Real-time observation of adaptive evolution in the wild is rare and limited to cases of marked, often anthropogenic, environmental change. Here we present the case of a small population of reed warblers (Acrocephalus scirpaceus) over a period of 19 years (1996–2014) after colonizing a restored wetland habitat in Malta. Our data show a population decrease in body mass, following a trajectory consistent with a population ascending an adaptive peak, a so-called Ornstein–Uhlenbeck process. We corroborate these findings with genetic and ecological data, revealing that individual survival is correlated with body mass, and more than half of the variation in mean population fitness is explained by variation in body mass. Despite a small effective population size, an adaptive response has taken place within a decade. A founder event from a large, genetically variable source population to the southern range margin of the reed warbler distribution likely facilitated this process.

Populations of migratory bird species have suffered a sustained and severe decline for several decades. Contrary to non-migratory species, understanding the causal mechanisms proves difficult (for migratory bird species) as underlying processes may operate across broad geographic ranges and stages of the annual cycle. Therefore, the identification of migration routes, wintering grounds, and stopover sites is crucial for the development of relevant conservation strategies for declining migrant bird species. We still lack fundamental data of the non-breeding movements for many migratory species, such as European turtle doves Streptopelia turtur, a trans-Saharan migrant. For this species, knowledge of non-breeding movements is mainly based on ringing data that are limited by a low recovery rate in Africa, and tracking studies with a strong bias towards individuals breeding in France. We used Argos satellite transmitters to obtain detailed year-round tracks and provide new insights on migration strategies and winter quarters, of turtle doves breeding in Central and Eastern Europe. The tracking data along with analysis of land cover data confirm previously assumed use of multiple wintering sites and the use of a wide range of forest and agricultural landscapes at the breeding grounds. Tracking data in combination with environmental parameters demonstrated that most environmental parameters and niche breadth differed between breeding and wintering grounds. “Niche tracking” was only observed regarding night-time temperatures. Furthermore, we provide evidence for breeding site fidelity of adult individuals and for home range size to increase with an increasing proportion of agricultural used areas. Significance statement The European turtle dove, a Palearctic-African migrant species, is one of the fastest declining birds in Europe. The rapid decline is presumed to be caused mainly by habitat modification and agricultural changes. Here, we represent data on migration strategies, flyways, and behavior on European breeding and African non-breeding sites of turtle doves breeding in Central and Eastern Europe equipped with satellite transmitters. Our results confirm the use of different migration flyways and reveal an indication for “niche switching” behavior in terms of environmental factors during the different annual phases. The migratory behaviors revealed by the tracking approach, e.g., prolonged stopovers during autumn migration in Europe overlapping with time of hunting activities, stopovers in North Africa during spring migration, or evidence for loop migration, are important protection-relevant findings, particularly for the Central-Eastern flyway, for which no tracking data has been analyzed prior to our study.

The ecological effects from artificial light are complex and can affect species and life-stages differently. Ships are a dynamic source of light pollution, often brightly lit and temporarily increasing light levels in otherwise relatively dark areas. Because several nocturnal seabird species display reduced activity and avoidance of natural or artificial light, we expect that bright vessel lights may affect colony attendance patterns. Here, we test whether the presence of ships in front of coastal cliffs affects colony attendance in the Yelkouan Shearwater (Puffinus yelkouan). Ship presence at the site was obtained from an automatic identification system database, and a data logger measured light levels at the colony autonomously for four breeding seasons (2017–2020). Moreover, a Radio Frequency Identification (RFID) system was deployed at a cavernous colony entrance to register arrivals and departures of shearwaters. Direct illumination from ships increased cliff face brightness, and colony attendance was significantly reduced in brighter conditions. Ship presence reduced the number of shearwaters entering the colony per hour by a mean of 18% (SD ± 24). Disruption of natural attendance patterns is likely to have short- and long-term effects on breeding success, physiological condition, and colony viability. Therefore, we propose mitigation measures to reduce the impact from commercial shipping on burrow-nesting seabirds. Local regulations are necessary for colony-specific impact reduction, while incorporation of measures such as black-out blinds, fixture shielding and maximum brightness limits into international conventions can have additional far-reaching benefits.

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