Impact of Blackbird Damage to Sunflower: Bioenergetic and Economic Models

Abstract

We constructed bioenergetic and economic models to estimate the potential impact of Red‐winged Blackbirds (Agelaius phoeniceus), Common Grackles (Quiscalus quiscula), and Yellow‐headed Blackbirds (Xanthocephalus xanthocephalus) on production yields of sunflower in the northern Great Plains of North America. The amount of sunflower consumed annually by males and females, after considering field metabolic rates, energy value and moisture content of achenes, and percentage of sunflower in diets was, respectively: Red‐winged Blackbirds 277 g and 168 g; Common Grackles 267 g and 230 g; and Yellow‐headed Blackbirds 248 g and 139 g. The per capita annual economic damage was: male Red‐winged Blackbirds $0.09 (U.S. dollars), females $0.05; male Common Grackles $0.09, females $0.07; and male Yellow‐headed Blackbirds $0.08, females $0.05. Annual loss was $5.4 ± 1.3 × 106 for all three species in aggregate, with Red‐winged Blackbirds accounting for 52% of the loss. Blackbird damage represented 1.7% of the dollar value of the 1999 sunflower harvest in the northern Great Plains. This loss would be inconsequential if damage were distributed evenly; however, bird damage is often localized around wetlands and can be economically debilitating to individual producers. Although our model was based on regional population estimates, it should perform well at local scales, provided that a local population can be defined, accurately estimated, and remains stable in size over the six‐week length of the damage period. Because of the large numbers of blackbirds that congregate in the region during August and September prior to migration, sunflower producers should expect some crop losses. The solution to the conflict appears to be one that focuses not on eliminating all damage, but on preventing it from exceeding 5% per field. Corresponding Editor: S. J. Hannon.

Wildlife collisions with aircraft: A missing component of land-use planning for airports

“…Further, extensive work has been directed at bird damage to agriculture (e.g., blackbird [Icteridae] damage to corn (Dolbeer et al, 1984), sunflowers (Blackwell et al, 2003;Peer et al, 2003), and vegetables (Mott et al, 1972); waterfowl damage to cereal grains (Mott et al, 1972), and European starling damage to fruits (Feare, 1985;Stevens, 2008)). In a review of studies documenting bird damage to crops in the USA, Sterner et al (1984) found damage reported for grains, seeds, and silages (18 of 24 crop types), vegetables (15 of 25), fruits (17 of 20), and nuts (5 of 6).…”

Spring Dispersal Patterns of Red-winged Blackbirds, <em>Agelaius phoeniceus</em>, Staging in Eastern South Dakota

“…Based on current population estimates and bioenergetic models, Red-winged Blackbirds cause $3 million of the $5.5 million lost yearly to blackbirds in the core area of sunflower production (Peer et al 2003). Most of the damage occurs between mid-August and early September, when the calorie content of immature sunflower achenes is low and the birds must eat more to reach satiation (Cummings et al 1989;Conner and Hall 1997).…”

“…Most will remain within 200 km of their natal sites until molt completion (or near completion) in late August and early September (Dolbeer 1978;Besser et al 1983;Linz et al 1983 Linz et al 2002). By late summer, the Red-winged Blackbird population responsible for most of the sunflower damage in the Prairie Pothole Region is about 39 (±8.8) million (Peer et al 2003).…”

“…The definition of overabundance is subjective and based upon one's interests, likes, and dislikes; and therefore is controversial. It has been defined generally as that point of abundance where all positive values of the species have been overwhelmed by negative values created by the sheer numbers of individuals (Conover 2002 Because blackbird damage to sunflower is a localized phenomenon occurring within the broader region of the northern Great Plains (Peer et al 2003), it is necessary to identify specific origins of local populations before implementing any strategy of population management. Although leg-banding has provided valuable insights into migratory timing and dispersal of Red-winged Blackbirds (Dolbeer 1978), this method draws its samples randomly from regional populations.…”

Cowbirds, conservation, and coevolution: potential misconceptions and directions for future research

“…In contrast, habitat restoration is long-term and the results are not immediate. Similar lethal management approaches with nuisance blackbird species have also failed (Peer et al, 2003;Blackwell et al, 2003). In short, while controlling cowbirds was an appropriate decision in the early days of several endangered species recovery programs, we contend that much and perhaps most funding devoted to current control programs would be better utilized in habitat management.…”