Wood warbler population dynamics in response to mast seeding regimes in <scp>E</scp>urope

Maag, Nino; Korner‐Nievergelt, Fränzi; Szymkowiak, Jakub; Hałas, Natalia; Maziarz, Marta; Neubauer, Grzegorz; Luepold, Shannon Buckley; Carlotti, Sandro; Schaub, Michael; Flade, Martin; Scherrer, Daniel; Grendelmeier, Alex; Riess, Michael; Stelbrink, Pablo; Pasinelli, Gilberto

doi:10.1002/ecy.4227

Cited by 4 publications

(1 citation statement)

References 77 publications

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“…Peak seed crops represent a resource pulse to a wide variety of seed consumers and their predators. For instance, beech mast has been associated with migration of seed consuming birds like bramblings that depend on mast as a winter food (Jenni, 1987;Lithner & Jönsson, 2002), increased rodent densities (Bregnard et al, 2021;Reil et al, 2016), as well as higher densities of secondary consumers such as owls and pine martens (Lithner & Jönsson, 2002;Maag et al, 2024). Birds may also suffer from increased densities of rodents, for instance through higher nest predation rates (Elliott & Kemp, 2016;Szymkowiak & Thomson, 2019).…”

Section: Potential Consequencesmentioning

confidence: 99%

Widespread breakdown in masting in European beech due to rising summer temperatures

Foest,

Bogdziewicz,

Pesendorfer

et al. 2024

Global Change Biology

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Climate change effects on tree reproduction are poorly understood, even though the resilience of populations relies on sufficient regeneration to balance increasing rates of mortality. Forest‐forming tree species often mast, i.e. reproduce through synchronised year‐to‐year variation in seed production, which improves pollination and reduces seed predation. Recent observations in European beech show, however, that current climate change can dampen interannual variation and synchrony of seed production and that this masting breakdown drastically reduces the viability of seed crops. Importantly, it is unclear under which conditions masting breakdown occurs and how widespread breakdown is in this pan‐European species. Here, we analysed 50 long‐term datasets of population‐level seed production, sampled across the distribution of European beech, and identified increasing summer temperatures as the general driver of masting breakdown. Specifically, increases in site‐specific mean maximum temperatures during June and July were observed across most of the species range, while the interannual variability of population‐level seed production (CVp) decreased. The declines in CVp were greatest, where temperatures increased most rapidly. Additionally, the occurrence of crop failures and low seed years has decreased during the last four decades, signalling altered starvation effects of masting on seed predators. Notably, CVp did not vary among sites according to site mean summer temperature. Instead, masting breakdown occurs in response to warming local temperatures (i.e. increasing relative temperatures), such that the risk is not restricted to populations growing in warm average conditions. As lowered CVp can reduce viable seed production despite the overall increase in seed count, our results warn that a covert mechanism is underway that may hinder the regeneration potential of European beech under climate change, with great potential to alter forest functioning and community dynamics.

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Section: Potential Consequencesmentioning

confidence: 99%

Widespread breakdown in masting in European beech due to rising summer temperatures

Foest,

Bogdziewicz,

Pesendorfer

et al. 2024

Global Change Biology

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Wood warbler population dynamics in response to mast seeding regimes in Europe

Maag,

Korner‐Nievergelt,

Szymkowiak

et al. 2024

Ecology

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Mast seeding is the episodic, massive production of plant seeds synchronized over large areas. The resulting superabundance of seeds represents a resource pulse that can profoundly affect animal populations across trophic levels. Following years of high seed production, abundances of both seed consumers and their predators increase. Higher predator abundance leads to increased predation pressure across the trophic web, impacting non‐seed consumers such as the wood warbler Phylloscopus sibilatrix through increased nest predation after tree mast years. Over the past 30 years, the frequency of tree seed masts has increased while wood warbler populations have declined in several regions of Europe. We hypothesised that increasing mast frequencies may have contributed to the observed population declines by creating suboptimal breeding conditions in years after masting. We measured reproductive output in four study areas in central Europe, which was between 0.61 and 1.24 fledglings lower in years following masting than non‐masting. For each study area, we used matrix population models to predict population trends based on the estimated reproductive output and the local mast frequencies. We then compared the predicted with the observed population trends to assess if the frequency of mast years contributed to the population dynamics. In Wielkopolska National Park (PL) and Hessen (DE), masting occurred on average only every 4 years and populations were stable or nearly so, whereas in Jura (CH) and Białowieża National Park (PL), masting occurred every 2 and 2.5 years, respectively, and populations were declining. The simple matrix population models predicted the relative difference among local population trends over the past 10–20 years well, suggesting that the masting frequency may partly explain regional variation in population trends. Simulations suggest that further increases in mast frequency will lead to further declines in wood warbler populations. We show that changes in a natural process, such as mast seeding, may contribute to the declines of animal populations through cascading effects.

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Drivers of nest site selection and breeding success in an Alpine ground-nesting songbird

Rime,

Korner,

Helm

et al. 2024

J Ornithol

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Birds breeding in high-Alpine habitats must select a suitable breeding site and achieve successful reproduction within a restricted time. During four breeding seasons, we monitored nest sites of the Northern Wheatear (Oenanthe oenanthe), a high-Alpine long-distance migrant. We investigated how ecological factors predicted the selection of a site for nesting within the home range, using conditional logistic regression. Birds preferred south-exposed productive pastures on gentle slopes, interspersed with non-vegetated ground and human-made rockpiles. The direct vicinity of conspecific nests was avoided, as were shrubby or north-exposed areas. We investigated if habitat also influenced breeding success. We analysed the impact of environmental factors on breeding success, which was primarily driven by predation. The probability of the brood fledging successfully decreased on north-exposed slopes or on areas with low coverage of non-vegetated ground. The vicinity of conspecific nests did not have a clear effect. Further, we describe how breeding success varied within and between years. Within years, replacement broods had a higher breeding success. The apparent absence of variation in breeding success between years and a delay of the breeding period in the year with late spring onset suggest a high level of tolerance with respect to inter-annual variation of meteorological conditions. Since the preferred habitat is still widely available in the Alps and given the negative population trends in Western Europe, the Alpine range might serve as a refuge for the Northern Wheatear, as long as low-intensity management and heterogenous habitats are maintained.

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Wood warbler population dynamics in response to mast seeding regimes in Europe

Cited by 4 publications

References 77 publications

Widespread breakdown in masting in European beech due to rising summer temperatures

Widespread breakdown in masting in European beech due to rising summer temperatures

Wood warbler population dynamics in response to mast seeding regimes in Europe

Drivers of nest site selection and breeding success in an Alpine ground-nesting songbird

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