Genetic data are increasingly being used to prioritize species conservation in a fiscally constrained age of seemingly boundless conservation crises. Such data can also reveal previously cryptic biodiversity requiring further revision of conservation management guidelines. Using a combination of mitochondrial (control region) and nuclear (beta fibrinogen intron 7) DNA, and morphology, we reveal that the endemic New Zealand Spotted Shag (Phalacrocorax punctatus) complex exhibits phylogenetic structure that is decoupled from previously recorded qualitative morphological variation. Crucially, the most genetically distinct populations within P. punctatus are from northern New Zealand; recent surveys show that these populations, which house important genetic diversity within Spotted Shags, are in danger of being extirpated. In contrast, we find the previously phenotypically differentiated nominate (P. punctatus punctatus) and Blue (P. punctatus oliveri) Shag subspecies show no genetic and morphological separation, and are of least conservation concern.