Birds in orchards: Economic, biological, and social aspects of ecosystem services
Fruit consumption enhances human health and fruit production is an increasingly important component of the global economy. Some bird species consume large quantities of cultivated fruit while others perform ecosystem services by eating species that damage fruit crops. In this interdisciplinary project we quantified 1) costs to fruit growers of damage caused by frugivorous birds, 2) diets of American kestrels, predatory birds with declining populations in much of the U.S. that we attracted to orchards by installing nest boxes and 3) potential price premiums consumers will pay for fruit produced with predator nest boxes.
We documented economic effects of bird damage through a survey of fruit growers in five states. Growers (n=1590) were asked to estimate bird damage in 2011. Using these estimates, along with state-specific price, production, and acreage data, we calculated states' financial losses. We quantified kestrel diets through video recordings of prey brought to nestlings at nest boxes in a fruit-growing region in the northern lower peninsula of Michigan in 2013 and 2014. We employed a national online survey and a choice modeling approach to assess 1000 consumers' willingness to pay for various pest management practices in fruit.
Growers estimated bird damage to sweet cherries as between 4.8 and 31.4%, to blueberries between 3.8 and 18.2%, and to wine grapes between 2.9 and 9.2%. For sweet cherries statewide financial losses ranged from $1.2 million in New York to $32 million in Washington. Wine grape losses ranged from $2.5 million in Michigan to $49.1 million in California.
Data from 375 hours of recordings showed that kestrels consume many species that damage fruit plants, including arthropods (e.g. grasshopper species), mammals (e.g. meadow voles), and birds (e.g. European starlings). Data also suggested that kestrels responded to prey availability. In 2013 only one of eight nest boxes showed more than 10% mammal deliveries while in 2014 11 of 14 did.
Consumer respondents indicated that they would pay an average of 64 to 72 cents more per pound for fruit grown with the pest management practice of attracting predatory birds with nest boxes.
Installing predator nest boxes is a low-cost way to potentially enhance the ecosystem service of crop pest consumption. Results indicate that disclosing the use of predator nest boxes to consumers could elicit modest price premiums for fruit growers. In addition, nest box installation may increase local population sizes of kestrels.