Single logs from this month:
Just like April, May started off dry, yet saw the weather shift towards the second half of the month.
Species that already were seen in April and returned:
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Species making their first appearances:
Just on my last observation day, A. urticae made its first appearance in one of my main zones since 2023. C. argiades expands its territory further, though currently prefers the path leading to "Bog Hill". P. malvae also increased its populations and moved exclusively to Zone I, claiming the areas once occupied by E. tages that hasn't made any appearances so far and is set to not make any appearances this year. L. megera saw its strongest season ever with three individuals on just a single day in spring – a season it made no appearances before.
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Just like in 2023 and 2024, there has been a sharp decline among all butterfly species, this time after 20 May. Poorer weather conditions do not explain this pattern, as all three months saw vastly different weather (a short drought in 2023, short periods of calm weather in 2024, a nearly balanced mix of dry and rainy days in 2025).
What did change significantly between 2024 and 2025, however, is a sudden dominance of less than a handful of tall grass species within all zones, particularly affecting areas that used to be mowed three times or more before 2025 (waysides) but also extensively mowed hay fields (Zone II) and areas grazed by sheep (Zone I). Merely judging by the height of the grasses (ranging between 1.30 and 1.70 m) and how fast they began to dominate every zone, even pushing still-blooming nectar plants aside or weighting heavy on them, it moderately supports an opinion piece analyzing the phenomenon of "nutrient dilution" (ND) within the United States that highlights a strong correlation between grass height and decreasing amounts of sodium, phosphorus, nitrogen and calcium, yet increasing amounts of CO2 in plants, even in areas under active conservation and thus effectively turning them into "fast food". Some species such as P. bellargus have been disappearing entirely just after two weeks of its first, freshly-hatched appearances, indicating the possibility that they largely end up starving during May in particular.
=>https://www.cell.com/trends/ecology-evolution/fulltext/S0169-5347(24)00112-5?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0169534724001125%3Fshowall%3Dtrue Kaspari et al.: "Nutrient dilution and the future of herbivore populations" (Trends in Ecology & Evoluion, Volume 39, Issue 9, September 2024)
Still, what actually boosted this monoculture-like dominance of "Futtergräser" was the insane amount of mowing conducted by my municipality that actively targeted flowers and left self-pollinating grasses mostly untouched. I don't understand what their rationale behind this really may be, as one former member of our "Stadtrat" harbored an intense hatred of dandelions and complained about "the ugliness of wheat in front of the Bürgerüro" in our local newspaper just a year ago, but this may extend the annual "May crash" to at least another week. Our new local governments (even the ones from neighboring municipalities in my district – and in my district only!) so far have refused to mow their overgrowing waysides, slowly becoming dangerous to drivers who now barely can make out the traffic behind usually-clear corners.
Just to further highlight that something's awfully off within my study areas after four springs of collecting species data, the following species appear within just two weeks or less in a given season (only including those with a consistent pattern since 2022/2023):
Spring: A. agestis (complete disappearance), C. argiolus, C. arcania, C. minimus, G. rhamni, I. lathonia, P. napi, P. bellargus, P. icarus (sharp drop)
Summer: A. hyperantus (complete disappearance), A. paphia (sharp drop to complete disappearance in some areas), P. argus
Two species were last seen in 2022 and have been missing since, namely N. antiopa and P. aegeria. T. betulae (2023), S. w-album (2022) and S. pruni (2023) were not seen at all in 2024 and no eggs have ever been counted again, making their recoveries just as unlikely. I don't want to throw the towel just yet, however with Zone I reverting back to its poor state due to spontaneous mowing and grazing practices that so far only have destroyed important nectar plants, I'm not exactly looking forward to June, either.