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Duration and intensity of primary molt in two neotropical grasslands Passerines Translated title: Duración e intensidad de la muda de plumas primarias en dos Passeriformes neotropicales de pastizales

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      Abstract

      ABSTRACT Description of patterns and mechanics of bird molt have permitted understanding and have clarified temporal and spatial dynamics in the life cycles of several temperate species. Few studies evaluate these aspects in Neotropical birds, which hinders their discussion in functional and evolutionary contexts. Here we compare primary molt duration and intensity of flight feather molt in two Neotropical passerine species, Blue-black Grassquit and Gray Seedeater. The study took place north of the department of Tolima-Colombia. Birds were captured and were marked with colored bands. Molt duration estimates follow Pimm’s and Rohwer and Wang’s methods, while molt intensity was evaluated using Rohwer’s proposal. Primary molt duration of Blue-black Grassquit was between 59 days (CI 95 % = 48-74) and 80 days (CI 95 % = 64-96), while the duration for Gray Seedeater was between 80 days (CI 95 % = 66-105) and 100 days (CI 95 % = 75-124). Estimates were consistent with those of other Neotropical Passerines with similar body mass, with a longer duration than that of temperate birds, evidence in favor of the hypothesis of slower pace of life in tropical birds. Method by Rohwer and Wang presents methodological advantages that would permit evaluating molt duration in species with low capture rates, suspended molts, or low molt synchrony between individuals. Molt intensity was higher in Gray Seedeater (13 feathers) than Blue-black Grassquit (9.3 feathers), and both were greater compared with other Passerines, which may represent an adaptive response to specific ecological pressures.

      Translated abstract

      RESUMEN La descripción de patrones y mecánica de muda de las aves ha permitido esclarecer la dinámica en ciclos de vida de especies de zonas templadas. Pocos estudios evalúan estos aspectos en aves neotropicales, dificultando su discusión funcional y evolutiva. Acá comparamos la duración de muda de primarias e intensidad de muda de vuelo en dos especies de paseriformes neotropicales, V. jacarina y S. intermedia. Desarrollamos el estudio al norte del departamento de Tolima (Colombia); capturamos las aves en un matorral y las marcamos con anillos de colores. Utilizamos los métodos de Pimm, y Rohwer y Wang para estimar la duración, y calculamos la intensidad de muda según Rohwer. La duración de muda de V. jacarina fue de 59 días (IC 95 % = 48-74) y 80 días (IC 95 % = 64-96), mientras que para S. intermedia fue de 80 (IC 95 % = 66-105) y 100 días (IC 95 % = 75-124). Estos resultados fueron consistentes con la duración de muda de paseriformes con masas similares, aunque mayores que en especies de latitudes altas, apoyando la hipótesis del bajo ritmo de vida en evaluar la duración en especies con baja captura, con muda suspendida, o baja asincronía entre individuos. La intensidad de muda fue mayor en S. intermedia (13 plumas) que en V. jacarina (9,3 plumas), resultados mayores que otros paseriformes neotropicales, que pueden representar una respuesta adaptativa a presiones ecológicas específicas.

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      Rate of moult affects feather quality: a mechanism linking current reproductive effort to future survival.

      Life-history theory proposes that costs must be associated with reproduction. Many direct costs are incurred during breeding. There is also evidence for indirect costs, incurred after breeding, which decrease survival and future reproductive success. One possible indirect cost identified in birds is that breeding activity in some way compromises plumage quality in the subsequent moult. Here we propose a mechanism by which this could occur. Breeding activity delays the start of moult. Birds that start to moult later also moult more rapidly--an effect of decreasing daylength. Could this result in poorer quality plumage? We kept two groups of male European starlings, Sturnus vulgaris, one on constant long days and the other on decreasing daylengths from the start of moult. Decreasing daylengths reduced the duration of moult from 103 +/- 4 days to 73 +/- 3 days (p < 0.0001). Newly grown primary feathers of birds that moulted fast were slightly shorter, weighed less (p < 0.05) and were more asymmetrical. They had a thinner rachis (p < 0.005), were less hard (p < 0.01) and less rigid (p < 0.05). They were also less resistant to wear so that differences in mass and asymmetry increased with time. There was no difference in Young's modulus. Poorer quality plumage will lead to decreased survival due to decreased flight performance and increased thermoregulatory costs. Thus, reproduction incurs costs through a mechanism that operates after the end of breeding.
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        Slow pace of life in tropical sedentary birds: a common-garden experiment on four stonechat populations from different latitudes.

        It has been hypothesized that organisms living at different latitudes or in different environments adjust their metabolic activity to the prevailing conditions. However, do differences in energy turnover simply represent a phenotypic adaptation to the local environment, or are they genetically based? To test this, we obtained nestling stonechats (Saxicola torquata) from equatorial Kenya (0 degrees N), Ireland (51.5 degrees N), Austria (47.5 degrees N) and Kazakhstan (51.5 degrees N). Birds were hand-raised and kept in Andechs, Germany. We measured their resting metabolic rates (RMR) and locomotor activity at an age of ca. 14 months (July) and 20 months (January), when birds went through postnuptial moult (July), and neither moulted nor exhibited enlarged gonads or migratory activity (January). RMR was generally higher during moult, but differed among populations: RMR was lowest in the resident Kenyan birds, higher in mostly sedentary Irish birds, and highest in migratory Austrian and Kazakhstan birds. Thus our data demonstrate that even in birds kept from early life under common-garden conditions, the 'pace of life', as indicated by metabolic turnover, is lower in sedentary tropical than in north-temperate migratory individuals of the same species. Such intrinsically low energy expenditure in sedentary tropical birds may have important implications for slow development, delayed senescence and high longevity in many tropical organisms.
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          THE MOULT OF THE BULLFINCH PYRRHULA PYRRHULA

           I. Newton (1966)
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            Author and article information

            Affiliations
            Ibagué Tolima orgnameUniversidad de Ibagué orgdiv1Faculty of Natural Sciences and Mathematics orgdiv2NATURATU Research Group Colombia
            Bogotá Bogotá orgnamePontificia Universidad Javeriana orgdiv1Faculty of Environmental and Rural Studies orgdiv2Department of Ecology and Territorial Development Colombia
            Ibagué Tolima orgnameUniversidad del Tolima orgdiv1Faculty of Sciences orgdiv2Zoology Research Group Colombia
            Contributors
            Role: ND
            Role: ND
            Role: ND
            Journal
            cal
            Caldasia
            Caldasia
            Instituto de Ciencias Naturales, Facultad de Ciencias-Universidad Nacional de Colombia (Bogotá, Cundinamarca, Colombia )
            0366-5232
            June 2018
            : 40
            : 1
            : 27-40
            S0366-52322018000100027
            10.15446/caldasia.v40n1.68817

            This work is licensed under a Creative Commons Attribution 4.0 International License.

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            Product Information: SciELO Colombia

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