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Despite molting is an important and expensive activity in the life cycle of birds, this process is poorly known for neotropical species and even less so for species inhabiting urban zones. We studied molt patterns, aging and sexing criteria, and morphometrics for seven common resident species in an urban area of Lima city, Peru. All species evidenced complete prebasic molts. Partial to eccentric incomplete preformative molts were evidenced for six species (Camptostoma obsoletum, Pyrocephalus rubinus, Catamenia analis, Poospiza hispaniolensis, Coereba flaveola, and Thraupis episcopus); whereas Columbina cruziana exhibited a complete molt. All thraupid species exhibited partial prealternate molts. Preformative and prebasic molts were recorded mostly during the dry season, and the few records of prealternate molts might suggest its occurrence soon after the wet season. Our species also exhibited low molt synchrony, with some of them (C. cruziana, P. rubinus, and C. flaveola) exhibiting extensive molt periods likely explained by its potential to reproduce throughout the year and/or the existence of suspended/ protracted molts. Morphometric analysis evidenced significant differences according to sex for C. cruziana, P. rubinus, and C. analis, with the wing chord being the most common characteristic for distinguishing between sexes. Our study covers an important gap in the knowledge of the natural history of urban birds and provides information to test hypotheses of molt pattern variation on species with widespread distribution throughout the Americas. RESUMEN A pesar de que la muda constituye una actividad importante y costosa en el ciclo de vida de aves, este proceso es poco conocido en especies neotropicales y lo es aún menos para especies que habitan ambientes urbanos. Estudiamos los patrones de muda, criterios de determinación de edad y sexo y datos mor-fométricos correspondientes a siete especies de aves residentes comunes en un área urbana de la ciudad de Lima, Perú. Todas las especies evidenciaron muda prebásica completa. Mudas preformativa parcial a incompleta excéntrica fueron evidenciadas para Camptostoma obsoletum, Pyrocephalus rubinus, Cata-mema analis, Poospiza hispaniolensis, Coereba flaveola y Thraupis episcopus; mientras que Columbina cruziana evidenció una muda completa. Todos los traúpidos exhibieron mudas prealterna parcial. Las mudas preformativa y prebásica fueron registradas principalmente durante la temporada seca, y los pocos registros de muda prealterna sugieren su ocurrencia poco después de la temporada húmeda. Nuestras especies también exhibieron una baja sincronía de muda, y algunas de ellas (C. cruziana, P. rubinus y C. flaveola) exhibieron períodos extensos de muda probablemente explicados por su potencial para reproducirse durante el año o la existencia de mudas suspendida / prolongada. El análisis morfométrico evidenció diferencias significativas según sexo para C. cruziana, P. rubinus y C. analis, siendo la cuerda alar la característica más común para distinguir sexos. Nuestro estudio cubre un vacío importante en conocimiento de la historia natural de aves urbanas y proporciona información para probar hipótesis sobre la variación de patrones de muda en especies con amplia distribución en las Américas.

Here, I present the first quantitative data on parental behavior in a nest of the Southern Beardless Tyrannulet Camptostoma obsoletum (Temminck, 1824) in southeast Brazil. The nest was in a bromeliad (Tillandsia tricholepis) 1.93 m above ground. Eggs were laid in alternate days, measured 1.71 × 1.18 mm and 1.60 × 1.16 mm, and weighed 1.2 and 1.0 g, respectively. Eggshell had a whitish background and small light brown blotches near the blunt pole. Mean nest attentiveness was 87.5% and decreased across the incubation period. The eggs hatched with 16 and 17 days of incubation. In the nestling period, parents made 8.89 ± 3.52 provisioning trips/h (range: 5–17), which lasted on average 7.5 ± 5.69 s (range: 1–30 s). Provisioning trip rate increased with nestling age, whereas visit duration decreased. Nestlings fledged asynchronously, 16 days after hatching, relatively well feathered. Although based on a single nest, the data suggest that C. obsoletum presents an uncommonly high nest attentiveness compared to closely related species and Neotropical birds in general.

We recorded for the first time in Cuatro Cienegas Basin, Coahuila, Mexico, 43 species, 33 of them represented by specimens and 10 only by visual observations. These records increase the species known for the basin by 38.4%. The fieldwork was conducted during 1996 and 1997. Two species are new records for the state of Coahuila: Larus atricilla and Camptostoma imberbe.

northwestern section), Eastern Colombia, and northern Brazil. The range of the species, of which a number of races have been described, extends from Costa Rica southward over South America to Bolivia, southeastern Brazil, and northern Argentina. In the coastal region of Surinam, birds of the race napaeum are rather common in light forests and perhaps even commoner about coffee plantations and gardens with scattered bushes and trees. Camptostoma obsoletum is a small tyrannid flycatcher, the weights of specimens collected by me in Surinam being: 3 males, 8, 9.4, and 9.5 grams: 3 females, 10.6, 11.4, and 9.8 grams. The general color above is olive, the crown being darker than the back and inclining to dusky brown. The throat is pale gray and the breast, abdomen, and under tail-coverts are sulphur-yellow. The bird has two yellowish wing-bars and a whitish stripe over the eye. The coloration of the sexes is similar. Although Euler (1900) and Snethlage (1935) gave good descriptions of nests of Camptostoma obsoletum from Brazil, the Penard brothers (1910) and Belcher and Smooker ( 1937) failed to do so. The Penards in fact gave no description of the nest but, instead, referred the reader to another species, Phaeomyias murina, which makes an open nest of the Elaenia type. Belcher and Smooker described a nest from Trinidad as "a shallow cup, made of grass stems, fibres and small pieces of bark, and lined with plant down, externally . . . decorated with lichens fastened on with spider's web." This was certainly the nest of another species, probably Phaeomvias murina, for Camptostoma obsoletum builds a domed nest with a side entrance, as ably described by both Euler and Snethlage (op. cit.), and as borne out by my own more recent findings. I had suspected that the nest would prove to be of this type, as the nest of a closely related species, Camptostoma imberbe, is well known and is also domed with a side entrance