  When hybridization or other forms of lateral gene transfer have occurred,
evolutionary relationships of species are better represented by phylogenetic
networks than by trees. While inference of such networks remains challenging,
several recently proposed methods are based on quartet concordance factors --
the probabilities that a tree relating a gene sampled from the species displays
the possible 4-taxon relationships. Building on earlier results, we investigate
what level-1 network features are identifiable from concordance factors under
the network multispecies coalescent model. We obtain results on both
topological features of the network, and numerical parameters, uncovering a
number of failures of identifiability related to 3-cycles in the network.
