Feedlots can attract thousands of European starlings. These birds eat valuable livestock feed; defecate on livestock, structures, and 

 feed; and are a potential reservoir of diseases transmissible to livestock and humans. (NWRC photo by H. J. Homan.) 



Blackbird Repellants — NWRC scientists evaluated 

 the repellancy of caffeine and garlic oil for reducing 

 depredations by blackbirds on intact sunflower 

 heads. Damage was significantly reduced on 

 heads treated with caffeine (compared to untreated 

 heads), but not on heads treated with garlic. 

 Average consumption of sunflower by blackbirds 

 was less for the caffeine-treated heads (2,826 pg/ 

 mL) than for those treated with garlic oil (0.02 g/ 

 mL). Overall, mean consumption (cm^ of seeds per 



Researchers are developing new repellants to protect ripening 

 sunflowers from blackbirds. (Photo by R. Wimberly) 



bird) was significantly less for the birds fed 3 mL 

 (4,747 Mg/mL) of caffeine per head than for birds 

 fed 2 mL (2,212 pg/mL) of caffeine per head. 



Garlic oil had no apparent effect on sunflower 

 consumption. In the tests conducted in 2005, 

 when the entire seeds were coated with garlic oil at 

 2 percent, 1 percent, and 0.5 percent by weight, 

 feeding was reduced 80 percent, 40 percent, and 

 22 percent, respectively, compared to consumption 

 of untreated sunflower heads. This suggests that 

 treating only the exposed portion of the seeds with 

 garlic oil — as was done in the 2007 experiments — is 

 not sufficient to deter feeding, particularly when the 

 birds do not have access to alternate foods. 



Additional studies are needed to determine whether 

 free-ranging birds are deterred by low levels of garlic 

 oil when alternative foods are available. During 

 September 2006, three treatments of a water- 

 caffeine solution applied by helicopter to sunflower 

 did not provide a sufficient amount of repellant to 

 the drooping seed heads. This study adds to the 

 growing body of evidence indicating that caffeine 

 can reduce feeding by blackbirds, provided that 

 birds encounter the repellant. However, additional 

 research is needed to develop methods of applying 

 adequate spray coverage on developing seeds in 

 ripening sunflower fields. 



Developing Methods 11 



