Study
Scale-free correlations in starling flocks
Cavagna, A.; Cimarelli, A.; Giardina, I.; Parisi, G.; Santagati, R.; Stefanini, F.; Viale, M.
Proceedings of the National Academy of Sciences, 2010
Three-dimensional reconstructions of flocks of differing size were analysed for correlations in velocity fluctuations between birds as a function of their separation, and the correlation length compared against the size of each flock.
- Studied in
- Sturnus vulgaris
- Sample size
- many reconstructed flocks spanning a wide range of sizes
Correlations in velocity fluctuations extended across the whole flock whatever its size: the correlation length scaled with flock size rather than settling at some fixed value.
What it means
The authors' reading, and ours. Where they differ, that difference is the point.
How the authors put it
Flocks are in a scale-free correlated state, so that a perturbation anywhere is felt throughout the group regardless of how large it is.
How NatureHQ reads it
This is the reason a large flock does not respond more sluggishly than a small one. In most systems, influence fades with distance and a bigger group would be slower to react as a whole. Here the correlation stretches to fit the flock, so a turn started at one edge reaches the other undiminished — which is what the behaviour looks like from the ground.
- One species; whether other flocking or schooling animals share the property is not established here.
- Establishes the statistical state, not the mechanism producing it.
What this study is used for on NatureHQ
One study can inform several subjects. Here is everywhere this one is cited.
Published by: Proceedings of the National Academy of SciencesPublished in PNAS.
doi.org/10.1073/pnas.1005766107
Checked against Crossref on 2026-09-28, and they agree on the title, the authors and the year.
NatureHQ summarises research in its own words and does not reproduce published text. Reviewed 2026-09-03.