This paper by Smith, Gehara, and Harvey was released earlier this year (currently behind a paywall): The demography of extinction in eastern North American birds. Supplementary material can be viewed here. The DNA study included passenger pigeon and four other extinct bird species.
From the abstract:
We found extinct species harboured lower genetic diversity and effective population sizes than extant species, but both extinct and non-extinct birds had similar demographic histories of population expansion. These demographic patterns are consistent with population size changes associated with glacial–interglacial cycles. The lack of support for overall population declines during the Pleistocene corroborates the view that, although species that went extinct may have been vulnerable due to low diversity or small population size, their disappearance was driven by human activities in the Anthropocene.
Reference: Smith BT, Gehara M, Harvey MG. 2021 The demography of extinction in eastern North American birds. Proceedings of the Royal Society B: Biological Sciences Vol. 288, Issue 1944: 20201945.
An interesting article on the California Condor (Gymnogyps californianus), which faced extinction but has so far survived. Analysis of its genome implies a relatively large population about 1 million years ago followed by a decline in population around 10,000 years ago (or very roughly, the end of the Pleistocene). Note that the techniques used do not allow an estimation of recent (less than 10,000 years) population history.
For a species that was briefly extinct in the wild, the California condor has unexpectedly high genome-wide diversityp. 5
our results show that the turkey vulture was historically less abundant than the California condor, though it is the most abundant and wide-ranging New World vulture today.p. 6
Though the history of the California condor shows evidence of past decline, it retains a high degree of ancestral variation and, perhaps, the potential for future adaptation. As exemplified by the passenger pigeon (Ectopistes migratorius) and Carolina parakeet (Conuropsis carolinensis), high genetic diversity is by no means a barrier to extinction, but the variation present in the California condor is nonetheless reassuring. The species continues to repro- duce naturally and expand its range in the wildp. 6
Robinson et al., Genome-wide diversity in the California condor tracks its prehistoric abundance and decline, Current Biology (2021), https://doi.org/10.1016/j.cub.2021.04.035
Featured image: Don Graham, CC BY-SA 2.0 https://creativecommons.org/licenses/by-sa/2.0, via Wikimedia Commons
A recent editorial in PLOS Biology is asking, but not really answering, some important questions: