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The Brown Pelican and Certain
Environmental Pollutants in Louisiana
by Lawklnck J. Bi.us
' .
VS. Fish ami II ildltfv Service
ralnjc/t/ Wildlife Research Center
tMurct, Md.
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Louisiana If'iM Life and Fisheries Commission Rockefeller If ildltfe fic/turr, /htfdc I, Ha.x 2U-H
Grand Chenier, Ln. 700 J.i
Andrf. A. IHrusi.t: ami K. M. Provtt
VS. Fish and If ihllife Service Patuxent Wiltlhlc Research Center
Laurel, Md. mil
`
The recent history of the eastern brown pelican (Pelecanus occidentalis carolinensis) in Louisiana has involved the extirpation of a once flourishing population; a small breeding population has now been reestablished from birds taken from the stable Florida population. The elimination of the pelican as a breeding bird in Louisiana came about with little publicity, and
the process was complete by the early 1960's.
The pelican population in Louisiana was a large one, but it is difficult to determine the thoroughness and accuracy of the early counts. BAILEY (1920) reported 50,000 brown pelicans on the Mud Lumps, which are small islands at the mouth of the Mississippi River. PEARSON (1919) reported 65,000 brown pelicans on the Gulf Coast from Texas to Florida. 0BERH0LSER (1938) listed about 5,000 breeding pairs for the entire State and estimated only 4,550 pelicans on the Mud Lumps. The last record of nesting brown pelicans in Louisiana was in 1961 when VAN TETS (1965) found 200 breeding pairs and 100 nestlings on North Island. We do not know the reasons for the population decline, although J0ANEN and DUPU1E (1969) theorized that hurricanes, diseases, and pesticides were the major causes. Pelicans have been exposed to hurricanes and diseases throughout their existence, but the addition of adverse effects induced by pesticides or other pollutants may have been enough to push them into extinction in Louisiana. Now that transplanted pelicans from Florida have established a small breeding population, it it important to determine the levels of environmental pollutants in these pelicans and to determine the
effects of these pollutants.
METHODS
Field work involved collecting eggs from the colony, counting nests and young, and transplanting the young. The transplanting program involved 465 nestlings imported from Florida from 1968 through 1973. Fifty of these birds were released at Rockefeller Refuge, and the remainder were released at Grand Terre. The Rockefeller release failed, but a small breeding colony has been established at Grand Terre where birds began nesting in 1971. The period of this study includes 1971 through 1973.
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In the 3 years of study, 67 eggs were collected. Freshly laid eggs and both viable and addled eggs in all stages of incubation were collected. The eggs were frozen soon after collection, and they were sent to the Patuxent Wildlife Research Center several months later. The egg contents were then removed from the shell and refrozen. The shells were thoroughly washed and allowed to dry. The eggshell thickness was measured to the nearest 0.01 mm at three points along the waist of the egg with a Starrett 1010M micrometer.
The contents of 36 eggs were analyzed individually for residues of organochlorine pesticides, their metabolites, and polychlorinated biphenyls (PCB's) at the Patuxent Center. The methodology used in analyzing the eggs collected in 1971 (MULHERN et al., 1970) was modified and improved when later samples were analyzed (BLUS et al., 1974a). Electron capture gas Chromatography and several types of columns were used each year. Thin layer chromatography was used to analyze PCB residues in eggs collected in 1971 and a portion of the eggs collected in 1972 (MULHERN et al., 1971). . The major change in the analytical techniques involved use of the silicic acid column in 1972 and 1973; this permitted the ' separation of the organochlorine residues into three fractions. DDF. was quantitated by peak height to avoid errors from PCB interference; the other organochlorines were measured by digital integration of area and PCB's were estimated by comparing total area of PCB peaks with that of Aroclor 1260. Mass spectrometry was utilized in confirming residues in some of the eggs. Recoveries from eagle tissue spiked with the organochlorine pesticides and Aroclor 1254 ranged from 90% to 109%. Residues in the pelican eggs were not corrected for recovery values.
Five Of the eggs analyzed for organochlorines were also analyzed for six metals by the Environmental Trace Substances Center, Columbia, Missouri, Atomic absorption was used to detect residues of mercury, zinc, copper, cadmium, and lead; neutron activation analysis was used to detect nickel. The lower limit of sensitivity in detecting residues (ug/g) was 0.01 for pesticides or their metabolites, 0.5 for the PCB's, 0.005 for cadmium, 0.01 for nickel, 0.025 for lead and mercury, and 0.05 for zinc and copper. The residues are expressed on a fresh wet weight basis. Certain external egg measurements (length x breadth2) were significantly correlated (P<0.01) with weight of the contents of fresh eggs. The resulting regression equation was used to convert egg content weight to fresh wet weight (STICKEL ot al., 1973). Freshly laid pelican eggs contained 85 percent moisture (determined by lyophi1ization) and 4.4 percent lipids.
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RESULTS AND DISCUSSION
The Transplanting Program -- In 1971, transplanted brown pelicans produced eight young; this was the first indication that the program had a real potential for replenishing the brown pelican population in Louisiana. The number of nests and number of young fledged increased through 1973 (Table 1). The number of fledglings produced per nesting effort was less than the 1.2 to 1.5 young estimated as necessary to maintain a stable population (HENNY, 1972). The pelicans initially selected a low shell bank for nesting, and some nests were flooded periodically by high tides. This problem was largely alleviated when the birds selected another island and constructed their nests in low black mangroves (Avicenna nitida).
TABLE 1
Reproductive success of brown pelicans transplanted in Louisiana.
Year
Number of Nests
Number of Young Fledged
Total
Per Nest
1971 1972 1973
13 28 50
8. 14 26
0.62 0.50 0.52
The current increase in the breeding population (Table 1), is related to transplanted pelicans attaining breeding status rather than to recruitment of the young reared in Louisiana Into the breeding population. Because of current subnormal reproductive success, the long-term outcome of the transplanting program is still somewhat in doubt. The continued growth and future of the brown pelican population in Louisiana is dependent upon the identification and alleviation of the agent or agents that Induced the extirpation of this species. Population growth may be affected adversely by numerous factors including pollution, loss of nesting habitat, or other adverse alteration of the ecosystem that either played a role in the demise of the pelican or have emerged since its extirpation.
Eggshel1 thickness -- On the basis of eggshell thickness measurements "obTaTned-from 24 brown pelican eggs located in museums, the mean pre-1947 eggshell thickness of Louisiana eggs was 0.554 mm (ANDERSON and HICKEY, 1970). The shell thickness of contemporary eggs averaged 0.517 mm in 1971, 0.406 mm in 1972, and 0.4B8 mm in 1973 (Table 2). The pre-1947 eggshell thickness
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was significantly greater (P<0.05) than that measured in either of the 3 later years, but the 1971 thickness was significantly greater (P<0.05) than either the 1972 thick ness or the 1973 thickness (Table 2). Although it is not definitely established that the 7 percent eggshell thinning In 1971 and 12 percent thinning in 1972 and 1973 are affecting reproduction, thinning of 18 percent or less has been associated with lowered reproductive success in other birds used in experimental studies (HEATH et al., 1969; LONGCORE et al., 1971). Eggshells of brown pelicans are thinning in all sections of this species' range in North America (BLUS 1970; BLUS et al., 1971; KEITH et al., 1970).
TABLE 2
Eggshell thickness of brown pelican eggs from Louisiana.
Year
Humber of f99S
Pre-1947l/ 1971 1972 1973
24 7
39 21
Thickness (mm) Mean _+ standard error Range
0.554 + 0.007 it1 0.517 + 0.007 b 0.486 + 0.006 c 0.488 + 0.009 c
0.49-0.53 0.41-0.57 0.40-0.54
Pre-1947 eggshell thickness data from Anderson and Hickey (1970) range not listed.
2/ A significant difference (P<0.05) among thickness
means is indicated for those means not sharing a common letter. Means were separated using the
.
new multiple range test with an extension for
unequal replication (KRAMER, 1956).
.
*
Residues -- Each of the 36 eggs analyzed contained measur-
able residues of p,p`-DDE, p,p'-DDD, dieldrin, and PCB's
(Table 3). Most of the eggs contained measurable quantities
of p.p'-ODT and heptachlor epoxide; none of the eggs contained
mirex. Small residues of cis-nonachlor were found in all eggs
analyzed in 1972 and 1973, and all but one of these eggs
contained cis-chlordane and/or trans-nonachlor. Neither
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TABLE 3 Residues of organochlorine pollutants in eggs of the brown pelican from Louisiana.
Year 1971
---------------------------------------------
uq/q (fresh wet weight)-^ J-------------------- hepiachTor-------UT-------"
p.d'-ODE
p.p*-ODD
p.p*-DDT 1 Dieldrin
epoxide chlordane^
nonachlor _PCB's
.. Toxaphene_
1.30 1.20 0.58
0.18 0.32 0.40
0.14 0.13
Tr
0.24 0.54 0.27
Tr Tr Tr
NI NI NI
NI 5.0 NI NI 4.0 NI NI 3.0 NI
G.M.--^
0.97
0.28
0.10
0.33
--
--
--
3.91
--
1972
2.58 1.37 0.99 1.12 1.30 1.61 1.27
2.25 0.83 1.65 1.27 0.98
0.52 0.29 0.17 0.18 0.27 0.27 0.09 0.35 0.17 0.45 0.22 0.21
0.28 0.15 0.16 0.16 0.26 0.26 0.13 0.32
HD HO 0.12 0.15
.
0.65 0.47
0.31 0.36 0.63 0.46 0.41
0.79 0.30 0.50 0.35 0.36
NO 0.12
HO ND 0.11 NO ND 0.24 NO 0.19 0.10 ND
0.30
0.22 3.8 m
0.29
0.47 3.5 NQ
0.13
0.16 2.7 NQ
0.20
0.18 3.2 NI
0.21
0.28 3.7 NI
0.27
0.26 4.6 NI
0.16
0.14 3.3 NI
0.46
0.36 6.4 NI
ND - 0.12 2.5 NI
0.25
0.28 4.7 NI
0.12
0.17 3.1 NI
0.10
0.17 2.3 NQ
GM
1.36
0.26
0.15
0.45
C.L.
1.10-1.68 0.20-6.32 0.10-0.22 0.33-0.61
o
Ranoe
0.82-2.58 0.17-0.52
N0-0.32 0.30-0.79
--
-- --
0.18 0.13-0.27
ND-0.46
0.22 0.17-0.28 0.12-0.47
3.51
2.92-4.21 2.3-6.4
-- -- --
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77--Tr= trace';' NO = mfresidue detected; NI = residues were not identified by the chemical methodology;
.
u mq = not'quantified. 2/ and/or trans-nonachlor. 3/ G.M. = geometric mean; C.L. = 95% confidence limits.
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Year 1973
8
p.p'-DDE
p.p'-DDD
1.34 1.29
0 78 0 91 0 99 0.89 1 80 2.09 1.06 1 .54 1.79 1.18 1.14
1.61 1.98 0.58 1.44 4/
1.17 4/ 1.84 1.90 1.74 4/
0.24 0.17 0.14 0.12 0.15 0.24 0.27
0.13 0.34
0.19 0.60 0.13 0.15 0.16 0.24
Tr 0.25 0.18 0.16 0.22 0.31
'
p.p1-DOT
0.27 0.13 0.14
o.n
0.11 ND
0.22 0.12 0.25 0.21 0.22 0.13 0.14 0.20 0.29
Tr 0.26
Tr 0.31 0.17 0.27
\I ug/g (fresh wet weiaht)-
Heptachior
ClS" ?/
` Dieldrin
epoxide chlorcTane?/
0.71 0.59 0.53 0.47 0.57 0.42 0.70 0.54 0.96 0.74 0.72 0.50 0.64 0.67 0.86 0.30 0.98 0.61 0.83 0.12 0.55
0.16 0.11 0.12 0.11 0.13 0.15 0.14 0.12 0.25 0.14 0.19
0.11 0.16 0.18 0.17
ND 0.18 0.13 0.20 0.24 0.21
0.37 0.28 0.16 0.21 0.25 0.18 0.34 0.21 0.46 0.28 0.38 0.23 0.26 0.30
0.31 0.13 0.34 0.27 0.36 0.33 0.82
Cisnonachlor
0.22 0.17 0.20 0.14 0.17 0.20 0.25 0.16
0.30 0.21 0.23 0.17 0.18 0.23 0.29 0.10 0.22 0.16 0.27 0.28 0.28
,
PCB's
2.7 2.6 1.8 1.9 3.7 1.8 3.1 4.7 2.2 3.6 5.3 2.5 2.8 3.1 4.1 1.1 3.1 2.8 4.3 4.3 3.2
Toxaphene
0.44
0.28 0.27 0.23 0.25 0.12 0.45 0.52 0.22 0.38 0.38 0.25 0.28 0.41
0.53 0.17 0.43 0.28 0.43 0.41
0.58
.
G.M. C.L. Range
1.31 1.03-1.85 0.53-2.09
0.19 0.16-0.24
Tr-0.60
0.16 0.12-0.20
ND-0.31
0.64 0.56-0.73 0.30-1.12
0.15 0.13-0.17
ND-0.25
0.28 0.24-0.34
0.13-0.82
0.20
2.89 0.32
0.18-0.23 2.44-3.44 0.27-0.:
0.10-0.30 1.1-5.3 0.12-0.:
Tj Trace of hexachlorobenzene
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cis-chlordanc nor cls-nonachlor would have been Identified by the residue analysis techniques used for the 1971 eggs. Toxaphene was identified in all of the eggs collected in 1973. The residue methodology employed in analyzing the eggs collected in 1971 did not permit the identification of toxaphene. Toxaphene was present in 1972 eggs, but not quantified. A trace of hexachlorobenzene was found in a few of the eggs collected in 1973.
The heavy metals listed in Table 4 do not seem to be of sufficient magnitude to pose a threat to the pelicans in Louisiana, but our knowledge of the potential hazard of such low levels is incomplete. The mercury levels are much lower than those found in eggs from Florida, South Carolina or California {BLUS et al.f 1974a). Otherwise, the residues of the other metals are similar to those found in the other areas.
TABLE 4
Residues of six heavy metals in eggs of the brown pelican from Louisiana, 1972.
-*-*"*-j|| |
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1 ug/g (fresh wet weight) Cd. Cu, Zn. Ni. Hq. Pb.
Tr 1.20 6.0 0.044 0.08 Tr
:
.*
. Tr
1.06' 5.6 Tr
0.06 Tr
i 0.008 1.49 6.8 0.035 0.07 Tr
\ Tr 1.04 6.2 0.044 0.10 0.040 4 ' AJ1 0.006 1.03 5.1 0.022 0.08 Tr ;
G.M. 0.004 1.15 5.9 0.024 0.08 0.016
The PCB's in the pelican eggs resembled Aroclor 1260 or
j those Aroclors lying near 1260. The PCB's occurred at higher levels than the other residues followed by DDE and dieldrin.
The DDE:PCB ratio was 0.4:1.0. One of the most encouraging t1 findings was the absence of endrin. This highly toxic j insecticide caused massive fish kills in the lower
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Mississippi River in the early 1960's (MOUNT and PUTN1CK1, 1966) -- about the time that the pelicans disappeared in
Louisiana. According to LONG et al. (1961), the use of
endrin in Louisiana became widespread by 1958.
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ROWE et al. (1971) found that residues of endrin and dieldrin had greatly declined in oysters and in water from the Mississippi River in Louisiana from 1964-1966 to 1968 1969. Whether endrin was related to the extirpation of the brown pelican in Louisiana is unknown because tissues or eggs of these birds were never analyzed for residues. Endrin was not detected in tissues or eggs of brown pelicans col lected from Florida, California, and South Carolina from 1969 through 1972 (BLUS et al., 1971).
Relationships between residues in the egg and biological effects -- The relationsnip of DDE to shell thinning of the Louisiana brown pelican eggs followed that described in an earlier study in which DDE accounted for all or most of the shell thinning of brown pelican eggs from South Carolina, Florida and California (BLUS et al., 1971). The relation ship of DDE.to eggshell thinning was significant (P<0.05; r * 0.374; Y = 91.16 - 16.561 Tog-jq X where is the percent of the pre-1947 eggshell thickness and X_ is the logarithm of the DDE residue).
The percentage thinning of eggshells of Louisiana pelicans was less than the DDE-induced thinning associated with reduced reproductive success of captive birds of other species (HEATH et al., 1969; L0.TGC03E et al., 1971). Furthermore, eggshell thinning and residues of the eggs of Louisiana pelicans were similar to that found in eggs of pelicans from Florida (BLUS, 1970; BLUS et al., 1971; BLUS et al., 1974a). The breeding population of brown pelicans in Florida has been stable since 1968 when the population census of the nesting colonies was originated (WILLIAMS and MARTIN, 1968; LOVETT E. WILLIAMS, JR,, 1974 Personal Communication); the reproductive success of one large Florida colony is said to be normal (SCHREIBER and RISEBROUGH, 1972).
The residues of DDE in the Louisiana eggs are generally below those associated with subnormal reproductive success of the brown pelican in South Carolina (BLUS et al., 1974b). However, the level of dieldrin tends to be slightly higher In the Louisiana eggs, and 18 of the 36 eggs contain a level of dieldrin considered potentially detrimental to reproductive success (BLUS et al., 1974b). Thus, there is the possibility that dieldrin may have some influence on reproductive success in Louisiana brown pelicans, but the effects of dieldrin were not satisfactorily separated from those of DDE in the South Carolina study (BLUS et al., 1974b). The low rate of reproduc tive success may be influenced by the unusual conditions existing in establishment of a small breeding colony in an
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area without an existing breeding population. There is some suggestive evidence (LOVETT E. WILLIAMS, JR., 1974, Personal Communication), that the pelicans in Louisiana began to breed at an earlier age than normal; none of the pelicans breeding in 1971 or 1972 were in complete adult breeding plumage. '
A series of studies should be made to clarify the past, present, and future status of the brown pelican population fn Louisiana. We have made a start, but many other avenues of research need to be explored -- such as effects of metals, other pollutants, and disease organisms; extent of habitat loss including nesting islands; and the possibility of food shortages or losses.
ACKNOWLEDGMENTS
We thank Lovett Williams, Larry Martin, and other members of the Florida Game and Fresh Water Fish Commission for pro viding birds used in the transplanting. Appreciation is expressed to Allen Ensiminger, Larry McNease, Howard Dupie, Dan Neal, and Larry Escuriex for help with the field work and to Larry McNease and Eugene H. Dustman for reviewing the manuscript.
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, A/X BELISLE, and R. M. PROUTY:
' Pestic. Mon\t. J. 1_, 181 (1974a).
, R. G. HEATH, C. D. GISH, A. A. BELISLE,
and R. M. PROUTY: BioScience 21_, 1213 (1971).
____________, B. S. NEELY, JR., A. A. BELISLE, and
~ ~ R. M. PROUTY: Environ. Pollut. In Press, (1974b).
HEATH, R. G.. J. W. SPANN, and J. F. KREITZER: Nature 224.,
47 (1969).
HENNY,. C. J.: U.S. Fish and Wildlife Service, Wildl. Res.
Rept. No. 1, 99 pp. (1972).
JOANEN, T., and H. 11. DUPIE: Forest and People V9, 23
(1969).
KEITH, J. 0., L. A. WOODS, and E. G. HUNT: Trans. North
Amer. Wildl. Nat. Res. Conf. 35, 56 (1970).
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LONGCORE, J. R., F. B. SAMSON, and T. W. WHITTENDALE, JR.:
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485 (1971).
MOUNT, D. 1., and G. J. PUTN1CKI: Trans. North Amer. Wildl.
Nat. Res. Conf. 3, 177 (1966).
HULHERN, B. M., E. CROMARTIE, W. L. REICHEL, and A. A.
BELISLE: J. A. 0. A. C. 54, 548 (1971).
MULHERN, B. M., W. L. REICHEL, L. N. LOCKE, T. G. LAMONT,
A. A. BELISLE, E. CROMARTIE, G. E. BAGLEY, and R. M.
PROUTY: Pestic. Monit. J. 4, 141 (1970).
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834 pp. (1938).
PEARSON, T. G.: Nat. Hist. 19, 40 (1919).
ROWE, D., R., L. W. CANTER, P. J. SNYDER, and J. W. MASON:
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Union, 88 pp. (1965).
WILLIAMS, L. E., JR., and L. MARTIN: Quart. J. Fla. Acad.
S. 31, 130 (1968).
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