Hill III JR. Nest-Depth Preference in Pipe-Nesting Northern Rough

Home , Purple martin, Riparia, Stelgidopteryx

j. Field Ornithol., 59(4):334-336

NEST-DEPTH PREFERENCE IN PIPE-NESTING NORTHERN ROUGH-WINGED SWALLOWS

JAMESR. HILL, III Purple Martin ConservationAssociation Institutefor Researchand CommunityServices EdinboroUniversity of Pennsylvania Edinboro,Pennsylvania 16ddd USA

Abstract.--The placementdepths of 44 Northern Rough-wingedSwallow (Stelgidopteryx serripennis)nests built insideidentical drainage pipes at a dam in northwesternPennsylvania were determinedusing a "ripariascope."The averageplacement depth was 82.4 cm (32.45•') with an observedrange of 53-117 cm (21"-46").

PROFUNDIDAD DE NIDO PREFERIDA POR STELGIDOPTERYX RUFICOLLIS Rcsumcn.--La profundidada la cual individuosdc Stelgidopteryxruficollis construycron 44 nidos dcntro dc tubcrias dc drcnajc cnun rcprcsa cn cl norocstcdc Pcnsilvania, fuc dctcr- minada utilizando un "raparioscopio"(rapariascopc). La profundidad promcdio dcl nido fuc dc 82.4 cm (32.45 pulgadas)con un alcanccdc 53-117 cm (21-46 pulgadas).

The Northern Rough-wingedSwallow (Stelgidopteryxserripennis) is a burrow-nesting,nest-site opportunist that rarely, if ever, excavatesits own nest burrow (Coues 1878, Gaunt 1963, Lunk 1962). Little detailed information has been publishedon the placementdepths of nestsin this species.The literature on the subjectis either of a very general nature, lists only burrow depthsand not actual nest depths,or representssingle observations.For instance, Macoun and Macoun (1909:584) said that nestsof the roughwing "have been found at all depths," Howe (1900) statedthat roughwingnests are "dug into the bank aboutan arm'slength," and Bailey (1913:262) statedthat the nest of the roughwingis in the "end of a burrow or hole in a bank, from two to five feet from the entrance." Referencesthat give only burrow depths and not the actual nest depthsinclude Headstrom(1970:60) who listed the length of the burrow "from 9 inchesto 6 feet," Blake (1953:107) who gavethe depths of two burrows used for nesting as "20 inches deep" and "28 inches deep," Eynon (1936:84) who said the tunnel "was aboutthree feet long," and Graber et al. (1972:15) who statedthat the burrows"varied in depth from 10 inchesto 3 feet, 18-20 inchesbeing most common." Burrow measurements,such as thosecited above,are relatively mean- inglessin relation to the actual depth of nestplacemement in the Northern Rough-wingedSwallow, sinceit doesnot typically build its nest at the innermostends of burrows(see Skutch 1960, this study)unless they are relativelyshallow. Some exact depths of nestplacement by the roughwing have been given in the literature, but theseare basedon singleobserva- tions.For example, Best (1977) reporteda nest "at the end of a burrow 68 cm deep," Blake (1907:104) describedfinding a nestat the end of a

334 Vo•.59, •o. ,• Rough-wingedSwallow Nest-depth Preference [3 3 5

tunnel "20 inchesin length," and Sargent(1893) discovereda nest "27 inchesdeep." Today, roughwingscommonly nest in man-madecavities such as those providedby drainage pipes (Harrison 1975). In order to quantify nest- depth preferencein this species,I measuredthe placementdepths of 44 nestsbuilt inside metal seeptilepipes at the Union City Dam in Erie County, Pennsylvania.The study was conductedduring the summer of 1981, but the nestswere the productof severalyears of activity at the siteby roughwings.The pipeswhere the nestswere built were embedded in a nearly-vertical,cement retaining wall 1.9 m, 4.9 m, and 7.9 m above the groundand functionedto facilitatewater seepagefrom the cut sand- stone/shalerock layersbehind the wall. They were flushwith the cement wall on their outer end and abuttedthe cut rock layersinternally. The amountof water observedseeping from thesepipes, even after prolonged, heavyrains, was insufficientto dislodgethe roughwings'nests; therefore, the observednest depths were assumedto accuratelyrepresent the species' preferencein nest-placementdepth. The pipeswere straight,122 cm long, had inner diameters of 102 mm, and were embedded in the wall at a four-degreegrade. Becauseall of the pipeswere identical,they provided a uniform burrow type, ideal for testingnest-depth preference in roughwings. By eliminating differencesin tunnel topography,any observed variation in depth of nest-placementcan be attributedto preference. To determinenest depth, a calibrated"ripariascope" was insertedinto eachof the pipes (Demong and Emlen 1975). Nest depthwas definedas the distancefrom a pipe's outer edgeto the center of the nest cup. The averageplacement depth of the 44 nestsmeasured was 82.4 cm (32.45") with a range of 53-117 cm (21"-46"); SD was 16.1 cm. Both the modal andmedian nest depth was 79 cm (3 !"). Only threeof the 44 nests(6.8%) were built againstthe rock walls at the extreme inner endsof the pipes. These findingsare in agreementwith Skutch (1960) who observedthat, when roughwingsused completed kingfisher burrows as nest sites,they did not build their nest in the expandeddistal nest chamber,but instead used the center of the tunnel. What evolutionaryforces might have shapednest-depth preference in the Northern Rough-wingedSwallow? Probablythe factor which acted to setthe minimum nest-placementdepth was the arm reachof its mam- malian predatorsplus the distancethese predators typically dig into mud or sandbanks while attemptingto raid suchnests. Alternatively, at least two factorsmight have actedto reducemaximum nest-placementdepths. One might be a need to keep tunnel distancesshort enough that the entrancehole remains visible to the nestlingsin the nest. This would allow the backgroundlight to be blockedwhen the parentsentered the burrow to feed the young,causing an abrupt changein light intensityas perceivedby the nestlings.Abrupt changesin light intensityhave been shownto be the stimulusfor elicitingthe food-gapingresponse in nestlings of otherbird speciesraised in dimly lit places,including the Bank Swallow Riparia riparia (Fulk 1967) and the Barn SwallowHirundo rustica (Jack- 336] J.R. Hill, III J.Field Ornithol. Autumn 1988 sonand Burchfield1975, pers.obs.). The samestimulus/response system probably operatesin the Northern Rough-wingedSwallow. The other factorprobably acting to reducemaximum nest-placementdepths, is the needto minimize tunnel exit/entry timeswhen feedingnestlings. If the parentswere feedingat the maximum possiblerate, then youngin deeply placed nestswould be fed less frequently than young in more shallow nestsdue to the time required to negotiatethe extra tunnel length between feedings. The findingsof this studyhave management implications for the North- ern Rough-wingedSwallow. When artificial nestingtubes (after Lunk 1962) are designedand placedfor useby roughwings,their lengthsshould fall within the preferrednest-depth range of the speciesin orderto increase their attractiveness.

ACKNOWLEDGMENTS

I thank the Army Corps of Engineersfor permissionto study thesebirds at the Union City Dam and alsoK. E. Waterstripefor his tirelessfield assistancethroughout this project. A. F. Skutch,W. A. Lunk, A. J. Erskine, R. A. Wolinski, and E. H. Burtt, Jr. were kind enoughto commenton earlier drafts of this manuscript.

LITERATURE CITED

BAILEY,H.H. 1913. The Birds of Virginia. J.P. Bell Co., Inc., Lynchburg,Virginia. BEST,L. B. 1977. Bull snakepreys on Rough-wingedSwallow nest. Condor 79:509. BLA•E, C. H. 1953. Notes on the Rough-wingedSwallow. Bird-Banding 24:107-108. BLA•E, F. G. 1907. The nestingof Stelgidopteryxserripennis in Norwich, Vt. Auk 24: 103-104. Coup.s, E. 1878. Birds of the ColoradoValley. U.S. Geol. Surv. Misc. Publ. No. 11. DEMONG,N.J., AND S. T. EMLEN. 1975. An optical scopefor examining nest contents of tunnel-nesting birds. Wilson Bull. 87:550-551. EYNON,A. E. 1936. Rough-winged Swallow breeding in Rhode Island. Auk 53:83-84. FULK, G. W. 1967. The gaping responseof nestlingBank Swallows. Wilson Bull. 79: 344-345. GAUNT,A.S. 1963. Fossorialadaptations in the Bank Swallow, Riparia riparia (Linnaeus). Univ. of Kansas, Ph.D. diss. GRABER,R. R., J. w. GRABER,AND E. L. KIRK. 1972. Illinois birds: Hirundinidae. Ill. Nat. Hist. Surv. Biol. Notes No. 80:1-36. HARRISON,H. H. 1975. A field guide to birds' nests in the United States east of the Mississippi River. Houghton Mifflin Co., Boston. HEADSTROM,R. 1970. A completefield guideto nestsin the United States.Ives Washburn, Inc., New York. HOWE,JR., R.H. 1900. The Rough-wingedSwallow breedingin Connecticut,and other notes. Auk 17:389. JACKSON,J. A., AND P. G. BURCHFIELD. 1975. Nest-site selectionof Barn Swallows in East-centralMississippi. Am. Midi. Nat. 94:503-509. LUN•, W.A. 1962. The Rough-wingedSwallow: a studybased on its breedingbiology in Michigan. Publ. Nuttall Ornithol. Club, No. 4. MACOUN,J., AND J. M. MACOUN. 1909. Catalogue of Canadian birds. Government Printing Bureau, Ottawa. SARGENT,H. B. 1893. Breedingof the Rough-wingedSwallow at Shelter Island, New York. Auk 10:369. S•UTCH, A. F. 1960. Life Histories of Central American birds. Part II. Pacific Coast Avif. No. 34. Received13 Feb. 1987; accepted4 Mar. 1988.