North Dakota is the top sunflower-producing state in the United States, annually harvesting about 404,686 ha (1 million acres). Since the early 2000s, corn also has become a major crop within the state due to increases in corn prices. Blackbirds (Icteridae) can cause significant damage to both ripening corn and sunflower. The National Sunflower Association considers blackbird depredation to be a key factor in the reduction in sunflower acreage in the Prairie Pothole Region (PPR). In order to better quantify the amount of damage caused by blackbirds, we assessed blackbird damage to ripening sunflower and corn in 120 randomly selected plots during 3 growing seasons, 2008–2010. On average, damage to sunflower was more intense than damage to corn, with sunflower in the southeastern region experiencing the greatest levels of damage. Further analysis will determine possible landscape characteristics associated with this damage

Bleier, William J.

Klosterman, Megan E.

Linz, George M.

Slowik, Anthony A.

English

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln USDA National Wildlife Research Center - Staff Publications U.S. Department of Agriculture: Animal and Plant Health Inspection Service 2012 Assessment of Bird Damage to Sunflower and Corn in North Dakota Megan E. Klosterman North Dakota State University, Megan.e.klosterman@ndsu.edu George M. Linz USDA/APHIS/WS National Wildlife Research Center, george.m.linz@aphis.usda.gov Anthony A. Slowik U.S. Department of Agriculture William J. Bleier North Dakota State University, William.Bleier@ndsu.nodak Follow this and additional works at: https://digitalcommons.unl.edu/icwdm_usdanwrc Klosterman, Megan E.; Linz, George M.; Slowik, Anthony A.; and Bleier, William J., "Assessment of Bird Damage to Sunflower and Corn in North Dakota" (2012). USDA National Wildlife Research Center - Staff Publications. 1155. https://digitalcommons.unl.edu/icwdm_usdanwrc/1155 This Article is brought to you for free and open access by the U.S. Department of Agriculture: Animal and Plant Health Inspection Service at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in USDA National Wildlife Research Center - Staff Publications by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. 119Proceedings of the 14th WDM Conference (2012)                                                                S. N. Frey, editorBirdsAssessment of Bird Damage to Sunflower and Corn in North DakotaMEGAN E. KLOSTERMAN, Department of Biological Sciences, North Dakota State University, Fargo, ND, USAGEORGE M. LINZ, U.S. Department of Agriculture, Wildlife Services, National Wildlife Research Center, Bismarck, ND, USAANTHONY A. SLOWIK, U.S. Department of Agriculture, PPQ, Bismarck, ND, USAWILLIAM J. BLEIER, Department of Biological Sciences, North Dakota State University, Fargo, ND, USAABSTRACT North Dakota is the top sunflower-producing state in the United States, annually harvesting about 404,686 ha (1 million acres). Since the early 2000s, corn also has become a major crop within the state due to increases in corn prices. Blackbirds (Icteridae) can cause significant damage to both ripening corn and sunflower. The National Sunflower Association considers blackbird depredation to be a key factor in the reduction in sunflower acreage in the Prairie Pothole Region (PPR). In order to better quantify the amount of damage caused by blackbirds, we assessed blackbird damage to ripening sunflower and corn in 120 randomly selected plots during 3 growing seasons, 2008–2010. On average, damage to sunflower was more intense than damage to corn, with sunflower in the southeastern region experiencing the greatest levels of damage. Further analysis will determine possible landscape characteristics associated with this damage.KEY WORDS  blackbirds, common grackle, corn, crop damage, North Dakota, Prairie Pothole Region, red-winged blackbird, sunflower, wetlands, yellow-headed blackbird.in the season, especially by grackles and male RWBL and YHBL, which have larger bodies and beaks than do females (Dolbeer 1980, Homan et al. 1994, Linz et al. 1984).Red-winged blackbird population densities in the Dakotas and Minnesota are among the highest in the nation (Peer et al. 2003). Yellow-headed blackbirds breed in regions of the Dakotas and Minnesota where sunflower production is high (Twedt et al. 1991), and their numbers in North Dakota have increased over 300% from 1967–1981 (Besser 1985). Likewise, grackle numbers in North Dakota have also grown, increasing from 334,500 breeding pairs in 1967 to 777,000 pairs in 1990 (Stewart and Kantrud 1972, Nelms et al. 1994). Blackbird populations in North Dakota reach their peak in August and September when sunflowers are reaching maturity (Peer et al. 2003). These resident and migrating populations have led to extensive damage in agricultural fields such as sunflower and corn.Complaints of blackbird damage to corn have in-creased in recent years. Thus, corn may be providing an alternative food for foraging blackbirds. Quantitative surveys of blackbird damage to corn, however, have not been conducted in North Dakota. In 2008, 2009, and 2010, we assessed blackbird damage in ripening sunflower and cornfields. We will determine possible landscape characteristics correlated to this damage and report on these results at a later date. North Dakota is the top sunflower-producing state in the United States, annually harvesting about 404,686 ha (Peer et al., 2003). Recently, corn has become a major crop within the state. Red-winged blackbirds (Agelaius phoeniceus), common grackles (Quiscalus quiscula) and yellow-headed blackbirds (Xanthoceph-alus xanthocephalus) can cause significant damage to these crops. The National Sunflower Association considers blackbird depredation to be a key factor in the reduction of sunflower acreage in the Prairie Pot-hole Region (PPR) (L. Kleingartner, NSA, Bismarck, ND, unpublished report).In 1979 and 1980, a field survey of bird damage to sunflower in North Dakota estimated an economic loss between $ 4–11 million (Hothem et al. 1988). This was the last comprehensive field damage survey. Peer et al. (2003) used a bioenergetics model and es-timated that blackbird damage was valued at $ 5–10 million. Sunflower prices have increased since these monetary losses were calculated.Red-winged blackbirds (RWBL), yellow-headed blackbirds (YHBL) and common grackles (hereaf-ter, “grackles”) are three of the leading contributors to sunflower damage in North Dakota (Cummings et a1.1989, Dolbeer 1975, Sedgewick et al. 1986). Blackbirds tend to feed on corn during the milk and dough stage when the kernels are soft and in sunflower during early ripening. Some damage can occur later 120Proceedings of the 14th WDM Conference (2012)                                                                S. N. Frey, editorBirdsSTUDY AREAOur study area is the 95,200 km2 Prairie Pothole Region (PPR) in North Dakota (Figure 1). Topo-graphy of the PPR consists of undrained depressions, known as potholes, sloughs, or wetlands, which were formed during the Pleistocene Epoch (Johnson et al. 2005, Neimuth and Solberg 2003, Stewart and Kantrud 1973). These wetlands are scattered through-out a matrix of grasslands, agricultural fields, and Conservation Reserve Program (CRP) land (Johnson at al. 2005, Stewart and Kantrud 1973). In 1967, total wetland acreage was estimated at 3.2 million acres (Stewart and Kantrud 1973). In a previous study (Ralston et al. 2007), the PPR was stratified into four strata: the Missouri Coteau, Northwestern Drift Plains, Northeastern Drift Plains and Southern Drift Plains (Stewart and Kantrud 1972, 1973). Ralston et al. (2007) proportionally allocated 120 3.2 x 3.2-km (1,036 ha) sample plots to the four strata.METHODSI assigned a 1.6-km2 (160 ha) area plot to the center of each of the 120 “Ralston Plots.” In late September 2008, 2009, and 2010, we estimated bird damage in all corn and sunflower fields located within the 1.6-km2 core area. In the event that no sunflower or corn-fields were within the 1.6-km2 area section, then no field was surveyed for that site. In 2010 we sought to increase the sample size, in cases where no fields were located in the core area, we searched a 4.8-km (3 mi) radius around the center of the core area for the pres-ence of a sunflower or corn field. The first sunflower or cornfield observed in this area was surveyed for damage.We divided each sampled field down the middle into two strata, each containing an equal number of rows. One row was randomly selected from each stra-tum. The location of the first field plot, consisting of five consecutive sunflower heads or corn ears, was a randomly selected distance in meters between 0 m (i.e., the edge of the field) and 135 m. After establish-ing the first plot, we sampled plots of five consecu-tive sunflower heads or corn ears every 135 m in the row. If an uncultivated area existed within the sampled row, this area was walked through as if it were a culti-vated area. We estimated percentage damage for each sunflower head or corn ear. Sunflower damage was measured using the template method (Dolbeer 1975), and damage to corn was measured by comparing the area of damaged kernels to the possible area of undamaged kernels. For undamaged heads/ears, 0% Figure 1: The Prairie Pothole Region of North Dakota separated into four sample strata. Study sites were randomly selected and proportionately allocated among the strata.121Proceedings of the 14th WDM Conference (2012)                                                                S. N. Frey, editorBirdsdamage was recorded. The percent loss for each field was calculated by averaging the percent loss of all heads across both strata. The cost of the estimated damage for each crop was calculated by dividing the total average percent damage for each crop by the value of production using the USDA Crop Values Summary (2011).PRELIMINARY RESULTSIn 2008, we  surveyed 38 cornfields and 14 sun-flower fields for blackbird damage. Most of the corn was planted in the southeast (Southeastern Drift Plains) and sunflower was planted in the northern region (Northeastern and Northwestern Drift Plains), respectively. In 2009, we surveyed 30 cornfields and 15 sunflower fields, with the distribution of corn and sunflower fields following the same regional trend as in 2008. In 2010, the number of fields surveyed was nearly doubled using the expanded sample scheme. We surveyed 65 cornfields and 23 sunflower fields, with field location following the same trend as the previous two years. We compared damage across years using only the fields within the 1.6-km2 sample plots (Figure 2). We also conducted a separate analysis for the entire data set for 2010.In 2008, sunflower damage averaged 0.95% (range: 0%-10.16%), and corn damage 0.69% (range: 0%-5.27%). In 2009, sunflower damage averaged 2.17% Figure 3: Average percentage of sunflower and corn damage in 2008, 2009, and 2010. Lines represent standard error for each crop per year.Figure 2: Locations of study fields, within the 1.6 km2 core area, within the Prairie Pothole Region of North Dakota in 2010. Sample size was augmented to improve the variance associated with damage estimates.(range: 0%-19.79%), and corn damage 0.18% (range: 0%-1.52%). In 2010, sunflower damage averaged 3.29% (range: 0%-13.57%), and damage to corn was calculated at 0.13% (range: 0%-1.28%). In 2010, using the expanded sample scheme, sunflower dam-age averaged 2.32 % (range: 0%-13.57%) with corn damage averaging 0.21 % (range: 0%-2.85%) (Table 1 and Figure 3).Table 1: Average percent of sunflower and corn damage for each year within the study period.Year ^ƵŶŇŽǁĞƌĂŵĂŐĞn Corn ĂŵĂŐĞn2008 0.95% 14 0.69% 382009 2.17% 15 0.18% 302010 3.29% 12 0.13% 382010 (extended sample)2.32% 23 0.21% 65Sunflower fields near the Southern Drift Plains tended to have higher damage estimates than those located in the Northern Drift Plains. The cost of damage in 2008, based on overall production value in the state, was $ 7.3 million for corn and $ 3 million for sun-flower (Figure 4). In 2009, the cost was $ 1.25 million and $ 4 million for corn and sunflower, respectively. In 2010, the cost was $ 1.7 million for corn and $ 8.9 million for sunflower.122Proceedings of the 14th WDM Conference (2012)                                                                S. N. Frey, editorBirdsDISCUSSIONOur data show an overall increase, from 2008 to 2010, in damage to sunflower and a decrease in damage to corn. Corn production has increased in the state, with many farmers in the Southern Drift Plains plant-ing corn rather than other crops, such as sunflower. Sunflower production is primarily confined to the north central region of state (Northwestern Drift Plains and Northeastern Drift Plains), with sunflower crops planted in the southern areas receiving more damage than those further north. Our data show that blackbirds forage in both sunflower and corn fields. In locations where corn and sunflower are grown in close proximity, blackbirds might forage in both crops, thus reducing overall damage in each one.ACKNOWLEDGMENTSI thank D. Stonefish and J. Schanandore for com-ments and contributions to this manuscript. M. Bion-dini provided statistical advice and guidance.LITERATURE CITEDBesser, J. F. 1985. Changes in breeding blackbird numbers in North Dakota from 1967 to 1981–82. Prairie Naturalist 17:133–142.Cummings, J. L., J. L. Guarino, and C. E. Knittle. 1989. Chronology of blackbird damage to sunflowers. Wildlife Society Bulletin 17:50–52.Dolbeer, R. A. 1975. A comparison of two methods for estimating bird damage to sunflowers. Journal of Wildlife Management 39:802–806.Dolbeer, R. A. 1980. Blackbirds and corn in Ohio. United States Department of the Interior: Fish and Wildlife Service Resource Publication 13, Washington, D.C., USA.Homan, H. J., G. M. Linz, and W. J. Bleier. 1994. Effect of crop phenology and habitat on the diet of common grackles (Quiscalus quiscula). American Midland Naturalist 131:381–385.Homan, H. J., G. M. Linz, W.J. Bleier, and R. B. Carlson. 1996. Colony-site and nest-site use by common grackles in North Dakota. Wilson Bulletin 108:104–114.Hothem, R. L., R. W. DeHaven, and S. D. Fairaizl. 1988. Bird damage to sunflower in North Dakota, South Dakota, and Minnesota, 1979–1981. United States Department of the Interior: Fish and Wildlife Technical Report 15, Washington, D.C., USA.Jenson, J. R. 2005. Introductory digital image processing: a remote sensing perspective. Third edition. Pearson Prentice Hall, Upper Saddle River, New Jersey, USA.Johnson, W. C., B. V. Millett, T. Gilmanov, R. A. Voldseth, G.R. Guntenspergen, and D. E. Naugle. 2005. Vulnerability of northern prairie wetlands to climate change. BioScience 55:863–872.Linz, G. M., D. L. Vakoch, J. F. Cassel, and R. B. Carlson. 1984. Food of red-winged blackbirds, Agelaius phoeniceus, in sunflower fields and corn fields. Canadian Field Naturalist 98:38–44.Nelms, C. O., W. J. Bleier, D. L. Otis, and G. M. Linz. 1994. Population estimates of breeding blackbirds in North Dakota, 1967, 1981–1982, and 1990. American Midland Naturalist 132:256–263.Niemuth, N. D., and J. W. Solberg. 2003. Response of waterbirds to number of wetlands in the Prairie Pothole Region of North Dakota, U.S.A. International Journal of Waterbird Biology 26:233–238.Figure 4: Estimate of economic losses associated with blackbird damage to sunflower and corn crops, in the Prairie Pothole Region of North Dakota, for 2008 and 2009. Lines represent standard error for each crop per year123Proceedings of the 14th WDM Conference (2012)                                                                S. N. Frey, editorBirdsPeer, B. D., H. J. Homan, G. M. Linz, and W. J. Bleier. 2003. Impact of blackbird damage to sunflowers: bioenergetic and economic models. Ecological Applications 13:248–256.Ralston, S. T., G. M Linz, W. J. Bleier, and H.J. Homan. 2007. Cattail distribution and abundance in North Dakota. Journal of Aquatic Plant Management 45:21–24.Sedgewick, J. A., J. L. Oldemeyer, E. L. Swenson. 1986. Shrinkage and growth compensation in common sunflowers: refining estimates of damage. Journal of Wildlife Management 50:513–520.Stewart, R. E., and H. A. Kantrud. 1972. Population estimates of breeding birds in North Dakota. Auk 89:766–788.Stewart, R. E., and H. A. Kantrud. 1973. Ecological distribution of breeding waterfowl populations in North Dakota. Journal of Wildlife Management 37:39–50.Twedt, D. J., W. J. Bleier, and G. M. Linz. 1991. Geographic and temporal variation in the diet of yellow-headed blackbirds. Condor 93:975–986.United States Department of Agriculture: National Agricultural Statistics Service [NASS], 2011. Crop values 2010 summary. <http://usda01.library.cornell.edu/usda/nass/CropValuSu//2010s/2011/CropValuSu-02-16-2011.pdf>. Accessed 1 January 2012.

Assessment of Bird Damage to Sunflower and Corn in North Dakota

UNL | Libraries

University of Nebraska - Lincoln 
DigitalCommons@University of Nebraska - Lincoln 
USDA National Wildlife Research Center - Staff 
Publications 
U.S. Department of Agriculture: Animal and 
Plant Health Inspection Service 
2012 
Assessment of Bird Damage to Sunflower and Corn in North 
Dakota 
Megan E. Klosterman 
North Dakota State University, Megan.e.klosterman@ndsu.edu 
George M. Linz 
USDA/APHIS/WS National Wildlife Research Center, george.m.linz@aphis.usda.gov 
Anthony A. Slowik 
U.S. Department of Agriculture 
William J. Bleier 
North Dakota State University, William.Bleier@ndsu.nodak 
Follow this and additional works at: https://digitalcommons.unl.edu/icwdm_usdanwrc 
Klosterman, Megan E.; Linz, George M.; Slowik, Anthony A.; and Bleier, William J., "Assessment of Bird 
Damage to Sunflower and Corn in North Dakota" (2012). USDA National Wildlife Research Center - Staff 
Publications. 1155. 
https://digitalcommons.unl.edu/icwdm_usdanwrc/1155 
This Article is brought to you for free and open access by the U.S. Department of Agriculture: Animal and Plant Health 
Inspection Service at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in USDA 
National Wildlife Research Center - Staff Publications by an authorized administrator of DigitalCommons@University 
of Nebraska - Lincoln. 
119
Proceedings of the 14th WDM Conference (2012)                                                                S. N. Frey, editor
Birds
Assessment of Bird Damage to Sunflower and Corn in North Dakota
MEGAN E. KLOSTERMAN, Department of Biological Sciences, North Dakota State University, Fargo, ND, USA
GEORGE M. LINZ, U.S. Department of Agriculture, Wildlife Services, National Wildlife Research Center, Bismarck, 
ND, USA
ANTHONY A. SLOWIK, U.S. Department of Agriculture, PPQ, Bismarck, ND, USA
WILLIAM J. BLEIER, Department of Biological Sciences, North Dakota State University, Fargo, ND, USA
ABSTRACT North Dakota is the top sunflower-producing state in the United States, annually harvesting about 404,686 
ha (1 million acres). Since the early 2000s, corn also has become a major crop within the state due to increases in corn 
prices. Blackbirds (Icteridae) can cause significant damage to both ripening corn and sunflower. The National Sunflower 
Association considers blackbird depredation to be a key factor in the reduction in sunflower acreage in the Prairie Pothole 
Region (PPR). In order to better quantify the amount of damage caused by blackbirds, we assessed blackbird damage to 
ripening sunflower and corn in 120 randomly selected plots during 3 growing seasons, 2008–2010. On average, damage to 
sunflower was more intense than damage to corn, with sunflower in the southeastern region experiencing the greatest levels 
of damage. Further analysis will determine possible landscape characteristics associated with this damage.
KEY WORDS  blackbirds, common grackle, corn, crop damage, North Dakota, Prairie Pothole Region, red-winged 
blackbird, sunflower, wetlands, yellow-headed blackbird.
in the season, especially by grackles and male RWBL 
and YHBL, which have larger bodies and beaks than 
do females (Dolbeer 1980, Homan et al. 1994, Linz 
et al. 1984).
Red-winged blackbird population densities in the 
Dakotas and Minnesota are among the highest in the 
nation (Peer et al. 2003). Yellow-headed blackbirds 
breed in regions of the Dakotas and Minnesota where 
sunflower production is high (Twedt et al. 1991), 
and their numbers in North Dakota have increased 
over 300% from 1967–1981 (Besser 1985). Likewise, 
grackle numbers in North Dakota have also grown, 
increasing from 334,500 breeding pairs in 1967 to 
777,000 pairs in 1990 (Stewart and Kantrud 1972, 
Nelms et al. 1994). Blackbird populations in North 
Dakota reach their peak in August and September 
when sunflowers are reaching maturity (Peer et al. 
2003). These resident and migrating populations have 
led to extensive damage in agricultural fields such as 
sunflower and corn.
Complaints of blackbird damage to corn have in-
creased in recent years. Thus, corn may be providing an 
alternative food for foraging blackbirds. Quantitative 
surveys of blackbird damage to corn, however, have 
not been conducted in North Dakota. In 2008, 2009, 
and 2010, we assessed blackbird damage in ripening 
sunflower and cornfields. We will determine possible 
landscape characteristics correlated to this damage and 
report on these results at a later date. 
North Dakota is the top sunflower-producing state in 
the United States, annually harvesting about 404,686 
ha (Peer et al., 2003). Recently, corn has become a 
major crop within the state. Red-winged blackbirds 
(Agelaius phoeniceus), common grackles (Quiscalus 
quiscula) and yellow-headed blackbirds (Xanthoceph-
alus xanthocephalus) can cause significant damage 
to these crops. The National Sunflower Association 
considers blackbird depredation to be a key factor in 
the reduction of sunflower acreage in the Prairie Pot-
hole Region (PPR) (L. Kleingartner, NSA, Bismarck, 
ND, unpublished report).
In 1979 and 1980, a field survey of bird damage to 
sunflower in North Dakota estimated an economic 
loss between $ 4–11 million (Hothem et al. 1988). 
This was the last comprehensive field damage survey. 
Peer et al. (2003) used a bioenergetics model and es-
timated that blackbird damage was valued at $ 5–10 
million. Sunflower prices have increased since these 
monetary losses were calculated.
Red-winged blackbirds (RWBL), yellow-headed 
blackbirds (YHBL) and common grackles (hereaf-
ter, “grackles”) are three of the leading contributors 
to sunflower damage in North Dakota (Cummings 
et a1.1989, Dolbeer 1975, Sedgewick et al. 1986). 
Blackbirds tend to feed on corn during the milk and 
dough stage when the kernels are soft and in sunflower 
during early ripening. Some damage can occur later 
120
Proceedings of the 14th WDM Conference (2012)                                                                S. N. Frey, editor
Birds
STUDY AREA
Our study area is the 95,200 km2 Prairie Pothole 
Region (PPR) in North Dakota (Figure 1). Topo-
graphy of the PPR consists of undrained depressions, 
known as potholes, sloughs, or wetlands, which were 
formed during the Pleistocene Epoch (Johnson et 
al. 2005, Neimuth and Solberg 2003, Stewart and 
Kantrud 1973). These wetlands are scattered through-
out a matrix of grasslands, agricultural fields, and 
Conservation Reserve Program (CRP) land (Johnson 
at al. 2005, Stewart and Kantrud 1973). In 1967, 
total wetland acreage was estimated at 3.2 million 
acres (Stewart and Kantrud 1973). In a previous study 
(Ralston et al. 2007), the PPR was stratified into 
four strata: the Missouri Coteau, Northwestern Drift 
Plains, Northeastern Drift Plains and Southern Drift 
Plains (Stewart and Kantrud 1972, 1973). Ralston et 
al. (2007) proportionally allocated 120 3.2 x 3.2-km 
(1,036 ha) sample plots to the four strata.
METHODS
I assigned a 1.6-km2 (160 ha) area plot to the center 
of each of the 120 “Ralston Plots.” In late September 
2008, 2009, and 2010, we estimated bird damage in 
all corn and sunflower fields located within the 1.6-
km2 core area. In the event that no sunflower or corn-
fields were within the 1.6-km2 area section, then no 
field was surveyed for that site. In 2010 we sought to 
increase the sample size, in cases where no fields were 
located in the core area, we searched a 4.8-km (3 mi) 
radius around the center of the core area for the pres-
ence of a sunflower or corn field. The first sunflower 
or cornfield observed in this area was surveyed for 
damage.
We divided each sampled field down the middle 
into two strata, each containing an equal number of 
rows. One row was randomly selected from each stra-
tum. The location of the first field plot, consisting of 
five consecutive sunflower heads or corn ears, was a 
randomly selected distance in meters between 0 m 
(i.e., the edge of the field) and 135 m. After establish-
ing the first plot, we sampled plots of five consecu-
tive sunflower heads or corn ears every 135 m in the 
row. If an uncultivated area existed within the sampled 
row, this area was walked through as if it were a culti-
vated area. We estimated percentage damage for each 
sunflower head or corn ear. Sunflower damage was 
measured using the template method (Dolbeer 1975), 
and damage to corn was measured by comparing 
the area of damaged kernels to the possible area of 
undamaged kernels. For undamaged heads/ears, 0% 
Figure 1: The Prairie Pothole Region of North Dakota separated into four sample strata. Study sites were randomly selected and 
proportionately allocated among the strata.
121
Proceedings of the 14th WDM Conference (2012)                                                                S. N. Frey, editor
Birds
damage was recorded. The percent loss for each field was 
calculated by averaging the percent loss of all 
heads across both strata. The cost of the estimated 
damage for each crop was calculated by dividing the total 
average percent damage for each crop by the value of 
production using the USDA Crop Values Summary 
(2011).
PRELIMINARY RESULTS
In 2008, we  surveyed 38 cornfields and 14 sun-
flower fields for blackbird damage. Most of the corn 
was planted in the southeast (Southeastern Drift 
Plains) and sunflower was planted in the northern 
region (Northeastern and Northwestern Drift Plains), 
respectively. In 2009, we surveyed 30 cornfields and 
15 sunflower fields, with the distribution of corn and 
sunflower fields following the same regional trend as 
in 2008. In 2010, the number of fields surveyed was 
nearly doubled using the expanded sample scheme. 
We surveyed 65 cornfields and 23 sunflower fields, 
with field location following the same trend as the 
previous two years. We compared damage across years 
using only the fields within the 1.6-km2 sample plots 
(Figure 2). We also conducted a separate analysis for 
the entire data set for 2010.
In 2008, sunflower damage averaged 0.95% (range: 
0%-10.16%), and corn damage 0.69% (range: 0%-
5.27%). In 2009, sunflower damage averaged 2.17% 
Figure 3: Average percentage of sunflower and corn damage in 2008, 
2009, and 2010. Lines represent standard error for each crop per year.
Figure 2: Locations of study fields, within the 1.6 km2 core area, within 
the Prairie Pothole Region of North Dakota in 2010. Sample size was 
augmented to improve the variance associated with damage estimates.
(range: 0%-19.79%), and corn damage 0.18% (range: 
0%-1.52%). In 2010, sunflower damage averaged 
3.29% (range: 0%-13.57%), and damage to corn was 
calculated at 0.13% (range: 0%-1.28%). In 2010, 
using the expanded sample scheme, sunflower dam-
age averaged 2.32 % (range: 0%-13.57%) with corn 
damage averaging 0.21 % (range: 0%-2.85%) (Table 
1 and Figure 3).
Table 1: Average percent of sunflower and corn damage for each year 
within the study period.
Year ?????????
??????
n Corn 
??????
n
2008 0.95% 14 0.69% 38
2009 2.17% 15 0.18% 30
2010 3.29% 12 0.13% 38
2010 (extended 
sample)
2.32% 23 0.21% 65
Sunflower fields near the Southern Drift Plains tended 
to have higher damage estimates than those located 
in the Northern Drift Plains. The cost of damage in 
2008, based on overall production value in the state, 
was $ 7.3 million for corn and $ 3 million for sun-
flower (Figure 4). In 2009, the cost was $ 1.25 million 
and $ 4 million for corn and sunflower, respectively. 
In 2010, the cost was $ 1.7 million for corn and $ 8.9 
million for sunflower.
122
Proceedings of the 14th WDM Conference (2012)                                                                S. N. Frey, editor
Birds
DISCUSSION
Our data show an overall increase, from 2008 to 2010, 
in damage to sunflower and a decrease in damage to 
corn. Corn production has increased in the state, with 
many farmers in the Southern Drift Plains plant-
ing corn rather than other crops, such as sunflower. 
Sunflower production is primarily confined to the 
north central region of state (Northwestern Drift 
Plains and Northeastern Drift Plains), with sunflower 
crops planted in the southern areas receiving more 
damage than those further north. Our data show that 
blackbirds forage in both sunflower and corn fields. In 
locations where corn and sunflower are grown in close 
proximity, blackbirds might forage in both crops, thus 
reducing overall damage in each one.
ACKNOWLEDGMENTS
I thank D. Stonefish and J. Schanandore for com-
ments and contributions to this manuscript. M. Bion-
dini provided statistical advice and guidance.
LITERATURE CITED
Besser, J. F. 1985. Changes in breeding blackbird 
numbers in North Dakota from 1967 to 1981–
82. Prairie Naturalist 17:133–142.
Cummings, J. L., J. L. Guarino, and C. E. Knittle. 
1989. Chronology of blackbird damage to 
sunflowers. Wildlife Society Bulletin 17:50–52.
Dolbeer, R. A. 1975. A comparison of two methods 
for estimating bird damage to sunflowers. Journal 
of Wildlife Management 39:802–806.
Dolbeer, R. A. 1980. Blackbirds and corn in Ohio. 
United States Department of the Interior: Fish 
and Wildlife Service Resource Publication 13, 
Washington, D.C., USA.
Homan, H. J., G. M. Linz, and W. J. Bleier. 1994. 
Effect of crop phenology and habitat on the diet of 
common grackles (Quiscalus quiscula). American 
Midland Naturalist 131:381–385.
Homan, H. J., G. M. Linz, W.J. Bleier, and R. B. 
Carlson. 1996. Colony-site and nest-site use 
by common grackles in North Dakota. Wilson 
Bulletin 108:104–114.
Hothem, R. L., R. W. DeHaven, and S. D. Fairaizl. 
1988. Bird damage to sunflower in North Dakota, 
South Dakota, and Minnesota, 1979–1981. 
United States Department of the Interior: Fish 
and Wildlife Technical Report 15, Washington, 
D.C., USA.
Jenson, J. R. 2005. Introductory digital image 
processing: a remote sensing perspective. Third 
edition. Pearson Prentice Hall, Upper Saddle 
River, New Jersey, USA.
Johnson, W. C., B. V. Millett, T. Gilmanov, R. A. 
Voldseth, G.R. Guntenspergen, and D. E. Naugle. 
2005. Vulnerability of northern prairie wetlands 
to climate change. BioScience 55:863–872.
Linz, G. M., D. L. Vakoch, J. F. Cassel, and R. B. 
Carlson. 1984. Food of red-winged blackbirds, 
Agelaius phoeniceus, in sunflower fields and corn 
fields. Canadian Field Naturalist 98:38–44.
Nelms, C. O., W. J. Bleier, D. L. Otis, and G. M. Linz. 
1994. Population estimates of breeding blackbirds 
in North Dakota, 1967, 1981–1982, and 1990. 
American Midland Naturalist 132:256–263.
Niemuth, N. D., and J. W. Solberg. 2003. Response 
of waterbirds to number of wetlands in the 
Prairie Pothole Region of North Dakota, U.S.A. 
International Journal of Waterbird Biology 
26:233–238.
Figure 4: Estimate of economic losses associated with blackbird 
damage to sunflower and corn crops, in the Prairie Pothole Region of 
North Dakota, for 2008 and 2009. Lines represent standard error for 
each crop per year
123
Proceedings of the 14th WDM Conference (2012)                                                                S. N. Frey, editor
Birds
Peer, B. D., H. J. Homan, G. M. Linz, and W. J. Bleier. 
2003. Impact of blackbird damage to sunflowers: 
bioenergetic and economic models. Ecological 
Applications 13:248–256.
Ralston, S. T., G. M Linz, W. J. Bleier, and H.J. 
Homan. 2007. Cattail distribution and 
abundance in North Dakota. Journal of Aquatic 
Plant Management 45:21–24.
Sedgewick, J. A., J. L. Oldemeyer, E. L. Swenson. 1986. 
Shrinkage and growth compensation in common 
sunflowers: refining estimates of damage. Journal 
of Wildlife Management 50:513–520.
Stewart, R. E., and H. A. Kantrud. 1972. Population 
estimates of breeding birds in North Dakota. Auk 
89:766–788.
Stewart, R. E., and H. A. Kantrud. 1973. Ecological 
distribution of breeding waterfowl populations in 
North Dakota. Journal of Wildlife Management 
37:39–50.
Twedt, D. J., W. J. Bleier, and G. M. Linz. 1991. 
Geographic and temporal variation in the diet of 
yellow-headed blackbirds. Condor 93:975–986.
United States Department of Agriculture: National 
Agricultural Statistics Service [NASS], 2011. Crop 
values 2010 summary. <http://usda01.library.
cornell.edu/usda/nass/CropValuSu//2010s/2011/
CropValuSu-02-16-2011.pdf>. Accessed 1 
January 2012.


https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=2153&amp;context=icwdm_usdanwrc

Assessment of Bird Damage to Sunflower and Corn in North Dakota

Abstract

Similar works

Full text

Available Versions

DigitalCommons@University of Nebraska

UNL | Libraries