It is suggested that the observed scale-free correlations of speed fluctuations in flocks of birds are a consequence of the spontaneous breakdown of translational symmetry to a discrete group, and not an indication that the system is near a critical point in phase space. The observed long-range correlation length could then be attributed to the presence of a phonon mode in the flock.
@article{arxiv.1702.08067,
title = {A note on Spontaneous Symmetry Breaking in flocks of birds},
author = {Alejandra Melfo},
journal= {arXiv preprint arXiv:1702.08067},
year = {2017}
}