3 9999 06317 802 2 / ENVIRONMENTAL POLLUTANTS AND EGGSHELL THICKNESS: ANHINGAS AND WADING BIRDS IN THE EASTERN UNITED STATES c£/& UNITED STATES DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE SERVICE Special Scientific Report— Wildlife No. 216 Library of Congress Cataloging in Publication Data Ohlendorf, Harry M. Environmental pollutants and eggshell thickness. (Special scientific report— wildlife; no. 216) Bibliography: p. Includes index. Supt. of Docs, no.: I 49.15/3:216 1. Ciconiiformes— United States. 2. Anhinga anhinga. 3. Birds— Eggs and nests. 4. Pollution— Environmental aspects— United States. 5. Birds- United States. I. Klaas, Erwin E., joint author. II. Kaiser, T. Earl, joint author. III. Title. IV. Series: United States. Fish and Wildlife Service. Special scientific report— wildlife; no. 216. Sk361.A256no. 216 [QL696.C5] 639'.97 '90973s [598.3 '4 '0424] 79-1517 NOTE: Use of trade names does not imply U.S. Government endorsement of commercial products. ENVIRONMENTAL POLLUTANTS AND EGGSHELL THICKNESS: ANHINGAS AND WADING BIRDS IN THE EASTERN UNITED STATES By Harry M. Ohlendorf Erwin E. Klaas T. Earl Kaiser ^o wnxnjS* UNITED STATES DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE SERVICE Special Scientific Report— Wildlife No. 216 Washington, D.C. • 1979 Contents Page Abstract 1 Methods 2 Collection Sites 3 Organochlorine Residues 7 Geographic Differences 7 Frequency of Residue Occurrence 7 Residue Concentration 9 Species Differences 11 Frequency of Residue Occurrence 11 Residue Concentration 17 Eggshell Thickness 18 Discussion and Conclusions 19 Acknowledgments 21 References 21 Appendix I 23 Appendix II 24 Appendix III 39 Appendix IV 82 Appendix V 89 Environmental Pollutants and Eggshell Thickness: Anhingas and Wading Birds in the Eastern United States by Harry M. Ohlendorf, Erwin E. Klaas,1 and T. Earl Kaiser U.S. Fish and Wildlife Service Patuxent Wildlife Research Center Laurel, Maryland 20811 Abstract In 1972 and 1973 we collected 1,339 clutches of eggs of anhingas (Anhinga anhinga) and 17 species of waders (herons, egrets, bitterns, ibises, and storks). We analyzed the eggs for organochlorine residues and compared shell thickness of these eggs and others collected since 1946 (and now in museum collections) with shell thickness of eggs collected before the widespread use of organochlorine pesticides. The overall frequency of residue occurrence was higher in eggs from the Great Lakes region, then in those from the Northern Atlantic Coast, Southern Atlantic Coast, Inland, and Gulf Coast regions. Residue concentrations also were usually higher in eggs from the Northern Atlantic Coast and Great Lakes than in those from the other three regions, but there was no consistent pattern among those three regions. Among species, the highest residue frequencies and concen- trations were usually in eggs of great blue herons (Ardea herodias), wood storks (Mycteria americana), black-crowned night herons (Nycticorax nycticorax), and great egrets [Casmerodius albus). Lowest frequencies and concentrations were usually in eggs of white ibises (Eudocimus albus), glossy ibises {Plegadis falcinellus), least bitterns (Ixobrychus exilis), green herons {Butorides striatus), and yellow-crowned night herons (Nyctanassa violacea). Eggshells were significantly thinner in one or more regions for post- 1946 samples of anhinga, great blue heron, black-crowned night heron, and wood stork. We detected no significant change in the other species. Residues of organochlorine and heavy metal pollu- tants occur commonly in environmental samples, and these pollutants have been associated with adverse effects in numerous avian species (Cooke 1973; L. F. Stickel 1973; W. H. Stickel 1975; Ohlendorf et al. 1978a, 1978cf). The affected species are usually ter- minal consumers (i.e., at the top of the food chain), gen- erally those feeding on aquatic organisms (primarily fish) or birds. Certain herons have been included in general sur- veys of organochlorine residues in fish-eating birds in the United States and Canada (Keith 1966; Vermeer and Reynolds 1970; Anderson and Hickey 1972; Baetcke et al. 1972). Such residues and their possible effects in herons and related wading birds also have 'Present address: Iowa Cooperative Wildlife Research Unit, Iowa State University, Ames 50010. been studied at more restricted localities (Causey and Graves 1969; Greenberg and Heye 1971; Faber et al. 1972; Flickinger and Meeker 1972; Vermeer and Rise- brough 1972; Lincer and Salkind 1973). Brown pelicans (Pelecanus occidentalis) and double-crested cormorants (Phalacrocorax auritus) also have been studied (see Ohlendorf et al. 1978d for review), but we found no published information on occurrence or ef- fects of pollutant residues in anhingas (Anhinga anhinga) before beginning our study. Populations of black-crowned night herons (Nycti- corax nycticorax) (see Ohlendorf et al. 1978a for review), great blue herons (Ardea herodias), reddish egrets (Dichromanassa rufescens), American bitterns (Botaurus lentiginosus), wood storks (Mycteria amer- icana), white-faced ibises (Plegadis chihi), and white ibises (Eudocimus albus), have apparently declined, at least in some regions (Bull 1964; Peterson 1969; Wallace 1969, 1977; Bond 1971; Arbib 1971, 1972, 1973, 1974, 1975, 1976; Ogden 1975, 1978; McWhirter and Beaver 1977). In 1972, we began a study to determine: (1) geo- graphic differences in the occurrence of environmental pollutants in anhingas and waders in the eastern United States; (2) differences in environmental pollu- tant concentrations among those species nesting at the same localities; and (3) whether eggshell thickness had changed since the widespread use of organo- chlorine pesticides began in the mid-1940's. The wader species included in our study were: great blue heron, green heron (Butorides striatus), little blue heron (Florida caerulea), cattle egret (Bubulcus ibis), reddish egret, great egret (Casmerodius albus), snowy egret (Egretta thula), Louisiana heron (Hydranassa tricolor), black-crowned night heron, yellow-crowned night heron (Nyctanassa violacea), least bittern (Ixobrychus exilis), American bittern, wood stork, glossy ibis (Plegadis falcinellus), white-faced ibis, white ibis, and roseate spoonbill (Ajaia ajaja). Our success in collecting eggs of these species varied widely: we were not able to collect any eggs of the reddish egret in either year of our study, and we col- lected only one clutch of American bittern eggs, but eggs of some other species were collected easily. A summary of the results of our study has already been published (Ohlendorf et al. 1978c). A few minor errors in residue frequencies that appeared in that paper are corrected here in Table 2. Methods Eggs were collected at 50 localities in the eastern United States in 1972 and 1973. Seventeen species were represented by a total of 1,339 clutches of eggs. Entire clutches were collected; when the clutches consisted of two or more eggs, two eggs from each clutch were wrapped in aluminum foil and placed in plastic containers to retard moisture loss. These eggs were refrigerated until they could be processed. Contents were then removed, placed into chemically cleaned jars, and then frozen pending analysis. Only one egg per clutch was analyzed, except those collected at five localities (Rhode Island; Martha's Vineyard, Clark's Island, and House Island, Mass.; and Michigan), from which we analyzed each egg of the black-crowned night heron in all clutches and used arithmetical clutch means in the data tables and comparisons. Shells of all eggs were rinsed gently in tap water and saved for determination of eggshell thickness. Egg volumes were measured to the nearest 1.0 ml by water displacement before the contents were removed. Residues were adjusted to fresh wet weight, assuming specific gravity of 1.0 as suggested by Stickel et al. (1973). After egg contents were homogenized in a mixer, a 5- or 10-g subsample was blended with sodium sulfate and extracted 7 to 8 h with hexane in a Soxhlet appa- ratus. Cleanup of the extract, and separation and quantitation of pesticides and polychlorinated biphenyls (PCB's) were similar to the procedure used for the analysis of eagle carcasses (Cromartie et al. 1975). In summary, a portion of hexane extract equivalent to 5 g of subsample was passed through a Florisil column to remove lipids. An aliquot of this eluate was column chromatographed on silicic acid to separate the pesticides and PCB's. The organo- chlorines separated into three silicic-acid eluates were identified and quantitated by gas chromatography on a 1.83-m glass column packed with 4% SE-30/6% QF-1 on 100-120 mesh Supelcoport. PCB's were quantitated by comparing total peak area, measured by computing integrator, with that of either Aroclor 1254 or 1260, whichever most closely resembled the gas chromato- graphic profile of the sample. Residues in 10% of the samples were confirmed with a combined gas Samples were analyzed for DDE, DDD, DDT, dieldrin, heptachlor epoxide, mirex, oxychlordane, cis- chlordane (and/or £raras-nonachlor), ci's-nonachlor, HCB, toxaphene, endrin, and PCB's. Chemical names for these compounds are given in Appendix I. Recoveries of pesticides and PCB's from spiked egg tissue ranged from 83% to 104%. Residues given in this report were not adjusted on the basis of these recoveries. Gas chromatograph sensitivity of detec- tion was 0.1 ppm for pesticides and 0.5 ppm for PCB's. When PCB's were detected in trace amounts (less than 0.5 ppm), they were listed as 0.25 ppm. A "frequency index" was computed by dividing "total occurrences" by the number of "possible occur- rences" to reflect the frequency of organochlorine residue occurrences. Total occurrences are the number of times any of the 13 organochlorines were detected in eggs from that region (or locality); possible occur- rences are the number of clutches from that region (or locality) x 13 chemicals. Mean organochlorine concentrations in the samples were computed on individual sample values (the residue concentration + 1) transformed to common logarithms. The addition of 1 facilitated the trans- formation of zero values to logs. After computing these values, we took their antilogs and subtracted 1 from that value, which returned our measurements to the original units. The data were analyzed on a Control Data Corpora- tion 6400 computer, with packaged subroutines from Nie et al. (1975). In some instances the presence of many zero values prevented transformation to the normal distribution, but we also calculated means of these log-transformed data (see Ohlendorf et al. 1978a for further explanation). We performed a one-way analysis of variance (ANOVA) on the log-transformed data for DDE and PCB's to detect significant dif- ferences {P < 0.05) among the mean levels of these chemicals in eggs of the same species from the dif- ferent localities (or from different regions) and among different species from the same locality (or region). We used the Scheffe procedure (Scheffe 1959) of multiple comparison of means to group the localities by mean chemical concentration into homogeneous subsets. Eggshell thickness was measured to the nearest 0.01 mm with a modified Starrett micrometer after the shells had dried at room temperature for at least 1 month. Three measurements were taken at the "equator" of each egg and included the shell and shell membranes. Measurements were averaged to yield a single value for each egg in the clutch, and clutch means were obtained by averaging values for all eggs in the clutch. Statistical testing (two-way, nonrandom model, ANOVA) of eggshell thickness was based on clutch mean thickness. Collection Sites We collected many of the eggs from nesting colonies on or near National Wildlife Refuges (NWR) (Fig. 1 and Table 1) because of logistical considerations and because of the presence of favorable nesting habitat. Samples from refuges are considered to be repre- sentative of the general area because herons, ibises, and storks often travel at least several kilometers from the nesting area to feed (Dusi et al. 1971; Custer and Osborn 1978). These birds also disperse widely during the nonbreeding season, but it appears that organochlorine residue levels, at least in black- crowned night heron eggs, reflect contamination levels in the vicinity of the nesting areas (Ohlendorf et al. 1978a). For convenience in discussing geographic variation in occurrence and concentrations of residues, collec- tion sites have been grouped into five major classes or geographic regions: Great Lakes, Northern Atlantic Coast, Southern Atlantic Coast, Gulf Coast, and Inland. Collection sites included in the Great Lakes and Inland regions are freshwater, whereas those referred to as coastal are essentially estuarine. The latter, however, included several sites where herons were nesting at freshwater pools within a few kilo- meters of tidal waters. In our treatment of eggshell thickness data, collec- tion sites were grouped into smaller classes than those used in treating residues to avoid obscuring true dif- ferences in thickness and to enable more precise testing of geographic variation. The collection site of Fig. 1. Collection sites for eggs of anhingas and wading birds, 1972-73. Numbers inside circles indicate coastal and Great Lakes sites; those inside squares indicate Inland sites. Specific locations are identified in Table 1. each clutch of pre- 1947 eggs was plotted for each species on an outline map of the United States. This procedure generally resulted in discrete clusters of samples which probably reflected partly the distribu- tion of major heron breeding colonies but also partly the activities of early egg collectors. Eggshell thick- ness means were calculated from clutch means for each cluster with five or more complete clutches repre- sented. To increase sample sizes, adjoining clusters were pooled if means were obviously similar or if F-tests obtained in ANOVA procedures were nonsignifi- cant (P > 0.10). Pooling was not done when biological or ecological information suggested that pooling would be imprudent. 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CJ c CO en G -* O cj +f OS :3 X bC CD a> — - & _0j 4J 15 II CO < II CO 0) fc II i; IB 1-3 O pq Z CO S3 o B c &, -E a) a> _E _CJ 3 -*J 4J E eg 3 -E w w E E ii 1 . +3 m h -° CD jj| 0 0 a SE = a hero = yel CO cp *-< eg CU -t-T CD M CO CP hM CO o g&g II sKc K oo 2 m 11 H.3 13 P§S Cu co' cu E 5 j « i> «g § ° S Sb o . jo O II -^ S§ II ffi^"S OO II 0.250) at each site in the Northern Atlantic and Great Lakes regions; the notable excep- tion was Martha's Vineyard, Mass. (Fig. 2). Overall frequency in New Jersey samples (0.249) was higher than at any other Southern Atlantic site, and further reflects the increasing frequency of occurrence in northern coastal areas (Fig. 2). Frequency of occur- rence also was high ( > 0.250) at four sites where two or more species were sampled (Yazoo NWR, Miss.; Sarasota Bay, Fla.; Santee NWR, S.C.; and Pelican Lake-Lake Johanna, Minn.) and four where only great blue heron eggs were collected (Loxahatchee NWR, Fla.; Wyeville, Wis.; Rice Lake, Minn.; and Iowa). Frequency of residue occurrence was low ( < 0.125) at six sites where two or more species were sampled (Salvador, La.; Chassahowitzka NWR, Everglades NP, Lake Okeechobee, and Lake Istokpoga, Fla.; and Okefenokee NWR, Ga.) and at Blountstown, Fla., where only yellow-crowned night heron eggs were col- lected (Fig. 2). 8 Table 2. Frequencies of organochlorine residues in eggs of anhingas and wading birds (all species; by region), 1972-73. Compound Number (percent) with residues Great Lakes (AT=25) Northern Atlantic8 (JV=186) Southern Atlanticb Inland (JV=384) (JV=338) Gulf Coast Total (#=406) (N= 1,339) DDE DDD DDT Dieldrin Heptachlor epoxide Mirex Oxychlordane G's-chlordanec O's-nonachlor HCB Toxaphene Endrin PCB's Total occurrences Frequency indexd 25(100) 186(100) 21 (84.0) 101(54.3) 10 (40.0) 89(47.8) 23 (92.0) 124(66.7) 5 (20.0) 11 ( 5.9) 6 (24.0) 6( 3.2) 6(24.0) 72(38.7) 22 (88.0) 124(66.7) 3(12.0) 14 ( 7.5) 10(40.0) 5( 2.7) 4(16.0) 0 0 0 25 (100) 172(92.5) 160 904 0.492 0.374 379(98.7) 36 ( 9.4) 82(21.4) 105(27.3) 2( 0.5) 60(15.6) 20 ( 5.2) 39(10.2) 3( 0.8) 1( 0.3) 5( 1.3) 0 285(74.2) 1,017 0.204 316(93.5) 31 ( 9.2) 73(21.6) 94 (27.8) 14( 4.1) 36(10.7) 20 ( 5.9) 25 ( 7.4) 8( 2.4) 12 ( 3.6) 18 ( 5.3) 2( 0.6) 141(41.7) 790 0.180 386(95.1) 30 ( 7.4) 31 ( 7.6) 88(21.7) 8( 18( 22 ( 2.0) 4.4) 5.4) 33 ( 8.1) 5( 1.2) 0 0 0 195 (48.0) 816 0.155 1,292 219 285 434 40 126 140 243 33 28 27 2 818 3,687 0. (96.5) (16.4) (21.3) (32.4) ( 3.0) ( 9.4) (10.5) (18.1) ( 2.5) ( 2.1) ( 2.0) ( 0.1) (61.1) 212 "Coastal colonies from New York to Massachusetts. bCoastal colonies from Florida to New Jersey. cOr Jrarcs-nonachlor, or both. dComputed as: Total occurrences Possible occurrences. Total occurrences = number of times any of the 13 organochlorines were detected in eggs from that region. Possible occurrences = number of clutches from that region x 13 chemicals. Residues of DDE were detected in all eggs of all species from the Great Lakes, northern Inland, and Atlantic Coastal sites except Merritt Island NWR, Fla., where it occurred in 96% of the samples (see Appendix III for specific data on each species, locality, and chemical). DDE occurred in 90-100% of the samples at each Gulf Coast or southern Inland site except for six (Salvador, La.; Stapleton, Ala.; Chassa- howitzka NWR, Everglades NP, and Lake Istokpoga, Fla.; and Okefenokee NWR, Ga.), where it occurred in less than 90% of the eggs. Residues of DDD usually were found in more than half of the eggs of all species at each coastal locality from New Jersey northward (except Martha's Vine- yard, Mass., where it was only 15.8%) and at each Great Lakes locality. DDD was also detected in 55% of the samples from Yazoo NWR, Miss., but only nine eggs from there were analyzed. Frequency of DDD was less than 50% at other collection sites. Residues of DDT occurred in more than 25% of the eggs from Pea Island NWR, N.C., and coastal sites farther north, and in samples from four Inland sites (Atchafalaya Basin, La.; Yazoo NWR, Miss.; Santee NWR, S.C.; and Missouri). Dieldrin was detected in more than 35% of the total samples from Sabine NWR, Lacassine NWR, and Atchafalaya Basin, La.; Sarasota Bay, Fla.; Savannah NWR, Cape Romain NWR, and Santee NWR, S.C.; Potomac River, Md.; and all Northern Atlantic Coastal, Great Lakes, and northern Inland collection sites. Heptachlor epoxide usually was found in only one or two species per site without a clear geographic pat- tern, except for its generally more frequent occurrence in samples from the Great Lakes and less frequent occurrence in those from the Southern Atlantic Coastal localities. Mirex occurred more frequently in the samples (usually more than 30% of all samples) from Tampa Bay and Sarasota Bay, Fla., and from central Florida through South Carolina (including all of those collected at Savannah NWR, S.C.). It also was found in many of the eggs from the individual Great Lakes sites and in eggs of cattle egrets from three Inland sites (Salvador, La.; Yazoo NWR, Miss; and Stapleton, Ala.). Oxychlordane was detected in more than 15% of the total samples from six southern collection sites (Yazoo NWR, Miss.; Stapleton, Ala.; Tampa Bay, Sarasota Bay, and Payne's Prairie, Fla.; and Drum Island, S.C.), from each Northern Atlantic Coastal site, and from Ohio, Iowa, and Shiawassee NWR, Mich. Cis-chlordane occurred in more than 20% of the eggs from four southern sites (Sarasota Bay, Loxahatchee >- u z UJ 8 -3 if GULF COAST A INLAND O SOUTHERN ATLANTIC • NORTHERN ATLANTIC "fr GREAT LAKES iir * A *A *• A A A o 0o o 20 COLLECTION SITES Fig. 2. Frequency of organochlorine residue occurrence in eggs of anhingas and wading birds, 1972-73, by collection sites and region. Overall mean frequency index (0.212) is based on all eggs analyzed in the study (1.339 clutches). NWR, and Payne's Prairie, Fla.; and Drum Island, S.C.), and each Northern Atlantic Coastal and Great Lakes site, Iowa, and Pelican Lake-Lake Johanna, Minn. Its frequency approached 20% in samples from Darling NWR, Fla., and New Jersey. Cis-nonachlor was found in less than 10% of the eggs from each collection site except three in the South (Yazoo NWR, Miss.; Stapleton, Ala.; and Sarasota Bay, Fla.); Rhode Island; Middle Brewster Island, Mass.; Ohio; Shiawassee NWR, Mich.; and Iowa. Although cis-nonachlor did occur at 1 1 other sites, it was found in only one or two eggs at each. Residues of HCB occurred in the samples from Iowa, Merritt Island NWR, Fla., the three inland Louisiana sites, two inland Minnesota sites, and several North- ern Atlantic Coastal and Great Lakes sites. It usually occurred in less than 10% of the eggs. Toxaphene was widely distributed in the Inland and Great Lakes regions, occurring in a few samples at most of those collection sites. Except for Merritt Island NWR, Fla. (where it occurred in great blue heron and wood stork eggs), it was not detected in eggs from coastal sites. Endrin was found only in two eggs of great egrets from the Atchafalaya Basin, La. Residues of PCB's were found in more than 85% of all samples from Chincoteague Bay, Md.-Va., and each coastal site farther north. They occurred in all of the eggs from each site in Massachusetts, the Great Lakes region, and in two southern coastal sites (Cat Island, Ala., and Drum Island, S.C.) that are near large indus- trialized areas. In addition, PCB's occurred in all of the eggs collected at four other collection sites where only great blue herons were sampled (Loxahatchee NWR, Fla.; Wyeville, Wis.; Rice Lake, Minn.; and Iowa). Residue Concentration Within species, there were often significant dif- ferences (P < 0.05) among regional means for DDE and PCB's (Table 3); mean residue levels for other chemicals were not tested. Means were always higher in the samples from the Great Lakes or Northern Atlantic regions than in those from other regions. Dif- ferences among the other regions were not consistent, 10 Table 3. Mean DDE and PCB residue concentrations (ppm, wet weight) in eggs of anhingas and wading birds, 1972-73, ranked by region within species. Only species collected in more than one region are included. DDE PCB's Region Inland Gulf Coast Southern Atlantic Great Lakes Inland Southern Atlantic Gulf Coast Southern Atlantic Inland Gulf Coast Southern Atlantic Inland Gulf Coast Southern Atlantic Inland Gulf Coast Inland Southern Atlantic Gulf Coast Northern Atlantic Southern Atlantic Gulf Coast Inland Inland Southern Atlantic Gulf Coast Northern Atlantic Great Lakes Southern Atlantic Gulf Coast Inland Inland Gulf Coast Inland Gulf Coast Southern Atlantic Northern Atlantic Southern Atlantic Southern Atlantic Gulf Coast Inland Geometric3 mean Region Anhinga 1.61 A Southern Atlantic 0.50 B Inland 0.39 B Gulf Coast Great blue heron 6.76 A Great Lakes 3.90 AB Inland 2.13 AB Southern Atlantic 1.39 B Gulf Coast Green heron 0.79 A Southern Atlantic 0.70 A Inland 0.42 A Gulf Coast Little blue heron 0.92 A Southern Atlantic 0.82 A Inland 0.34 B Gulf Coast Cattle egret 1.04 A Southern Atlantic 0.88 A Inland 0.35 A Gulf Coast Great egret 2.06 A Inland 1.82 A Southern Atlantic 0.74 B Gulf Coast Snow y egret 2.66 A Northern Atlantic 1.12B Southern Atlantic 0.80 B Gulf Coast 0.80 B Inland Louisiana heron 0.73 A Inland 0.59 A Gulf Coast 0.56 A Southern Atlantic Black-crowned night heron 4.75 A Northern Atlantic 2.96 AB Great Lakes 1.86 BC Southern Atlantic 0.82 C Gulf Coast 0.71 C Inland Yellow-crowned night heron 0.59 A Gulf Coast 0.16 A Inland Least bittern 0.96 A Southern Atlantic 0.46 B Gulf Coast 0.29 B Inland Glossy ibis 1.64 A Northern Atlantic 1.46 A Southern Atlantic White ibis 0.27 A Southern Atlantic 0.19A Gulf Coast 0.14 A Inland Geometric8 mean 1.07 A 0.32 AB 0.15B 13.65 A 2.95 B 2.42 B 1.70B 0.27 A 0.15 A 0.07 A 1.37 A 0.28 B 0.14 B 0.37 A 0.14 AB 0.0 B 1.44 A 1.32 A 0.35 B 5.00 A 0.90 B 0.78 B 0.60 B 0.70 A 0.61 A 0.49 A 8.73 A 7.10A 1.77 B 0.39 C 0.31 C 0.0 0.0 0.17 A 0.07 A 0.0 A 0.50 A 0.14 A 0.21 A 0.08 AB 0.0 B "For each species, regional means that do not share the same letters are significantly different (P < 0.05) from each other (DDE and PCB's considered separately). Means of 0.0 ppm reflect that PCB's were not detected in certain regions for that species. 11 probably in part because all of the species usually were not collected at the same nesting colonies. Particularly among the Inland sites, residues in the eggs seemed to reflect local usage of organochlorines; residue concen- trations of pesticides and their metabolites in eggs from Inland colonies were often higher than in those from nearby coastal sites (Table 4 and Appendix III). In the Inland region, mean DDE concentrations for each species were higher than the mean PCB levels. However, among the other regions (particularly the Great Lakes and Northern Atlantic), PCB concen- trations were often greater than DDE. This difference probably reflects agricultural use of DDT in the Inland areas and the industrial sources of PCB's in the Great Lakes and Northern Atlantic regions. Mean residue concentrations of DDE (18.0 ppm) and PCB's (29.0 ppm) were higher in great blue heron eggs from Shiawassee NWR, Mich., than in any other samples we analyzed (Table 4 and Appendix III). Mean DDE residue levels for most species were lowest in the eggs from the various Gulf Coast sites; the exception was St. Marks NWR, Fla., where snowy egrets, Louisiana herons, and least bitterns had somewhat higher residue concentrations than at most other sites where their eggs were collected. Although there were exceptions, mean PCB concentrations for most species were lowest in the samples from Atlantic Coastal sites south of Virginia and from Inland and Gulf Coast sites. The most consistent exception was that PCB concentrations in eggs from Merritt Island NWR, Fla., tended to be relatively high. PCB levels in eggs of one or more of the species were relatively high at the Atchafalaya Basin, Salvador, and Barataria Bay, La.; Yazoo NWR, Miss.; Cat Island, Ala.; and St. Marks NWR, Fla. (when compared with means at other sites for these species). In comparing eggs of all species collected at both locations (great egret, snowy egret, black-crowned night heron, and glossy ibis), concentrations of PCB's were much higher (usually at least double) in eggs from Long Island, N.Y., than in those from New Jersey. Concentrations in the eggs from New Jersey also were higher than (sometimes twice that) in those from Chincoteague Bay, Md.-Va. In black-crowned night herons, DDE levels followed the same pattern (Ohlen- dorfetal. 1978a). Among the collection sites, PCB/DDE ratios tended to be higher than 1.0 in samples from New Jersey northward along the coast (except for Gardiner's Island, N.Y.) and from Great Lakes sites than in other samples (Appendix III). The ratio also exceeded 1.0 in one or two species at several sites in the other regions, particularly in eggs of the snowy egret (Appendix III-F) and Louisiana heron (Appendix III-G) from the Gulf Coast and Louisiana Inland sites. Among the South- ern Atlantic sites, the PCB/DDE ratio in samples from Merritt Island NWR, Fla., was greater than 1.0 in seven species; in the other species the ratio usually was higher in samples from Merritt Island than at other sites in the three southern regions, although the ratio did not exceed 1.0. Species Differences Eggs of the great blue heron (frequency index 0.359), wood stork (0.331), black-crowned night heron (0.309), and great egret (0.265) usually had the greatest fre- quency of residue occurrence and the highest mean concentrations (Table 5 and Appendix II; also Ohlen- dorf et al. 1978a, 19786). Eggs of green heron (0.118), white-faced ibis (0.115), white ibis (0.100), least bittern (0.100), and yellow-crowned night heron (0.095) usually had the lowest frequencies and mean concentrations. Although the overall frequency of residue occur- rence in glossy ibis eggs (0.224; Appendix II-L) was considerably higher than in eggs of other ibises, many of the glossy ibis eggs were collected at Northern Atlantic sites. Among the species from those sites, residues were less frequent and at lower concen- trations in the glossy ibis eggs than in other species. Endrin was detected in great egret eggs (from the Atchafalaya Basin, La.), but not in any other species. It was the only chemical not detected in great blue heron, little blue heron, and cattle egret eggs. Frequency of Residue Occurrence For each chemical except DDT, overall frequency of occurrence (i.e., when all collection sites were included) was higher in great blue herons than the average for all species combined (Table 2 and Appendix II-A). Within the Southern Atlantic, Inland, and Gulf Coast regions, the frequency was often at least twice the average. Except for DDE, mirex, and czs-nonachlor, fre- quency of all chemicals in green heron eggs was consid- erably lower than the average for all species combined (Table 2 and Appendix II-B). Mirex was unusually common in green heron samples from the Southern Atlantic region. However, all seven green heron eggs from that region that contained mirex were from Savannah NWR, S.C.; all eggs of other species collected there also contained mirex. However, mirex was not found in green heron eggs from the Inland region, where overall frequency in all species combined averaged 10.7%. Cis-nonachlor was found in only one green heron egg from the Atchafalaya Basin, La.; heptachlor epoxide, HCB, toxaphene, and endrin were not detected. Frequency of PCB's was usually less than half the average for all species combined. Frequencies of most chemicals in little blue heron eggs were below the averages for all species combined. 12 Table 4. Mean DDE and PCB residue concentrations (ppm, wet weight) in eggs of anhingas and wading birds, 1972-73, ranked by collection site within species. Only species collected at more than one site are included. DDE PCB's Site Geometric3 mean Site Geometric8 mean Yazoo NWR, Miss. 3.5 Atchafalaya Basin, La. 2.1 Lacassine NWR, La. 0.79 Payne's Prairie, Fla. 0.76 AB Okefenokee NWR, Ga. 0.42 J.N. "Ding" Darling NWR, Fla. 0.41 B Merritt Is. NWR, Fla. 0.39 B Shiawassee NWR, Mich. 18.0 Loxahatchee NWR, Fla. 12.0 Rice Lake, Minn. 7.0 Iowa 4.2 Ohio 4.2 A Sabine NWR, La. 3.8 Wyeville, Wis. 3.3 Pelican Lake, Minn. 2.2 A Payne's Prairie, Fla. 2.2 Merritt Is. NWR, Fla. 2.1 A J. N. "Ding" Darling NWR, Fla. 1.4 A Chassahowitzka NWR, Fla. 0.46 Savannah NWR, S.C. 1.4 A Atchafalaya Basin, La. 1.3 A Chincoteague Bay, Md.-Va. 1.1 A New Jersey 0.77 Blackbeard Is. NWR, Ga. 0.62 Lake Okeechobee, Fla. 0.56 Stapleton, Ala. 0.56 Potomac River, Md. 0.51 Okefenokee NWR, Ga. 0.50 A Lake Boeuf, La. 0.49 A Merritt Is. NWR, Fla. 0.49 A Mattamuskeet NWR, N.C. 0.47 Lacassine NWR, La. 0.47 A Sabine NWR, La. 0.41 A St. Marks NWR, Fla. 0.40 A J.N. "Ding" Darling NWR, Fla. 0.28 Chincoteague Bay, Md.-Va. 1.9A Santee NWR, S.C. 1.6 A Lake Istokpoga, Fla. 1.5 Missouri 1.4 A Gould Island, R.I. 1.3 New Jersey 1.2 A St. Marks NWR, Fla. 0.87 A Atchafalaya Basin, La. 0.82 A Pea Is. NWR, N.C. 0.81 A Lake Boeuf, La. 0.68 A Stapleton, Ala. 0.50 A Okefenokee NWR, Ga. 0.46 A Savannah NWR, S.C. 0.45 Merritt Is. NWR, Fla. 0.41 A Anhinga Merritt Is. NWR, Fla. 1 . 1 A Payne's Prairie, Fla. 0.58 A Okefenokee NWR, Ga. 0.25 Atchafalaya Basin, La. 0.23 A J.N. "Ding" Darling NWR, Fla. 0.21 A Yazoo NWR, Miss. 0.11 Lacassine NWR, La. 0.0 Great blue heron Shiawassee NWR, Mich. 29.0 Ohio 9.6 A Iowa 8.1 Payne's Prairie, Fla. 6.5 Rice Lake, Minn. 5.5 J.N. "Ding" Darling NWR, Fla. 2.6 AB Wyeville, Wis. 2.5 Merritt Is. NWR, Fla. 2.4 B Pelican Lake, Minn. 1.9 B Loxahatchee NWR, Fla. 1.5 Sabine NWR, La. 1.2 Chassahowitzka NWR, Fla. 0.43 Green heron PotomacRiver.Md. 1.6 Atchafalaya Basin, La. 0.6 A Merritt Is. NWR, Fla. 0.44 A New Jersey 0.25 Chincoteague Bay, Md.-Va. 0.23 A St. Marks NWR, Fla. 0.15 A Sabine NWR, La. 0.077 A Savannah NWR, S.C. 0.0 A Blackbeard Is. NWR, Ga. 0.0 Lake Okeechobee, Fla. 0.0 Stapleton, Ala. 0.0 Okefenokee NWR, Ga. 0.0 A Lake Boeuf, La. 0.0 A Mattamuskeet NWR, N.C. 0.0 Lacassine NWR, La. 0.0 A J.N. "Ding" Darling NWR, Fla. 0.0 Little blue heron Lake Istokpoga, Fla. 8.4 Tampa Bay, Fla. 3.2 New Jersey 3.1 A Gould Island, R.I. 2.8 Sabine NWR, La. 1.6 Savannah NWR, S.C. 1.4 Chincoteague Bay, Md.-Va. 0.83 AB Merritt Is. NWR, Fla. 0.54 B Lake Boeuf, La. 0.50 B Santee NWR, S.C. 0.47 B Stapleton, Ala. 0.42 B Pea Is. NWR, N.C. 0.35 B Okefenokee NWR, Ga. 0.04 B Atchafalaya Basin, La. 0.012 B 13 Table 4 (continued) DDE PCB's Geometric0 Geometric8 Site mean Site mean Little blue heron (continued) Sabine NWR, La. 0.32 Missouri 0.0B Salvador, La. 0.32 A St. Marks NWR, Fla. 0.0B Tampa Bay, Fla. 0.21 Salvador, La. 0.0B J.N. "Ding" Darling NWR, Fla. 0.14 A J.N. "Ding" Darling NWR, Fla. 0.0B Lacassine NWR, La. 0.11 A Lacassine NWR, La. Cattle egret 0.0B Savannah NWR, S.C. 7.0 Yazoo NWR, Miss. 0.88 A Yazoo NWR, Miss. 4.3 A Savannah NWR, S.C. 0.70 Santee NWR, S.C. 1.9 AB Merritt Is. NWR, Fla. 0.53 A Potomac River, Md. 1.2 AB Blackbeard Is. NWR, Ga. 0.25 Merritt Is. NWR, Fla. 0.93 AB Potomac River, Md. 0.24 A Orange Lake, Fla. 0.66 AB Santee NWR, S.C. 0.19 A Stapleton, Ala. 0.60 Okefenokee NWR, Ga. 0.14 A Lake Istokpoga, Fla. 0.58 AB Orange Lake, Fla. 0.12A Tampa Bay, Fla. 0.53 Sabine NWR, La. 0.0 Sarasota Bay, Fla. 0.38 Salvador, La. 0.0 Okefenokee NWR, Ga. 0.38 AB Stapleton, Ala. 0.0 Blackbeard Is. NWR, Ga. 0.38 St. Marks NWR, Fla. 0.0 Salvador, La. 0.27 B Tampa Bay, Fla. 0.0 St. Marks NWR, Fla. 0.24 Sarasota Bay, Fla. 0.0 A Sabine NWR, La. 0.10 Lake Istokpoga, Fla. Great egret 0.0 A New Jersey 4.2 A Long Island, N.Y. 8.6 Pea Is. NWR, N.C. 3.8 Detroit River, Mich. 6.4 Long Island, N.Y. 2.8 New Jersey 4.0 A Chincoteague Bay, Md.-Va. 2.4 AB Pelican Lake, Minn. 2.9 AB Okefenokee NWR, Ga. 2.3 Pea Is. NWR, N.C. 1.6 Cape Romain NWR, S.C. 2.2 AB Merritt Is. NWR, Fla. 1.5 ABC Atchafalaya Basin, La. 2.1 AB Chincoteague Bay, Md.-Va. 1.3 ABC Blackbeard Is. NWR, Ga. 2.1 Atchafalaya Basin, La. 0.97 ABC Pelican Lake, Minn. 2.0 AB Cape Romain NWR, S.C. 0.83 ABC Detroit River, Mich. 1.9 Drum Island, S.C. 0.77 Wassaw NWR, Ga. 1.4 J.N. "Ding" Darling NWR, Fla. 0.65 BC Cedar Keys NWR, Fla. 1.0 Sarasota Bay, Fla. 0.54 J.N. "Ding" Darling NWR, Fla. 0.98 B Barataria Bay, La. 0.43 Sabine NWR, La. 0.78 B Sabine NWR. La. 0.30 C Merritt Is. NWR, Fla. 0.66 B Wassaw NWR, Ga. 0.25 Barataria Bay, La. 0.49 Blackbeard Is. NWR, Ga. 0.16 Chassahowitzka NWR, Fla. 0.42 B Chassahowitzka NWR, Fla. 0.13C Drum Island, S.C. 0.38 Cedar Keys NWR, Fla. 0.0 Sarasota Bay, Fla. 0.28 Okefenokee NWR, Ga. Snowy egret 0.0 Gardiner's Island, N.Y. 11.0 Long Island, N.Y. 7.9 A House Island, Mass. 3.1 A House Island, Mass. 6.1 AB Gould Island, R.I. 2.8 A Gardiner's Island, N.Y. 4.2 Long Island, N.Y. 2.0 A Gould Island, R.I. 3.0 ABC Chincoteague Bay, Md.-Va. 2.0 A New Jersey 2.3 ABC St. Marks NWR, Fla. 1.9 A St. Marks NWR, Fla. 1.9 ABC Atchafalaya Basin, La. 1.9 Chincoteague Bay, Md.-Va. 1.7 ABC New Jersey 1.8 A Martha's Vineyard, Mass. 1.6 Cat Island, Ala. 1.2 A Cat Island, Ala. 1.5 ABC Pea Is. NWR, N.C. 1.0A Sarasota Bay, Fla. 1.5 14 Table 4 (continued) DDE PCB's Site Geometric3 mean Site Geometric" mean Snowy egret (continued) Lake Boeuf, La. Lake Istokpoga, Fla. Blackbeard Is. NWR, Ga. Cape Romain NWR, S.C. Okefenokee NWR, Ga. Sarasota Bay, Fla. J.N. "Ding" Darling NWR, Fla. Sabine NWR, La. Merritt Is. NWR, Fla. Martha's Vineyard, Mass. Cedar Keys NWR, Fla. Salvador, La. Barataria Bay, La. Wassaw NWR, Ga. Everglades NP, Fla. St. Marks NWR, Fla. Atchafalaya Basin, La. Sarasota Bay, Fla. New Jersey Cat Island, Ala. Chincoteague Bay, Md.-Va. Lake Boeuf, La. Blackbeard Is. NWR, Ga. Pea Is. NWR, N.C. Lacassine NWR, La. Sabine NWR, La. Savannah NWR, S.C. Salvador, La. Lake Istokpoga, Fla. Merritt Is. NWR, Fla. Barataria Bay, La. J.N. "Ding" Darling NWR, Fla. Tampa Bay, Fla. Cape Romain NWR, S.C. Wassaw NWR, Ga. Cedar Keys NWR, Fla. Everglades NP, Fla. Chassahowitzka NWR, Fla. Long Island, N.Y. Middle Brewster Island, Mass. Gardiner's Island, N.Y. House Island, Mass. Clark's Island, Mass. Gould Island, R.I. Detroit River, Mich. New Jersey Martha's Vineyard, Mass. Chincoteague Bay, Md.-Va. Ohio Drum Island, S.C. St. Marks NWR, Fla. 1.0 A Atchafalaya Basin, La. 0.96 A Okefenokee NWR, Ga. 0.80 A Lake Boeuf, La. 0.79 A Cape Romain NWR, S.C. 0.74 Merritt Is. NWR, Fla. 0.64 Sabine NWR, La. 0.59 A Barataria Bay, La. 0.57 A Lake Istokpoga, Fla. 0.54 A Salvador, La. 0.53 Pea Is. NWR, N.C. 0.37 A J.N. "Ding" Darling NWR, Fla 0.26 A Cedar Keys NWR, Fla. 0.25 Blackbeard Is. NWR, Ga. 0.25 Wassaw NWR, Ga. 0.19 Everglades NP, Fla. Louisiana heron 1.3 A Sarasota Bay, Fla. 1.2A St. Marks NWR, Fla. 1.1 Barataria Bay, La. 1.1 Cat Island, Ala. 0.98 A New Jersey 0.88 A Atchafalaya Basin, La. 0.68 A Salvador, La. 0.68 A Tampa Bay, Fla. 0.60 A Chincoteague Bay, Md.-Va. 0.60 Merritt Is. NWR, Fla. 0.55 A Wassaw NWR, Ga. 0.54 Savannah NWR, S.C. 0.50 A Sabine NWR, La. 0.50 A Lake Boeuf, La. 0.49 A Lacassine NWR, La. 0.42 A Blackbeard Is. NWR, Ga. 0.41 A Pea Is. NWR, N.C. 0.38 Chassahowitzka NWR, Fla. 0.36 A Lake Istokpoga, Fla. 0.33 Cape Romain NWR, S.C. 0.21 J.N. "Ding" Darling NWR, Fla. 0.16 A Cedar Keys NWR, Fla. 0.15 A Everglades NP, Fla. Black-crowned night heron 7.0 A Middle Brewster Island, Mass. 5.8 AB House Island, Mass. 5.3 ABC Gould Island, R.I. 4.5 ABCD Detroit River, Mich. 4.5 ABCD Long Island, N.Y. 4.5 ABCD Clark's Island, Mass. 3.8 ABCD Martha's Vineyard, Mass. 3.6 ABCD New Jersey 2.7 ABCD Gardiner's Island, N.Y. 2.4 ABCD Ohio 1.6 Chincoteague Bay, Md.-Va. 1.5 ABCD Merritt Is. NWR, Fla. 1.5 BCD Blackbeard Is. NWR, Ga. 1.2 0.81 0.67 BC 0.57 BC 0.53 BC 0.51 BC 0.46 0.46 BC 0.43 BC 0.29 BC 0.29 BC 0.24 C 0.21 C 0.0 0.0 2.0 1.4 A 1.4 A 1.3 A 1.3 1.2 A 1.1 A 1.0 0.97 A 0.81 A 0.51 0.50 0.49 A 0.32 A 0.31 A 0.28 A 0.21 A 0.20 A 0.19 A 0.17 A 0.13 A 0.12 0.0 A 22.0 A 12.0 AB 10.0 AB 9.9 ABC 8.4 ABC 7.3 ABCD 6.0 ABCD 4.3BCDE 3.4BCDE 3.1 1.8 CDE 1.8 CDE 1.1 CDE 15 Table 4 (continued) DDE PCB's Geometric" Geometric8 Site mean Site mean Black-crowned night heron (continued) Pea Is. NWR, N.C. 1.3 BCD Pea Is. NWR, N.C. 0.73 DE Merritt Is. NWR, Fla. 1.0 BCD Drum Island, S.C. 0.71 E Blackbeard Is. NWR, Ga. 0.95 BCD St. Marks NWR, Fla. 0.68 E Sabine NWR, La. 0.89 CD Sabine NWR, La. 0.46 E Lake Johanna & Pelican Lake, Minn. 0.85 CD Lake Johanna & Pelican Lake, Minn. 0.35 E Lacassine NWR, La. 0.69 D Lacassine NWR, La. 0.25 E Atchafalaya Basin, La. 0.35 Atchafalaya Basin, La. 0.20 J.N. "Ding" Darling NWR, Fla. 0.33 D J.N. "Ding" Darling NWR, Fla. 0.20 E Chassahowitzka NWR, Fla. 0.31 D Chassahowitzka NWR, Fla. 0.14E Yellow-crowned night heron Drum Island, S.C. 1.5 Drum Island, S.C. 0.0 Atchafalaya Basin, La. 0.88 A Atchafalaya Basin, La. 0.0 A Blountstown, Fla. 0.35 A Blountstown, Fla. 0.0 A Wassaw NWR, Ga. 0.31 Wassaw NWR, Ga. 0.0 Lacassine NWR, La. 0.18A Lacassine NWR, La. 0.0 A St. Marks NWR, Fla. 0.0 St. Marks NWR, Fla. Least bittern 0.0 St. Marks NWR, Fla. 1.1 St. Marks NWR, Fla. 0.48 Lake Okeechobee, Fla. 1.0 A Merritt Is. NWR, Fla. 0.17 A Payne's Prairie, Fla. 0.67 Sabine NWR, La. 0.0 A Sabine NWR, La. 0.35 B Lake Okeechobee, Fla. 0.0 A Merritt Is. NWR, Fla. 0.29 B Payne's Prairie, Fla. Glossy ibis 0.0 Chincoteague Bay, Md.-Va. 2.0 A Long Island, N.Y. 0.59 A Pea Is. NWR, N.C. 1.8 A New Jersey 0.29 A Long Island, N.Y. 1.8 A Chincoteague Bay, Md.-Va. 0.16 A Cape Romain NWR, S.C. 1.5 A Gardiner's Island, N.Y. 0.11 New Jersey 1.5 A Pea Is. NWR, N.C. 0.032 A Gardiner's Island, N.Y. 0.96 Cape Romain NWR, S.C. 0.0 A Merritt Is. NWR, Fla. 0.34 A Merritt Is. NWR, Fla. 0.0 A Barataria Bay, La. 0.23 Barataria Bay, La. White-faced ibis 0.0 Sabine NWR, La. 0.35 Sabine NWR, La. 0.0 Barataria Bay, La. 0.27 Barataria Bay, La. White ibis 0.0 Tampa Bay, Fla. 0.67 Tampa Bay, Fla. 0.25 Sarasota Bay, Fla. 0.29 Merritt Is. NWR, Fla. 0.21 A Barataria Bay, La. 0.28 A Barataria Bay, La. 0.12 A Merritt Is. NWR, Fla. 0.27 A Cedar Keys NWR, Fla. 0.12 A Lake Istokpoga, Fla. 0.14 A Sarasota Bay, Fla. 0.0 Cedar Keys NWR, Fla. 0.12A Lake Istokpoga, Fla. 0.0 A J.N. "Ding" Darling NWR, Fla. 0.11 J.N. "Ding" Darling NWR, Fla. 0.0 Everglades NP, Fla. 0.08 A Everglades NP, Fla. Roseate spoonbill 0.0 A Sabine NWR, La. 0.76 Sabine NWR, La. 0.19 Everglades NP, Fla. 0.42 Everglades NP, Fla. 0.12 "Although all site means are listed in this table for visual comparison (if eggs for that species were collected from more than one locality), statistical comparisons included only those sites with at least five samples for that species, and these means are fol- lowed by letters A-E in the table. For each species, site means that do not share the same letters are significantly different (P < 0.05) from each other (DDE and PCB's considered separately). Means of 0.0 ppm reflect that DDE or PCB's were not detected in certain collection sites for that species, or that the mean was less than 0.01 ppm. 16 Table 5. Mean DDE and PCB residue concentrations (ppm, wet weight) in eggs of anhingas and wading birds, 1972-73, ranked by species within regions. DDE PCB's Geometric3 Geometric3 Species mean Species mean Great Lakes Region Great blue heron 6.76 A Great blue heron 13.65 A Black-crowned night heron 2.96 A Black-crowned night heron Northern A tlan tic Region 7.10A Black-crowned night heron 4.75 A Black-crowned night heron 8.73 A Snowy egret 2.66 B Snowy egret 5.00 B Glossy ibis 1.64 B Glossy ibis Southern Atlantic Region 0.50 C Wood stork 4.00 A Great blue heron 2.42 A Great blue heron 2.13 AB Black-crowned night heron 1.77 A Black-crowned night heron 1.86 AB Little blue heron 1.37 A Great egret 1.82 AB Great egret 1.32 A Glossy ibis 1.46 AB Wood stork 1.19 AB Snowy egret 1.12AB Anhinga 1.07 AB Cattle egret 1.04 AB Snowy egret 0.90 AB Little blue heron 0.92 B Louisiana heron 0.49 AB Green heron 0.79 B Cattle egret 0.37 AB Louisiana heron 0.59 B Green heron 0.27 AB Anhinga 0.39 B White ibis 0.21 AB Least bittern 0.29 B Least bittern 0.17 AB White ibis 0.27 B Glossy ibis Inland Region 0.14B Great blue heron 3.90 A Great blue heron 2.95 A Great egret 2.06 AB Great egret 1.44 AB Anhinga 1.61 ABC Louisiana heron 0.70 BC Least bittern 0.96 ABC Snowy egret 0.60 BC Cattle egret 0.88 BC Anhinga 0.32 BC Little blue heron 0.82 BC Black-crowned night heron 0.31 BC Snowy egret 0.80 BC Little blue heron 0.28 C Louisiana heron 0.73 BC Green heron 0.15C Black-crowned night heron 0.71 BC Cattle egret 0.14C Green heron 0.70 BC White ibis 0.0 C Yellow-crowned night heron 0.59 BC Least bittern 0.0 C White ibis 0.14C Yellow-crowned night heron Gulf Coast Region 0.0 C Great blue heron 1.39 A Great blue heron 1.70 A Black-crowned night heron 0.82 AB Snowy egret 0.78 AB Snowy egret 0.80 AB Louisiana heron 0.61 AB Great egret 0.74 AB Black-crowned night heron 0.39 B Roseate spoonbill 0.69 AB Great egret 0.35 B Louisiana heron 0.56 AB Roseate spoonbill 0.18B Anhinga 0.50 AB Anhinga 0.15B Least bittern 0.46 AB Little blue heron 0.14B Green heron 0.42 AB White ibis 0.08 B Cattle egret 0.35 AB Least bittern 0.07 B Little blue heron 0.34 AB Green heron 0.07 B White-faced ibis 0.32 AB White-faced ibis 0.0B White ibis 0.19B Yellow-crowned night heron 0.OB Yellow-crowned night heron 0.16B Cattle egret 0.0B 3For each region, species means that do not share the same letters are significantly different (P < 0.05) from each other (DDE and PCB's considered separately). Means of 0.0 ppm reflect that PCB's were not detected in certain species from that region. 17 but in Southern Atlantic and Gulf Coast samples, DDT and cis-chlordane were considerably less frequent in this species than in others (Table 2 and Appendix II-C). DDD and PCB's were less frequently detected in little blue heron eggs from the Gulf Coast, and PCB's also in samples from Inland localities, than the average for all species combined. Residues of DDE, DDD, cis-chlordane, and PCB's occurred in cattle egret eggs less commonly than the average for all species combined, but mirex was con- sistently more frequent in cattle egret samples than in those of other species (Table 2 and Appendix II-D). In eggs from the Southern Atlantic, DDT and dieldrin also were more common in cattle egrets than the average for all species combined. Almost all chemicals were consistently more common in great egret eggs than the average for all species combined, and two eggs of this species from Atchafalaya Basin, La., were the only samples with detectable residues of endrin (Table 2 and Appendix II-E). Mirex was found in fewer snowy egret eggs than the average for all species combined (Table 2 and Ap- pendix II-F). However, DDT and dieldrin (Inland), heptachlor epoxide and oxychlordane (Northern Atlantic), and cis-chlordane (Northern Atlantic and Southern Atlantic, but not Gulf Coast) also were less frequent in snowy egret samples from some regions than in eggs of other species. HCB, toxaphene, and endrin were not detected. Residues of PCB's occurred at higher frequency in the snowy egret and Louisiana heron eggs from the Inland and Gulf Coast regions than the overall average for all samples from these two regions, but they were detected in none of the 32 yellow-crowned night heron eggs and in only 1 of 22 least bittern eggs from these regions (Table 2 and Appendices II-F, -G, -H, -J). Almost all other chemicals also were detected substantially less often in yellow-crowned night herons and least bitterns than the average for all species combined. Frequency of DDD was low, especially in Southern Atlantic samples, and HCB and endrin were not detected in Louisiana heron eggs. Heptachlor epoxide, cis-chlordane, cis-nonachlor, HCB, toxaphene, and endrin were not detected in yellow-crowned night herons. Heptachlor epoxide, mirex, oxychlordane, cis- nonachlor, HCB, toxaphene, and endrin were not found in least bittern eggs. By contrast, residues of most chemicals, but especially oxychlordane and cis-chlordane (in both Atlantic Coastal regions) and PCB's (in Inland and all coastal areas), occurred more frequently in black- crowned night heron eggs than the average for all species combined (Ohlendorf et al. 1978a). However, in the samples from the Inland region all chemicals except DDE, dieldrin, and PCB's occurred at below average frequency in the black-crowned night heron eggs, although samples for this species were few (12). Toxaphene and endrin were not detected in black- crowned night heron samples. The only chemical detected in the single American bittern egg that we analyzed was DDE (Appendix II-K). When glossy ibis eggs from the Southern Atlantic region were compared with eggs of other species, residues of DDD, DDT, and dieldrin occurred rela- tively often, but PCB's were less commonly found in the glossy ibis eggs from both Atlantic Coastal regions (Table 2 and Appendix II-L). Heptachlor epoxide, mirex, oxychlordane, cis-nonachlor, toxa- phene, and endrin were not detected in glossy ibis eggs from any region. The only chemicals detected in the 14 white-faced ibis eggs we analyzed were DDE and dieldrin (Appen- dix II-M). In white ibis eggs, the frequency of each chemical was lower than the average for all species combined (Table 2 and Appendix II-N). In particular, DDE, DDT, dieldrin, and PCB's were substantially less common in the white ibis eggs; DDD, cis-chlordane, cis-nonachlor, HCB, toxaphene, and endrin were not detected. In roseate spoonbill eggs DDT, DDD, and dieldrin were much more common than in most other eggs from the Gulf Coast region (Table 2 and Appendix II-O). Frequency of DDE and PCB's in spoonbill eggs was similar to that in other species. Heptachlor epoxide, mirex, oxychlordane, cis-nonachlor, HCB, toxaphene, and endrin were not detected. Residue Concentration The differences in residue concentration among species are not distinct, in part because of the dif- ferences in species composition of egg collections as well as in levels of exposure at the various localities. Mean DDE and PCB concentrations for each of the species at individual sites probably reflect reasonably well the differing levels of exposure among the species. These means for selected collection sites are compared in Appendix IV. Significant differences (P < 0.05) were noted among species-mean DDE concentrations at seven sites (Cedar Keys NWR, Darling NWR, Everglades NP, and Merritt Island NWR, Fla.; Cape Romain NWR, S.C.; New Jersey; and Long Island, N. Y.). At those sites and at others where the differences were not significant, DDE residue concentrations usually were higher in eggs of the great blue heron, great egret, black- crowned night heron, and roseate spoonbill than in those of other species. DDE concentrations usually 18 were lower in eggs of the green heron, little blue heron, yellow-crowned night heron, least bittern, and ibis (except glossy ibis from Pea Island NWR, N.C., and Chincoteague Bay, Md.-Va.) than in those of other species. Eggs of other species were not consistently in either the high or low group, but were sometimes in one or the other. Species-mean PCB concentrations were significantly different (P < 0.05) at 14 sites (Lacassine NWR, Atchafalaya Basin, Salvador, and Barataria Bay, La.; St. Marks NWR, Darling NWR, and Lake Istokpoga, Fla.; Blackbeard Island NWR, Ga.; Pea Island NWR, N.C.; Chincoteague Bay, Md.-Va.; New Jersey; Long Island, N.Y.; Rhode Island; and House Island, Mass.). PCB residue concentrations usually were higher in eggs of the great blue heron, great egret, snowy egret, Louisiana heron, and black-crowned night heron than in those of most other species, and lower in eggs of green heron, cattle egret, yellow-crowned night heron, least bittern, and ibis than in those of most other species. Wood stork eggs were collected only at Merritt Island NWR, Fla.; they contained relatively high mean concentrations of both DDE and PCB's. The PCB/DDE ratio was usually lower in eggs of the green heron, little blue heron, cattle egret, yellow- crowned night heron, least bittern, and ibises than in those of other species (Appendix III). The ratio was usually higher (often greater than 1.0) in eggs of the snowy egret and Louisiana heron from the Gulf Coast and Louisiana Inland sites than in those of other species from the same colonies. Eggshell Thickness Eggshell thinning was detected in four species: anhinga, great blue heron, black-crowned night heron, and wood stork (Appendix V). The data for black- crowned night heron have been subjected to extensive statistical analysis and discussion (Ohlendorf et al. 1978a). Highly significant decreases (P < 0.001) in mean shell thickness during recent times (compared with the pre-1947 period) were detected for black- crowned night herons in samples from New Jersey (-12.3%), Massachusetts (-9.3%), and New York, Rhode Island, and Connecticut (combined into one region, -7.1%). Significant decreases (P < 0.01) of 4.6% to 5.6% occurred also in recent eggs from Ohio, Michigan, Florida, Georgia, and South Carolina. Samples of eggs from North Carolina, Maryland, Virginia, and Minnesota were slightly thinner, but the differences were not statistically significant {P > 0.05). Changes in eggshell thickness could not be definitely related to specific organochlorine residues because of the intercorrelation of chemical concen- . trations, but concentrations of DDE residues were consistently correlated with eggshell thinning in various statistical tests (see Ohlendorf et al. 1978a for a discussion of the problems in correlating and regress- ing residues with shell thickness changes). The wood stork has been experiencing a severe decline in population numbers in Florida for several years (Ogden 1978). We were able to collect wood stork eggs only at Merritt Island NWR, Fla., where the species nested with anhingas and several species of herons. Recent eggs of this species averaged 8.9% thinner than pre-1947 samples {P < 0.001). A decrease in shell thickness (-7.5%; P < 0.05) was detected in anhinga eggs recently collected in Loui- siana and Mississippi, but there was no significant change in thickness among a pooled sample of eggs from three sites in Florida. DDE has been implicated as the cause of shell thinning in correlation analyses between concentrations of residues and changes in shell thickness in both anhinga and wood stork (see Ohlendorf et al. 19786 for a more complete discussion of anhinga and wood stork). Thickness measurements from recent collections of eggs of great blue herons from five localities in Florida were pooled and compared with a large sample of eggs collected in Florida and Tennessee before 1947. The difference in means (-5.2%) was significant (P < 0.001). Similar comparisons were made for eggs collected in midwestern States of Minnesota, Michigan, and Ohio; a significant decrease (-7.9%; P < 0.001) in shell thickness was also found in these samples. Although we measured thickness in a large sample of previously collected great blue heron eggs from other areas of the eastern United States, we were unable to collect comparable recent eggs. Mean thick- nesses for these pre-1947 eggs from a large number of sites are given for reference (Appendix V). Shell thickness changes were not detected in eggs of 11 other species studied, even though substantial numbers of clutches were available from many sites for both periods. We tested eggshell thickness means for sites as grouped in Appendix V within each period, using 2- way ANOVA procedures. Significant site differences (P < 0.05) in both periods were detected for anhinga, great blue heron, great egret, snowy egret, Louisiana heron, black-crowned night heron, least bittern, and glossy ibis. However, interactions were significant only for the anhinga, great blue heron, and black- crowned night heron, species in which differences were detected over time. Site differences were not detected in the green heron, little blue heron, white ibis, or roseate spoonbill. Thus, the "site effect" is consistent over time for all species except the three in which a "time effect" occurred. Presumably, this time effect on eggshell thickness is related to the introduction of 19 DDT to the environment and its occurrence at ele- vated levels in eggs of these species at certain sites. For a few species in which sample sizes were suffi- cient, we also tested for differences in shell thickness relative to other factors. Significant differences (P < 0.05) were found between complete and incom- plete clutches in recent eggs of the black-crowned night heron, but incomplete clutches were thinner than complete clutches at some sites and thicker at others (Ohlendorf et al. 1978a). Thicknesses of complete clutches were not significantly different (P > 0.05) from incomplete clutches in the anhinga, great blue heron, or great egret in either period. No significant differences were detected between clutch means grouped according to stages of incubation (fresh, slight, moderate, or advanced) in the Louisiana heron or black-crowned night heron in either period. Conspicuous gaps occur in the data in Appendix V for certain species and collection sites in one or the other of the two periods. For instance, we were unable to find pre- 1947 eggs of the cattle egret in museums because the species did not breed in the United States before the 1950's (Peterson 1954). The snowy egret, little blue heron, Louisiana heron, and glossy ibis have expanded their breeding ranges northward within the last 30-40 years (Palmer 1962). Thus, we were able to collect samples of recent eggs for these species from localities where they did not formerly breed. Wherever gaps occur in the data for recent eggs, it is usually because of our inability to be in an area when the species was breeding (e.g., great blue heron) or because of the relative difficulty in locating nests of species that tend to nest solitarily rather than in colonies (e.g., green heron, least bittern). Additional information on residues and shell thick- ness in recent eggs is needed for the great blue heron in all eastern coastal States from Georgia to Maine, for the green heron in the North Atlantic region and all midwestern States, for the least bittern in all States except Florida, and for the great white heron in the Florida Keys. Discussion and Conclusions Interpretation of differences in the geographic distribution of persistent pollutants in the environ- ment is difficult. We do not know usage patterns of the various chemicals, but they probably vary widely among geographic areas and with time. Species and individual differences in feeding habitats, biologic magnification in higher trophic levels, and migration of individual birds to different localities may further complicate interpretation. In spite of the variation in residue concentrations among eggs of the same species from the same collec- tion site, we were able to detect statistically signifi- cant regional and local differences in the occurrence of organochlorine residues in certain species. Likewise, we found differences in organochlorine residue concentra- tions among different species nesting at the same site. Significant geographic and species differences were more easily detected when we deleted from the com- parisons those species or sites from which we had fewer than five samples. We found that 10 eggs (one from each of 10 clutches) per species at each site were generally adequate and that 5 eggs per species still could be used in comparing sites and species, but when we had fewer than 5 eggs, the amount of variation in residue concentrations was usually too great for us to detect statistically significant differences. However, some samples (great blue heron from Shiawassee NWR, Mich., for example) that were excluded from the statistical comparisons contained high concentrations of organochlorine residues that probably were af- fecting the birds. Consequently, we included all samples in the tables to enable visual comparisons of the data. We were especially concerned about the impact of environmental pollutants on black-crowned night herons, because drastic population declines of this species had been reported in southern New England and in Michigan (see Ohlendorf 1978a for review). By analyzing band recovery (encounter) data for this species and other data, we concluded that most of the differences in residues found in the night heron eggs resulted from differences in exposure while in the breeding areas. The same principle seems to apply to other species, but there is no doubt that birds also acquire organochlorine residues in migration and at winter feeding grounds. For example, herons that nested in Minnesota and Wisconsin may have been exposed to mirex and heptachlor epoxide in areas farther south, where mirex and heptachlor were used for attempted control of the imported fire ant (Solen- opsis invicta). Field and experimental evidence indicates that declines in eggshell thickness observed in certain species in North America and Great Britain since the mid- 1 940 's have been largely caused by residues of DDE or other compounds or metabolites of the DDT group (Cooke 1973; L. F. Stickel 1973; W. H. Stickel 1975; Ohlendorf et al. 1978a, 1978d). At moderate or high levels of DDE, shell thinning is severe and eggs may break during incubation. High DDE levels have been recorded in California; species affected there have included brown pelicans (Risebrough et al. 1971), double-crested cormorants (Gress et al. 1973), great egrets, and great blue herons (Faber et al. 1972). Much of the DDE probably originated from an insecticide manufacturing plant in southern California. Eggshell thinning has occurred in several other 20 species that occupy freshwater or estuarine habitats or that nest on coastal islands. In 1967, shell thickness in eggs of herring gull (Larus argentatus) from five States decreased with increases in chlorinated hydro- carbon residues (Hickey and Anderson 1968). Compari- son of eggshells taken before 1946 with those taken since then reveals that several species, including the peregrine falcon (Falco peregrinus), brown pelican, double-crested cormorant, black-crowned night heron, bald eagle (Haliaeetus leucocephalus), and osprey (Pandion haliaetus), have sustained shell-thickness and shell-weight decreases of 20% or more, at least for brief periods (Anderson and Hickey 1972). In some of these, regional population declines are known. Shell thickness was significantly and inversely cor- related with the concentration of DDE in 40 great blue heron eggs from Alberta (Vermeer and Reynolds 1970; Vermeer and Risebrough 1972). In the upper Great Lakes States, 9 of 13 species of fish-eating birds were found in 1969-70 to have sus- tained statistically significant decreases in eggshell thickness since 1946 (Faber and Hickey 1973). Maxi- mum changes in a thickness index occurred in great blue herons (-25%), red-breasted mergansers {Mergus serrator; -15%), and double-crested cormorants (-15%). Heron eggs taken in Louisiana generally dis- played a smaller post-1946 change than herons in the Middle West. Although DDE was a prominent factor for most groups, especially herons, in relation to the eggshell thinning observed, dieldrin and PCB's also were associated with thinning in some species. This relationship, however, may have been due to correla- tion in concentrations of these chemicals and concen- trations of DDE. The thinning of eggshells of the brown pelican has proven to be related to the concentrations of DDE in the eggs (Blus et al. 1971; Blus et al. 1972a, 19726). Nearly all brown pelican eggs collected from 13 colonies in South Carolina, Florida, and California in 1969 and from 17 colonies in South Carolina and Florida in 1970 exhibited eggshell thinning (Blus 1970; Blus et al. 1974a). Of the 100 eggs analyzed for residues of pollutants, all contained measurable quan- tities of DDE; most eggs contained measurable quan- tities of DDD, DDT, dieldrin, or PCB's. DDE appears to have been responsible for virtually all the eggshell thinning. Nest success of brown pelicans in South Carolina was related to residues of DDE and dieldrin in sample eggs (Blus et al. 19746). Residues of DDE seemed pri- marily responsible for nest failure; however, dele- terious effects of this pollutant on nest success were not satisfactorily separated from those induced by dieldrin. Significant intercorrelation of all five organo- chlorine residues identified in the eggs complicated evaluation of the relationship of residues to nest success. Maximum DDE residues in an egg from a successful nest were 2.4 ppm and in an egg from an unsuccessful nest, 8.5 ppm. Comparable maximum residues for dieldrin in sample eggs were 0.54 ppm (successful) and 0.99 ppm (unsuccessful). Residues of DDD, DDT, or PCB's in sample eggs were not signifi- cantly related to nest success. Reproductive success in the brown pelican colony was subnormal in the 2 years of study (1971-72), but reproductive success was normal in those nests in which the sample egg con- tained either 2.5 ppm or less of DDE or 0.54 ppm or less of dieldrin. Residues of DDE, DDD, DDT, dieldrin, and PCB's exhibited a significant decline in South Carolina brown pelican eggs from 1969 through 1973 (Blus et al. 1977), but the decrease in DDD was greatest. In 1973, the pelicans experienced excellent reproductive success for the first time in many years, and the decline in residues was related to this improvement. DDE was implicated as the agent responsible for most pollutant- induced nest failure; residues greater than 3.7 ppm in the sample egg were associated with total failure of those eggs remaining in the nest. The improvement in reproductive success was not associated with an in- crease in average eggshell thickness. Reproductive success of a colony of great egrets in California declined between 1967 and 1970 (Pratt 1970; Faber et al. 1972). Successful nesting attempts de- creased progressively from 52% to 28%, and nests losing eggs increased from 30% to 54%. Reproductive success of this colony's great blue herons showed no comparable trends over this period, but there was significant eggshell thinning (when compared with pre- 1947 samples) in both species. Although no eggs were analyzed for dieldrin and endrin, levels of these chem- icals (5 to 7 ppm dieldrin; 0.10 to 0.28 ppm endrin) in the brains of four adult egrets found dead or moribund suggest death by organochlorine poisoning. DDE and PCB residue levels in the four eggs analyzed were lower than the levels found in some of the eggs we analyzed, but comparisons based on so few samples may not be valid. The most comprehensive studies of the effects of environmental pollutants on a heron species have been made on the gray heron (Ardea cinerea) in Great Britain (Milstein et al. 1970; Prestt 1970; Cooke et al. 1976). Of particular interest are the observations of high incidences of deliberate egg destruction by brooding herons, seemingly induced by organo- chlorines. On a heronry basis, the proportion of pairs breaking their eggs was linearly related to mean residues of DDE and dieldrin in surviving eggs. Although more than half the pairs broke their eggs during some years, heron populations have not declined overall, perhaps because of the ability of this species to lay repeat clutches. DDE and PCB residue 21 levels in the gray heron eggs are similar to those in some of our heron colonies, but dieldrin levels are considerably higher than in the eggs we analyzed. We cannot positively relate the organochlorine residues we found in eggs to the population declines of any species that have been reported, but circum- stantial evidence suggests these chemicals may contribute to impaired reproduction in the more contaminated areas. Acknowledgments We appreciate the assistance of National Wildlife Refuge staff who helped collect eggs. At other loca- tions, S. R. Aycock, L. J. Blus, P. A. Buckley, R. Chandler, R. D. Curnow, J. B. Elder, R. D. Hoff- man, J. A. Jackson, E. R. Ladd, J. L. Lincer, J. E. Myers, S. A. Nesbitt, J. C. Ogden, J. A. Rodgers, S. N. Wiemeyer, J. H. Wiese, and J. Withers were especially helpful in obtaining eggs, but others also collected samples for us. Many individuals in the Patuxent Wildlife Research Center's Environmental Residue Chemistry Project helped in analyzing the samples. We also appreciate the cooperation of personnel at museums and of private collectors who allowed us to measure eggshells in their collections: American Museum of Natural History, Carnegie Museum, Charleston Museum, Clemson University, Delaware Museum of Natural History, Florida State Museum, Louisiana State University, Museum of Comparative Zoology, Ohio State University, Peabody Museum of Natural History, Philadelphia Academy of Natural Sciences, University of Kansas, University of Massa- chusetts, and U.S. National Museum; E. Cutts, and H. H. Harrison. K. P. Burnham, D. E. Coyne, F. R. Fieher, G. L. Hensler, L. F. Stickel, and W. F. Stout wrote or modi- fied the computer programs and provided useful sug- gestions relative to statistical treatment and inter- pretation of data. T. J. Fergin, J. P. Hughes, and R. D. McArthur assisted in performing the statistical analyses. D. J. Snyder assisted in preparing the tables and also typed the manuscript. A. S. Federighi and S. N. Wiemeyer reviewed the manuscript and offered useful suggestions. References Anderson, D. W., and J. J. Hickey. 1972. Eggshell changes in certain North American birds. Pages 514-540 in K. H. Voous, ed. Proc. XVth Int. Ornith. Congr., The Hague, Netherlands. Arbib, R. 1971. Announcing— The Blue List: an "early warning system" for birds. Am. Birds 25(5):948-949. Arbib, R. 1972. The Blue List for 1973. Am. Birds 26(6):932- 933. Arbib, R. 1973. The Blue List for 1974. Am. Birds 27(6):943- 945. Arbib, R. 1974. The Blue List for 1975. Am. Birds 28(6):971- 974. Arbib, R. 1975. The Blue List for 1976. Am. Birds 29(6):1067- 1072. Arbib, R. 1976. 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Mclntyre and C. F. Mills, eds. Ecological toxicology research— effects of heavy metal and organohalogen compounds. Plenum Press, New York. Vermeer, K, and L. M. Reynolds. 1970. Organochlorine resi- dues in aquatic birds in the Canadian prairie provinces. Can. Field-Nat. 84(2):117-130. Vermeer, K., and R. W. Risebrough. 1972. Additional in- formation on egg shell thickness in relation to DDE concen- trations in great blue heron eggs. Can. Field-Nat. 86(4):384- 385. Wallace, G. J. 1969. Endangered and declining species of Michigan birds. Jack-Pine Warbler 47(3):70-75. Wallace, G. J. 1977. Environmental status of the Lake Michigan Region. Vol. 14. Birds of the Lake Michigan drainage basin. Argonne National Laboratory, Argonne, Illinois, prepared for the U.S. Energy Research and Development Administration (Contract W-31-109-Eng-38). 112 pp. Appendix I Chemical names of compounds discussed in this article, 23 Cis-chl ordane Ci s-nonachlor DDD DDE DDT Die! drin Endrin HCB Heptachlor epoxide Mi rex Oxychl ordane PCB (pol ychl orinated bi phenyl s) Toxaphene Trans-nonachl or l-exo,2-exo,4,5 ,6,7,8 ,8-octachloro-2,3 ,3a, 4 ,7 , 7a-hexahydro-4, 7-methanoindene 1-exo , 2-exo , 3-exo ,4,5,6,7,8 , 8-nonachl or o-2 , 3 , 3a, 4, 7,7a-hexahydro-4, 7-methanoindene 1 , l-dichloro-2 ,2-bi s(p-chl orophenyl )ethane 1 , l-dichloro-2 ,2-bis(p-chl orophenyl )ethyl ene 1,1-1 -trichloro-2,2-bi s(p-chl orophenyl ) ethane 1 ,2, 3,4,10, 10-hexachl oro-6, 7-epoxy-l ,4, 4a, 5, 6, 7,8, 8a-octahydro-l ,4-endo-exo-5 ,8-dimethanonaphtalene 1,2,3,4,10, 10-hexachl oro-6, 7-epoxy-l ,4, 4a, 5, 6, 7,8, 8a-octahydro-l ,4-endo-endo-5 ,8-dimethanonaphthalene hexachlorobenzene 1,4,5,6, 7,8,8-heptachl oro-2,3-epoxy-3a,4, 7,7a- tetrahydro-4 ,7-methanoindane dodecachlorooctahydro-1 , 3 ,4-metheno-lH-cycl obuta (cd)pental ene 1-exo , 2-endo ,4,5,6,7,8, 8-oc t achloro-2 , 3-epoxy-2 , 3 ,3a ,4, 7 ,7a-hexahydro-4, 7-methanoindene Mixtures of chlorinated biphenyl compounds having various percentages of chlorination Chlorinated camphene (content of combined chlorine, 67-69%) 1-exo, 2-endo, 3-exo ,4,5,6, 7, 8, 8-nonachl or o-2, 3, 3a, 4,7 ,7a-hexahydro-4, 7-methanoindene 24 Appendix II Frequencies of organochlorine residues in eggs of wading birds by species, 1972-73. (For frequencies in anhinga, black-crowned night heron, and wood stork eggs, see Ohlendorf et al. 1978a, 1978b). The following notes apply to all species, as appropriate: 1. Northern Atlantic colonies were coastal locations from New York to Massachusetts. 2. Southern Atlantic colonies were coastal locations from Florida to New Jersey. 3. Cis-chlordane was not separable from trans -nonachlor. 4. Frequency index was computed as Total occurrences Possible occurrences Total occurrences = Number of times any of the 13 organochlorines were present in eggs from that region. Possible occurrences = number of clutches from that region x 13 chemicals. 5. Chemicals not listed for a particular species were not detected in any eggs of that species. 6. Regions are given in the same sequence as in Table 2, but when no eggs of a particular species were collected from a region that region is omitted from this Appendix. 25 I— I oo CO m J-> II , O Z H ^ co CO /-^ O en CJ> >— I II y-i S=l ^ 3 U c o s- 01 -C 0i 3 CO n; < i •H c a; a a, co a; 3 •a •H co — I I— I r~i—i CM r. ITl CM i— 'ON SI •a c 3 o (X § o o o o O CO CM i— O CO CM i— i o o o o o 4 NCI rt o o cm r- -J" CM CO i— i o cm r^ /-v en cm ^ co o • • o • O CM O O O oo in co ■— m r-i /-v • ••••• o O OO CM CO ^- CO O CO CO 0-. CM vD CM i— l CO CM \£> CO <}• ~d"inCMCO00cOCO u « Q H 01 O Q O — < Q O Q O o X. u CO a. i/ EC 01 •IM X O o. 01 V c C CO CO T3 •a t- ^ o O i-i ■-> x: x: o u I >-. CO o o l- o I — I o CO C o c I en 0) c 0) a. co CO - x m o o H P- co CM o CN St CM o en m-Cf HNlO-tn O in CM i— i— • CM o en m en CM ON CO 01 o C 0i >-* 3 00 in o> c o >. CJ o o C 0) 1—1 3 CO cr 4-1 o; o k H tn 26 o H ON 00 CO m 3 XI •H CO cu CO O O 3 no CN C o S-i cu x c cu cu u o ec I XI a & & c cu t-H r^ r-l On i— I rH \DHvOCNHHH00 ON iH CM iOH»DO>SHHHin 00 CNJ On 00 r-. • • oo ■ en u-lOfHCNOOOOi-H CNI vO 00 On O CN • HO^.CC(J\ 0> ^ Cn fO r-. 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