We evaluated the effects of sea surface temperature anomalies (SSTA) in the southern California Current Ecosystem on the annual Guadalupe fur seal (Arctocephalus townsendi) pup production, a species recovering from near extinction. Pup counts from 1991 to 1993 and from 2006 to 2019 were used to estimate deviations from a long-term trend as a proxy for the population's reproductive success. We estimated interannual SSTA as a subtraction from the linear trend spanning 1991–2019 for a 778,000 km2 area, which represents the primary foraging range of adult females. The long-term increase in pup production followed an exponential curve ( ${\rm{R}}_{\rm{B}}^2 = {\rm{\ }}1$), typical of species in a recovery phase. Pup production deviations from this trend responded to SSTA during the gestation period as a cubic polynomial function ( ${\rm{R}}_{\rm{B}}^2 = {\rm{\ }}0.837$), revealing that SSTA < −0.2°C and between ∼0.6 and 1.38°C increased pup production in the subsequent breeding season, whereas normal to slightly warm (−0.17 to 0.6°C) and extreme SSTA (>1.4°C) decreased pup counts, arguably resulting from low prey availability and quality. This model allowed us to estimate pup production for years without observations, needed to understand the environmental variability influence on the recovery process of this species, and therefore constitutes a practical tool for its conservation and management.

The evolution of host–parasite interactions as host lineages colonize new geographic regions and diversify over evolutionary time is poorly understood. To assess whether haemosporidian parasite diversity has changed during the diversification of an avian host, we surveyed the diversity and prevalence of blood parasite lineages (genera Plasmodium, Haemoproteus, and Leucocytozoon) across the range of the songbird genus Junco, which has diversified recently as it recolonized North America following the last glacial maximum ~18,000 years ago. We report the diversity and prevalence of parasites in junco taxa sampled from Costa Rica to Canada, and examine the influence of local avian species richness in the prevalence and diversity of parasites in junco samples. We screened for parasites in each individual by sequencing a fragment of their cytochrome b gene, identifying the different lineages, and quantifying the prevalence per junco taxon and locality. Of 304 juncos sampled, 178 tested positive for 1 or more parasite genera (58.5% overall prevalence). We found high parasite diversity in genera Haemoproteus and Leucocytozoon and much lower diversity in Plasmodium. Among the 63 parasite lineages detected, 32 of which have not been previously described, we found generalist lineages with widespread but low prevalence in Junco, but also some that appear to have remained specialized on this genus as it diversified across North America over thousands of years. Our results suggest a range of parasitic strategies, ranging from specialized to generalist lineages within single parasite genera.