Nest predation and adult mortality relationships with post-natal metabolic rates and growth among songbird species

Metabolism is thought to mediate the connection between environmental
selection pressures and a broad array of life history tradeoffs, but tests
are needed. High juvenile predation correlates with fast growth, which may
be achieved via fast juvenile metabolism. Fast offspring metabolism and
growth can create physiological costs later in life that should be
minimized in species with low adult mortality. Yet, relations between
juvenile metabolism and mortality at offspring versus adult stages are
unexplored. We found that post-natal metabolism was correlated with adult
mortality but not nest predation rates among 43 songbird species on three
continents. Nest predation, but not adult mortality, explained additional
variation in growth rates beyond metabolism. Our results suggest that
metabolism may not be the mechanism underlying the relations between
growth and mortality at different life stages.