Pluvianellus socialis en la provincia de Buenos Aires, Argentina

First records of the Magellanic Plover (Pluvianellus socialis) wintering in southem Buenos Aires Province are given

Notes on the nesting of 20 species of Northwestern Argentina birds

Se presenta información sobre la nidificación de 20 especies en las Yungas de Salta y Jujuy. Se describen fecha, localidad, forma, tamaño, materiales y contenido de los nidos hallados. Los nidos de Sittasomus griseieapillus, Poeeilurus seutatus, Syndaetyla rujosupereiliata, Todirostrum plumbeieeps y Contopusjumigatus, son poco conocidos. Se detectó a tres adultos trayendo alimento a un nido de Hirundinea jerruginea, y ayudantes se notaron en nidos de Cyanoeorax ehrysops. Los datos presentados permiten concluir que las especies consideradas nidifican durante la estación húmeda, salvo Phaethornis pretrei, que lo hace durante la estación seca.We present dat on nesting of 20 bird species of the Yungas (montane forests) of Salta and Jujuy provinces. We provide information on date, location, shape, size, materials and contents of the nests. Breeding information is presented for the little-known nest of Sittasomus griseieapillus, Poecilurus seutatus, Syndaetyla rujosupereiliata, Todirostrum plumbeieeps and Contopus jumigatus. Chicks in a nest of Cliff Flycatchers Hirundinea jerruginea were fed by three adults. Helpers were detected in nests of Plush-capped Jays Cyanoeorax ehrysops. Most avian species bred principally in the wet season, but the hermit hmmingbird Phaethornis pretrei nested in the dry season