Foraging behavior of tyrant flycatchers (Aves, Tyrannidae) in Brazil

Effects of natural and anthropogenic storm-stranded debris in upper-beach arthropods: Is wrack a prey hotspot for birds?

Storm-stranded debris (i.e., wrack) are important components for the functioning of beach ecosystems. With the current increase in extreme storm events, beached wrack is expected to change globally. However, little is known about how different types of wrack can affect beach biodiversity. Here, we hypothesized that natural debris (algae and land-plant debris) would optimize the short-term aggregation of benthic arthropods on the beach ecosystem, while anthropogenic debris (plastics) would not perform this function. We also expected that short-term aggregations of arthropods in the natural debris would create a transient prey hotspot (i.e., points of high prey concentration) for birds on the beach. Thus, we performed manipulative field experiments with debris addition and predator exclusion by cage on a short temporal scale (maximum 20 days). We found that natural debris aggregated higher community abundances than anthropic debris and treatments without debris, while community richness was not affected by wrack. No differences were noted when comparing the community aggregation on plastic debris and treatments without debris. The coleopterans were the group responsible for this aggregation, mainly represented by Phaleria testacea, which aggregated on natural debris with abundances five times greater than those on plastic debris. Nevertheless, we did not find any evidence of increased predation by birds on the coleopterans aggregated in the natural debris. We conclude that arthropod aggregation in the wrack is a phenomenon primarily associated with natural debris, not occurring in plastic debris, although the role of this faunal aggregation as a prey hotspot for birds was not evident in the short term. These results showed that the wrack type matters in terms of consequences for beach arthropods, creating concerns against beach cleaning methods that are adopted indiscriminately, also signaling the need for long-term studies to proceed with investigating the wrack functions for top predators on sandy beaches.

Morphology of migration: associations between wing shape, bill morphology and migration in kingbirds (Tyrannus)

Morphology is closely linked to locomotion and diet in animals. In animals that undertake long-distance migrations, limb morphology is under selection to maximize mobility and minimize energy expenditure. Migratory behaviours also interact with diet, such that migratory animals tend to be dietary generalists, whereas sedentary taxa tend to be dietary specialists. Despite a hypothesized link between migration status and morphology, phylogenetic comparative studies have yielded conflicting findings. We tested for evolutionary associations between migratory status and limb and bill morphology across kingbirds, a pan-American genus of birds with migratory, partially migratory and sedentary taxa. Migratory kingbirds had longer wings, in agreement with expectations that selection favours improved aerodynamics for long-distance migration. We also found an association between migratory status and bill shape, such that more migratory taxa had wider, deeper and shorter bills compared to sedentary taxa. However, there was no difference in intraspecific morphological variation among migrants, partial migrants and residents, suggesting that dietary specialization has evolved independently of migration strategy. The evolutionary links between migration, diet and morphology in kingbirds uncovered here further strengthen ecomorphological associations that underlie long-distance seasonal movements in animals.

Both Palatable and Unpalatable Butterflies Use Bright Colors to Signal Difficulty of Capture to Predators

Birds are able to recognize and learn to avoid attacking unpalatable, chemically defended butterflies after unpleasant experiences with them. It has also been suggested that birds learn to avoid prey that are efficient at escaping. This, however, remains poorly documented. Here, we argue that butterflies may utilize a variety of escape tactics against insectivorous birds and review evidence that birds avoid attacking butterflies that are hard to catch. We suggest that signaling difficulty of capture to predators is a widespread phenomenon in butterflies, and this ability may not be limited to palatable butterflies. The possibility that both palatable and unpalatable species signal difficulty of capture has not been fully explored, but helps explain the existence of aposematic coloration and escape mimicry in butterflies lacking defensive chemicals. This possibility may also change the role that putative Müllerian and Batesian mimics play in a variety of classical mimicry rings, thus opening new perspectives in the evolution of mimicry in butterflies.

Annual changes in a bird assembly on artificial perches: Implications for ecological restoration in a subtropical agroecosystem

Artificial perches are used in tropical forest restoration projects to increase the dispersal of seeds into restored areas. The ability of perches to enhance seed deposition depends on their ability to attract seed dispersing birds, as well as the correlation between the season of bird visits to perches and the phenology of fruit production in adjacent forests. Using data collected from a large-scale restoration project, we characterized the community of birds that utilize artificial perches over the course of one year. We hypothesized that the structure of a bird assemblage that uses artificial perches is affected by seasonal variation. We aimed to describe the richness, abundance and diversity of a bird assemblage on artificial perches in a subtropical Atlantic forest restoration experiment in Southern Brazil. Richness and abundance estimates of the avian fauna were obtained from eight artificial perches placed in four experimental plots (∼2 y-old). Parameters of richness and abundance were compared using ANOVA. The bird assemblage was described using SHE analysis [richness (S), diversity (H') and evenness (E)], with additional estimates of occurrence and dominance. In total, 451 records of 32 ± 3.16 SD species were obtained. Thraupidae was the most numerous family (nine species, 28.12% of the total). Richness and abundance varied seasonally and were highest during spring and summer. Five migratory species of flycatchers were recorded between spring and early autumn. Perches were ineffective in attracting specialized frugivorous birds, emphasizing that seed dispersal tends to be carried out primarily by generalist omnivores in the initial phase of forest regeneration.

Foraging behavioral of Phylloscartes ventralis (Aves, Tyrannidae) in native and planted forests of southern Brazil

Few studies have related the effects of silviculture practices to the behavior of bird species in the Neotropics. The present study examined the foraging behavior of Phylloscartes ventralis (Temminck, 1824) in a native forest and in silviculture areas of Pinus elliotti and Araucaria angustifolia with different structures and ages. We tested two general hypotheses: (1) areas of commercial forest plantation change the foraging behavior of P. ventralis in relation to native forest, and (2) the foraging behavior of P. ventralis in silviculture areas with understories (complex structures) is different from its behavior in areas without understory. The results showed that P. ventralis changed its foraging behavior depending on the type of forest, and on the presence of an understory in silviculture areas. Main changes involved the height and angle of substrate where the prey was captured. Phylloscartes ventralis showed the same set of attack maneuvers, with more maneuvers type in young Pinus planted without understory. The frequency of use of attack maneuvers was more similar in areas of silviculture with understory and in the native forest. The results highlight the importance of an understory structure and the utilization of native plant species in silviculture practices, to the foraging behavior of native bird species.

Foraging of Great Kiskadees (Pitangus sulphuratus) and food items offered to nestlings in the Pantanal

Feeding of Pitangus sulphuratus (Tyrannidae) nestlings have been poorly studied. Here we describe the foraging behavior of a P. sulphuratus pair and the searching and offering time of food items to nestlings in the Pantanal, Brazil. Data collection was carried out over 25 days on the outskirts of the Base de Estudos do Pantanal building, inhabited by insectivorous bats. Records were based on direct observations with the help of binocular. The pair required little time for searching for small insects and fruits, but these items comprised a little amount of food per event of capture. Some large prey was more time-costly for searching, but the long period that these food items were offered to nestlings overcompensated the searching time. Considering the time of feeding nestlings (benefit) in relation to the searching time by the parents (cost), bats and snails are the most advantageous items for P. sulphuratus parents feeding nestlings at the study site.

Determinants of partial bird migration in the Amazon Basin

1. Little is known about mechanisms that drive migration of birds at tropical latitudes. Because most migratory bird species in South America have populations that are present year-round, partial migration (in which only some individuals of a given population migrate at the end of the breeding season) is likely to be common, providing an opportunity to assess proximate mechanisms of migration. 2. Two non-mutually exclusive hypotheses explaining intraspecific variation in migratory behaviour were tested in a Tropical Kingbird Tyrannus melancholicus population in the southern Amazon Basin, where a dramatic dry season decrease in the abundance of insect food for kingbirds may promote migration of some individuals. 3. The Dominance hypothesis predicts sub-dominant individuals migrate at the end of the breeding season and dominant individuals do not, whereas the Body Size hypothesis predicts smaller individuals migrate and larger individuals do not. 4. Based on 4 years of data on individually-marked birds, strong support was found for occurrence of partial migration in the study population. 5. In the best model, the largest males (which are typically older and dominant to younger individuals) had the highest probability of migrating. Younger females (which are the smallest individuals in the population) were also more likely to migrate than other kingbirds, except the largest males. Thus, an individual's probability of migrating was associated with a more complex interaction of size, age and sex than predicted by current hypotheses. 6. These results suggest that determinants of migratory behaviour differ between North temperate and tropical latitudes. Most tests of partial migration theory have been conducted on granivores (e.g. emberizids) or omnivores (e.g. turdids and icterids) at North temperate latitudes, where seasonality is primarily defined by temperature cycles. In tropical South America, however, the most common long-distance migrants are primarily insectivorous (i.e. tyrannids), and seasonality is largely defined by rainfall cycles. 7. We propose a hypothesis based on seasonal food limitation to explain partial migration of primarily insectivorous species in seasonal tropical habitats.

Birds foraging for fruits and insects in shrubby restinga vegetation, southeastern Brazil

Understanding how birds use vegetation to obtain food resources has implications for habitat conservation and management. Restinga is a poorly known and threatened tropical habitat, associated to the Atlantic forest, that could benefit from this kind of information to know which plants can be used and dispersed by birds that can help on the maintenance of this habitat. Frugivorous and insectivorous birds are important components of tropical ecosystems, such as restinga. To provide more information regarding the ecology of restinga, we studied the feeding behavior and spatial use of this vegetation by birds at Restinga de Jurubatiba National Park, southeastern Brazil. We found that feeding behavior was similar to that recorded for the same species in other vegetation types. In addition, spatial use of the restinga vegetation by the most abundant species did not overlap greatly, except for two insectivorous species that used different foraging maneuvers and two frugivorous birds that foraged in flocks. The two most abundant species were generalists in their diet and were capable of feeding at the ground level on sand substrate.

Comportamento de forrageamento e dieta de Polystictus superciliaris (Aves, Tyrannidae) no sudeste do Brasil

O presente artigo descreve o comportamento de forrageamento e a dieta de Polystictus superciliaris (Wied, 1831), espécie pouco conhecida e de distribuição geográfica restrita às montanhas do leste do Brasil. Este trabalho foi realizado entre abril e dezembro de 2005 no Parque Estadual da Serra do Rola Moça, município de Nova Lima, Minas Gerais (20°03'S, 44°00'W). Para cada observação de forrageamento foram registrados os comportamentos de ataque, a direção e o substrato do ataque, a altura do substrato de forrageamento e a fitofisionomia onde o ataque ocorreu. Para a determinação da dieta da espécie foram feitas observações diretas de campo, sendo também analisado o conteúdo estomacal de 16 indivíduos. Polystictus superciliaris usa preferencialmente a canga couraçada (93,3%), tendo como substrato principal as folhas (69,1%) das plantas mais abundantes na área. A espécie é generalista quanto ao comportamento de ataque. A análise de conteúdos estomacais revelou a presença exclusiva de artrópodes. As observações confirmaram o caráter insetívoro de P. superciliaris, que não foi observado consumindo frutos ou outro material de origem vegetal.