. Diseaselimited distributions? Contrasts in the prevalence of avian malaria in shorebird species using marine and freshwater habitats. Á/ Oikos 109: 396 Á/404.Migratory shorebirds show strong dichotomies in habitat choice during both the breeding and nonbreeding season. Whereas High Arctic breeding species are restricted to coastal marine and saline habitats during the nonbreeding season, more southerly breeding species tend to use freshwater habitats away from coasts. It has been proposed that this co-variation in habitat use is a consequence of a single axis of adaptation to pathogens and parasites, which are hypothesized to be relatively scarce in High Arctic, marine, and saline habitats and relatively common at lower latitudes and in freshwater habitats. Here we examine this contrast by comparing the prevalence of avian malaria infections in shorebirds occupying different habitats. We used a PCR-based assay on 1319 individuals from 31 shorebird species sampled in the Arctic, in temperate Europe and in inland and marine habitats in West Africa. Infections mainly occurred in tropical wetlands, with the shorebirds in freshwater inland habitats having significantly higher prevalence of malaria than birds in marine coastal habitats. Infections were not found in birds migrating through Europe even though conspecifics did show infections in tropical Africa. Adults should resist infection better than juveniles, but showed higher malaria prevalence, suggesting that infection probability increases with cumulative exposure. We argue that exposure to vectors is the main factor explaining the habitat-related differences in malaria prevalence.

No abstract

P. 2005. Differential migration of chiffchaffs Phylloscopus collybita and P. ibericus in Europe and Africa. Á/ J. Avian Biol. 36: 184 Á/190.Differential migration is a widespread, but poorly understood, phenomenon in birds. In this paper, we present the first detailed field study of differential migration in the Old World warbler (Sylviidae) family. We studied two chiffchaff Phylloscopus [collybita ] semispecies: the common chiffchaff P. [c. ] collybita and the Iberian chiffchaff P. [c. ] ibericus. Using data collected at several latitudes in Europe and Africa, we present convincing evidence for differential distance migration of sexes in chiffchaffs, with females moving further than males. Interestingly, while there was a pronounced gradient in the sex-ratios in Europe and North Africa (with an increasing proportion of females with declining latitude), no clear pattern was found south of the Sahara, where sex-ratios were more male-biased than predicted by a simple latitude model. This suggests that, amongst the chiffchaffs wintering in West Africa, a large proportion is composed by Iberian birds, and provides support to previous suggestions that Iberian chiffchaffs are long distance migrants. Results from detailed studies in Senegal also show that chiffchaffs display differential timing of spring migration, with males leaving the winter quarters considerably earlier than females. The results are discussed in the framework of the three main (non-mutually exclusive) hypotheses attempting to explain the latitudinal segregation of the sexes. Given the relative failure of standard comparative studies to discriminate between competing single-factor hypotheses to explain differential migration, it is argued that the chiffchaff species complex might be particularly suited to study this issue using a new approach suggested by Cristol et al. (1999): detailed (further) comparisons between closely related species (such as the common and the Iberian chiffchaffs) could help identifying the key factors to be incorporated into optimality models that can predict relative distance of migration of different sex or age classes.

Vultures constitute an important functional group in many ecosystems, providing crucial ecosystem services both in natural and humanized environments. These scavengers are facing massive declines worldwide, but in several African countries virtually nothing is known on populations’ status and threats, hampering the development of adequate conservation strategies. In Guinea-Bissau, globally important populations of Hooded Necrosyrtes monachus and African white-backed vultures Gyps africanus were recently reported. Using the country as a study area, we aim to characterize human-vulture interactions in West Africa applying a multidisciplinary approach. We assessed the status and distribution of vulture populations using data from 1711 km of roadside transects, examined predictors of their distribution, and produced a nationwide population estimate for the Hooded Vulture, using an innovative method based on the relationship between the size of human population in settlements and vulture numbers. We conducted 47 stakeholder interviews to assess perceived roles played by vultures, and to investigate potential anthropogenic threats. Hooded vultures were strongly associated with high human population densities, whereas no relation was found between African white-backed and Rüppell’s vultures and any of the tested predictors, which included cattle density, precipitation and Normalized Difference Vegetation Index, among others. We estimate a national population of 43347 Hooded vultures, the largest population reported in the species range. Respondents were generally aware of the services provided by vultures, especially waste and carcass removal, including in urban areas. Hunting for witchcraft and traditional medicine was the most frequently recognised threat, while poisoning was ranked as having the highest impact. We hypothesise that poisoning-related mortality may be affecting African white-backed and Rüppell’s vultures’ distribution and explain their scarcity in apparently highly suitable habitats. Our results suggest a mutualistic rather than a commensalistic relationship between vultures and humans, with important implications for designing and implementing conservation strategies.

1. Anthropogenic changes in the marine environment and global climate change have led to population declines in several seabird species worldwide. Rockhopper penguins (Eudyptes chrysocome and Eudyptes moseleyi) have experienced a dramatic population decline, potentially linked to increasing sea surface temperatures (SST). Among Southern Ocean diving seabirds, rockhopper penguins typically occupy a low trophic level, and might therefore be expected to mirror climate-driven bottom-up changes to the food web sensitively and on a short time scale.2. Using passive integrated transponders, survival rates of adults in a colony of southern rockhopper penguins (E. chrysocome) on the Falkland Islands were monitored over five consecutive years. Mean annual survival rates were in the range 84 to 96%.3. These values are high compared with other crested penguin species and reflect the generally good conditions during the study period, when low SST prevailed. However, survival rates were lower in 2010, corresponding to very cold conditions. Curve fits showed a best-fit quadratic relationship between average SST anomaly and survival rates for the present data, as well as for a data set including two additional years from a different study at Staten Island.4. Results of this study suggest that rockhopper penguins survive best at SSTs that are lower than the average of the last four decades. In accordance with previously observed rockhopper penguin population declines, the present data suggest that rockhopper penguins are highly sensitive to changes in SST and their effects on the food web, a worrying perspective in times of global climate change. It seems likely that these changes could, in the long term, also affect population trends of other seabird species with similar ecological preferences.5. The most promising conservation approach should aim at enhancing ecosystem resilience, mainly by reducing industrial fishing and oil exploitation. This would allow the currently over-exploited fish and squid stocks to recover, offering larger food resources to seabirds and other vertebrate species.