Geographic variation in morphology of Northern Cardinals: possible application of Bergmann’s Rule? by M. Susan DeVries, Meg Waraczynski, Daniel T. Baldassarre, Morgan C. Slevin, Rindy Anderson, Jodie M. Jawor

“…Northern and southern populations were not as clearly distinguished by tail or crest feather length. Our findings suggest that Bergmann’s rule could apply to the Northern Cardinal. …”
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Qualitative mutant traits within the indigenous chicken population in selected ecological zones of Ghana by P. Mensah, K. Adomako, B.A. Hagan, J.A. Hamidu, S.O. Olympio

“…The individual birds were phenotypically observed for the presence of the following genes; frizzle, naked neck, silkiness, polydactyl, ptilopody, crest feathered and flightless. Data on flightless chickens were not available except their gene frequencies since the respondents do not keep them for economic purposes. …”
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