Data from: Resolving the paradox of environmental quality and sociality: the ecological causes and consequences of cooperative breeding in two lineages of birds

Cooperatively breeding animals occur in virtually every ecosystem on
earth. Comparative and biogeographic studies suggest that that both benign
and harsh, as well as stable and fluctuating, environments can favor the
evolution of cooperative breeding behavior. The fact that cooperative
societies occur in environments of such contrasting quality creates a
paradox of environmental quality and sociality. The dual-benefits
framework—which leads to the prediction that the ecological consequences
of sociality (e.g. range size) vary depending on the benefits that
individuals of each species receive by forming social groups—offers a
potential resolution to this paradox. Here, we use a case study of two
avian lineages, starlings (Sturnidae) and hornbills (Bucerotidae), in
which environmental unpredictability appears to have opposite effects on
the evolution of cooperation to test the dual-benefits framework.
Consistent with previous work, harsh and unpredictable environments
promote cooperative breeding behavior in starlings, which in turn leads to
larger geographic ranges. However, cooperatively breeding hornbills occur
in benign and stable environments, but sociality does not influence range
size. Our study suggests that the paradox of environmental quality and
sociality arises largely because cooperative breeding is an umbrella term,
encompassing social species that form groups for different reasons.
Differentiating between these reasons that social groups form is crucial
for developing a predictive framework for understanding the evolution of
cooperative breeding behavior.