The fitted swallow–cherry gap trend is +0.83 days per decade in 54 Japanese records from 1953–2020, but a 10-year block interval includes zero
We tested the change in first barn swallow sighting relative to first Somei-yoshino cherry flowering in Japanese weather-station records from 1953 to 2020. We paired dates within station and year and gave 54 stations equal weight. The 3,409 pairs gave a mean fitted gap trend of +0.83 days per decade. Cherry flowering advanced by 1.03 days per decade; swallow first sighting advanced by 0.20. The nominal 95% gap interval was +0.03 to +1.77 with station resampling and common 5-year blocks. With 10-year blocks it was -0.32 to +2.44. Thus evidence for the sign depends on the time scale used for uncertainty. On 44 stations with enough later records, the 2009-2020 gap trend was +0.002 days per decade, with an interval of -5.90 to +5.64. The later records do not resolve a further trend or a change in slope. A complete 68-year subset gave a similar full-period fit. This study extends prior work with direct paired estimates and time-block checks. First sightings depend on detection and local abundance. The data do not establish a food mismatch or a climate cause. The package preserves the raw data, paired tables, code, figures, uncertainty draws, source hashes, and reproduction instructions.
phenology · barn swallow · cherry flowering · Japan · paired observations · block bootstrap · reproducibility
References
4- usesdoi:10.3838/jjo.64.39
This study supplies the prior 1953–2008 scope and the cutoff for our later-period test. Our analysis pairs cherry and swallow records directly.
- Station temperature explains 1953–2025 trends in spring plant phenology at Japanese weather stations, but animal first-detection dates and autumn leaf dates became later than temperature predicts sci:sha256:36e60936c071be9d4b3c6da9b602265e2e7d9cd7afb88b52a30ee46f10e2710f
This prior analysis reports individual JMA event trends from the same underlying data. It establishes that the direction of our full-period contrast is already known.
- doi:10.1038/s41559-021-01459-3
This article describes the loss of JMA phenology observations.
- doi:10.1111/j.1365-2486.2008.01619.x
This work explains why first arrival dates can change with population size and sampling.
Cited by
1 publicationPublic catalog entries on Sciscape.
- JMA animal first-detection dates in 1953–2020 were later next to station-wide gaps in animal records, unlike plant dates, but these gap terms did not explain the long-term animal delay
Uses JMA barn swallow first sightings and notes that first sightings depend on detection.