Steller's Jays (Cyanocitta stelleri) with swollen legs and feet resembling the signs of scaly leg have been commonly seen around Arcata, California, US. The clinical signs are thought to be caused by knemidokoptic mites, a group of parasites specialized on avian hosts. Between February 2019 and March 2020, we analyzed the long-term database of Steller's Jays collected by Humboldt State University for trends in the prevalence of signs of scaly leg, compared the gripping position in the feet of Steller's Jays with variable signs of this condition as an index of their ability to perch, identified the mites using a partial sequence of the cytochrome oxidase subunit I gene, and examined genetic distances between mites collected from different host species both sequenced in this study and from GenBank. Overall, 27% of jays recorded in the long-term database had shown signs of scaly leg. Jays with signs captured in this study had greater variability in and a reduced degree of contraction in the gripping position of their feet compared to jays without signs, suggesting that infestation may have an impact on the host's ability to perch. The cytochrome oxidase subunit I sequence (578 base pairs) from mites collected from Steller's Jays was compared to sequences from Knemidokoptes jamaicensis, Knemidokoptes derooi, and to unidentified Knemidokoptes spp. collected from different hosts. The mites from Steller's Jays were most closely related to Knemidokoptes jamaicensis but had a relatively high sequence divergence, 7.8%, supporting the possibility that the form infesting these jays may be an undescribed species.
Keywords: Cyanocitta stelleri; Knemidokoptes; cytochrome oxidase subunit I (COI); Steller's Jay; perching; scaly leg.
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