LA CALIDAD DEL NÉCTAR AFECTA LA CONDUCTA TERRITORIAL Y DE FORRAJEO EN HEMBRAS DEL COLIBRÍ LUCIFER (CALOTHORAX LUCIFER): UN EXPERIMENTO

Resumen ∙ Los colibríes para vivir dependen de la energía que les brinda el néctar floral, un recurso  variable espacial y temporalmente. Por ello, deben recabar información sobre su cantidad y calidad en las flores que visitan. Esta información moldea la toma de decisiones durante el forrajeo en los colibríes. En el presente estudio analizamos el efecto de la exposición previa a una fuente de volumen constante de néctar pero de calidad variable, sobre el comportamiento de defensa contra intrusos durante el forrajeo de hembras del Colibrí Lucifer (Calothorax lucifer). Para probarlo realizamos experimentos de campo utilizando bebederos con tres calidades energéticas de néctar (baja, media y alta). Registramos la frecuencia de encuentros agonísticos contra intrusos a lo largo de treinta días de exposición a los bebederos y el éxito de forrajeo de los intrusos en los bebederos. A lo largo de los días la probabilidad de defensa aumentó en las hembras que establecieron territorios en torno a bebederos con néctar de media y alta calidad, pero disminuyó para los bebederos con néctar de baja calidad. Además, el número de intrusos no exitosos fue mayor en torno a los bebederos con néctar de media y alta calidad. Nuestros resultados sugieren que las hembras de Calothorax lucifer pueden modificar su conducta agonística y de forrajeo a lo largo del tiempo de acuerdo a la experiencia e información que reúnen sobre la calidad de los recursos presentes en el ambiente.  Abstract ∙ Nectar quality affects foraging and territoriality in female Lucifer Hummingbirds (Calothorax lucifer): an experiment Hummingbirds depend for survival on the energy contained in nectar, a resource that shows both spatial and temporal variation. Therefore, they should gather information on the quantity and quality of the flowers they visit, which should affect decision‐making of hummingbirds during their foraging. In the present study, we analyzed the effect of prior exposure to a source of constant volume of nectar, but of varying quality (sugar concentration), on the territorial behavior against intruders of female Lucifer Hummingbirds (Calothorax lucifer) during foraging. We carried out field experiments using feeders containing three different qualities of nectar (low, medium, and high energy). We recorded the frequency of agonistic encounters with intruders over thirty days of exposure to the feeders and the foraging success of the intruders on feeders. Throughout the study the probability of defense against intruders increased in females, who established territories around nectar feeders with medium and high quality nectar, but decreased for those with territories around low quality nectar feeders. In addition, the number of unsuccessful intruders was greater around medium and high quality feeders. Our results suggest that females of Calothorax lucifer can modify their agonistic and foraging behavior throughout time in accordance to experience and gather information about the quality of resources present in the environment

LA CONDUCTA TERRITORIAL DEL ZAFIRO OREJA BLANCA (HYLOCHARIS LEUCOTIS) ES AFECTADA POR LA DISPONIBILIDAD DE ENERGÍA

White-eared Hummingbird (Hylocharis leucotis) territorial behavior is affected by energy availability. – Territoriality is a costly-foraging strategy. As a result, territorial animals must ensure that the energy within their territories is sufficient to support the costs of its defense. Hummingbirds are territorial and depend on nectar-containing flowers as their main energy source. In this study, we hypothesized that White-eared hummingbirds (Hylocharis leucotis), depending on the amount of energy (nectar) available in the environment, modify four aspects of their behavior (i.e., time spent for perching, foraging, and actively and passively defending territory), as well as territory size and response to intrusions into their territory. We monitored 30 individual territories during the winter flowering season at El Chico National Park, Mexico, and did not detect a significant effect of the energy available on time spent for perching or foraging, respectively. However, White-eared hummingbirds invested significantly more time in active and passive defense when the intrusion pressure was higher, and successful intrusions increased when the territories were bigger. Moreover, although territory size increased or decreased, a similar amount of energy therein was maintained throughout the duration of the study. Our results indicate that in this hummingbird species energy availability determines the size of their territories and the time spent on its defense

MORPHOMETRIC TRAITS AND THEIR ASSOCIATION WITH SEX IN THE KEEL-BILLED TOUCAN RAMPHASTOS SULFURATUS

Sexing monomorphic birds is essential for reproduction in conservation programs. In ramphastids (toucans) species, males have longer beaks than females, making beak morphometry potentially useful for sexing. In this study, we measured the following traits: curved beak length, total culmen length, straight beak length, curved and straight length of the ventral line of the gnathotheca, beak width, lateral area of the rhinotheca, and cloacal opening in 44 Keel-billed Toucans, as well as previously reported morphometric data from 17 additional individuals. Measurements were obtained using two methods (manual and image processing software), and the reliability between the two methods was assessed using the intraclass correlation coefficient (ICC). Individuals of unknown sex were sexed via PCR tests. The ICC showed poor reliability between the two measurement methods, so we only used manual measurements for comparisons between the sexes. We used GLMMs to determine whether the morphometric traits we measured could be used to determine sex in keel-billed toucans. In addition, we evaluated GLMMs to determine which morphometric trait was the strongest predictor of sex in this species. Beak length was longer in adult males than in females. The GLMMs indicated that beak traits associated with sex in this species are beak curved length, beak straight length, straight length of the ventral line of the gnathotheca, and total culmen length. The straight length of the ventral line of the gnathotheca was the strongest predictor of sex in the Keel-billed Toucan. Unlike previous research, the development of GLMMs allows us to determine the probability of a toucan’s sex based on continuous variables, facilitating sexing and allowing us to evaluate the reliability of the estimation of the sexing of each toucan. This method is an alternative for situations where other sexing methodologies cannot be performed

Reporte de un colibrí oreja blanca (Hylocharis leucotis) afectado por el trastorno de queratina aviar

El trastorno de la queratina aviar ocasiona un crecimiento anormal del pico y afecta a varias especies de aves en América y Europa. Sin embargo, hasta la fecha, no se había registrado en el grupo de los colibríes. En este trabajo reportamos a un individuo de Hylocharis leucotis con dicho trastorno, el cual fue capturado en la localidad de San Bernardino Lagunas, Vicente Guerrero, Puebla. Es posible que esta alteración afecte la alimentación y polinización de los colibríes que la padecen

Community-level reorganizations following migratory pollinator dynamics along a latitudinal gradient.

Predicting how communities re-arrange in response to changes in species composition remains a key challenge in ecology. Migratory species, which enter and leave communities across latitudinal gradients, offer us a unique opportunity to evaluate community- and species-level responses to a shift in community composition. We focused on a migratory hummingbird and the communities that host it along a latitudinal and species diversity gradient. Our results show higher niche overlap in more diverse communities, allowing resident species to compensate for the loss of the migrant in providing pollination services. Contrastingly, in less diverse communities, the migrant behaves as a specialist, monopolizing abundant resources. In its absence, its role is not fully covered by resident species, resulting in a decrease in the fruit set of the migrant's preferred plant species. These results help us understand the potential impacts of biodiversity loss and have important implications for community persistence given expected changes in the migratory behaviours of some species