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Scientists Reject Live-Decoy Method for Counting Wild Finches

Two people wait beside a clap-trap while live finch decoys stand in small cages in the background
Conservation · Threats

A proposed way of estimating wild finch populations with caged live birds has drawn a detailed scientific and ethical rebuttal. In a letter published online in Ecological Indicators on 27 February 2026, 33 researchers argue that the method cannot provide reliable population estimates and should not be used as a conservation-monitoring tool.

The disputed method was presented as an “attraction-point” census. According to the letter, the SEFRICAM project involved about 700 volunteers and more than 9,500 sampling points over five years in the Madrid region of Spain. Live European goldfinches (Carduelis carduelis), European greenfinches (Chloris chloris) and common linnets (Linaria cannabina) were kept individually in small cages as decoys whose calls and songs were used to attract free-living birds towards a clap-trap.

Why Attraction Is Not the Same as Abundance

The letter’s authors say the central problem is that the number of birds attracted to a decoy cannot simply be converted into the number living in the surrounding area. A free-living finch’s response may vary with sex, age, social rank, body condition, migratory status, personality and whether it is travelling alone or in a flock. The identity, behaviour and song of the caged decoy can also change the response.

These differences matter because an attraction count measures a flow of responding birds rather than population density. The signatories also question the assumed distance over which the decoys could be heard, and they say the method was not validated against an independent estimate of finch abundance. In their assessment, this leaves the resulting absolute population estimates unsupported.

The critique also addresses sampling design and statistical analysis. The authors say the study did not stratify its sampling across the Madrid region’s heterogeneous habitats, although the three finch species are not distributed uniformly. They also argue that seasonal coverage was uneven and that assuming a Gaussian distribution was inappropriate for clustered count data. Together, these issues could distort comparisons between places and seasons.

Live Birds Used as Survey Equipment

The disagreement is not only methodological. The letter describes the capture and confinement of wild finches for use as living lures, and says the original study did not report the ethical approval or permits required for this work. The signatories argue that the practice conflicts with the protective purpose of the European Union’s Birds Directive and risks giving scientific legitimacy to trapping traditions associated with keeping wild finches.

They contrast the attraction-point approach with Spain’s established SACRE and SACIN bird-monitoring programmes. Those schemes record around 100 species through standardised, non-invasive surveys. The criticised project, by comparison, required extensive effort and live decoys to target only three species.

The publication is a scientific commentary rather than a new field study and introduces no new dataset. Its contribution is a point-by-point assessment of the assumptions behind the proposed census method, which the authors conclude should not be adopted.

Sources and image credit

  1. Negro, J. J., Camacho, C., Tella, J. L., Serrano, D., Tejedo, M., Figuerola, J., Redondo, T., Galván, I., Rodríguez, A., Carrascal, L. M., Amo, L., Arroyo, B., Mougeot, F., Valera, F., Arizaga, J., Mendoza, I., Prenda, J., Atienza, J. C., Senar, J. C., … Margalida, A. (2026). Letter to the editor concerning the paper ‘Attraction points: A new sampling design method to quantify common finches’ populations’ published by Marazuela Pinela et al. in Ecological Indicators, 171, 113155 (2025). Ecological Indicators, 184, 114719. https://doi.org/10.1016/j.ecolind.2026.114719Primary scientific letter, available online 27 February 2026. Thirty-three signatories critique the methodological, statistical, ethical and legal basis of the live-decoy attraction-point method. The article is open access under CC BY 4.0.

Image: Negro et al. (2026) / Ecological Indicators, Figure 1 — finch-trappers waiting beside a clap-trap, with live finch decoys in cages in the background. Representative image for this story; not presented as an animal or scene from the reported study or event. · CC BY 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

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European Greenfinch Chloris chloris Explore species European Goldfinch Carduelis carduelis Explore species Common Linnet Linaria cannabina Explore species

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