Natural predators as a means to limit wildlife damage at the dairy-fruit interface

Project Overview

Project Type: Farmer/Rancher
Funds awarded in 2014: $24,287.00
Projected End Date: 12/31/2016
Region: Western
State: Washington
Principal Investigator:
John Steensma
Steensma Dairy

Annual Reports


  • Agronomic: corn, grass (misc. perennial), hay
  • Fruits: apples, berries (other), berries (blueberries), cherries, grapes, berries (strawberries)
  • Additional Plants: native plants
  • Animal Products: dairy


  • Animal Production: feed/forage
  • Crop Production: food product quality/safety
  • Education and Training: demonstration, extension, farmer to farmer, on-farm/ranch research, participatory research, workshop, youth education
  • Farm Business Management: agritourism, value added
  • Natural Resources/Environment: biodiversity, habitat enhancement, hedgerows, riparian buffers, wildlife, hedges - woody
  • Pest Management: biological control, integrated pest management, prevention
  • Production Systems: holistic management
  • Sustainable Communities: urban/rural integration



    European starlings on dairy barn

    European starlings are an invasive species in North America


    The purpose of this study was to examine possibilities for natural predators, primarily native birds of prey, to serve as biocontrols for pest birds and rodents on Washington dairy and berry farms. We estimated bird and rodent damage on dairies in Washington State through farmer surveys; performed bird counts on 10 Whatcom County dairies within <1 mile of fruit crops; implemented measures to enhance the presence of native birds of prey in Whatcom County agricultural areas; introduced and encouraged bird abatement falconry on dairies; worked on youth, farmer, and general public outreach highlighting the ecosystem services of farmland birds; hosted a conference and an on-farm demonstration related to agricultural birds; created and posted an educational video about using native raptors and trained falcons for nuisance bird control; developed and distributed a laminated bird ID card; and successfully collaborated with additional researchers to build a longer-term project as we realized the scope of the problem of European starlings on dairy farms.


    Wildlife damage to fruit crops in Washington and Oregon has been cost-estimated from $400- $3000/acre/year in grapes, cherries, blueberries and apples (1). With expansion of blueberry acreage in Whatcom County and other western Washington counties over the past decade, dairies are increasingly located adjacent to blueberries. The invasive European starling is responsible for much damage to both fruit and stored dairy grain and forages, but other birds and rodents are also implicated. Though not rigorously examined previously, estimated losses to dairy operations range from $2000-$10,000/herd/year or more with a typical 1,000-bird starling flock easily consuming a ton of silage each month (2).


    The pattern for starlings includes roosts at dairies, where high energy foods are available at open faces of bunker silos, in grain rations fed to cows in feeding areas, and in manure lagoons. Starlings on dairies contaminate feed, water, and housing year-round, and eat and contaminate fruit during blueberry season. They also damage silage tarps. Similar patterns may be seen where livestock feeding occurs near other fruit crops (e.g. beef feedlots/dairies near Yakima cherry orchards in eastern Washington).


    Rodent problems include rats eating corn and grain on dairies and chewing silage tarps and wiring, and voles chewing roots and bark in fruit crops (3).


    Use of scare tactics such as propane cannons and bird distress calls are widely perceived to be ineffective; these measures also disturb farm and non-farm neighbors. Lethal management methods include trapping, shooting, and poisons. Farm employees may have little time or ability to distinguish between "pest" and "beneficial" birds, sometimes using a guiding principle that "the only good bird is a dead bird." Starling and rodent traps can remove individuals but may inadvertently trap beneficial birds such as swallows and raptors, or harm other non-target species. Poisons have potential to move through the food chain, harming beneficial species such as raptors and even domestic cats and dogs (4,5).


    The intent of this project was to quantify the extent and impact of bird damage on dairy farms. Using interview and survey tools, we quantified annual feed losses attributable to birds (feed consumption and fecal contamination) and time and money spent on shooting, trapping, poisoning and other techniques. Adjacent blueberry growers were also interviewed about damage.


    Several dairies with proximity <1 mile to fruit crops were selected for implementation of ecologically sustainable, biocontrol techniques including installation of barn owl and kestrel falcon nest boxes.


    We connected area falconers to dairy owners willing to allow falconers access to their facilities. Placement of carrion (undiseased dairy placentas and stillborn calves) for natural decomposition in sufficiently isolated fields (under Washington State Department of Agriculture regulations) was tested as a means of keeping natural predators in the targeted study area.


    Cessation of rodenticide use was requested on participating dairies to minimize risk of secondary poisoning or trapping of raptors. Dairy owners and employees were provided with bird identification instruction to prevent shooting of beneficial and non-target species. We also encouraged adjacent fruit growers to discontinue rodenticide use and shooting of non-target birds.


    Bird counts were taken at each of the chosen dairy field sites. Each dairy farmer was asked to estimate damage levels and perceptions of effectiveness of the various techniques attempted. Based on these numbers (pest counts, farmer estimates of damage, and farmer perception of effectiveness), a few techniques were selected for highlighting at a conference and a demonstration event to which area dairy producers were invited.


    Area 4-H and FFA youth helped with this project by meeting with falconers and installing kestrel falcon nest boxes. Additional outreach included presentations and emails to Washington State Dairy Federation (WSDF) members; presentations to dairy farmers at two Whatcom Conservation District (WCD) annual workshops; presentations to scientists, farmers, and other agricultural employees at conferences; articles on the Washington State University (WSU) Extension webpage; an educational nest box webcam; a native raptor and falconry video posted on WSU and Whatcom Family Farmers (WFF) websites; bird and wildlife stations at several agriculture education events; and a bird identification card distributed to farmers, rural landowners, and other citizens.


    The scope of the problem was so much greater than anticipated that a second and larger WSARE Research and Education grant project was created to measure bird impacts on cow welfare. This project is now successfully underway in conjunction with WSU and USDA/APHIS collaborators.


    The expectation of this Farmer-Rancher WSARE project was that enhancement of habitat for birds of prey, or other means of providing "natural" controls for pest birds and rodents, could prove economically beneficial for farmers, while reducing direct and indirect mortality of raptors and other beneficial species (6,7). Farmers were able to envision economic benefits of native raptors and biocontrols, increase public perception of the value of agriculture for wildlife species, and improve the overall quality of rural community life through these efforts.


    1. Anderson et al 2013. Bird damage to select fruit crops: The cost of damage and the benefits of control in five states. Crop Protection 52:103-109.

    2. Johnston 2013. Coping with sky-high feed. Successful Farming (Nov):BI1-2.

    3. Ashkam 1988. A two-year study of the physical and economic impact of voles on mixed maturity apple orchards in the Pacific Northwestern US. Proceedings Vertebrate Pest Conference 13:151-155.

    4. Rattner et al. 2011. Acute toxicity, histopathology, and coagulopathy in American kestrels following administration of the rodenticide diphacinone. Environmental Toxicology & Chemistry 30:1213-1222.

    5. Thomas et al. 2011. Second generation anticoagulant rodenticides in predatory birds: Probabilistic characterisation of toxic liver concentrations and implications for predatory bird populations in Canada. Environmental International 37:914-920.

    6. Baldwin et al. 2014. Perceived damage and areas of needed research for wildlife pests of California agriculture. Integrative Zoology 9:265-279.

    7. Steensma et al. 2016. Bird damage to fruit crops: a comparison of several deterrent techniques. Proceedings Vertebrate Pest Conference 27:xx-xx (in press).

    Project objectives:

    Original objectives of the project proposal / measured performance:

    1. Estimate bird/rodent damage to dairies through farmer surveys. About 22% of Whatcom County dairies, and about 21% of surveyed dairies across the state, responded to the survey. Of respondents, 98% indicated birds were a problem on their farm(s) and 49% indicated rodents as at least a slight problem.
    2. Measure numbers of pest birds and rodents at dairies and adjacent fruit fields through field data collection. Bird counts were conducted at 10 Whatcom County dairies over 2 seasons. Numbers ranged from 100-4,000/dairy/day at peak times. Rodents were not counted directly.
    3. Implement bio-control methods for managing problem birds and rodents in dairies/adjacent fruit. In Whatcom County: Kestrel falcon nest boxes were installed/maintained at 38 sites; owl nest boxes were monitored at 3 sites; and carrion feeding stations were established at 2 sites.
    4. Estimate any changes in pest damage levels and raptor presence resulting from project implementation. In Whatcom County: Kestrel box occupancy was 5-10%; owl box occupancy was 66%; and carrion feeding drew eagles and turkey vultures each time carrion was placed, but these raptors were transient. The limited duration of the raptor enhancement project prevented accurate estimates of changes in pest damage levels.
    5. Host demonstration days at dairies. A falconry and raptor nest box demonstration was hosted at a Whatcom County dairy in fall 2015. This demonstration, along with additional similar demonstrations targeted to youth and adults through various events in 2015-2016, educated at least 1,200 people, including at least 300 directly employed in agriculture. Additionally a “virtual demonstration” by means of a video link about birds on dairies reached 1,200 views within a week of being posted online.


    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.