Data for: The evolution of enclosed nesting in passerines is shaped by competition, energetic costs and predation threat

Many bird species breed in enclosed nests which may provide better
protection against predation and climatic conditions compared to open
nests and are generally associated with larger clutch sizes and
slower offspring growth. Here we show that different enclosed nesting
strategies are each linked to behaviors with very different costs and
benefits on a macroevolutionary scale. Using a detailed dataset of nest
structure and location from the order Passeriformes we employed
phylogenetic comparative methods to evaluate (1) how predation,
competition, design complexity and energetic costs have shaped
evolutionary transitions between different nesting strategies and (2)
whether these strategies also have distinct relationships with
life-history traits. We find that flexible strategies (i.e., nesting in
both open and enclosed sites) as well as energetically demanding
strategies are evolutionarily unstable, indicating the presence of
underlying ecological trade-offs between anti-predator protections,
construction costs and competition. We confirm that species with
enclosed nests have larger clutch sizes and longer development and
nestling periods compared to open nesters, but only species that construct
enclosed nests rather than compete for pre-existing
cavities spend more time incubating and are concentrated in the
tropics. Flexible strategies prevail in seasonal environments and are
linked to larger clutches – but not longer development – compared to
nesting in the open. Overall, our results suggest that predation,
competition and energetic costs affect the evolution of nesting
strategies, but via distinct pathways, and that caution is warranted when
generalizing about the functions of enclosed nest designs in birds.