History of a Pair of Pacific Horned Owls

Abstract

T OWARD the east end of the Escondido Valley, San Diego County, California, there arises from the valley floor a steep and rocky ridge. On the eastern slope of this ridge and in the big trees of the creek bottom directly beneath, two Pacific Horned Owls (Bubo virginianus pacificus) have made their home for years. This pair of birds was selected for observation because they were close to my home, and their surroundings were typical for this bird in our section. To the east and south of this location the Escondido valley stretches away, covered with orchards, vineyards, and fields of alfalfa and grain. Two creek bottoms cross this part of the valley, and there are a few small ponds scattered throughout during the spring of the year. To the north and west are rolling, brush-covered hills, with an occasional inland valley of small acreage. The edges of the small valleys and clearings are thickly populated with the smaller mammals which make up the principal diet of the Horned Owl. Records of nesting dates for this pair of birds are available for the past thirteen years. During this time, to my knowledge, there have been killed in this immediate vicinity four adult Horned Owls, but apparently the remaining bird had very little trouble in securing a mate, as the site has never missed being occupied for a single season. Glancing over the records we find that this pair has nested in old hawk's nests in trees three times, in an old hawk's or raven's nest in a cliff, twice, and in every other instance has made its home on some rocky ledge on this steep hillside. The variations in nesting dates have been very slight, considering the great variation in the weather of the different seasons during this series of years. The earliest date recorded for a complete set of eggs was January 29 (I9II), with two eggs; the latest date was February 14 (1907), when a set of three