J. Field Ornithol., 67(2):222-235 EASTERN MEADOWLARKS NESTING IN RANGElANDS AND CONSERVATION RESERVE PROGRAM FIELDS IN KANSAS DIANE A. Gv•c•o• 1 Departmentof Range and Wildlife TexasTech University Lubbock, Texas 79409 USA KEVIN E. CHURCH Wildlife ResearchSection Nebraska Game and Parks Division Lincoln, Nebraska USA LOREN M. SMITH Departmentof Range and Wildlife TexasTech University Lubbock, Texas 79409 USA Abstract.---EasternMeadowlark (Sturndla magna)nesting habitat was studied to make man- agementrecommendations for fields enrolled in a federal land retirement program.We comparedavailable microhabitat, nest-site selection, and nest successon rangelandsand ConservationReserve Program (CRP) fields in easternKansas. Daily nest survivalrates and numbersfledged per femaledid not differ significantlybetween land-use types, but the power of thesetests was low. Predationwas the primary sourceof nest failure throughoutincuba- tion, hatching,and nestlingstages; abandonment, trampling, inviability, and unknowncauses alsowere importantduring incubation.Mowing CRP fieldswas a sourceof nest failure and alsoinduced adultsto abandonsome fields. CRP fieldshad a significantlyhigher percent, depth, and densityof litter cover;a taller herbaceouscanopy; less herbaceous cover; and more standingdead cover than rangelands.Differences in habitat structureindicate that CRP has increasedthe diversityof availablenesting habitats. Eastern Meadowlarks selected nestsites with significantlygreater litter cover,higher proportion of grass,more uncompacted litter, and more structuralhomogeneity than availableon randomplots. Delay of mowing and prescribedburning are recommendedto enhanceand maintainhabitat suitability for nestingEastern Meadowlarks in CRP fields. STURNELIA MAGNA ANIDANDO EN EXTENSIONES DE TIERRA Y TERRENOS DEL PROGRAMA DE RESERVAS DE CONSERVACI6N EN KANSAS Sinopsis.--Seestudi6 el habitatde anidamientode Sturneliamagna para producirrecomen- dacionesde manejo para terrenosenlistados en un programafederal de retraer fierras.Se compararonel 6xito de los nidos, el microhabitatdisponible ¾ la selecci6nde lugar para anidaren las extensionesde tierra ¾en terrenosdel Programade Reservasde Conservaci6n (PRC) en el estede Kansas.Ni las tasasdiarias de supervivenciade nido ni el ndmero de volantonespot hembravariaron significativamente entre terrenosde usodiferente, pero la potenciade la pruebaestadistica fu6 baja. La depredaci6nfu6 la causaprincipal de la mor- talidad en nidos durante las etapasde incubaci6n,eclosi6n ¾ de crecimientoen el nido, pero el abandono,el pisoteo,la infertilidad, ¾ otras causasdesconocidas tambi6n rueton importantesdurante la incubaci6n.Desyerbar los campos del PRC caus6mortandad de nidos • CurrentAddress: Department of Wildlifeand Fisheries, South Dakota State University, Brookings, South Dakota 57007 USA. 222 Vol.67, No. 2 EasternMeadowlark Nesting [223 y tambifin indujo al abandono de los predios. Los terrenos del PRC tuvieron mayorespor- centaje,profundidad y densidadde cubiertade materiales,un mayordosel herbficeo, menos cubiertaherbacea y m/rscubierta erecta muerta que las extensionesde tierra. Las diferencias en la estructurade hfibitat indican que el PRC ha aumentado la diversidadde habitatsde anidamiento. Los individuosde Sturnellamagma seleccionaron lugaree de anidaje con una cubierta de materialessignificativamente mayor, mayor proporci6n de hierbas, materiales poco compactosy mayor homogeneidadestructural que laos disponiblesen parcelasfortui- tas. Se recomiendaretrasar el corte de cespedy de quema prescritapara estimulary man- tener la adecuidadde habitat para el anidaje de Sturnellamagma en los prediosdel PRC. The ConservationReserve Program (CRP) of the 1985 Food Security Act converted >14.3 million ha of highly erodible cropland in the United Statesto a variety of permanent cover typesfor 10 yr. In Kansas,>1.1 million ha were enrolled in CRP with >90% planted in native grasses (U.S. Department of Agriculture 1993). The CRP wasintended to accom- modatewildlife and agriculturalconcerns and mayprovide quality habitat for grasslandbird populations. Quality of CRP habitat has been evaluatedby comparingpasserine den- sitiesin CRP versuscropland (Johnsonand Schwartz1993) and by apply- ing Habitat SuitabilityIndex (HSI) models (Hays et al. 1989). Although thesestudies use practicalmethodologies for regional scales,the assump- tion that densityor HSI alone reflect habitat quality may not be valid (Van Horne 1983, Vickery et al. 1992). Severalstudies have used produc- tivity as an indicator of CRP habitat quality for game species(e.g., Ber- thelsen et al. 1990, Kantrud 1993). Given high use of CRP by passerines (johnson and Schwartz1993), reproductive successof non-game species also needs to be investigated. We assessedthe quality of habitat in CRP fields by comparing the re- productive ecology of Eastern Meadowlarks (Sturnella maffna) in CRP fields and grazed, native grassrangelands. These habitats had similar plant speciescomposition, but hayingand grazingwere not permitted in CRP. Our objectiveswere to: (1) compare Eastern Meadowlark nest suc- cessin CRP and rangeland habitats,(2) identify causesof nest failure, (3) compare nest-sitemicrohabitat selection between CRP fields and range- lands, and (4) examine the importance of microhabitat to nest success. METHODS Our study was conducted 10 km north of Emporia in Lyon County, Kansas(38ø30'N, 96ø20'W). Topography was gently rolling with elevations ranging from 323-466 m. Winter wheat, row crops,rangeland, and hay- fields Were primary land uses.Climate was continental averaging0 C in winter and 25 C in summer,with a 6-mo growingseason. Annual precip- itation rangedfrom 63-114 cm with 73% fallingfrom April throughSep- tember (U.S. Departmentof Agriculture,Soil ConservationService 1981). To minimize variabilityassociated with different CRP practices,we ex- amined conversionto native grassbecause it promoted vegetationwith which Eastern Meadowlarks evolved and was the most common practice in Kansas(U.S. Department of Agriculture 1993). We used three CRP fields in 1990 and added one field in 1991. Field size ranged from 18-24 224] D. A. Granforset al. J.Field Ornithol. Spring 1996 ha. Mowing, without removal of cut material, was conductedin mid-June 1990 and in previousyears to control noxious weeds. One field was mowed only in selectedstrips, and mowingwas completed in late August. Only one of the four CRP fields was mowed in mid-June of 1991. We used five rangeland sitesin 1990. Stockingrates were -<1.63 animal unit months (AUM)/ha (cow/calf) and field size was 14-63 ha. Range siteshad a history of spring burning, but were not burned in 1990. We used four range sites in 1991, but only one 1990 site was reused. This field was not burned in 1991 and was stocked with cows and calves at 0.54 AUM/ha. Three replacementrange sites(178-259 ha) were burned in April 1991 and stockedwith steersat 1.85-3.09 AUM/ha. CRP fields were planted in 1988 or 1989 with a mix of big bluestem (Andropogongerardi•), little bluestem ( Schizachyriumscoparium), sideoats grama (Bouteloua curtipendula) , Indiangrass ( Sorghastrumnutans) , and switchgrass(Panicum virgatum). Cool-seasongrasses (Bromus spp.) also were common. The most common forbs were western ragweed (Ambrosia psilostachya)and mare'stail (Conyzacanadensis) in 1990 and lettuce (Lac- tucaspp.) and sweetclover(Melilotus spp.) in 1991. The abovenative grass species,tall dropseed(Sporobolus asper), and Kentuckybluegrass (Poa pra- tensis)were also characteristicof rangelands.Clumping of native grasses, which occurred in CRP fields, was prevented in rangelandsby grazing and burning. The most common forbs in rangeland were western rag- weed and Baldwin's ironweed (Vernonia baldwin•). Nest success.--Wecaptured female Eastern Meadowlarkswith mist nets and by night-lighting(Drewien et al. 1967) in April-June 1990 and 1991. We placed mist nets in areasof meadowlarkactivity and near nests.We moved nets within each field to avoid concentratingthe sample in one area. We night-lighted by walking through fields and dragging a rope to flush meadowlarks.We determined sex on the basisof plumage, bill color, and body size (Kemmerer 1981). We fitted femaleswith 2.5-g transmitters(-<3% body mass), each at- tached to the back with an elasticwing-loop harness.We obtained daily locationsby circling with a hand-held antenna systemto within 30-40 m of the radio-taggedbird. We found nestsby flushing femalesthat had the same location for >--2d. When we could not estimate incubation stage from the female's location record, we floated eggsto estimatehatch date (Westerskov1950). We also used any nests of unmarked birds that we found. When a radio-taggedfemale was off the nest, we checked the site to confirm nest status.We examined nests of unmarked birds about every third day.To prevent human-inducedpremature fledging, we did not visit nestsbetween the seventhand 12th day posthatch (Brown 1988). On the 13th day posthatch,we determinedif the attemptwas successful (>-1 nest- ling fledged; Nice 1957) by finding feather sheathsat the bottom of the nest (Roseberryand Klimstra1970). Successfulnests were alsocharacter- ized by an enlarged nest bowl and the presenceof fecal sacs.We consid- ered nests unsuccessful if feather sheaths were few or absent, or there Vol.67, No. 2 EasternMeadowlark Nesting [225 were signsof nest destruction.We placed nest lossesinto five categories: (1) depredated, (2) abandoned, (3) trampled, (4) inviable, and (5) un- known.Nests of radio-taggedbirds