Back Bay, Virginia and Currituck Sound, North Carolina have long been noted and highly acclaimed as prime waterfowl wintering and migration areas. Although no formal waterfowl surveys were conducted prior to 1937, some gauge of waterfowl abundance can be obtained from harvest record examination. Harvest estimates based on  extraordinarily well kept and recorded data  of ten major waterfowl hunting clubs in Back Bay and Currituck Sound between 1872 and 1962 (Sincock, 1966) suggest that five million (5,000,000) ducks and 560,000 Canada geese were taken by hunting during that 90-year period. Waterfowl population trends in Back Bay for the 37-year period 1954-90 are the subject of this paper

Schwab, Donald J.

Settle, Fairfax H.

English

Old Dominion University

Old Dominion UniversityODU Digital CommonsII. Fauna Proceedings of the Back Bay Ecological Symposium19901991Waterfowl Trends in Back Bay, Virginia from1954-1990Fairfax H. SettleVirginia Department of Game and Inland FisheriesDonald J. SchwabVirginia Department of Game and Inland FisheriesFollow this and additional works at: https://digitalcommons.odu.edu/backbay1990_faunaThis Conference Paper is brought to you for free and open access by the Proceedings of the Back Bay Ecological Symposium 1990 at ODU DigitalCommons. It has been accepted for inclusion in II. Fauna by an authorized administrator of ODU Digital Commons. For more information, pleasecontact digitalcommons@odu.edu.Repository CitationSettle, Fairfax H. and Schwab, Donald J., "Waterfowl Trends in Back Bay, Virginia from 1954-1990" (1991). II. Fauna. 1.https://digitalcommons.odu.edu/backbay1990_fauna/1Waterfowl Trends in Back Bay, Virginia from 1954 to 1990 Fairfax H. Settle and Donald J. Schwab Wildlife Division Virginia Department of Game and Inland Fisheries P.O. Box 1001, Tappahannock, Virginia 22560 Introduction Back Bay, Virginia and Currituck Sound, North Carolina have long been noted and highly acclaimed as prime waterfowl wintering and migration areas. Although no formal waterfowl surveys were conducted prior to 1937, some gauge of waterfowl abundance can be obtained from harvest record examination. Harvest estimates based on "extraordinarily well kept and recorded data" of ten major waterfowl hunting clubs in Back Bay and Currituck Sound between 1872 and 1962 (Sincock, 1966) suggest that five million (5,000,000) ducks and 560,000 Canada geese were taken by hunting during that 90-year period. Waterfowl population trends in Back Bay for the 37-year period 1954-90 are the subject of this paper. Methods Independent periodic waterfowl surveys have been conducted by personnel of Back Bay National Wildlife Refuge and the Virginia Depart-ment of Game and Inland Fisheries. Data from these surveys were not used in this analysis because of limited geographic coverage, surveys omitted some years, and the high rate of turnover of survey personnel and variability in experience and ability to census waterfowl populations. Usable data sets were narrowed to Audubon Christmas Bird Counts and Mid-Winter Water-fowl Inventories. The former counts have been conducted by qualified volunteers of the Audubon Society annually for fifty years during the week between Christmas and New Year's in conjunction with similar counts nationwide. The Back Bay Circle, the sampled area, is a 15-mile diameter circle with its center located approxi-mately 1 1/2 mile east of Back Bay Station in the City of Virginia Beach. The counts are made primarily from the ground by vehicle or walking, however boats and aircraft augment the ground survey some years. Mid-Winter Inventories (MWI) are annual waterfowl surveys conducted by U. S. Fish and Wildlife Service and/or state wildlife agency personnel. These surveys are coordinated nation-wide and are scheduled during the first week of January but occasionally continue into the second week. The Back Bay survey unit, Virginia Zone 4, Segment 14, extends from Dam Neck west to U.S. Route 17, south to the North Carolina state line, east along the state line to the Atlantic Ocean, then north to Dam Neck. The Back Bay survey is aerial and is coordinated with personnel in North Carolina so that Currituck Sound and Back Bay can be surveyed the same day, usually by the same personnel. Such coordination is done to minimize and hopefully eliminate duplication or omission errors of cohorts of birds utilizing habitats on both sides of the state line. Although Mid-Winter Inventories in the Back Bay survey unit date back to 1937, the waterfowl trends in this presentation will begin with the 1954 survey because data is missing for the years 1941, 1946, 1948, 1952 and 1953 (Sincock, 1966). Back Bay waterfowl counts from both Audubon Christmas Bird Counts and Mid-Winter Inventories were compared for the 37-year period, 1954-90. Both surveys showed similar fluctuations in waterfowl numbers. The Mid-Winter Inventory data are used in this paper because of the complete aerial coverage of the survey unit, the coordination of survey timing with North Carolina and the ability to relate to Virginia and Atlantic Flyway data for comparable periods. Linear regression analysis was made on certain waterfowl species or groups of species for the entire 37-year period 1954-90 as well as for the last IO-year period 1981-90. 188 As a note of interest, the trend in presence of submerged aquatic vegetation (SAV) in Back Bay was graphed and compared to certain species groups and to total waterfowl. Since the annual SAV surveys were conducted in late summer or early fall, the wild bird populations that utilized a summer or fall standing crop were the birds surveyed during the MWI in January of the following calendar year. Thus the SAV percent frequency values appearing in Figures 9-12 are included in the next calendar year to correspond to the correct generation of birds which utilized the plants. Trends Dabbliz:ig ducks (also known as puddle or tip-up ducks) m Back Bay show highly variable numbers over the 37-year period under consideration. The dabbling ducks have exhibited a statistically significant decline over the last 10-year period (P<0.04); however the 37- year· decline barely misses being statistically significant (P = 0.0532) (Figure 1). Dabbling duck trends declined but at a much slower rate over the last 10-year period in Virginia and in the Atlantic Flyway (FWS-OMBM files). Figure 2 graphically shows Back Bay population trends in gadwall and American wigeon, two dabbling duck species highly dependent on SAV food production in the bay habitat (Sincock, 1966). Diving duck species in Back Bay (Figure 3) have shown a statistically significant dramatically declining trend since 1954 (P<0.001) as con-trasted to a stable or only slightly declining trend at the Virginia and Flyway levels (FWS-OMBM files). The greater snow goose (Figure 4) has exhi-bited a significant decline since 1954 in Back Bay (P<0.03) while Flyway numbers of this species have increased from an annual average of 47,000 in 1954-59 to 163,000 in 1986-90 (FWS-OMBM files). The Canada goose (Figure 5) has shown a statistically significant decline in Back Bay since 1954 (P<0.001) while Virginia and Atlantic Flyway populations have increased during the same period (FWS-OMBM files). The Back Bay population of tundra swan (Figure 6) has declined significantly since 1954 (P<0.03) while the Atlantic Flyway population has steadily increased (FWS-OMBM files). Although the American coot is a member of the ~a?'i_ly Rallidae and not a true waterfowl species, 1t 1s mcluded here because of its close association with waterfowl groups addressed in this paper and because of coot dependence on submerged aquatic vegetation. Although the declining trend iz:t ~a~k Bay. coot numbers is not statistically significant, Figure 7 shows the dramatic varia-tions. No coots have been counted during the mid-winter inventory in Back Bay since 1980; ~u~ubon Christmas Bird Counts show a very s1m1lar trend. Coot populations in the Atlantic Flyway have remained stable since 1954 (FWS-OMBM files) . Total waterfowl numbers in the Back Bay survey unit (Figure 8) have exhibited a statisti-cally significant declining trend between 1954 and 1990 (P<o.001) (FWS-OMBM files). Many factors influence waterfowl populations: (a) natural and hunting mortality, (b) production affected by breeding populations and nesting/ brood habitat conditions, and (c) distribution which can be affected by all of the preceding factors plus the condition and abundance of migration and wintering habitat. The declining trend of many waterfowl species or species groups in Back Bay are contrary to Virginia or Atlantic Flyway trends. Such evidence suggests the declines are not entirely a result of mortality or production functions. Extreme care must be exercised not to over simplify cause and effect relationships in dynamic wild natural systems. The following data are presented for your interpretation. Figure 9 shows the percent frequency of submerged aquatic vegetation 1959-1990 (actually sampled early fall 1958-early fall 1989). (Coggin, 1966 and 1968; Schwab, 1985, et al. 1988; Settle and Coggin, 1975 and 1976; and Settle and Taylor, 1979). Two periods of abund-ant SAV occur from 1959 to 1964 and again from 1972 to 1981 where percent frequency of SAV equalled or exceeded 50. The periods of low SAV abundance below 50% frequency were 1965 to 1971 and from 1982 to 1990. The last six consecutive years, 1985-1990, have averaged below 10% SAV frequency in Back Bay. The 1 to ~ percent frequency of SAV noted in recent years 1s the lowest recorded in the 32 years of SAV monitoring. The graphs shown in Figures 10-12 show SAV abu~dance su_perimposed on dabbling ducks, bay feedmg dabblmg ducks (gadwall and wigeon) and total waterfowl numbers from Back Bay Mid-Winter Inventories. With few exceptions, it appears that when SAV is abundant in Back Bay, waterfowl numbers increase; when SAV is scarce, waterfowl numbers decrease. Sincock (1966) suggested that waterfowl distribution in Back Bay, Virginia was more influenced by SAV than in Currituck Sound, North 189 Carolina during his 1958-63 investigations. He also inferred that because many waterfowl species are relatively short lived, migratory patterns and habits could be negatively influ-enced by several years of poor food production on the wintering grounds. Summary Thirty seven (37) years of Mid-Winter Waterfowl Inventories of Back Bay, Virginia, 1954-90, indicate statistically significant declines in numbers of many waterfowl species or groups of species such as diving ducks, greater snow goose, Canada goose, tundra swan, American coot and total waterfowl. Dabbling duck numbers showed a significant decline over the past 10-year period. (Figures 1-8). Comparison of submerged aquatic vegetation abundance and waterfowl trends in Back Bay, Virginia is shown graphically in Figures 9 - 12. The graphs generally suggest a direct relation-ship between SAY abundance and waterfowl numbers. Acknowledgement Appreciation is expressed to David Steffen, wildlife biologist, Virginia Department of Game and Inland Fisheries, for performing the statisti-cal computations and analysis used with this presentation. Literature Cited Coggin, J .L., 1966. Aquatic vegetation trend study, p. 66-68. In: Va. Comm. Game & Inland Fisheries, Ann. Progress Rpt July 1, 1965-June 30, 1966, Richmond, VA. 70 pp. ----, 1968. Aquatic vegetation trend studies, 1 p. In: Va. Comm. Game & Inland Fisheries, Ann. Progress Rpt 1967-68, Richmond, VA. Fish and Wildlife Service, Office of Migratory Bird Management - files. Schwab, D., 1984. Aquatic vegetation investiga-tions, p. 283-287. In: Va. Comm. Game & Inland Fisheries, Ann. Rpt July 1, 1983-June 30, 1984, Richmond, VA. 417 pp. ----, 1985. Aquatic vegetation investiga-tions, p. 268-272. In: Va. Comm. Game & Inland Fisheries, Ann. Rpt July 1, 1984-June 30, 1985, Richmond, VA. 426 pp. 190 TOTAL DABBLING DUCKS - BACK BAY, VA Mid-Winter Inventories - 1954-1990 Thousands 30 ~----------------------~ 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 --"'!"--_.....,._,_....__._~---~-a.--.-~-..__.-~--"""--"µ.._ie;a___,;,.._______, 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 Figure 1. Total Dabbling Ducks - Back Bay, VA BAY FEEDING DUCKS - BACK BAY, VA Mid-Winter Inventories - 1954-1990 Gadwall and Wigeon Thousands 20 ~----------------------~ 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 ----"'P-~~4"'-T'--;--''~~t-rr"--"1"'"-"1f'-"P-"'1"-t-"'f'-'"l"'-"'i"'--4"'-''i"-"l"'-4""--''f"-'"1"'--"'f"--"'f"--t---"i"'--t--"'F--+---,--+--"i"--+' 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 Figure 2. Bay Feeding Ducks - Back Bay, VA TOTAL DIVING DUCKS - BACK BAY, VA Mid-Winter Inventories - 1954-1990 Thousands 2 6 ~----------------------~ 2 4 22 20 18 16 14 12 10 8 6 4 2 0 __,____..___._'----+-'--"'i"-l----r----t---,,.......---.----9"-----r--1----T_____,"i"-"1"'--"'f"-"'F-r-"f"'-r-+---,--1----r--+-r-+-~ 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 Thousands Figure 3. Total Diving Ducks - Back Bay, VA SNOW GEESE - BACK BAY, VA Mid-Winter lnventorie~ - 1954-1990 so ~--------------------------, 4 5 40 35 · 30 25 20 15 10 5 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 Figure 4. Snow Geese - Back Bay, VA CANADA GEESE - BACK BAY, VA Mid-Winter Inventories - 1954-1990 Thousands 28 ~----------------------~ 26 24 22 20 18 16 14 12 10 8 6 4 2 0 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 Figure 5. Canada Geese - Back Bay, VA TUNDRA SWAN - BACK BAY, VA Mid-Winter Inventories - 1954-1990 Thousands 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 Figure 6. Tundra Swan - Back Bay, VA 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0 COOTS - BACK BAY, VA Mid-Winter Inventories - 1954-1990 Thousands 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 figure 7. Coots - Back Bay, VA TOTAL WATERFOWL - BACK BAY, VA Mid-Winter Inventories - 1954-1990 Thousands 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 figure 8. Total Waterfowl - Back Bay, VA 100 90 80 70 60 50 40 30 20 10 0 PERCENT FREQUENCY OF SUBMERGED AQUATIC VEGETATION Back Bay, VA - 1959-1991 Thousands Percent ~------------------------r- 100% ,---t 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 Figure 9. Percent Frequency of Submerged Aquatic Vegetation. DABBLING DUCKS AND % FREQUENCY OF SUBMERGED AQUATIC VEGETATION Back Bay, VA - 1954-1991 Thousands Percent 75% 50% 25% 30 ~----------------------~ 100% 28 26 24 22 20 18 16 14 12 10 8 6 4 2 75% 50% 25% 0 0% 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 Figure 10. Dabbling Ducks and Percent Frequency of Submerged Aquatic Vegetation. BAY FEEDING DUCKS AND % FREQUENCY OF SUBMERGED AQUATIC VEGETATION Back Bay, VA - 1954-1991 Thousands Percent 20 ---,--------------------------,- 100% 19 18 17 16 15 14 13 12 1 1 10 9 8 7 6 5 4 3 2 1 75% 50% 25% 0 -"'f"--'-"14-"l"--T---+--"1'"-"f'-'"i"-+...,...-"!~-'---+-"--.._..-__.,,"-"f<LI"i"--+------1----"i"-+--e-+-' _ __._ 0% 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 Figure 11. Bay Feeding Ducks and Percent Frequency of Submerged Aquatic Vegetation. TOTAL WATERFOWL AND % FREQUENCY OF SUBMERGED AQUATIC VEGETATION Back Bay, VA - 1954-1991 Thousands Percent 150 ---,-------------------------~ 100% 140 130 120 110 100 90 80 70 60 50 40 30 20 10 75% 50% 25% 0.-l"f'.J-~~-~µiaJ-~~-~~-~~-~--u,,,..,:......,.___,_0% 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 Figure 12. Total Wa!erfowl and Percent Frequency of Submerged Aquatic Vegetation. 

Waterfowl Trends in Back Bay, Virginia from 1954-1990

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Waterfowl Trends in Back Bay, Virginia from 1954-1990

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