The diversity and abundance of birds was studied on 6 agroforestry plantations and 5 agricultural types (alfalfa, cotton, tomatoes, sugar beets, and fallow land) in the San Joaquin Valley, California, from June 1987 through May 1989. Based on 1,750 6- minute samples, taken during the 8 quarters of the study, 74 species of birds were observed in the agroforestry plantations while an additional 48 species were seen over and in close proximity to the plantations. Seven species of birds, based on 13,475 total sightings during the study, dominated tree plantation use: house finches (Carpodacus mexicanus) (19%), mourning doves (Zenaida macroura) (13%), yellow-rumpcd warblers (Dendroica coronata).(l3%), song sparrows (Melospiza melodia) (10%), red-winged blackbirds (Agelaius phoencieus) (8%), brewer?s blackbirds (Euphagus cyanocephalus) (8%), white-crowned sparrows (Zonotrichia leucophrys) (6%). Song sparrows (61%), red-winged blackbirds (23%), western meadowlarks (Stumella meglecta) (6%), and house finches (4%) were the most common birds using agricultural habitats. Species similarity indices between the agroforestry plantations varied from 0.17 to 0.79 depending on the season-of-the-year. Species diversity indices varied from 3.40 to 6.40 per agroforestry site and averaged 4.12 (SE = 0.38, n = 48). Little nesting occurred in the eucalyptus until the trees were 3 years old; nest density in 1989 varied from 2 to 17 nests per ha. The oldest plantation (5 years old) had significantly more nesting activity than did younger sites (P < 0.005). Most of the nesting, based on 103 active nests in 1989, was by house finches (41%), mourning doves (31%), and brewer's blackbirds (16%). The agroforestry plantations provided needed nesting habitat and resting sites for migrating species of birds in an area devoid of this type of habitat. These agroforestry sites probably act as biological magnets for birds.
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