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While doing a websearch this morning for birds of the Puente Hills, I came across a fascinating tidbit buried in a 1929 issue of the journal The Condor ("Some results of bird banding in 1928" by John McB. Robertson):
"Nestling Long-eared Owl no. 543281 banded April 10, 1928, at Rancho de los Tres Hermanos, in the Puente Hills of southeastern Los Angeles County, was taken four miles from Lancaster, California, between December 29, 1928 and January 3, 1929, a distance of about fifty miles."
Old journal articles were notoriously vaguely-worded, and as this is no exception, I missed this reference entirely in previous literature searches of birds of the Puente-Chino Hills. This note is significant for several reasons. First, it provides evidence that this scarce owl (a California Bird Species of Special Concern, pictured here) once occurred and even nested in the Puente Hills. This species, once common in ranches and riverbottoms throughout the region, is now nearly extirpated from all of southern California, with only a handful of nesting pairs known from interior valleys, remote mountain ranges, and desert oases.
Also, it illustrates the importance of the hills as a nesting area for raptors that may disperse widely for the winter and return to breed in the spring. The article also mentions a Red-tailed nestling from Carbon Canyon found (in a coyote trap!) in Madera County in the Central Valley (the fact that both these birds flew north, rather than south, for the winter is also interesting).
Finally, it suggests that scarce species like the Long-eared Owl may yet be holding out in some of the more remote canyons and properties of the Puente Hills, awaiting discovery. This ranchland is still there, visible from Grand Ave. as it crosses from Diamond Bar into Chino Hills. As the surrounding area developed in the past 80 years, maybe the owls left at some point - but maybe they've been there all along...