EVOLUTIONARY STASIS OF GOLDEN EAGLES OVER THE LAST GLACIAL-INTERGLACIAL CYCLE (35KA TO PRESENT)

    Measurement of more than 700 tarsometatarsi from the golden eagle, Aquila chrysaetos, has provided insight into the morphological response to climate change of this species.  Pleistocene fossils from Rancho La Brea represent a period of dramatic climate change whose effects should be seen as morphological changes in the most commonly preserved bird, Aquila chrysaetos, over the last 35,000 years.  Five variables each were measured on 690 Pleistocene-aged tarsometatarsi from the Page Museum at Rancho La Brea, and the same measurements were taken from a sample of 63 extant golden eagle bones.  Change in size over time is shown through a bivariate comparison of the tarsometatarsi in the Pleistocene-aged and extant golden eagles.  Samples from Rancho La Brea represent 26,000 years of morphology, so additional elements of the humeri, ulnae, and tibiotarsi were measured to give more insight to overall morphological change over that period.  Interestingly, the data shows no significant change in size between 35,000 to 9,000 years b.p. or over the entire 35ka.  This suggests that Aquila chrysaetos experienced evolutionary stasis even during the climatic changes of the most recent glacial-interglacial cycle.