At least 10 species of parrots (Family Psittacidae). along with the Eurasian collared-dove (Columbidae: Streptopelia decaocto), orange [northern red] bishop (Ploceidae: Euplectes frandscanus), and nutmeg mannikin ["spice finch" or "spotted munia"] (Estrildidae: Lonchura punctulata). have recently established significant viable and generally increasing populations in California. Populations of all of these taxa are concentrated in highly modified urban and suburban habitats (parrots, doves) or in flood control basins and river channels with abundant rank annual growth (bishop, mannikin). With various collaborators, the author has monitored these taxa in southern California through the 1990s. Because of the potential for deleterious ecological interactions with native bird species and for damage to certain commercial crops, monitoring of these species and other potentially established exotic bird species must be ongoing. Here the author reports his present knowledge of population sizes and trends, geographical distribution, habitat relationships, and foraging and breeding ecology of these introduced species and suggest schemes for continued monitoring.

The Yellow Warbler (Setophaga petechia) is a small songbird in the wood-warbler family (Parulidae) that exhibits phenotypic and ecological differences across a widespread distribution and is important to California's riparian habitat conservation. Here, we present a high-quality de novo genome assembly of a vouchered female Yellow Warbler from southern California. Using HiFi long-read and Omni-C proximity sequencing technologies, we generated a 1.22 Gb assembly including 687 scaffolds with a contig N50 of 6.80 Mb, scaffold N50 of 21.18 Mb, and a BUSCO completeness score of 96.0%. This highly contiguous genome assembly provides an essential resource for understanding the history of gene flow, divergence, and local adaptation in Yellow Warblers and can inform conservation management of this charismatic bird species.

Understanding the source of non-native introduced populations is crucial for forecasting geographic invasion potential and understanding the ecological consequences of potential establishment. Here we use genomics to identify the source populations and invasion dynamics of two non-native introduced populations from the iconic avian lineage of ‘great speciators’ known as white-eyes (genus Zosterops). We established confidently for the first time that introduced Zosterops populations in Hawaii and southern California are completely unrelated and derived from independent introductions of the species Z. japonicus and Z. simplex, respectively. We used descriptive population genetic statistics to identify a reduction in genetic diversity and increase in private alleles in the southern California population supporting a recent, potentially ongoing, genetic bottleneck in this population. In contrast, the introduced population in Hawaii showed no such characteristics, likely due to a larger founding population size and repeated introductions in this intentionally introduced population. Ecological niche modeling indicated that there is little environmentally suitable habitat for Z. simplex across the continent of North America, suggesting limited invasion potential, assuming niche conservatism. Yet, portions of the introduced Z. simplex population have already surpassed areas projected as suitable, likely because the urbanized environment of southern California offers biotic resources and microhabitats not captured by our model. Because Z. simplex appears to have overcome both the ‘invasion paradox’ of low founding genetic diversity and relatively unfamiliar environmental conditions in southern California, we suggest that this population may continue expanding beyond our environmental niche model projections in other temperate, urban regions.

The great auk was once abundant and distributed across the North Atlantic. It is now extinct, having been heavily exploited for its eggs, meat, and feathers. We investigated the impact of human hunting on its demise by integrating genetic data, GPS-based ocean current data, and analyses of population viability. We sequenced complete mitochondrial genomes of 41 individuals from across the species' geographic range and reconstructed population structure and population dynamics throughout the Holocene. Taken together, our data do not provide any evidence that great auks were at risk of extinction prior to the onset of intensive human hunting in the early 16th century. In addition, our population viability analyses reveal that even if the great auk had not been under threat by environmental change, human hunting alone could have been sufficient to cause its extinction. Our results emphasise the vulnerability of even abundant and widespread species to intense and localised exploitation.