[Transiting species, phenologies and their trends]

[In order to contribute to the knowledge of the spatio-temporal progression of post-nuptial migration of birds across the Italian Alps, we present in detail the results of the analysis carried out for 69 species (4 non-Passeriformes; 65 Passeriformes) of the 191 ringed within the Progetto Alpi. Data were collected in 40 ringing stations located in different habitats and at different altitudes (mountain passes, slopes and valley floors) and active in the post-breeding migratory period (1 August - 30 November). Among these, those (n=15) with continuous activity (at least one month) and known sampling effort (daily capture effort described as product of net area in square meters by operating time in hours) were selected. Data from the 6 stations that operated continuously over the years (2001-2017) and with standardised capture effort were used for trend analyses. Species covered refer to those with more than 100 birds ringed within the first eight hours after sunrise (excluding local retraps). Species accounts contain detailed data from datasets from all stations participating in the Alps Project (1997-2017)]. [Article in Italian]

Revealing migratory path, important stopovers and non-breeding areas of a boreal songbird in steep decline

The Olive-sided Flycatcher (Contopus cooperi) is a steeply declining aerial insectivore with one of the longest migrations of any North American passerine. We deployed light-level geolocators and archival GPS tags on breeders in boreal Alaska to determine migratory routes, important stopovers and non-breeding locations. Data from 16 individuals revealed a median 23,555 km annual journey (range: 19,387, 27,292 km) over 95 days (range: 83, 139 days) with wintering occurring in three regions of South America (NW Colombia/Ecuador, central Peru and W Brazil/S Peru). We developed a new method to identify “Important Stopovers” by quantifying intensity of use (a function of bird numbers and stop durations) along migratory routes. We identified 13 Important Stopovers that accounted for ~66% of the annual migratory period, suggestive of refueling activities. Some sites coincided with key areas previously identified for other Neotropical-Nearctic migrants. Percent land “protected” at Important Stopovers, as defined by IUCN, ranged from 3.8% to 49.3% (mean [95% CI]: 17.3% [9.6, 25.0]). Total migration speed did not differ by season (median: 255 km day-1, range: 182, 295km day-1), despite greater spring travel distances. Birds with longer non-breeding periods, however, migrated north faster. Climate-driven mismatches in migratory timing may be less of a concern for western than for eastern flycatcher populations, given recent con-generic analyses (C. sordidulus, C. virens). However, accelerated high-latitude changes, may nonetheless impact boreal breeders.

The Effect of Migratory Beekeeping on the Infestation Rate of Parasites in Honey Bee (Apis mellifera) Colonies and on Their Genetic Variability

Migratory beekeeping is a widely extended practice aimed at increasing the yield of products and pollination services of honey bee colonies. However, it represents a stress factor, as it facilitates the dissemination of diseases and may compromise the genetic identity of the colonies involved. To analyze the extent of these effects, pathogens infestation rate and genetic composition were monitored in a field experiment comparing stationary and migratory colonies sharing the same environmental conditions but differing in management (stationary vs. migratory) and genetic background. We studied the pathogens infestation rate (Varroa destructor, Nosema spp., and Deformed Wing Virus (DWV)) at four different times: before migratory operation, two weeks later, at the end of the migratory period, and two weeks after the return of the migratory hives. An increased incidence of V. destructor and Nosema ceranae and a lower DWV viral load were found in migratory colonies. Temporary changes in genetic diversity were detected regardless of colony type, suggesting that stressors other than management affect the genetic diversity of the colonies. Our study demonstrates that migratory practices have variable effects on the health and genetic diversity of honey bee colonies, which should be taken into account for the development of sustainable beekeeping.

A hierarchy of compass systems in migratory birds

Migratory birds use several different sources of orientation information. They have at least three compass systems based on different cues: the sun and polarized light, the stars and their constellations, and the geomagnetic field. The concurrent information obtained from these three compasses is redundant, therefore the compasses need to have a hierarchy and must be calibrated relative to each other. One of the compasses should dominate the others, or some orientation cue should be used to calibrate the remaining compass systems. Results of experiments on a variety of songbird species demonstrate that while astronomical cues calibrate the magnetic compass during the pre-migratory period, strategies used during the migratory period are more diverse. In the present review, we analyze the results of all crucial cue-conflict studies, mostly performed in nocturnal songbird migrants; we also try to understand why some migratory species calibrate their magnetic compass on sunset cues while others use the geomagnetic field or stars as a primary cue source, and we examine why the previous hypothesis could not explain the findings of all cue-conflict experiments.

Host age shapes virome abundance and diversity in birds

Host age influences the ecology of many microorganisms. This is evident in one-host – one virus systems, such as influenza A virus in Mallards, but also in community studies of parasites and microbiomes. We used a meta-transcriptomic approach to assess whether host age is associated with differences in the abundance and diversity of avian viromes. We used samples from cohabiting Ruddy Turnstones (Arenaria interpres) across three age groups, collected at two contrasting points in their annual migratory cycle. Overall, we identified 14 viruses that likely infect birds, 11 of which were novel, including members of the Reoviridae, Astroviridae, Picornaviridae, and Phenuiviridae. Strikingly, 12 of the viruses identified were from juvenile birds sampled in the first year of their life, compared to only two viruses in adult birds. Similarly, both viral abundance and alpha diversity were higher in juvenile than adult birds. Notably, time of sampling had no association with virome structure such that the migratory period may not play a major role in structuring avian viromes. As well as informing studies of virus ecology, that host age impacts viral assemblages is a critical consideration for the future surveillance of novel and emerging viruses.

A STOP FOR A SNACK: apparent humpback whale (Megaptera novaeangliae) feeding behavior and association with gillnets during migration off south-eastern Brazil

Baleias-jubarte (Megaptera novaeangliae) migram anualmente desde as águas frias dos polos, onde alimentam-se de krill e pequenos peixes, em direção a regiões tropicais e subtropicais em busca de ambientes favoráveis para reprodução e cria de filhotes. Ainda pouco conhecidos são os casos de baleias-jubarte alimentando-se em áreas de reprodução. Nesse trabalho relatamos as primeiras observações em campo de uma baleia juvenil – yearling, em provável comportamento de forrageamento buscando por prováveis crustáceos ou cefalópodes em curtos mergulhos fundos. São relatadas outras observações semelhantes nas quais das baleias pareciam aproximar-se de redes de emalhe, provavelmente atraídas por peixes ali enredados e disponíveis. Considera-se que em alguns desses casos a aproximação das baleias em direção às redes tenha causado emalhamentos, que pelo menos em um caso o exemplar libertou-se das redes. Em outros casos as redes podem ter causados ferimentos e lesões nas baleias-jubarte. Recomenda-se um acompanhamento dessas interações pela costa brasileira a longo prazo para uma melhor avaliação dessas interações.Palavras-chave: Baleia-jubarte; Enredamento; Forrageamento; Brasil.ABSTRACTHumpback whales (Megaptera novaeangliae) migrate annually from the cold waters of the poles, where they feed on krill, towards subtropical and tropical regions in search of favorable environments for breeding and calving. Cases of humpback whales feeding on breeding grounds are still poorly known in the world. This study reports field observations of a juvenile whale - yearling, in Brazilian waters, with evidence of foraging behavior, in search of prey that seemed to be prawn or squid, during short dives. In addition, other similar observations are reported in southeastern Brazil in which the whales showed interest and approach gillnets, probably attracted by entangled fish. In some of these cases, it is considered that whale approaching towards the nets has caused entanglements, and in at least one case the specimen freed itself from nets. In other cases, nets may have caused humpback whale injuries. A follow-up of these interactions throughout the Brazilian coast is recommendedfor a better evaluation of these interactions with fishing nets, since they may represent a new form of behavior of these whales in their migratory period.

Haemosporidian parasites and leukocyte profiles of pre-migratory rosy starlings (Pastor roseus) brought into captivity

Immune response to pathogens such as avian malaria (Plasmodium spp.) and related haemosporidian parasites (Haemoproteus spp. and Leucocytozoon spp.) can lead to increases in energy demands of birds. Migrations are energetically costly for birds and require resources that could be otherwise invested in immune defence against pathogens. Here, we examined the prevalence and intensity of haemosporidian parasites (Apicomplexa, Haemosporida) in rosy starlings (Pastor roseus), an irruptive migrant on the Balkans, during their pre-migratory period. We further evaluated if these infections affected the stress levels of birds brought into overnight captivity, using leukocyte profiles (ratios of heterophils to lymphocytes, or H/L ratios). Haemosporidian parasites were detected based on microscopic examination, PCR and sequencing. We found high prevalence of haemosporidian parasites (83.9%) in rosy starlings (n=31), with predominant infections of Haemoproteus pastoris (cytochrome b lineage LAMPUR01) (80.1%). All birds had high heterophil/lymphocyte ratios (mean = 3.86), indicating the transition to captivity was stressful. However, there was no added stress from blood parasite infection during captivity, since infected birds did not have significantly higher heterophil/lymphocyte ratios than uninfected birds, despite all birds facing the same stress conditions. There was a negative correlation between intensity of H. pastoris and monocyte proportions, which may indicate an association with infection, or an artefact of the stress-induced shift in leukocyte profile following captivity. Our findings suggest that blood parasites have minimal additional impact on rosy starlings during an acute stress scenario (overnight captivity), arguing that they carry little cost to the energetically challenging migratory flight.

De novo annotation of the transcriptome of the Northern Wheatear (Oenanthe oenanthe)

We have sequenced a partial transcriptome of the Northern Wheatear (Oenanthe oenanthe), a species with one of the longest migrations on Earth. The transcriptome was constructed de novo using RNA-Seq sequence data from the pooled mRNA of six different tissues: brain, muscle, intestine, liver, adipose tissue and skin. The samples came from nine captive-bred wheatears collected at three different stages of the endogenous autumn migratory period: (1) lean birds prior the onset of migration, (2) during the fattening stage and (3) individuals at their migratory body mass plateau, when they have almost doubled their lean body mass. The sample structure used to build up the transcriptome of the Northern Wheatears concerning tissue composition and time guarantees the future survey of the regulatory genes involved in the development of the migratory phenotype. Through the pre-migratory period, birds accomplish outstanding physical and behavioural changes that involve all organ systems. Nevertheless, the molecular mechanisms through which birds synchronize and control hyperphagia, fattening, restlessness increase, immunity boosting and tuning the muscles for such endurance flight are still largely unknown. The use of RNA-Seq has emerged as a powerful tool to analyse complex traits on a broad scale, and we believe it can help to characterize the migratory phenotype of wheatears at an unprecedented level. The primary challenge to conduct quantitative transcriptomic studies in non-model species is the availability of a reference transcriptome, which we have constructed and described in this paper. The cDNA was sequenced by pyrosequencing using the Genome Sequencer Roche GS FLX System; with single paired-end reads of about 400 bp. We estimate the total number of genes at 15,640, of which 67% could be annotated using Turkey and Zebra Finch genomes, or protein sequence information from SwissProt and NCBI databases. With our study, we have made a first step towards understanding the migratory phenotype regarding gene expression of a species that has become a model to study birds long-distance migrations.

Divergent migratory behaviours associated with body size and ocean entry phenology in juvenile sockeye salmon

Survival during early marine life stages is hypothesized to contribute disproportionately to variation in salmonid recruitment, yet estimates of cumulative mortality are constrained by knowledge of how long juveniles reside in specific regions. We used otolith microstructure techniques to examine the relationship between migratory rate and ocean entry characteristics of juvenile sockeye salmon (Oncorhynchus nerka). We observed differences in migratory rate between catch locations that are consistent with divergent migratory behaviours. Individuals captured in northern regions were typically older, larger at ocean entry, and migrated more rapidly. Migratory rate was also correlated with entry size, phenology, population group, and year. Next, we compared “lingering” individuals captured nearshore during fall surveys to juveniles from the same populations captured during the peak summer migratory period. We determined that individuals that entered after 24 May and at smaller sizes (<85 mm) had a greater probability of being captured late in the year. Our findings demonstrate that the entry characteristics of sockeye salmon are strongly correlated with migratory variation within populations and suggest these traits may directly influence juvenile behaviour.

Initiation of migration and movement rates of Atlantic salmon smolts in fresh water

Timing of ocean entry is critical for marine survival of both hatchery and wild Atlantic salmon (Salmo salar) smolts. Management practices and barriers to migration such as dams may constrain timing of smolt migrations resulting in suboptimal performance at saltwater entry. We modeled influences of stocking location, smolt development, and environmental conditions on (i) initiation of migration by hatchery-reared smolts and (ii) movement rate of hatchery- and wild-reared Atlantic salmon smolts in the Penobscot River, Maine, USA, from 2005 through 2014 using acoustic telemetry data. We also compared movement rates in free-flowing reaches with rates in reaches with hydropower dams and head ponds. We compared movement rates before and after (1) removal of two mainstem dams and (2) construction of new powerhouses. Initiation of movement by hatchery fish was influenced by smolt development, stocking location, and environmental conditions. Smolts with the greatest gill Na+, K+-ATPase (NKA) activity initiated migration 24 h sooner than fish with the lowest gill NKA activity. Fish with the greatest cumulative thermal experience initiated migration 5 days earlier than those with lowest cumulative thermal experience. Smolts released furthest from the ocean initiated migration earlier than those released downstream, but movement rate increased by fivefold closer to the ocean, indicating behavioral trade-offs between initiation and movement rate. Dams had a strong effect on movement rate. Movement rate increased from 2.8 to 5.4 km·h−1 in reaches where dams were removed, but decreased from 2.1 to 0.1 km·h−1 in reaches where new powerhouses were constructed. Movement rate varied throughout the migratory period and was inversely related to temperature. Fish moved slower at extreme high or low discharge. Responses in fish movement rates to dam removal indicate the potential scope of recovery for these activities.