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First specimen of Cassin’s Sparrow from San Diego County

Dear friends, This afternoon Joe Alsadi brought to the San Diego Natural History Museum a bird he had found floating dead in the swimming pool at his home in Allied Gardens on Friday 22 October 2021. A very drab slender sparrow with plain underparts and streaked upperparts—insofar as the upperparts were visible, as a lot of the back feathers had been lost. As had rectrices 1-4 on the left side. The bird had evidently been captured by a predator, then dropped in the pool. Maybe a raccoon killed the sparrow, then took it to the pool to wash it but lost it? Anyway, thanks to Joe for recognizing that it was unusual, fishing it out, and drying it off. In spite of the damage, the bird was clearly a Cassin’s Sparrow (and not Botteri’s) by the distinctly streaked hindneck, obscurely barred central rectrix (fortunately one was left), and whitish patches or streaks on several of the lateral rectrices (fortunately all 6 rectrices on the right side remained intact). The rectrices are all remarkably narrow, almost like Bushtit rectrices, lacking the beveled or pointed tips of some similar sparrows. Dissection revealed the bird to be an immature female (skull not pneumatized, ovary filmy and indistinct, with no discrete ova visible even with a hand lens). Whatever killed the bird ripped the skin around the base of the right thigh and made a hole in the upper back but fortunately didn’t damage the pelvic area.  Only 5 previous occurrences of Cassin’s Sparrow in San Diego County are known: One singing and displaying in the springs of 1970, 1976, and 1978 at the family home of Tom Oberbauer on the east edge of El Cajon, one at Coronado 21-25 October 2017, and one singing in Camp Pendleton in June 2019. Though nearly 100 Cassin’s Sparrows are known from California, nearly 2/3 are from just three irruption years, 1978, 1993, and 2019, in the spring/summer following a wet winter. Obviously this fall’s bird isn’t part of that pattern. Only 3 specimens have been preserved from California previously: from Southeast Farallon Island in September 1969 and July 1970 and from the Lanfair Valley in the eastern Mojave Desert in May 1993. So even if our new San Diego County specimen isn’t perfect, it confirms a remarkable occurrence. Joe commented he had never found a dead bird in the pool before—what were the chances that it should represent our first specimen of its species? Now preserved as SDNHM 56893. Good birding, Philip UnittSan Diego