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q-bio.PE · Populations and Evolution

Equal list lengths reversed the change in bird-list similarity on 2,069 Finnish squares, 2006–2010 to 2022–2025

We tested spatial change in recorded breeding bird lists on 2,069 Finnish 10 km squares. Each square had the same survey activity class in the 2006–2010 and 2022–2025 atlases. We used 163 matched public taxa that were not marked sensitive. Mean full-list Simpson dissimilarity rose from 0.19522 to 0.20475. The change was +0.00953, with a 95% spatial block interval of +0.00551 to +0.01377. Mean list length fell from 76.26 to 74.71 species. Holding list length fixed within each square reversed the direction. We set each target length to the smaller of its two lists, then calculated the exact expected dissimilarity after independent uniform species draws. This gave a change of -0.00852 (-0.01297 to -0.00377). This check was added after a planned 30-species check gave the same reversal. The planned check used the same 2,039 eligible squares in both periods. It gave -0.00294 (-0.00449 to -0.00128), compared with +0.00950 for full lists. The reversal also occurred on the best-surveyed squares and with 50 and 200 km spatial blocks. The decrease after matching list length was unclear when records required probable or confirmed breeding. The results show that the direction of recorded spatial change depends on list-length control. The controls change the question and do not correct all detection effects. These data cannot identify one direction of change in true communities. The package preserves the fixed source snapshot, code, provenance, all estimates, figures and offline repeat instructions.

Finnish Bird Atlas · spatial beta diversity · survey detection · species lists · list length · exact subsampling · reproducibility

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References

7
  1. usesIn four Finnish bird atlases (1974–2025), southern species moved north at 1.6 km/yr before 2008 but 0.5 km/yr after, and the earlier shift of a species did not predict its later shift sci:sha256:ef24a009ace0534c076c7444cd3d3350fe5dd3a27ffb3fd63b69c4825d1509b1

    We reuse its fixed Finnish atlas snapshot, tidy tables and MIT table-building code. We test spatial similarity and list-length controls.

  2. Recorded losses account for the mean northward shift of 21 northern bird species on 1,943 Finnish atlas squares from 2006–2010 to 2022–2025 sci:sha256:15306b8d0510e9aec6e6f3ec6771fb95a3adb5338589e0babed09ae97e3cc492

    This study separates recorded gains and losses in northern Finnish bird range shifts. It supplies context for the difference between a range shift and spatial community similarity.

  3. Swedish bird lists showed weak support for spatial homogenization from 2000–2009 to 2016–2025 under survey controls sci:sha256:986ad9fe6d9428e9771ce981fb24e8017edc27b39e1d29c759726ff04648fa10

    This Swedish bird study tests spatial similarity under survey controls. It supplies prior context; it uses different data.

  4. usesdoi:10.1111/j.1466-8238.2009.00490.x

    We use the established Simpson, Sorensen and nestedness component definitions.

  5. doi:10.1371/journal.pone.0043648

    This paper measured shifts with the first three Finnish bird atlases.

  6. doi:10.1111/1365-2656.12035

    This paper reports bird spatial diversity change and temperature associations in Sweden.

  7. doi:10.1038/s41559-024-02326-7

    This paper reports changes in species richness and community similarity across British taxa.

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