Sara Pardal

Long-term declines of wader populations at the Tagus estuary, Portugal : a response to global or local factors?

Summary Migratory wader populations face global threats, mainly related to increasing rates of habitat loss and disturbance driven by human activities. To a large extent, the long-term survival of these populations requires the conservation of networks of sites along their migratory flyways. The Tagus estuary, Portugal, is among the most important wetlands for waders in the East Atlantic Flyway. Annual winter wader counts have been carried in this wetland since 1975 and a monthly roost-monitoring programme was implemented in 2007. Wintering populations of three out of the five most abundant species, Dunlin Calidris alpina, Grey Plover Pluvialis squatarola and Redshank Tringa totanus, showed significant population declines over the past three decades, which are most likely due to the loss and degradation of roost sites as a result of increasing human activity. The situation is unlikely to improve, as a high proportion of the wintering waders use roost sites that are situated in highly urbanised areas with no legal protection. The use of different roost sites by waders is highly variable both temporally and spatially, thus emphasizing the need for a network of good quality roost sites. Additionally, during migration, 60–80% of all the waders of the Tagus estuary concentrate at a single refuge, thus increasing the risk for wader populations during these periods.

Host-parasite associations and host-specificity in haemoparasites of reed bed passerines.

The host specificity and host sharing of avian haemoparasites (genera Haemoproteus and Plasmodium) is still poorly known, although they infect a large proportion of several studied bird populations. This study used molecular techniques to detect haemoparasites in marsh warblers and in other passerines that feed in reed beds, at 4 sites in Portugal. The host-specificity of the parasite lineages was analysed and compared with other cases described in the literature to assess whether apparent host specificity changes according to the studied system. Nine lineages of Haemoproteus and 15 of Plasmodium were found, of which only 10 Plasmodium were proven to have local transmission. Each lineage was confined to a distinct set of host species. The distribution of parasites in the host species was non-nested, meaning that specialist lineages did not always share hosts with generalists. The most prevalent lineages were those with a wider host range, indicating that the ability to infect more hosts will enhance a parasites prevalence in its entire host range. We also found that in our areas, a specialist parasite (H. MW1) appears to have a more generalist character than described in the literature, suggesting that a parasites apparent specialization can depend on the type of host species sampled.

Hidden haemosporidian infections in Ruffs (Philomachus pugnax) staging in Northwest Europe en route from Africa to Arctic Europe

In their African freshwater wintering habitats, shorebirds show a high prevalence of blood parasites, whereas no parasites are detected elsewhere along the migration route. We looked at two genera of haemosporidian parasites, Haemoproteus and Plasmodium, in the long-distance migrating Ruff (Philomachus pugnax) along a geographical/seasonal gradient to verify the infection pattern and examine possible hidden organ infections at European staging areas. We amplified parasite DNA from blood of 53 healthy birds wintering in Mali, 53 samples of seven organ tissues (spleen, liver, kidneys, heart, lungs, brain, and pectoral muscle) from healthy individuals caught during spring migration, and 18 weak birds found sick in summer in The Netherlands. We confirm that Ruffs wintering in Africa carried blood infections and that some infections developed into hidden organ infections during spring migration. Moreover, sick birds either had new infections (in one juvenile) or relapses (in an adult harboring an African lineage). Our results suggest that some parasites develop latency. This strategy may be beneficial for the parasite as it may take control over reappearance in the blood to help further transmission.

Borrelia garinii and Francisella tularensis subsp. holarctica detected in migratory shorebirds in Portugal

Migratory shorebirds use, among many, the East Atlantic Flyway that links breeding areas as north as Tundra habitats to aquatic wintering grounds in West Africa. As a consequence, they are potentially important in the spread of global zoonotic diseases transmitted by ticks, such as Lyme borreliosis and tularemia—two diseases previously detected in Portugal. In this study, we looked at the infection status of seven populations of shorebirds during their migration, breeding, or wintering in the Portuguese wetlands to access if they carry these pathogens and to discuss their potential risk in the Portuguese wetlands. A total of 212 migratory shorebirds captured in the Tagus and Sado estuaries; key staging and wintering sites in this flyway and important breeding areas for some species were analyzed for the presence of Borrelia burgdorferi sensu lato and Francisella tularensis. In the present study, B. garinii was identified in seven (3%) specimens (five black-tailed godwits Limosa limosa, one common redshank Tringa totanus, and one little stint Calidris minuta), whereas F. tularensis subsp. holarctica was identified in one (0.4%) little stint. To our knowledge, this is the first evidence that shorebirds that migrate through or winter in Portugal transport these pathogens, potentially contributing for their introduction along the flyway, including the Mediterranean region.

Contrasting estuary-scale distribution of wintering and migrating waders: the potential role of fear

In estuaries hosting both wintering and migrating populations of waders of the same species, the distinct ecological constraints on birds in different seasons may result in different criteria being used for selection of suitable foraging habitat. We analysed the distribution patterns of dunlins Calidris alpina in the Tagus estuary, Portugal, during the non-breeding season and investigated the roles of prey availability and predation risk to explain those patterns. The southern estuary provided higher prey availability but their narrower flats may induce greater fear of predation in waders than the open northern flats. However, our data suggest that the real risk was similar. Migrating birds avoided the southern estuary, favouring areas perceived as safer over better feeding opportunities. In contrast, wintering dunlins favoured the southern flats, despite their proximity to cover. Presumably, wintering waders have a better knowledge of the estuary, including its real predation risks, taking advantage of the best foraging areas. Without such knowledge, waders in short stopovers have to select their foraging areas based on indirect indicators of predation risk, such as distance to cover. This study illustrates the importance of incorporating specificities of habitat preferences by wintering and migrating wader populations in conservation planning for large estuaries.

Characterization of MHC class I in a long distance migratory wader, the Icelandic black-tailed godwit

The major histocompatibility complex (MHC) encodes proteins that are central for antigen presentation and pathogen elimination. MHC class I (MHC-I) genes have attracted a great deal of interest among researchers in ecology and evolution and have been partly characterized in a wide range of bird species. So far, the main focus has been on species within the bird orders Galliformes and Passeriformes, while Charadriiformes remain vastly underrepresented with only two species studied to date. These two Charadriiformes species exhibit striking differences in MHC-I characteristics and MHC-I diversity. We therefore set out to study a third species within Charadriiformes, the Icelandic subspecies of black-tailed godwits (Limosa limosa islandica). This subspecies is normally confined to parasite-poor environments, and we hence expected low MHC diversity. MHC-I was partially characterized first using Sanger sequencing and then using high-throughput sequencing (MiSeq) in 84 individuals. We verified 47 nucleotide alleles in open reading frame with classical MHC-I characteristics, and each individual godwit had two to seven putatively classical MHC alleles. However, in contrast to previous MHC-I data within Charadriiformes, we did not find any evidence of alleles with low sequence diversity, believed to represent non-classical MHC genes. The diversity and divergence of the godwits MHC-I genes to a large extent fell between the previous estimates within Charadriiformes. However, the MHC genes of the migratory godwits had few sites subject to positive selection, and one possible explanation could be a low exposure to pathogens.

Primary moult of continental Black-tailed Godwits Limosa limosa limosa in the Doñana wetlands, Spain

ABSTRACT Capsule: Most Continental Black-tailed Godwits Limosa limosa limosa using the Doñana wetlands during post-breeding migration appear to begin moult before they arrive and suspend moult before they migrate onwards to West Africa. Aims: We aim to describe the primary moult strategies and patterns in the Continental Black-tailed Godwits using the Doñana wetlands, a major passage and wintering area for waterbirds in southern Spain. Methods: Individual godwits were captured, marked and their primary moult was scored in Doñana during the non-breeding season (June–March) in 2011 and 2012. Data from resightings of colour-marked godwits and birds equipped with satellite transmitters were used to estimate stopover duration during post-breeding migration (June–September) to determine if godwits move to West Africa before completing their primary moult. Results: Average primary moult duration was estimated to be 84 days ± 9 se, during 29 June–21 September and did not differ between sexes. Only 2% of individuals were observed with suspended moult. We estimated stopover duration in Doñana to be 13 days ± 2 se before migrating to West Africa. Conclusions: Most godwits stage for about two weeks in the Doñana wetlands during southward migration, moult their primaries and appear to suspend moult before crossing the Sahara. Others may complete their primary moult in Doñana, or elsewhere in Europe and overwinter in Doñana where increasing numbers of godwits have been detected in recent years. A few individuals may finish the moult in Doñana and migrate to West Africa late in the post-breeding season.