Abstract. In western Panama, an unusual hybrid zone exists between white-collared manakins, Manacus candei, and golden-collared manakins, M. vitellinus. Unidirectional introgression of plumage traits from vitellinus into candei has created a region in which all definitively plumaged males have a collar that is lemon-colored. These males are nearly indistinguishable from white-collared candei genetically and morphometrically, but strongly resemble golden-collared vitellinus due to the introgression of secondary sexual plumage traits, particularly the lemon-colored collar. The introgression could be explained by sexual selection for golden-collared traits or by a series of mechanisms that do not invoke sexual selection (e.g., neutral diffusion, dominant allele). Sexual selection on male-male interactions implies behavioral differences among the plumage forms-specifically that golden-and lemon-collared males should be more aggressive than white-collared males. In contrast, the nonsexual hypotheses predict behavioral similarity between lemon-and white-collared males, based on their nearly identical genetics. We tested the sexual selection hypothesis experimentally, by presenting males with taxidermic mounts of the three forms. As response variables, we monitored vocalizations and attacks on the mounts by replicate subject males. Both golden-collared and lemon-collared males were more likely to attack than were white-collared males, as predicted under sexual selection but not by the nonsexual hypotheses. Lemon-collared males were more vocally reactive than either parental form, contrary to the prediction of the nonsexual hypotheses. Our study demonstrates that sexual selection on male-male interactions may play an important role in the dynamics of character evolution and hybrid zones.

In western Panama, an unusual hybrid zone exists between white-collared manakins, Manacus candei, and golden-collared manakins, M. vitellinus. Unidirectional introgression of plumage traits from vitellinus into candei has created a region in which all definitively plumaged males have a collar that is lemon-colored. These males are nearly indistinguishable from white-collared candei genetically and morphometrically, but strongly resemble golden-collared vitellinus due to the introgression of secondary sexual plumage traits, particularly the lemon-colored collar. The introgression could be explained by sexual selection for golden-collared traits or by a series of mechanisms that do not invoke sexual selection (e.g., neutral diffusion, dominant allele). Sexual selection on male-male interactions implies behavioral differences among the plumage forms-specifically that golden-and lemon-collared males should be more aggressive than white-collared males. In contrast, the nonsexual hypotheses predict behavioral similarity between lemon-and white-collared males, based on their nearly identical genetics. We tested the sexual selection hypothesis experimentally, by presenting males with taxidermic mounts of the three forms. As response variables, we monitored vocalizations and attacks on the mounts by replicate subject males. Both golden-collared and lemon-collared males were more likely to attack than were white-collared males, as predicted under sexual selection but not by the nonsexual hypotheses. Lemon-collared males were more vocally reactive than either parental form, contrary to the prediction of the nonsexual hypotheses. Our study demonstrates that sexual selection on male-male interactions may play an important role in the dynamics of character evolution and hybrid zones.

SummaryWe provide new information on all birds known from San Rafael National Park, Paraguay. Ornithological records from the period 1997 to 2006 have been reviewed, adding 112 new species to the reserve's avifauna. We provide data on the presence of 405 species in seven basic habitats types, and on their relative abundance. Biogeographically, San Rafael has a mixed avifauna, consisting of 70 Atlantic Forest endemic species, two Mesopotamian Grassland endemics, and many with a wider distribution in South America. At least 12 species are threatened and 16 nearthreatened, including important populations of Dryocopus galeatus, Platyrinchus leucoryphus, Alectrurus tricolor and Xanthopsar flavus. We provide brief comments on records of these 28 species within the study site. The avifauna of the reserve is one the most important in Paraguay, due to its high diversity and endemism. At the same time, it is under great threat and its viability is at risk unless urgent actions are taken. Fragmentation of the Atlantic Forest in Paraguay has left the San Rafael block almost totally isolated from other forests. The degradation of its forests through selective logging and clearance for agriculture still has severe impacts, as do hunting and frequent fires in grasslands and forests. Unfortunately, the legal situation of the National Park is extremely precarious, creating great uncertainty and problems for its conservation. ResumenAqui relatamos nuevas informaciones sobre todas las aves conocidas hasta el presente dentro del Parque Nacional San Rafael. Se han revisado registros ornitoló gicos comprendidos entre los añ os 1997 y 2006, que han permitido añ adir 112 especies nuevas para la reserva. De esta manera, San Rafael tiene un total de 405 especies registradas. Para cada una de ellas se facilitan datos que documentan su presencia en siete tipos de hábitats básicos diferenciados, y de su abundancia relativa. Biogeográficamente, la avifauna de San Rafael es una mezcla que está compuesta por 70 especies endémicas del Bosque Atlántico, dos endémicas de los Pastizales de la Mesopotamia, y el resto, son de distribución más amplia en Sudamérica. Al menos, 12 especies están amenazadas y 16 casi-amenazadas, incluyendo poblaciones importantes de Dryocopus galeatus, Platyrinchus leucoryphus, Alectrurus tricolor y Xanthopsar flavus. De éstas 28 especies, se proporcionan comentarios breves sobre sus registros en el área de estudio. La avifauna de la reserva resulta una de las más importantes dentro del Paraguay, tanto por su mayor diversidad y presencia de endemismos, como por ser una de las áreas con alto potencial para mantener la biodiversidad, al tiempo que se encuentra sometida a fuertes amenazas que ponen en peligro su viabilidad en caso de no tomarse medidas urgentes. La alta fragmentació n del Bosque Atlántico dentro del

Lek-mating Long-tailed Manakins (Chiroxiphia linearis) exhibit an unusual pattern of delayed plumage maturation. Each year, males progress through a series of predefinitive plumages before attaining definitive plumage in their fifth calendar year. Females also exhibit variation in plumage coloration, with some females displaying male-like plumage characteristics. Using data from mist-net captures in northwest Costa Rica (n = 1,315) and museum specimens from throughout the range of Long-tailed Manakins (n = 585), we documented the plumage sequence progression of males, explored variation in female plumage, and described the timing of molt in this species. Males progressed through a series of age-specific predefinitive plumages, which enabled the accurate aging of predefinitive-plumaged males in the field; this predefinitive plumage sequence is the basis for age-related status-signaling in these males. Females tended to acquire red coloration in the crown as they aged. However, colorful plumage in females may be a byproduct of selection on bright male plumage. Females exhibited an early peak of molt activity from February to April, little molt from May through July, and a second, more pronounced peak of molt activity in October. By contrast, males in older predefinitive-plumage stages and males in definitive plumage exhibited comparable unimodal distributions in molt activity beginning in June and peaking between July and October. Our data are consistent with selective pressure to avoid the costs of molt-breeding overlap in females and older males. Our findings have important implications for social organization and signaling in Long- tailed Manakins, and for the evolution of delayed plumage maturation in birds. Desarrollo del Plumaje y Muda en Chiroxiphia linearis: Variación de Acuerdo al Sexo y la Edad

A região de fronteira entre Brasil e Paraguai, no estado de Mato Grosso do Sul, encontra-se no centro de um dos Corredores Bioceânicos propostos e contempla áreas naturais de Chaco e Pantanal com exuberante biodiversidade. O ecoturismo tem na biodiversidade sua principal fonte de insumos, onde se destaca o turismo de observação de aves. Além de conectar territórios para viabilizar uma cadeia produtiva específica, o corredor logístico pode integrar pessoas e grupos sociais, e criar novas oportunidades de valorização dos ambientes naturais por meio do ecoturismo. O objetivo deste trabalho é propor roteiros integrados para o turismo de observação de aves na fronteira entre Brasil e Paraguai como estratégia de conservação da biodiversidade, inclusão social, dinamização econômica e valorização cultural das comunidades localizadas nos territórios de influência do Corredor Bioceânico. O trabalho foi desenvolvido entre 2002 e 2018 em Porto Murtinho (Brasil), Carmelo Peralta, departamento de Alto Paraguay, Concepción, Presidente Hayes e Boquerón (Paraguai). Foram identificados 10 potenciais roteiros para o turismo de observação de aves, dos quais, cinco encontram-se em Porto Murtinho, dois binacionais (Brasil/Paraguai), e outros três no Paraguai. Os roteiros envolvem locais com alta diversidade de aves: Parque Natural Municipal da Cachoeira do Apa, Parque Nacional Defensores del Chaco, Parque Nacional Médanos del Chaco, além de Reservas Privadas e a Reserva da Biosfera do Chaco no Paraguai. Ao todo, somam-se mais de 400 espécies de aves, entre endêmicas, migratórias, raras e ameaçadas. Esse segmento turístico representa um dos diversos modelos para o desenvolvimento sustentável da região do Corredor Bioceânico. Além disso, a proposta de roteiros integrados de birdwatching no Chaco reflete o potencial transfronteiriço do segmento e pode estimular a melhoria dos destinos, a geração de renda, a identificação de novos produtos e ampliar a qualidade da experiência do turista observador.

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