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Spotted Flycatchers Disappeared Less Often and Colonised More Often in River-Rich British Landscapes

Spotted flycatcher perched on a branch
Research: Ecology · Conservation: Habitat protection

A national study of spotted flycatchers (Muscicapa striata) found that river density was strongly associated with whether the species persisted in or colonised breeding-atlas squares across Britain. The researchers compared 2 × 2-km squares between the 1988–1991 and 2008–2011 breeding-atlas periods and related these changes to rivers and shifts in woodland, standing freshwater, arable and urban land cover.

The analysis was restricted to Britain, despite the source atlases covering Britain and Ireland. The models compared colonisation across 20,951 squares where spotted flycatchers were absent in the first atlas period and local loss across 7,356 squares where they had been present. These are changes in breeding occurrence, not changes in the number of flycatchers within each square.

River-rich landscapes were more likely to retain or gain flycatchers

Greater river density was associated with a higher probability that spotted flycatchers colonised previously unoccupied squares and a lower probability that they disappeared from occupied ones. In the authors’ model, river-rich landscapes were associated with more colonisation and less local loss, even after the other measured landscape variables were considered. They therefore identify running-water landscapes as an important correlate of persistence during a period of severe national decline.

Urban expansion showed the opposite pattern: increasing urban cover was associated with lower colonisation and greater local loss. Unexpectedly, increases in woodland and standing freshwater were also linked to reduced colonisation, and more standing freshwater was associated with greater loss.

The models explained only part of the overall variation, so river density and land-cover change cannot account for the decline on their own. The authors note that other factors may also act elsewhere in the species’ annual cycle.

Aquatic insects are a possible mechanism, not a measured one

The authors suggest that rivers may benefit this terrestrial insectivore through emergent aquatic insects, which transfer prey biomass from freshwater into surrounding land and can extend food availability beyond peaks in terrestrial insects. The study did not measure insect abundance, diet or breeding success, so this remains a biologically grounded explanation rather than a mechanism demonstrated by the atlas analysis.

The unexpected woodland result may partly reflect the time needed for newly created woodland to develop the structure and insect communities used by flycatchers. The reason for the negative association with increasing standing freshwater was less clear.

The conservation emphasis is on established habitat

The authors conclude that simply creating more woodland or water is unlikely to reproduce the benefits associated with established riverine landscapes quickly enough for a rapidly declining species. They argue for protecting and improving existing habitats, with particular attention to rivers and the ecological links between freshwater and surrounding terrestrial habitat.

Sources and image credit

  1. Eden, C. F., Gillings, S., Broughton, R. K., Donato, B., Hewson, C. M., & Sharp, S. P. (2026). Role of freshwater availability and terrestrial land-cover change in the distribution of a declining, terrestrial, insectivorous bird. Conservation Biology, 40, e70219. https://doi.org/10.1111/cobi.70219Primary open-access peer-reviewed study first published 14 January 2026. The analysis used British 2 × 2-km breeding-atlas tetrads from 1988–1991 and 2008–2011, not Irish tetrads. River density was associated with higher colonisation (OR 1.25) and lower local loss (OR 0.80); increasing urban cover was associated with lower colonisation (OR 0.74) and higher loss (OR 1.17).
  2. British Trust for Ornithology — Role of freshwater availability and terrestrial land-cover change in the distribution of a declining, terrestrial, insectivorous birdAuthor-institution summary used as supporting context for the study's conservation implications; the primary article remains the factual basis.

Image: Spotted flycatcher perched on a branch. Photo: Ivan Vezenkovic / Wikimedia Commons. Representative image for this story; not presented as an animal or scene from the reported study or event. · CC BY-SA 4.0 · Source

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