Data from: Swimming modes affect dive durations in diving birds

Dive duration and body mass are positively correlated across air-breathing
vertebrate species, but other factors affecting the dive duration are
inadequately studied. Here, we examined the effect of a previously
overlooked factor, swimming mode, using phylogenetically informed
statistics with data on the diving capabilities of 53 species of avian
divers. We predicted that wing-propelled birds would dive for longer
durations than similar-sized foot-propelled birds because of their lower
locomotion costs. The maximum dive duration was 1.1 times longer for the
wing-propelled birds than for the foot-propelled birds for a given body
mass and dive depth. In contrast, the mean dive duration was 1.1 times
longer for foot-propelled birds than for wing-propelled birds. Our results
indicate that swimming mode may be one of the factors influencing the
physiological limits on dive duration. Foraging style, which potentially
explains the effect of swimming mode, may also determine the maximum and
mean dive duration. For example, most foot-propelled birds are benthic
foragers and may routinely dive longer than expected from their higher
locomotion costs. In particular, blue-eyed shags have greater diving
capabilities than wing-propelled birds with similar body masses, despite
being foot-propelled birds. Physiological studies of their unusual diving
capabilities would provide important insights into the evolution of diving
behavior.