Morphology

Avian morphology encompasses external characters (plumage, bill shape, tarsus structure) and internal anatomy (skull bones, syringeal musculature, keel depth). Classic morphological taxonomy grouped birds by overall form — wading birds by long legs, raptors by talons — but molecular data frequently contradicts morphological groupings. Modern systematics integrates both, using morphological characters that can be scored for phylogenetic analysis alongside DNA sequence data to produce robust species trees.