Can endocranial volume be used as an estimate of brain size in birds?

  • Iwaniuk A
  • Nelson J
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Endocranial volumes of vertebrate skulls and brain masses
are often used interchangeably in comparative analyses of
brain size. We test whether endocranial volume can be used
as a reliable estimate of brain size in birds by comparing
endocranial volumes with brain masses across 82 species
using absolute values and with respect to body size. The
results of paired tests across all 82 species and within
two orders, Passeriformes and Psittaciformes, did not yield
a significant difference between the two measures. These
results were supported by correlational analyses that
showed a significant positive relationship between
endocranial volume and brain mass. Unpaired tests within
short-tailed shearwaters (Puffinus tenuirostris) and paired
tests within budgerigars (Melopsittacus undulatus) also
yielded no significant differences between endocranial
volume and brain mass. Thus, a combination of interspecific
and intraspecific comparisons indicates that endocranial
volume does provide a reliable estimate of brain size.
Although this may enable more rapid collection of avian
brain size data, endocranial volume should be used with
caution because it cannot account for seasonal and
age-related variation and cannot be used to measure
differences in brain structure.
Major Concepts: Nervous System (Neural Coordination); Skeletal System
(Movement and Support)
Super Taxa: Procellariiformes: Aves, Vertebrata, Chordata, Animalia;
Psittaciformes: Aves, Vertebrata, Chordata, Animalia
Organisms: Melopsittacus undulatus [budgerigar] (Psittaciformes);
Puffinus tenuirostris [short-tailed shearwater]
Taxa Notes: Animals; Birds; Chordates; Nonhuman Vertebrates;

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  • Andrew N Iwaniuk

  • John E Nelson

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