[A brief history about the ALPI project]

[Conceived by the National Ringing Centre ISPRA and MUSE (Trento, formerly MTSN), the Alps Project was launched in 1997 in order to understand the post-breeding migration strategies of birds across the Italian Alps. The project is realized thanks to the support offered by MUSE and several institutions at a local scale, not to mention the collaboration of over one hundred ringers. In more than twenty years, 40 stations located in sites of passage (alpine and pre-alpine passes) and stop-over (valley floors and slopes) have taken part in the project, leading to a dataset of 666,471 ringed individuals and 191 species (as to 2017). After a first exploratory phase (1997-2002), in which the migration was investigated in its many aspects of specific composition and spatial-temporal variation, the project has been restricted to a smaller number of stations since 2007. Those stations are characterized by working in a standardized and continuous way during the whole period (August-November) or during the migration period of the intra-Palearctic species (end of September-October). In this paper we describe the aims, protocols and organizational aspects of the project, with a special focus on monitoring trends and changes in the long-term phenology. This ongoing project (2021) is part of the ISPRA national ringing plan to monitor bird migration across the country]. [Article in Italian]

Acoustic signature reveals blue whales tune life history transitions to oceanographic conditions

1.Matching the timing of life history transitions with ecosystem phenology is critical for the survival of many species, especially those undertaking long-distance migrations. As a result, whether and how migratory populations adjust timing of life history transitions in response to environmental variability are important questions in ecology and conservation. Yet the flexibility and drivers of life history transitions remain largely untested for migratory marine populations, which contend with the unique spatiotemporal dynamics and sensory conditions found in marine ecosystems. 2.Here, using an acoustic signature of blue whales’ regional population-level transition from foraging to breeding migration, we document significant interannual flexibility in the timing of this life history transition (spanning roughly four months) over a continuous six-year study period. 3.We further show that timing of this transition follows the oceanographic phenology of blue whales’ foraging habitat, with a later transition from foraging to breeding migration occurring in years with an earlier onset, later peak, and greater accumulation of biological productivity. 4.These results indicate that blue whales use flexible cues, likely including individual sensing of foraging conditions and long-distance vocal signals from conspecifics, to match timing of this population-level life history transition with interannual oceanographic variability in their vast and dynamic foraging habitat. The use of flexible cues in timing a major life history transition may be key to the persistence of this endangered population facing the pressures of rapid environmental change. 5.Further, these findings extend theoretical understanding of the flexibility and drivers of population-level migration beyond insights derived primarily from group-living and terrestrial migrants, illuminating the drivers and flexibility of a life history transition in a relatively solitary marine migrant.

When to depart from a stopover site? Time since arrival matters more than current weather conditions

On the journey to wintering sites, most migratory birds alternate between flights and stopovers, where they rest and refuel. In contrast to the time-minimization strategy commonly assumed to drive the pre-breeding migration, birds are rather expected to follow an energy minimization during post-breeding migration. It is the cumulative duration of flights and stopovers that determines the total energy requirements and duration of the journey. Since migrating birds actually spend most of the time at stopovers sites, selection to minimize the amount of energy or time spent on migration is likely to operate on the effectiveness of stopover rest and refueling. Here, we address the relative contribution of factors acting on departure decisions from a stopover site during the post-breeding migration in a long-distance migratory songbird. When capture probability is low, it is impossible to measure fattening over the entire duration of the stopover. To get around this limitation, we use time since arrival (TSA) as a proxy for the progressive temporal change occurring in the internal state of an individual (i.e. rest, physiological recovery, and fuel loading) during the stopover. We develop a capture–recapture model to address the respective effects of estimated TSA and of weather conditions on departure probability. Using a 20-year dataset for Sedge Warblers (Acrocephalus schoenobaenus), we show that TSA served as a surrogate of the most important information that birds use when deciding to depart from a stopover site, while low humidity and rising atmospheric pressure only slightly increase daily departure probability. Hence, a bird would resume migration mainly according to the time it had to rest and refuel, and then fine-tuning departure decision according to weather conditions. The generality of these results needs to be assessed by applying this modeling framework to other migratory species and at sites or times with greater weather variability.

The role of anthropogenic disturbance and invasion of yellow crazy ant in a recent decline of land crab population

The yellow crazy ant, Anoplolepis gracilipes was first reported in Kenting National Park, Taiwan, in the 2000s, raising the concern of this invasive ant’s potential effects on the native land crab populations. We investigated the distribution and abundance of A. gracilipes and its adverse effect on the land crab populations at four land crab hotspots within the park. Our survey results indicated that A. gracilipes was widespread and abundant at three of the study sites (Hsiangchiaowan, Shadao, and Natural Spring), while the distribution was much more confined at the fourth site (Houwan). Land crab populations experienced a notable decline at all the study sites except Houwan, indicating an inverse relationship between the population of land crabs and distribution/abundance of A. gracilipes. Combining the results of visual observations, the decline of land crab populations can be attributed, at least partially, to direct attacks by A. gracilipes on land crabs in their natural habitat and during the breeding migration season. Generalized additive model showed that worker abundance of this ant is associated with human disturbance levels, suggesting that anthropogenic disturbance may have contributed to the decline in land crab populations via promoting the abundance of A. gracilipes.

Influence of roadkill during breeding migration on the sex ratio of land crab (Sesarma haematoche)

Adult land crabs generally live on land while their larvae live in the sea. In the case of Sesarma haematoche, female crabs migrate from land to sea to release the larvae at the high tide of syzygy night. Artificial structures along coastal areas are being obstacles for the migration of land crabs and causing synchronized roadkills on coastal roads during breeding migration. In this research, we compared the sex ratios of crab populations in coastal areas with coastal roads and uninhabited island areas with no road. The proportion of females in inland habitats with coastal roads was significantly smaller than island habitats. In particular, females are exposed to the risk of annually repeated roadkills, and the proportion of females decreases rapidly with their growth. If this tendency is general for land crab populations in the coastal areas with roads, significant road mortality of female land crabs during breeding migration can lead to severe population decline in coastal areas. Therefore, it is necessary to take an action to save land crabs crossing coastal roads.

Dunlin subspecies exhibit regional segregation and high site fidelity along the East Asian–Australasian Flyway

The degree to which individuals migrate among particular breeding, migration, and wintering sites can have important implications for prioritizing conservation efforts. Four subspecies of Dunlin (Calidris alpina) migrate along the East Asian−Australasian Flyway. Each subspecies has a distinct and well-defined breeding range, but their migration and winter ranges are poorly defined or unknown. We assessed the migratory connectivity of 3 of these subspecies by evaluating a dataset that encompasses 57 yr (1960–2017), and comprises more than 28,000 Dunlin banding records and 818 observations (71 recaptures and 747 band resightings). We present some of the first evidence that subspecific segregation likely occurs, with arcticola Dunlin wintering in areas of Japan, and other arcticola, actites, and sakhalina Dunlin wintering in areas of the Yellow and China seas. Observations indicate that whether an arcticola Dunlin winters in Japan or the Yellow and China seas is independent of their breeding location, sex, or age. Furthermore, observations indicate that ≥83% of arcticola Dunlin exhibit interannual site fidelity to specific wintering sites. This suggests that the degradation of specific wetland areas may negatively affect particular individuals of a particular subspecies (or combination of subspecies), and, if widespread, could result in population declines. Given the possible biases inherent in analyzing band recovery data, we recommend additional flyway-wide collaboration and the use of lightweight tracking devices and morphological and genetic assignment techniques to better quantify subspecies’ migratory movements and nonbreeding distributions. This information, when combined, will enable effective conservation efforts for this species across the East Asian−Australasian Flyway.

Orientation and navigation in Bufo bufo: a quest for repeatability of arena experiments

Research on navigation in animals is hampered by conflicting results and failed replications. In order to assess the generality of previous results, male Bufo bufo were collected during their breeding migration and translocated to two testing sites, 2.4 and 2.9 km away, respectively, from their breeding pond in the north of Vienna (Austria). There each toad was tested twice for orientation responses in a circular arena, on the night of collection and four days later. On the first test day, the toads showed significant axial orientation along their individual former migration direction. On the second test day, no significant homeward orientation was detected. Both results accord with findings of previous experiments with toads from another population. We analysed the potential influence of environmental factors (temperature, cloud cover and lunar cycle) on toad orientations using a MANOVA approach. Although cloud cover and lunar cycle had small effects on the second test day, they could not explain the absence of homeward orientation. The absence of homing responses in these tests may be either caused by the absence of navigational capabilities of toads beyond their home ranges, or by inadequacies of the applied method. To resolve this question, tracking of freely moving toads should have greater potential than the use of arena experiments.

Evolution of moult-migration is directly linked to aridity of the breeding grounds in North American passerines

To avoid energy allocation conflicts, birds generally separate breeding, migration and moult during the annual cycle. North American passerines typically moult on the breeding grounds prior to autumn migration. However, some have evolved a moult-migration strategy in which they delay moult until stopping over during autumn migration. Rohwer et al . (2005) proposed the ‘push–pull hypothesis' as an explanation for the evolution of this moult strategy, but it has not been empirically tested. Poor conditions on the breeding grounds at the end of the summer would push birds to depart prior to moult, while productive stopover locations would pull them. We tested for a relationship between moult-migration and breeding grounds aridity as measured by the normalized difference vegetation index. Our results strongly support the ‘push' aspect of the push–pull hypothesis and indicate that arid breeding grounds, primarily in western North America, would drive species to evolve stopover moult-migration, although this relationship may depend upon migration distance.