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The Tricolored Blackbird (Agelaius tricolor) is a range-restricted, colonial-nesting species in decline. Colonies include tens of thousands of individuals that forage in the surrounding landscape, at times commuting miles between nesting and foraging grounds. We explored the role of landscape composition on colony occupancy and mapped core and potential spring foraging habitat in California, USA. We used observations of spring Tricolored Blackbird nesting colonies from 2008, 2011, and 2014 and characterized changes in the surrounding landscape during an extended drought. Then, we constructed occurrence and abundance models in order to map core foraging habitat across 4 ecoregions in California. Finally, we used simulated land cover changes to identify potential habitat under restoration scenarios. Across the 3 survey years, surface water declined over time at unoccupied colony locations but remained stable at occupied colony locations, confirming that permanent surface water was a critical feature of persistent Tricolored Blackbird colonies. Average percent cover of nearly all land cover types suitable for foraging, as well as frequency of dairies and median NDVI, were all higher in current or historical colony sites than elsewhere. The proportion of surrounding alfalfa, grasslands, and surface water were the elements of foraging habitat best able to predict Tricolored Blackbird early breeding season colony presence and colony size. Core foraging habitat covered over 6 million acres in the study region, but only 18% was occupied in 2014. This result suggests a need to study additional factors determining colony occurrence and persistence, such as landscape connectivity, distributions of nesting substrates, and risk from predators. The vast majority (93.1%) of Tricolored Blackbird core habitat occurred on private land; therefore, saving the species will require engagement and partnership with private landowners.

The California Condor (Gymnogyps califomianus) has recently passed through a severe population bottleneck. Only 22 individuals persisted in 1982, of which 14 individuals became genetic founders (founders of the extant population). Previous studies have suggested that the California Condor possesses low levels of genetic diversity, however, it is unclear whether this is the result of a recent reduction in diversity or a historic lack of diversity. This is an important distinction, because loss of genetic diversity has been linked to reduced fitness and increases in inbreeding depression. To evaluate the effect of the population bottleneck on genetic diversity, we obtained DNA sequence from Domain I of the mitochondrial control region (324 bp) from 41 museum specimens collected near the turn of the 19111 to 20th century (prior to the severe bottleneck) and from 12 of the 14 genetic founders. Studbook data were used to infer the genotype of all condors in the post-bottleneck (current) population. A total of four haplotypes were present among the pre-bottleneck samples and among the genetic founders. However, one haplotype found in the pre-bottleneck sample is not present among the founders and one haplotype present among the founders was not discovered in the pre-bottleneck sample. Measures of genetic diversity from before, during and after the population bottleneck provide insight into the history of the California Condor and suggest that the effect of the severe population bottleneck on the current level of genetic diversity was minimal.