Skip to content

Dunnock Spring Passage Advanced by Up to 8.3 Days Over 61 Years at Hel

Dunnock perched in vegetation at the Lost Gardens of Heligan, Cornwall
Research · Ecology

Dunnocks (Prunella modularis) passed the southern Baltic coast progressively earlier in spring across the 1965–2025 study period, while the overall duration of passage remained almost unchanged. The Version 1 preprint, first posted on 18 September 2026, has not yet been peer reviewed. It used standardised mist-netting records from Hel Bird Ringing Station in northern Poland. Although the study spans 61 calendar years, the trend analysis used 50 spring seasons: the station was inactive in 2011 and 2020, and eleven additional years with fewer than ten captured dunnocks were excluded.

All three passage phases shifted earlier

The researchers defined the first, median and last phases as the dates when 10%, 50% and 90% of the season’s captured dunnocks had passed. Across 1965–2025, these phases shifted 4.8, 8.3 and 5.4 days earlier, respectively. Because the beginning and end advanced by broadly similar amounts, the interval containing the middle 80% of passage remained stable rather than becoming longer.

Temperature effects differed across the annual cycle

Year-to-year timing was associated with temperatures in different parts of Europe. Warm spring conditions along migration routes in Central Europe and farther south were generally linked to earlier passage at Hel, and the middle phase was earlier in years with warmer spring conditions in south-western European wintering areas. Warm winters in Central Europe, however, were associated with later first and last passage. Different parts of the annual cycle therefore did not influence spring timing in the same direction.

The first phase was also earlier after warm May–June conditions in northern European breeding areas during the previous year. The authors interpret this as a possible carry-over effect: conditions during one life stage may influence performance or timing in a later stage. They suggest that favourable early-summer conditions could affect breeding opportunities and later annual-cycle decisions. Other proposed mechanisms include greater spring food availability, lower thermoregulatory costs and increasingly northern wintering, but these are interpretations of statistical associations rather than experimentally tested mechanisms.

Earlier passage does not mean a healthier population

The long-term phenological shift should not be read as evidence that climate warming is improving the species’ overall status. Dunnock numbers have declined across Europe since the 1980s. The authors discuss habitat change, including altered forest structure, intensive farming and degradation of the litter layer, together with more frequent extreme weather, as pressures that may counteract some benefits of milder temperatures.

Sources and image credit

  1. Marynkiewicz, Z., & Remisiewicz, M. (2026). Carry-Over Effects of Temperatures at Wintering Grounds and Migration Routes on the Timing of Spring Migration of Dunnock Prunella modularis on the Southern Baltic Coast [Preprint, Version 1]. Preprints.org.Primary preprint, Version 1, submitted 17 September and first posted 18 September 2026. Full text checked. Standardised spring mist-netting data from Hel Bird Ringing Station covered 1965–2025. The first, median and last passage phases shifted 4.8, 8.3 and 5.4 days earlier respectively, while migration duration remained stable. This version has not been peer reviewed.

Image: Dunnock (Prunella modularis) at the Lost Gardens of Heligan, Cornwall, England, photographed 20 August 2025. Photo: Charles J. Sharp. Source: Wikimedia Commons. CC BY-SA 4.0. Representative image; not a bird from the Hel study. · CC BY-SA 4.0 · Source

About this content: This story was produced with AI assistance within an editorial workflow developed by Wildlife Vagabond. Editorial responsibility remains with Wildlife Vagabond.How AI is used

Ecology

SPECIES IN THIS STORY

Species in this story

Dunnock Prunella modularis Explore species

Independent research and conservation news archive

Did you find this information useful?

Wildlife Vagabond is independently built and maintained. Voluntary support helps cover source verification, hosting and continued work on research and conservation news.

Support Wildlife Vagabond

The news archive will remain freely available.