The Condor 86:383-389 0 The Cooper Omithologxal Society 1984 LEAD CONCENTRATIONS AND REPRODUCTION IN HIGHWAY-NESTING BARN SWALLOWS CHRISTIAN E. GRUE THOMAS J. O’SHEA AND DAVID J. HOFFMAN ABSTRACT. -Lead concentrationsin the carcassesand stomachcontents of adult and nestling Barn Swallows (Hirundo rustica) collected within the right-of-way of a major Maryland highway were greater than those found in Barn Swallowsnesting within a rural area. Lead concentrationsin the feathers of adults from the highway colony were also greater than those of rural adults, but concentrations in the feathers of nestlingsfrom the two locations were similar. Activity of &aminole- vulinic acid dehydratase in red blood cells was lower in highway-nesting adults and their young than in their rural counterparts, although hemoglobin concen- trations and hematocrits did not differ. The number of eggs,nestlings, and body weights of the latter at 16-l 8 days of age were similar in the two colonies, as were body weightsof adults from the two areas.These resultssuggest that contamination of roadside habitats bv lead from automotive emissionsdoes not pose a serious hazard to birds that are aerial feeders. Birds inhabiting highway rights-of-way (30.4 termine if reproduction in birds that are aerial million ha in the United States [Smith 19761) feeders is adversely affected by lead from mo- may be exposed to lead from automotive ex- tor vehicle emissions.We selectedBarn Swal- haust through inhalation or ingestion of con- lows for study because they frequently use taminated food or grit. Twenty-two to 58% of highway bridges and culverts as nest sites the lead emitted from motor vehicles (106- (Jacksonand Burchfield 1975, Barr 1979). The 1 18 thousand metric tons in the United States Parkway was selected as a study site because in 197 5 alone [Provenzano 19781) accumu- concentrationsof lead had been determined in lates in the soil or vegetation within highway soil and grass(Chow 1970), invertebrates(Gish rights-of-way (Ward et al. 1975, Little and Wif- and Christensen1973, Beyer and Moore 1980), fen 1978). Accumulation varies with traffic and small mammals (Clark 1979) collected density (Wheeler and Rolfe 1979) and distance there. Analysesof stomachcontents and guano from the road surface(Little and Wiffen 1978, samplesfrom bats collected closeto this Park- Ward et al. 1979). Lead concentrationsas high way suggestedthat some speciesof flying in- as 6,835, 1,180, and 682 ppm dry weight have sectsin the area contained high concentrations been reported in soils, vegetation, and inver- of lead (Clark 1979). tebrates, respectively (Williamson and Evans 1972, Little and Wiffen 1978). METHODS Lead concentrationshave been measured in The Parkway colony was located beneath a urban and rural pigeons (Columba livia; e.g., bridge above the Patuxent River (39”4’10”N, Hutton 1980, Hutton and Goodman 1980, Ohi 76”49’53”W). According to the Maryland De- et al. 1981), doves (Siegfried et al. 1972) and partment of Transportation, the average daily songbirds(Getz et al. 1977). However, the ef- traffic volume (ADT) on the bridge in 1979 fects of this metal on their survival and repro- was 37,925 vehicles per day. The right-of-way duction have not been assessed,although di- was bordered by eastern deciduous forest; the etary concentrations of lead as low as 1 ppm median at each end of the bridge was covered reduced eggproduction in JapaneseQuail (Co- by short grass. The reference colony was lo- turnix coturnix japonica, Edens et al. 1976). cated in two adjacent barns on a small farm The objective of our study was to compare rural Howard County, Maryland lead concentrations, hematological parame- ;t9°12r50”N, 76”58’18”W), about 0.4 km from ters, and reproductive successin two colonies a lightly traveled secondaryroad (ADT = 330 of Barn Swallows(Hirundo rustica),one within vehiclesper day in 1979; Howard County Pub- the right-of-way of a major highway (Balti- lic Works). The surroundingsof the reference more-Washington Parkway), the other within colony were typical of colonies on farms in a nearby rural area (reference colony), to de- eastern Maryland, consistingof pasture, crop- 13831 384 C. E. GRUE, T. J. OSHEA’ AND D. J. HOFFMAN land (corn fields), and a large water impound- The entire plumage, bill, feet, and gastroin- ment. This colony was selectedas the reference testinal tract were removed from each speci- colony because of its accessibility, distance men. Stomach contents of nestlings in each from a major road, and similarity to the Park- colony were pooled for lead analysis;those of way colony in the number of nests present. adults in each colony were pooled by sex. During May, June, and July 1979, we mon- Stomach contentsand carcasseswere then fro- itored reproductive activity in the two colo- zen (- 15’C) until analyzed for lead. Feathers nies. Forty nests in each colony, containing (entire plumage) were thoroughly washed in first clutches,were checked every two days un- 0.1 % EastmanRTriton X- 100 (Eastman Ko- til hatching to determine clutch size, and dak Co., Rochester, NY) to remove lead par- checked again 16-18 days after the eggs ticles adsorbed to the surface. Remiges and hatched. At this time, nestlingswere counted rectriceswere cut into piecesto facilitate wash- and collected. Two were randomly selected ing. Featherswere mechanically agitated in the from each of 14-2 1 nests in each colony in surfactantfor 30 min, drained, and then rinsed order to determine the d-aminolevulinic acid thoroughly in deionized water. This process dehydratase(ALAD, E.C. 4.2.1.24) activity (a was repeated five times for each sample. (Mi- sensitive indicator of lead exposure in birds croscopic examination of selected samples of [Hoffman et al. 198 1, Ohi et al. 198 11) and feathersbefore and after washingindicated that hemoglobin content of red blood cells (RBC), the majority of the dirt particles had been re- hematocrits, and lead concentrationsin stom- moved.) Afterwards, feathers were dried in an ach contents, carcasses,and feathers (a lead oven at 90°C for 48 h. Samples of feathers, as accumulator [Nezel and Vogt 19761).To make well as carcassesand stomach contents, were our selection random, we removed entire then transferred to separate chemically-clean broods from their nests,assigned a number to bottles, weighed, dried for at least 48 h at 90°C each nestling within a brood, and chose the and then reweighed. Twenty milliliters of con- nestlingsto be sacrificedusing a random num- centrated HN03 was then added to each sam- ber table. The remaining nestlingswere anes- ple and it was allowed to stand for at least one thetized by placing them in a plastic bag with week with mixing at least once a day. Samples cotton lightly moistened with MetafaneR (Pit- were then transferredto 1OO-ml Kjeldahl flasks, man-Moore, Inc., Washington Crossing, NJ. additional HNO, was added, and the contents [Use of trade names or names of suppliers is reduced to a volume of 3 ml by heating. Car- for identification purposesonly and does not cassand feather sampleswere then diluted to constitute endorsement by the federal govern- 50 g with deionized water, whereas stomach ment.]), and returned to their nests.We anes- contents were diluted to 10 g. thetized the nestlings so that they would not Lead concentrations in stomach contents, fledgeprematurely when replacedin their nests. carcasses,and feathers were determined (by We tried to collect nestlingsat each colony on the Environmental Trace SubstancesResearch the same dates. After most of the young from Center, University of Missouri, Columbia) with these first clutcheshad fledged,we mist-netted a furnace-atomic absorption spectrophotom- 10-l 3 adults of each sex at each location to eter (Perkin-Elmer Model 403 with a HGA- determine the ALAD activity and hemoglobin 2 100 graphite furnace) and an AS- 1 auto sam- content of RBCs, hematocrits, and lead con- pler. Background correction and the method centrations in the parts enumerated above. of standard additions were used. The lower We weighed all birds collected for blood and limit of reportable residuewas 0.0 1 ppm. High lead analyses and obtained a 4OOq.dblood values were checked by flame-atomic absorp- samplefrom each bird by decapitatingit. Blood tion spectrophotometry and agreement was sampleswere kept on ice prior to analyses.We satisfactory.Lead concentrations(ppm) are ex- determined ALAD activity in duplicate within pressedon a dry weight basisunless noted oth- 3 h of collection with methods described by erwise. Averages of lead concentrations are Burch and Siegel (1971), using 50 ~1 of blood presentedas geometric means becausethe data from nestlings because of their high ALAD were not normally distributed. levels, but 100 ~1 from adults. We defined a We netted an additional 23 adults from the unit of ALAD activity as the increase in ab- Parkway colony, individually color-marked sorbance (at 555 nm, 1.O-cm light path) per their feathers, and then releasedthem in order ml RBCs per h at 38°C. Hematocrits were de- to estimate the number of birds within the termined shortly after blood sampleswere col- colony that actually foraged within the right- lected using the microhematocrit method of-way. (Some swallowsfrom the Parkway col- (Davidsohn and Nelson 1974: 115). Additional ony had been seen foraging outside of the blood was used to determine hemoglobin con- right-of-way.) We observed swallowsfrom two centrations with the cyanomethemoglobin locations on each side of the Parkway, one on method (Hycel, Inc., Houston, TX). each side of the bridge, between 06:OO and 386 C. E. GRUE, T. J. OSHEA’ AND D. J. HOFFMAN TABLE 3. Comparisonof reproductivesuccess of Barn lessor soft-shelledeggs by interfering with cal- Swallowsnesting within the right-of-way of theBaltimore- cium metabolism (e.g., Edenset al.