Roostingofpasserin? over open water at mght Ronald E. Kirby

Duringnight-lighting operations for the captureof were observed over the water only on calm waterfowl on the Chippewa National forest in evenings,it is probablethat they were roostingon north-central Minnesota, I recorded data on the lakes after late evening feeding. Wind and speciesof found over openwater after dark. wave action could blow the away and Using an air-thrust boat equipped with high- render the reed grass and bulrush stands un- intensitylights, four largelakes that had emergent tenablefor roostingon windy nights. standsof wild rice (Zizania aquatica),hardstem Blackbirdflocks were found roostingonly in large bulrush (Scirpus acutus), and reed grass marsh areas that had been used previouslyby (Phragmitescommunis) were searched for ducks nestingbirds. Becausemost blackbirds in the area on 34occasions in late July,early August, and early moved to uplands after the breedingseason, the September1971 to 1974.The followingpasserines flocksseen were probablysmall groupsthat had were seen roostingin mixed flocks in the coarse been feeding near the lake margin earlier in the emergent vegetation (mostly reed grass and day and had moved to the emergentvegetation bulrush): Barn ( rustica), Cliff later in the evening, much as flocks of birds of Swallow ( pyrrhonota), Tree mixed age and sex did near breeding marshes Swallow (Iridoprocne bicolor), Bank Swallow earlier in the year. Roostingblackbird flocks are a ( riparia), Rough-winged Swallow well-known phenomenon in the eastern and (Stelgidopteryxruficollis), ( southernUnited Statesand present nuisanceand subis), Red-winged .Blackbird (Agelaius depredation problems in many areas (Meanley phoeniceus), and Yellow-headed Blackbird 1971).However, in Minnesota,upland flocks are {Xanthocephalusxanthocephalus). Tree , muchmore noticeablethan lowland congregations, Bank Swallows, and Barn Swallows were the most and even the largestflocks do not approachthe abundant roosting . Cliff Swallows and numbers found in the eastern and southern states Red-wingedBlackbirds were also abundant.Pur- during the winter. Blackbirdswere only rarely ple Martins (immatures only), Rough-winged mixed with swallows in the flocks observed. Swallows, and Yellow-headed Blackbirds were rarely observed. The use of night-lightingto capturewild animalsis Roberts (1932)referred to large flocks of mixed speciesof swallowsfound in the fall and their habit of roostingnear lakesand lowland areas.But consistentover-water roosting is not mentionedin the literature for Minnesota even though large flocks of swallows and.blackbirds are a common sightthroughout the statein the fall. Since 1970,late evening observationsof swallows on a number of lakes, ponds,and beaver (Castor canadensis)flowages showed that the birds were drinking from the surface and/or feeding on numerousinsects either emergingfrom the water or associated with the water surface and the emergentvegetation. On calm evenings,insects, mainly Trichopteraand Diptera, were abundant enoughto coverthe bow of our airboataround the lightsto a depthof 2 cm. Sinceroosting swallows

Page104 NorthAmerican Bander Vol.3, No. 3 not a new practice.Reeves (1966), Drewien, et al. Wildlife Service. L.M. Cowardin, J.H. Riechmann, (1967),and Labisky (1959)have summarizedthe and T.W. Schoenfelder assistedwith the night- history of the technique.Although most recent lighting operations.Constructive comments from effortshave been concernedwith gamebirds and S.H. Anderson,T.J. Dwyer, C.S. Robbins,and R.E. mammals (Lindmeier and Jessen1961, Labisky Stewart are acknowledged. 1968, Bishop and Barratt 1969, and others), Literature cited Cummingsand Hewitt (1964)captured 27 species of gameand non-gamemarsh birds withou( any Bishop,R.A., and R. Barratt,1969. Capturing water- concertedeffort to capturemiscellaneous species. fowl in Iowa by night-lighting. J. Wildl. Attempts to capture at night with Manage. 33(4):956-960. similar techniqueshave been generallylimited to Cummings,G.E., and O.H. Hewitt. 1964.Capturing work in blackbirdroosts (Neff and Meanley 1952, waterfowl and marsh birds at night with light Meanley 1956,Spencer and De Grazio 1962,West and sound.J. Wildl. Manage.28(1):120-126. and Besser1967, and others)and duringlate fall or Drewien, R.C., H.M. Reeves, P.F. Springer, and winter. T.L. Kuck. 1967.Back-packing unit for captur- ing waterfowl and upland game by night- Knowledge of the conditions pertaining to lighting.J. Wild. Manage.31(4):778-783. overwater night roosting of blackbirds and Huemphner, R.A., S.J. Maxon, G.J. Erickson,and swallowsin late summersuggests that observation R.J. Shuster. 1975. Recapturing radio-tagged and captureof largenumbers of localbirds would ruffed grouse by nightlighting and snow- be possiblein mid to late summer.The birds ! burrow netting.I. Wildl. Manage.39(4):821-823. observed fell into and on our airboat, struck and Labisky,R.F. 1959. Night-lighting:a techniquefor clungto the operators,and were easilycaptured by capturing birds and mammals. Illinois Nat. hand and with dip nets as we moved throughthe Hist. Surv.Biol. Notes 40. 11pp. roostingareas. Our speciallydesigned airboat was Labisky,R.F. 1968.Nightlighting: its use in captur- an excellentcraft for movingthrough thick vegeta- ing pheasants,prairie chickens,bobwhites and tion and shallow water areas. But much less ex- cottontails. Illinois Nat. Hist. Surv. Biol. Notes pensivenight-lighting 'outfits could be designed 62.11pp. from the plans of Bishopand Barratt (1969),the Lindmeier, J.P., and R.L. Jessen.1961. Resultsof back-packunit of Drewienet al. (1967),or theinex- capturingwaterfowl in Minnesotaby spotlight- pensiveportable unit used by Huempfner et al. ing. I. Wildl. Manage.25(4):430-431. (1975)to captureRuffed Grouse (Bonasa umbellus) Meanley,B. 1956.Banding blackbirds in a rice field in Minnesota. If capture efforts are confined to reservoir roost.Bird-Banding 27(4):170-171. warm, calm, overcastevenings and are utilized Meanley, B. 1971.Blackbirds and the southernrice only in areas where night roosting has been crop. USDI, Fish Wildl. Serv., Res. Publ. 100. observed,successful capture of many 64pp. speciesshould be possible. Neff, J.A., and B. Meanley. 1952. Experiencesin Whether or not capture for bandingor marking is bandingblackbirds in easternArkansas. Bird- attempted, late summer roosting and flock Banding23(4):154-157. behavior of these birds is worthy of detailed Reeves,H.M. 1966.Night-lighting and waterfowl behavioral and ecologicalresearch. These initial capture technique.Div. Manage. and Enforce- and casualobservations merely suggestthat feed- ment, Bur. Sport Fisheries and Wildl. ing factorsare involved in over-water night roost- Minneapolis,Minnesota. 12pp multilithed. ing. The effectsof predationhave not been even Roberts, T.S. 1932. Birds of Minnesota. Vol. II. preliminarilyassessed. Knowledge of the relative Univ. of Minn. Press.821pp. effectsof thesenot necessarilymutually exclusive Spencer,A.W., and J.W.De Grazio.1962. Capturing selection processesis sorely needed in avian blackbirdsand starlingsin marsh roostswith behavioral ecologyresearch. dip nets.Bird-Banding 33(1):42-43. West, R.R., and J.F. Besser, 1967. Dipnetting These data were collected incidental to a com- blackbirds in a marsh roost in Missouri. IBBA prehensivestudy of woodlandwaterfowl ecology News 39(4):91. • 1968-1974.Field researchwas a cooperativeeffort Departmentof Ecologyand BehavioralBiology, between the Department of Ecology and Universityof Minnesota,Minneapolis, MN 55455. BehavioralBiology of the Universityof Minnesota (NIH Training Grant 5 T01 GMO1779 and ERDA Presentaddress: U.S. Fish and Wildlife Service, Grant C00-1332-119),and the Northern Prairie Migratory Bird and Habitat ResearchLaboratory, Wildlife Research Center of the U.S. Fish and Laurel, MD 20811.

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