Imperfect mimicry of host begging calls by a brood parasitic cuckoo: a cue for nestling rejection by hosts?

Coevolutionary interactions between avian brood parasites and their hosts often lead to the evolution of discrimination and rejection of parasite eggs or chicks by hosts based on visual cues, and the evolution of visual mimicry of host eggs or chicks by brood parasites. Hosts may also base rejection of brood parasite nestlings on vocal cues, which would in turn select for mimicry of host begging calls in brood parasite chicks. In cuckoos that exploit multiple hosts with different begging calls, call structure may be plastic, allowing nestlings to modify their calls to match those of their various hosts, or fixed, in which case we would predict either imperfect mimicry or divergence of the species into host-specific lineages. In our study of the little bronze-cuckoo (LBC) Chalcites minutillus and its primary host, the large-billed gerygone Gerygone magnirostris, we tested whether: (1) hosts use nestling vocalizations as a cue to discriminate cuckoo chicks; (2) cuckoo nestlings mimic the host begging calls throughout the nestling period; and (3) the cuckoo begging calls are plastic, thereby facilitating mimicry of the calls of different hosts. We found that the begging calls of LBCs are most similar to their gerygone hosts shortly after hatching (when rejection by hosts typically occurs) but become less similar as cuckoo chicks get older. Begging call structure may be used as a cue for rejection by hosts, and these results are consistent with gerygone defenses selecting for age-specific vocal mimicry in cuckoo chicks. We found no evidence that LBC begging calls were plastic.

Sex role similarity and sexual selection predict male and female song elaboration and dimorphism in fairy-wrens.

Historically, bird song complexity was thought to evolve primarily through sexual selection on males; yet, in many species, both sexes sing and selection pressure on both sexes may be broader. Previous research suggests competition for mates and resources during short, synchronous breeding seasons leads to more elaborate male songs at high, temperate latitudes. Furthermore, we expect male-female song structure and elaboration to be more similar at lower, tropical latitudes, where longer breeding seasons and year-round territoriality yield similar social selection pressures in both sexes. However, studies seldom take both types of selective pressures and sexes into account. We examined song in both sexes in 15 populations of nine-fairy-wren species (Maluridae), a Southern Hemisphere clade with female song. We compared song elaboration (in both sexes) and sexual song dimorphism to latitude and life-history variables tied to sexual and social selection pressures and sex roles. Our results suggest that song elaboration evolved in part due to sexual competition in males: male songs were longer than female songs in populations with low male survival and less male provisioning. Also, female songs evolved independently of male songs: female songs were slower paced than male songs, although only in less synchronously breeding populations. We also found male and female songs were more similar when parental care was more equal and when male survival was high, which provides strong evidence that sex role similarity correlates with male-female song similarity. Contrary to Northern Hemisphere latitudinal patterns, male and female songs were more similar at higher, temperate latitudes. These results suggest that selection on song can be sex specific, with male song elaboration favored in contexts with stronger sexual selection. At the same time, selection pressures associated with sex role similarity appear to favor sex role similarity in song structure.

Conspicuous Plumage Does Not Increase Predation Risk: A Continent-Wide Test Using Model Songbirds.

The forces shaping female plumage color have long been debated but remain unresolved. Females may benefit from conspicuous colors but are also expected to suffer costs. Predation is one potential cost, but few studies have explicitly investigated the relationship between predation risk and coloration. The fairy-wrens show pronounced variation in female coloration and reside in a wide variety of habitats across Australasia. Species with more conspicuous females are found in denser habitats, suggesting that conspicuousness in open habitat increases vulnerability to predators. To test this, we measured attack rates on 3-D-printed models mimicking conspicuously colored males and females and dull females in eight different fairy-wren habitats across Australia. Attack rates were higher in open habitats and at higher latitudes. Contrary to our predictions, dull female models were attacked at similar rates to the conspicuous models. Further, the probability of attack in open habitats increased more for both types of female models than for the conspicuous male model. Across models, the degree of contrast (chromatic and achromatic) to environmental backgrounds was unrelated to predation rate. These findings do not support the long-standing hypothesis that conspicuous plumage, in isolation, is costly due to increased attraction of predators. Our results indicate that conspicuousness interacts with other factors in driving the evolution of plumage coloration.

[Evaluation of the nutritional status and physical performance in candidates to liver transplantation]. / Avaliação da capacidade física e do estado nutricional em candidatos ao transplante hepático.

OBJECTIVE: To evaluate the physical capacity and nutritional status of patients before orthotopic liver transplantation (OLT) and to correlate these parameters to the severity of liver function. METHODS: Thirty-two patients before OTL were classified as Child-Pugh A (25%), B (22%) and C (53%). Physical capacity was analyzed by the quadriceps and ankle strength, balance, coordination, gait velocity, 6 minute walk test, get up and go test, Barthel and Karnofsky indexes. Nutritional status was evaluated by using Mendenhall score and Blackburn classification. RESULTS: Quadriceps weakness was found in 32% of the patients. Impaired balance and coordination were detected in 34.8% and 15.6% of the patients. Low physical performance was found in 72.5% of the patients (6 min walk test: 31.6% severely; 40.9% moderately impaired) and 43.8% required considerable assistance when the Karnofsky index was applied. Malnutrition was found in 62.5% of the patients (34.37% moderately and severely malnourished and 28.13% mildly malnourished). Chi-square analysis showed no association between Child-Pugh classification and nutritional status, the 6 min walk test and Karnofsky index. The association between the two functional tests was statistically significant (p<0.001). CONCLUSION: The results show that physical impairment and nutritional deficit were highly prevalent in the patients studied, independent of the degree of hepatic dysfunction evaluated by the traditional Child-Pugh classification.

Avaliação da capacidade física e do estado nutricional em candidatos ao transplante hepático / Evaluation of the nutritional status and physical performance in candidates to liver transplantation

OBJETIVO: Avaliar o estado nutricional, os indicadores de capacidade física e suas relações com a função hepática, em pacientes candidatos ao transplante de fígado. MÉTODOS: Foram estudados 32 pacientes pré-transplante, classificados como Child-Pugh A (25 por cento), B (22 por cento) e C (53 por cento). A capacidade física foi avaliada pelos parâmetros: força muscular do quadríceps, dos flexores plantares e dorsais do pé; equilíbrio estático; coordenação; velocidade da marcha; teste de 6 minutos de caminhada e teste "timed get up and go"; índices de Barthel e de Karnofsky. O estado nutricional foi avaliado pelo escore de Mendenhall e classificado segundo Blackburn. RESULTADOS: Foi detectado déficit de força de quadríceps (32 por cento dos pacientes), do equilíbrio (34,8 por cento), da velocidade da marcha (66,7 por cento) e da coordenação (15,6 por cento). O teste de caminhada indicou baixo desempenho físico em 72,5 por cento dos pacientes (moderado em 40,9 por cento e grave em 31,6 por cento). O índice de Karnofsky revelou que 43,8 por cento dos pacientes necessitava assistência considerável. Foi identificada desnutrição em 62,5 por cento dos pacientes (leve em 28,13 por cento; moderada e grave em 34,37 por cento). O teste do qui quadrado não mostrou associação entre a classificação de Child-Pugh e o estado nutricional, o teste de caminhada e o índice de Karnofsky. A associação entre o teste de caminhada e o índice de Karnofsky foi altamente significante (p<0,001). CONCLUSÃO: Os resultados monstraram que a incapacidade física e a desnutrição foram altamente prevalentes nos pacientes estudados, independente do grau da disfunção hepática avaliada segundo a classificação tradicional de Child-Pugh