Migratory animals rely on multiple sites during their annual cycles. Deteriorating conditions at any site can have population-level consequences, with long-distance migrants seen as especially susceptible to such changes. Reduced adult survival caused by persecution at non-breeding sites has been suggested a major reason for the catastrophic decline of a formerly abundant, long-distance migratory songbird, the Yellow-breasted Bunting Emberiza aureola. However, it was unknown whether the ongoing extinction of this Eurasian species especially in the west of its range could be related to differences in survival or migration routes. 

In our new study, we investigated survival rates of populations from both western and eastern parts of the breeding range (based on colour-ringing) and successfully tracked the migration of individuals from two eastern populations (with light-level geolocators). We found moderate apparent local survival rates in eastern populations, but observed not a single returning bird in western populations. Our tracking data highlights (1) a joint migration corridor of eastern populations through eastern China, (2) long autumn stopovers likely used for moult and re-fuelling, and (3) very long occurrences at wintering sites. These areas should be given priority for future conservation measures. 

Heim W, Anisimov Y, Bastardot M, Davaasuren B, Nakul G, Anisimova V, Batbayar N, Beermann I, Dae We Aung T, Damrow L, Erdenechimeg T, Hahn S, Heim A, Heim RJ, Hölzel N, Kunz F, Levashkin A, Sander MM, Sankamethawee W, Thomas A, Kamp J (2024) Migration routes and adult survival of the Critically Endangered Yellow-breasted Bunting Emberiza aureola. Scientific Reports 14: 30593: [https://doi.org/10.1038/s41598-024-83138-4]

Migratory bats are exposed to an increased mortality risk when crossing ecological barriers, such as the open sea, caused by energetically demanding long-distance flights and unexpected bad weather events. How such barriers affect the migratory movements of bats is still poorly understood.
To investigate this, we radio-tagged 44 hoary bats (Pipistrellus nathusii) on the east coast of the United Kingdom (UK) in spring 2021 and 2022. We then tracked their migrations to continental Europe using the MOTUS Wildlife Tracking System.

Males left the UK later in the season than females. The migration speed was approximately 70 km/day. The values agree well with the speeds measured in a wind tunnel. Our bats also adaptively utilised the wind to reduce flight speed when flying into a tailwind and increase flight speed when flying into a crosswind. Departures over the sea coincided with tailwinds, allowing the bats to more than double their flight speed and reach speeds relative to the ground of up to 16.8 m/s (60.5 km/h). Our analysis suggests that bats select altitudes with favourable wind conditions and seek altitudes of several hundred metres, possibly up to 2,500 m.

Lagerveld, S., de Vries, P., Harris, J. et al. Migratory movements of bats are shaped by barrier effects, sex-biased timing and the adaptive use of winds. Mov Ecol 12, 81 (2024).
doi.org/10.1186/s40462-024-00520-7

In a recent article in the annual report of the Ornithological Working Group (OAG) Helgoland, we present the radio-tagged pied wheatear, a rarity in Germany, from Helgoland in autumn 2023 (Peter et al. 2024). By studying the behaviour of these birds out of their normal distribution area, we can gain insights into the evolution of migratory routes (Dafour et al. 2022), such as the establishment of new wintering areas. The latter has already been hypothesised for the Yellow-browed Warbler, which has now become a "frequent rarity" (Schmaljohann & Karwinkel 2020).

The OAG Helgoland articles are available upon request from the authors or here (https://www.oag-helgoland.de/index.php/jahresbericht-der-oag/).

Peter A, Karwinkel T, Dierschke J & Schmaljohann H (2024) Zur Evolution neuer Zugrouten: Was wir von Helgoländer Seltenheiten lernen können. Ornithologischer Jahresbericht Helgoland 34, 114-119

Dufour P, Åkesson S, Hellström M, Hewson C, Lagerveld S, Mitchell L, Chernetsov N, Schmaljohann H & Crocher, PA (2022) The Yellow-browed Warbler (Phylloscopus inornatus) as a model to understand vagrancy and its potential for the evolution of new migration routes. Movement Ecology 10, 59. https://doi.org/10.1186/s40462-022-00345-2

Schmaljohann H & Karwinkel T (2020) Neues über das Wanderverhalten des Gelbbrauen-Laubsängers Phylloscopus inornatus. Ornithologischer Jahresbericht Helgoland 30, 106-111

In September 2024, we launched a project in cooperation with BirdLife Norway and the ringing station in Lista to study the North Sea migration of songbirds. To this end, we have installed three new Motus radio receiving stations in Hanstholm (Denmark), at the southern tip of Norway in Lindesnes and at the ringing station in Lista itself. A total of 100 songbirds are to be equipped with radio transmitters this and next year. The aim is to analyse the significance and proportions of long or short North Sea crossings in order to assess how serious anthropogenic structures in the North Sea, e.g. offshore wind power, could be for the populations.

Artificial nest sites are often used to support endangered species, but their success depends on proper installation. In a study based on Gianna Allera´s bachelor thesis and conducted in collaboration with the Institute of Landscape Ecology at the University of Münster and the NABU Nature Conservation Station Münsterland, we investigated the factors influencing the occupation of artificial nests by the Northern House Martin Delichon urbicum. The key findings include: 

1) Artificial nests are often not occupied until several years after installation.

2) Occupation rates were positively influenced by the number of artificial nests at a site.

3) Higher proportions of sealed surfaces in the surrounding area and southward exposure had negative impacts on occupation.

The study's recommendations will enable artificial nests to be used more effectively in the future to protect the northern house martin. 

Allera G, Heim RJ, Förster A, Heim W (2024) Landscape structure and site factors influence whether the northern house martin Delichon urbicum occupies artificial nests. Ecology and Evolution 14: e70261. https://doi.org/10.1002/ece3.70261

Using barometer loggers and GPS data loggers, we were able to investigate the migration routes of the Siberian Rubythroat population breeding in Xinghai, China. We demonstrated that in autumn, the birds take a detour to avoid high mountain ranges, while in spring, they fly relatively directly over the mountains to their breeding areas. On average, the birds flew at an altitude of 2000 meters, but in some cases up to 4600 meters above sea level.

Zhao T, Heim W, Nussbaumer R, van Toor M, Zhang G, Andersson A, Bäckman J, Liu Z, Song G, Hellström M, Roved J, Liu Y, Bensch S, Lei F, Wertheim B, Helm B. Seasonal migration patterns of Siberian Rubythroat (Calliope calliope) facing the Qinghai–Tibet Plateau. Mov Ecol 12, 54 (2024). https://doi.org/10.1186/s40462-024-00495-5