AMERICAN ROBINS (TURDUS MIGRATORIUS) AND CEDAR WAXWINGS (BOMBYCILLA CEDRORUM) VARY IN USE OF CULTIVATED CHERRY ORCHARDS

摘要

Some fruit-eating bird species commonly consume cultivated fruit. Species-specific variation in diet preferences could result in varying use of orchards and impacts on the fruit-producing industry. However, species-specific studies of avian orchard use are lacking, particularly throughout the fruit-growing season. Our objectives were to quantify the frequency of daily bird visits to orchards and the amount of time birds spent visiting orchards each day over the fruit-ripening season. Birds are well-documented consumers of cultivated sweet cherries (Prunus avium), which are relatively high in sugar and low in proteins and lipids. American Robins (Turdus migratorius) and Cedar Waxwings (Bombycilla cedrorum) are common fruit-consumers in sweet cherry orchards. Robins often consume larger proportions of invertebrates and prefer lipid-rich fruits, while waxwings choose sugary fruits. Given these species-specific diet differences, we hypothesized waxwings would spend a greater proportion of days and more time each day in cherry orchards, compared to robins. We used radio telemetry to track the habitat use of 25 American Robins and 17 Cedar Waxwings in sweet cherry orchards of Michigan. Over their respective radio-tracking periods, waxwings visited orchards a greater percentage of days than robins (waxwings: mean = 21%, SD = 22; robins: mean = 6%, SD = 4). In addition, waxwings visited orchards for more time each day. Differences in diet preferences and nutritional physiology may translate into species-specific patterns of habitat use for birds in fruit-rich environments. Received 4 February 2015. Accepted 2 August 2015.