Birds and Mamals Damage to Crop

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The Ohio State University

1982-06

Bird and Mammal Damage to Field Corn in

Ohio, 1977-79

Kelly, Sean T.; Andrews, Douglas A.; Palmer, Donald T.

The Ohio Journal of Science. v82, n3 (June, 1982), 133-136

http://hdl.handle.net/1811/22854

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Ohio Journal of Science (Ohio Academy of Science) Ohio Journal of Science: Volume 82, Issue 3 (June, 1982)
http://hdl.handle.net/1811/22854http://kb.osu.edu/http://hdl.handle.net/1811/22854http://kb.osu.edu/


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Ohio J. Sci. BIRDS ON WILDLIFE VS. FARMLAND 13 3

Copyright 1982 Ohio Acad. Sci. OO3O-O95O/82/OOO3-O133 $2.00/0BIRD AND MAMMAL DAMAGE TO FIELD CORN IN OHIO, 1977-79'SEAN T. KELLY and DOU GLAS A. A ND REW S, U . S. Fish and W ildlife Service (WA ), Rm. 405 , FederalBldg., Columbus, OH 43215DONALD T. PALMER, U. S. Fish and Wildlife Service, 15 N. Laura St., Jacksonville, FL 32207ABSTRACT. Bla ckb ird and mam m al damage to corn is wide spread thr ou gh ou t Oh io .Surveys of dam ag e from 197 7-7 9 revealed, however, tha t black birds annually de stroyedless than 1% of the corn crops in Ohio, which amounts to a loss of 4-7 million dollarsper year statewide. Mammal damage averaged 0.13% over the 3-year period. Over 97%of the cornfields in Ohio receive less than 5% damage from blackbirds, and these lossescomprise more than 70% of the total dollar loss in the state.

OHIO J. SCI. 82(3): 133, 1982I N T R O D U C T I O N

Agriculturalis ts have long been con-cerned with crop losses due to blackbirds(Icteridae) in the United States. This con-cern has been particularly true for Ohio,which has the highest breeding season den-s i ty of red-winged blackbirds Agelaiuspboeniceus) of any state (Dolbeer and Stehn1979)- A ccurate estim ates ofloss s to birdsare fundam ental in evalu ating the necessityfor, and effectiveness of, damage control.In 1966 a survey was initiated in 8 Ohiocounties to obtain an estimate of blackbirddamage to ripening field corn. This surveywas expanded to 19 counties in 1969 andw a s c o n d u c t e d a n n u a l l y f ro m 1 9 6 6throu gh 1976, with the exception of 1973.These surveys employed a low samplingrate and were restricted primarily to high

'Manuscript received 7 August 1980 and in re-vised form 11 December 1980 ( 80 -4 3) .

damage counties. Thus, they could not beused to estimate statewide losses. In anattempt to secure an unbiased estimate ofblackbird damage to corn statewide, thesurvey was modified in 1977 to include allOhio counties. In addition, estimates ofmammal damage to r ipening corn were in-cluded in the 1977-79 surveys. Our papersummarizes the results of the statewide as-sessment of blackbird and mammal depre-dat ions on f ie ld corn in Ohio dur ing1977-79.M E T H O D S

The survey was conducted using a 3-step clustersampling technique described by Stickley et al.(1979a). The counties chosen for the survey wererandomly selected with replacement, and proba-bility of being chosen, proportional to the cornacreage in the county. Within each county, selectedsample plots equivalent to 2.6 km (one squaremile) sections were chosen at random, without re-placement. Further details and discussion of experi-mental design and data analysis are presented byStickley et al. (1979a).


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13 4 KELLYET AL. Vol. 82To quantify dam age to field corn, a visual esti-matewasmade of percentage surface area damagedonthecorn ear.A differentiation was made betweenprimaryand secondary damage,and both types wererecorded. Primary damage resulted directly fromananimal feedingon the corn kernel. Secondarydam-age resulted from the husk being openedby an ani-mal, thereby exposing the ripening ear of corn toatmospheric moisture. Under correct cl imatic condi-t ions, molding and/or sprouting sometimes devel-oped within the da ma ge d ear (Woronecki et al.1979) . Combining pr imary and secondary damagefigures produced an est imate of total damage. Werecorded the percent damage in increments of 1between 0 and 5 ,increments of 5 between5an d 30 , and increments of 10between 30 and100%. An ear of corn knocked to the groundwasconsidered as 100 mammal damage except tha tport ionof the eartha t wasobviously bird-dam agedprior to ma m ma l da m a ge .

RESULTSDuring the 3-year period from 1977 to1979, wesampled 1,027plots. Theaver-age timepersample p lot was1.4(1.11.8)man-hours, and the average annual costwas 3 ,837 ( 3 ,65 7-3 ,9 53 ) for salaries

and travel.IR DAMAGE.InOh io during the period1977-79, blackbird damage to ripeningfield corn ranged from 0.67 to 0.80sur face area damaged per ear, w h i c hamounted to a lossof 3-9 to 6.8 milliondollars (table 1). Stickley et al. (1979b)conducted similar surveys in 1977 andreported blackbird damage to field cornaveraged 0.48 and 0.39 surface areadamaged per ear in Ken tuck y and Tennessee,

respectively. These damage figures repre-sented losses of 1.22 million dollars inKentuckyand 0.39million dollarsinTen-nessee. In M ich igan , b l ackb i rd dep re -dations to field corn in 1979 averaged0 . 2 5 % surface area destroyed, representingan economic loss of 1.36 million dollars(Kelley 1979). Thus, Ohio appears to re-ceive a greater percent and dollar lossofcorn to blackbirds than do these nearbystates. Less intense surveys of blackbirddamage to corn on a nationwide basis in1970and 1971 byStoneet al. (1972)andStone and M ott (1973) support this find-ing. They found Ohiohad thethird high-est bushel lossin 1970and thehig hes t lossin 1971of themajor corn growin g states.MAMMAL DAMAGE. In pas t su rveys ,mammal damagehasbeen n eglectedin es-tim atin g corn lossesto theproducer.Mam-mal damage, principally raccoon Procyonlotor , was negligible on a statewide scale(table 1). High damage in a few sampleplots indicate, however, some individualgrowers incur red tangib le losses . Themammal damage est imate reported hereissimilar to estimates reported in Kentuckyand Tennessee (Stickley et al. 1979b) .

DISCUSSIONAlthough theoverall blackbird dam ageto ripening field corn in Ohio may reachseveral million dollars annually, the perhectare loss is qui te low in most fields.Assuming that thedistr ibution ofdamage

TABLE 1Primary, secondaryandtotalmeandamagetoripeningfieldcornattributabletoblackbirdsandmammalsin Ohio, 1977-79-

Total Blackbird Damage Total Mammal DamageYear

*Bushels**Millions

1 Blackbird 2 DamageDamage ( ) ( ) Bu.*(Mil.)**Dollars(Mil.) Bu.(Mil.)

Dollars(Mil.)

1977197819793 yr. Av.

0.590.600.670.62

0.080.200.040.11

0.670.800.710.73

2 .53 .02 .72 .7

3 .95.96 .85.50.160.100.130.13

0.600.380.490.49

0.930.751.240.97


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OhioJ. Sci. BIRD A N DMAMMAL DAMAGE T O CORN 135in sampled plots is representative of thedistribution of damage among fields, thenof the 1,027 fields sampled du rin g1977-79, 90% had less than 1% damageand 99% had less than 5% damage (table2). Jugenheimer (1976) reported thatlosses of corn caused by insects, weeds,disease and fungi total over 20% of poten-tial harvest and that harvesting techniquesoften lose 5% or more of the crop. Whencompared to losses from these othersources, corn losses due to blackbirds ap-pear insignificant for most farmers. Thefew farmers receiving high damage, how-ever, were hurt economically. Althoughonly about 1% of the fields received greaterthan 5% loss to birds, these fields incurredabout 25% of the total dollar loss (fig. 1).Dolbeer (1980) developed a cost-benefitgraph to compare the costs versus benefitsof bird-damage control in corn. His cost-benefit graphs revealed that, for most cornproducers, the damage is too insignificantin the context of a total farm program tojustify an economic investment in cur-rently available bird control techniques(e.g., Avitrol, propane exploders). Theemphasis in damage control should beplaced on tha t 1% group of fields that arereceiving 25% of the loss. Additional re-search effort should be directed toward thedevelopment of a safe, effective and eco-nomical avian repellent that can be used byall growers suffering losses to birds.ACKNOWLEDGMENTS. We are grateful to all thepeople w ho assisted in the collection of fielddata. W e also thank R. Dolbeer for his editorialcomments.

PERCENT D M GEFIGURE 1. Percent of total dollar loss caused byblackbirds in ripening field corn derived from fieldswith less than and greater than 5%damage.

LITERATURE CITEDDolbeer, R. A. 1980 Thechallengeof cost-benefitdeterminations inbird-damage control programs.Proc. 4 th Great Plains Wildlife Damage ControlWorkshop, Manhattan, KS. 267 p.and R. A. Stehn 1979 Population trendsof blackbirds and starlings in North America,1966-76. U.S . Dep . Inter., Fish and Wildl .Serv., Spec. Sci. Rep., Wildl. No. 214.Jugenheimer, R.W 1976 Corn:Improvem ent, seedproduction, and uses. Wiley-Interscience Publ.,John Wiley and Sons, NewYork, NY. 670 p.Kelly, S. T. 1979 Bird and mammal damage tomature corn in Michigan. Unpubl. Rep. ,Wildl.

Assistance Office, U . S . Fish and Wildl. Serv.,Columbus, OH . 3 p .Strickley, A. R., Jr. , D . L. Otis and D . T. Palmer1979a Evaluation an dresultsofasurveyofblack-TABLE2

Distribution of plots of field corn intovarious percent damagecategoriesfromsurvey of blackbirddamage to ripeningcorn in Ohio, 1977-79-

Year1977197819793yr. Av.

No. PlotsSampled

41227933 6342

No.CountiesSampled

30546048

0%20.411.4 '13.115.0

>o72.873.575.974.1

Percentage ofPlots inDamage Category1% > i - < 5 % > 5

6.313.39.29.6

10%0.20.40.90.5

PERCENTOFDOLRLOSSES


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13 6 KELLY ET AL. Vol. 82bird and mammal damage to mature field cornover a large three sta te) area, p. 169177.In Vertebrate pest control and managementmaterials, Amer. Soc. for Testing and MaterialsSpec. Tech. Publ. 680, Philadelphia, PA. 323 p.-, O. E. Bray, J. F. Heisterberg andT. D. Grandpre 1979b Bird and mam maldamage to mature corn in Kentucky and Tennes-see.Proc. Annu.Conf Southeast Assoc. Fish andWildl. Agencies 32: 228-233.Stone, C. P., D. F. Mott, J. F. Besser and J. W.

DeG razio 1972 Bird damage to corn in theUn ited States in1970.Wilson Bull. 84: 101-105.and 1973 Bird damage to ripeningfield corn in the United States, 1971. U.S.Dep. Inter., Fish and Wildl. Serv., Wildl.Leafl. 505. 8 p.Woronecki, P. P., R. A. Stehn and R. A. Dolbeer1979 Primary and secondary losses in cornfollowing simulated bird damage. In Proc. BirdControl Seminar, Bowling Green State Univ.,Bowling Green, OH. 8: 306-315.

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Birds and Mamals Damage to Crop