=c...,.,-""1 =en., _u;.. ~-::1: -o... oo===>= N-~ =o ====r 00 ;; =ITJ a-en ~~rtl ~ ~ STATUS OF THE MERLIN (Falco c. columbarius) IN INTERIOR ALASKA O.~rTJ VI===: =:I> o. ~ 1989 PROGRESS REPORT =;o.; -:I> I. fw~,l! /II'{ :kimberly Titus 1 Virginia Cooperative Fish and Wildlife Research Unit Department of Fisheries and Wildlife Sciences Virginia Polytechnic Institute and State University Blacksburg, VA 24061 Philip F. Schempf Raptor Management U.S. Fish and Wildlife Service P.O. Box 021287 Juneau, Alaska 99802 Key words: Merlin Falco c. columbarius Interior Alaska Denali National Park Abundance, Breeding Biology, Food, Pollution (pesticides), Population Dynamics, Reproduction, Status, Techniques January 1990 1 Present Address: Alaska Department of Fish and Game, Division of Wildlife Conservation, P.o. Box Mufg' AK 99824 Alaska Resources Library & Information Services I Anch
SUMMARY Seventeen merlin nests were located in the vicinity of the road corridor in Denali National Park and Preserve. Eleven nest sites were in live spruce trees, one was in a spruce snag, one was in a willow, and four were on the ground. Mean clutch size was 4.8 (n = 9). Fifty-two nestlings were banded, representing 3.25 young banded per active nest for nests where the outcome was known (n = 16). A total of 25 adult merlins were captured, representing 19 unhanded and six previously banded individuals. Since the adult trapping efforts began in earnest in 1987, four nestling males have been recaptured as breeders, while no females banded as nestlings have been encountered. Environmental contaminant analysis of three addled eggs collected in 1988 has been completed and the organochlorine scan indicated an arithmetic mean of 7.5 ppm wet weight DDE. Trace amounts of other organochlorines were found, notably mirex, which is used in the southern U.S., central and South America.
STATUS OF THE MERLIN (Falco c. columbarius.) IN INTERIOR ALASKA 1989 PROGRESS REPORT Many resource management agencies are increasing their monitoring programs for wildlife, particularly for nongame species. Some monitoring programs must begin as baseline data studies, insomuch as little is known about many wildlife species. Studies of the taiga merlin were begun in 1983 by the Raptor Management project of the U.S. Fish and Wildlife Service, because little was known about this species within Alaska and merlin populations had been impacted by pesticides in other portions of their range. Historical nesting records and ease of access to potential nesting habitat has been the impetus to focus the study within Denali National Park and Preserve. As we continue to study and monitor the autecology of the merlin; its status should remain of interest to National Park Service due to the hazards it encounters on its wintering ground in central and South America from environmental contaminants. The taiga merlin has received little study on its nesting areas in North America and we are aware of no other studies which are currently being undertaken to assess the population ecology of this species in northern latitudes. This report summarizes findings from the J989 field season. Our primary objectives this year were to evaluate: 1. productivity based on the number of successful nests and number of nestlings banded and/or fledged, 2. population turnover by trapping adults and observing color-marked individuals, 3. the occupancy of previously used nesting areas.to establish a basis for annual nesting area occupancy, 4. and the significance of biocide contamination by collecting eggshell fragments and having unhatched eggs analyzed for certain contaminants. These attributes are important in establishing baseline data for determining time-trends in the population. ACKNOWLEDGMENTS This study would not have been possible without the continued assistance of Joe VanHorn and Carol Mcintyre, along with other staff of Denali National Park and Preserve. The National Park Service provided a vehicle and lodging. Layne Adams, AI Lovaas, and Dale Taylor of the Park Service Regional Office assisted by providing encouragement for our continued studies. We also acknowledge the continued assistance of Pete and Gretchen
1989 PROGRESS REPORT 2 Pederson, and Pat Rudinsky. Bob Zepp was invaluable in the field during the banding and trapping period. Dr. Jim Scott provided the owl used for trapping. Finally, we owe a special thanks to Mike Owen, whose field skills were instrumental in making the field season a success. The U.S. Fish and Wildlife Service's Raptor Management project provided financial support to K. Titus. M. R. Vaughan, Virginia Cooperative Fish and Wildlife Research Unit, USFWS, provided administrative support. The continued support of W. S. Seegar was instrumental in the success of this field season. METHODS The study area encompassed those parts of the eastern portion of Denali National Park and Preserve accessible by hiking from the road corridor. K. Titus began field studies on 23 May, somewhat later than in previous years. The last day in the field was 18 July. Methods were essentially the same as in previous years. The only difference in field methods was that in 1989, cassette tapes of merlin distress calls were used early in the season to locate active territories. Merlin calls were played every few minutes while walking through stands of suitable nesting habitat to encourage a vocal response by territorial adults. Nest searches were conducted early in the season, with new sites being found until nearly the end of the field season. Areas near previous nest sites and other suitable habitat were searched on foot for adults or signs of their presence. When adults were located, they were watched until they returned to the nest site. Nests were visited from late May through June to determine clutch size. We began trapping adults on 30 June and captured the last adult on 18 July. A permanently crippled great horned owl was used as a lu~e by placing it near the nest tree tethered to a low perch. A mist net was stretched in a "V" around the owl beyond its reach. Adult merlins flew towards the owl and were caught in the mist net. Each adult was weighed, measured, photographed, banded and released near the point of capture. Physical condition, crop, and moult were noted. Nestlings were banded from 4-17 July. Each young falcon was aged, sexed, banded, weighed, measured and photographed. Addled eggs encountered at this time were collected. Addled eggs were wrapped in two sheets of aluminum foil and refrigerated until they were prepared for contaminant analysis. Each egg was drilled and blown into a chemically clean container and the contents were frozen. The shell was washed, dried, weighed and measured. The shells were shipped to the Western Foundation of Vertebrate Zoology for thickness measurements and permanent storage. The egg contents were mailed to a Fish and Wildlife Service approved analytical laboratory in September 1989, for analysis. Observations of nesting merlins and their young were made throughout the summer.
1989 PROGRESS REPORT 3 RESULTS Broadcasting merlin distress calls was clearly helpful in determining that a forest stand had merlins present in a few situations, notably at Savage Bridge and the Porcupine forest. The behavior that assisted in determining that an area was occupied included vocalizations and merlins flying toward the source of the call. This method was not an aid in finding the actual nest however. Unfortunately, the behavioral response by merlins to the tape in situations where we knew merlins were present was inconsistent. This observed behavior included the lack of a vocal and fly-over response in situations where the female was known to be incubating eggs and the male was perched nearby. We hope that these inconsistent results may have been largely due to our nest searching during the incubation period when pairs are notoriously quiet. With the assistance of volunteers and Park Service staff, we were able to obtain data from a total of 17 merlin nests (Table 1) that were located along the length of the Park road (Figure 1). Owing to our late start in the field in 1989, many of the nests were found later than in previous years and we were only able to determine clutch size for 9 nests. Modal clutch size was 5 and the mean was 4.8.
1989 PROGRESS REPORT 4 Table 1. Merlin nests found in Denali National Park and Preserve, 1989. LOCATION ADULTS NEST CLUTCH BROOD ADDLED NUMBER OBSERVED FOUND FOUND SIZE SIZE EGGS BANDED/COMMENT Carlo Creek 6/21 6/22 5 (6/22) 4 0 4 (7/9) Permafrost t> 6/21 6/22 Upper Upper Savage 6/10 6/17 5 (6/17) 5 (7/4) 0 5 (7/4) Lower Upper Savage 5/27 5/27 4 (6/21) 3 (7/4) 1 3 (7/15) Savage Bridge/Canyon 5/24 5!24 4 (5/24) 4 (7!3) 0 0 (7/13) Sanctuary Narmws 5!25 5!25 5 (5/25) 4 (716) 1 4 (7/6) Sanctuary Campground 5126 5/19 5 (5!28) 5 (7/5) 0 5 (7/5); banded 'runt' 7/13 Teklanika 5!26 5126 5 (5/26) 5 (711) 0 5 (717) Upper Igloo/Tattler 6!20 6/20 -- 4 (6/27) 1 4 (7/5) Lower East Fork 5/28 5/28 --- 3 (7/2) 1 3 (7/10) Upper East Fork 7/11 7111 --- 3 (7/2) 2c 3 (7/10) Porcupine 5126 7/12 -- - 1 4 (7/14) Toklat 5!28 5!28 5 (5!28) 5 0 5 (7/12) Grassy Pass/Thorofare 6/18 6!28 -- 2+(6/28) 1 0 (failed after 7/12) Delta Abba 7/8 -- -- 0 4 (7/12) W. L Water Tank 711 7/8 --- 3 (7/17) 1 3 (7/17) W. L Ranger Station 6/12 6/12 5 (6/12) 5 (6!28) 0 0 (7/8) failed avian predator One nestling hatching on this date. b Nest tree could not be climbed; status could not be determined. c Only one egg was present when collected during banding.
"- ~ NORTH e Active nest Figure 1. 1989 merlin breeding locations, Denali National Park, Alaska.
1989 PROGRESS REPORT 5 We attempted to capture adults at 15 nest sites, and captured 25 or 83 percent of the 30 adults (Table 2). Male merlins at Carlo Creek, Savage Bridge, Sanctuary Narrows and Upper East Fork were not captured. Despite hours of trapping effort at each site, adult males were not present when we trapped at the Sanctuary Narrows and Upper East Fork nest sites. Therefore, these birds had no opportunity to be captured. One adult female was not captured. Table 2. Adult merlins captured in 1989. LOCATION DATE SEX FWS BAND COLOR BAND Carlo Creek M not captured 6130 F 614-72153 Red-090 Permafrost 7/13 M. 1373-87086 Red-145 7/18 F 614-72197 Red-160 Upper Upper Savage 7/4 M 1333-92950 Blue-038* 7/4 F 614-72156 Red-094 Lower Upper Savage 7/4 M 1373-87066 Red-093 7/4 F 614-72155 Red-092 Savage Bridge M not captured Red# 713 F 614-72154 Red-091 Sanctuary Narrows M not captured 7/6 F 614-72106 Red-070* Sanctuary Campground 7/13 M 1373-87085 Red-144 7/5 F 614-72163 Red-104 Teklanika 1n M 1373-87073 Red-118 1n F 614-72171 Red-113 Upper Iglootrattler 7116 M 1373-87058 Red-048* 7/5 F 614-72160 Red-100 Lower East Fork 7/10 M 1333-92947 Red-061* F not captured Red# Upper East Fork M not captured 7/10 F 614-72182 Red-131 Porcupine 7/14 M 1333-92943 Blue-031* 7/14 F 614-47382 Red-055* Toklat 7/12 M 1373-87080 Red-132 7/12 F 614-72183 Red-133
1989 PROGRESS REPORT 6 Grassy Pass/fhorofare nest failed; no adults trapped Delta Abba 7/8 M 1373-87074 Red-120 7/8 F 614-72176 Red-119 W. L. Water Tank 7/17 M 1373-87091 Red-159 7/17 F 614-72194 Red-155 W. L. Ranger Station nest failed; no adults trapped F not captured Red# M not observed All red-banded adults have a FWS band on the left leg and a color band on the right leg. Blue-banded adults were first banded as nestlings and have the color band on the right leg and a FWS band on the left. "' Merlins banded in previous years. # Merlins that were not captured but were observed to have a red band on the right leg indicating that they were banded as adults in a previous year. A total of 52 nestlings were banded from 4-17 July (Table 3). Table 3. Merlin nestlings banded in Denali National Park and Preserve, 1989. LOCATION DATE SEX FWS BAND COLOR BAND carlo Creek 7/9 M 1373-87075 Red-121 M 1373-87076 Red-122 F 614-72177 Red-123 M 1373-87077 Red-124 Permafrost nest could not be climbed; checked >3 times but status unknown. Upper Upper Savage 7/4 F 614-72157 Red-095 M 1373-87067 Red-096 F 614-72158 Red-097 M 1373-87068 Red-098 F 614-72158 Red-099 Lower Upper Savage 7/15 F 614-72192 Red-152 F 614-72193 Red-153 M 1373-87089 Rcd-154
1989 PROGRESS REPORT 7 Savage Bridge nest failed with nestlings Sanctuary Narrows 7/6 F 614-72168 Red-109 F 614-72169 Red-110 M 1373-87071 Red-111 F 614-72170 Red-112 Sanctuary campground 1!5 F 614-72164 Red-105 F 614-72165 Red-106 F 614-72166 Red-107 F 614-72167 Red-108 7/13 F 614-72189 Red-143 Teklanika 1n F 614-72172 Red-114 F 614-72173 Red-115 M 1373-87072 Red-116 F 614-72174 Red-117 F 614-72175 Red-148 Upper Iglootrattier 7/5 F 614-72161 Red-149 M 1373-87069 Red-101 M 1373-87070 Red-102 F 614-72162 Red-103 Lower East Fork 7/10 M 1373-87078 Red-125 F 614-72178 Red-126 F 614-72179 Red-127 Upper East Fork 7/10 F 614-72180 Red-128 M 1373-87079 Red-129 F 614-72181 Red-130 Porcupine 7/14 M 1373-87087 Red-146 F 614-72190 Red-147 F 614-72191 Red-150 M 1373-87088 Red-151 Toklat 7/12 M 1373-87081 Red-134 F 614-72184 Red-135 M 1373-87082 Red-136 F 614-72185 Red-137 M 1373-87083 Red-138 Grassy Pass{fhorofare nest failed; no nestlings banded Delta Abba 7/12 F 614-72186 Red-139 F 614-72187 Red-140 F 614-72188 Red-141 M 1373-87084 Red-142 W. L. Water Tank 7!17 F 614-72195 Red-156
. - -- 1989 PROGRESS REPORT 8 F M 614-72196 1373-87090 Red-157 Red-158 W. L. Ranger Station nest failed with young about 14 days old; no young banded * One addled egg was collected from each of these nests. All color bands were placed on the left leg and FWS bands were placed on the right leg. Nest Sites DISCUSSION We were able to find as many nest sites as in 1988, despite a more limited search effort. Education and enthusiasm by Park staff proved a valuable asset in finding nest sites. Along with the support of Park Service staff and volunteers, we were able to obtain enough information on nest sites to continue the monitoring program. In addition, most historic sites were checked to determine activity. The sites at Carlo Creek and the entrance to the Upper Savage Canyon represent new nesting areas at the eastern end of the Park. No merlin nests were found at the Checkstation or Hogan Creek, where nests have been found in previous years. The Hogan Creek nesting area has now been vacant for two consecutive years after being occupied for four consecutive years. New ground nesting areas were found along the Thorofare River near Grassy Pass, and also near the Wonder Lake Campground Water Tank. This year, we documented one of the few instances of reuse of a n~st tree in a subsequent year. The nest tree at Lower East Fork was the same one used as in 1987. The male at this site was the same as in 1987. The female may also have been the same, as she was banded, but she could not be captured. As the. number of known nesting areas continues to increase, our ability to spend sufficient time at each site becomes more difficult. Nevertheless, some patterns are becoming apparent. We now know that even though the turnover rates of adults at a given site is high, most sites remain occupied over a number of years. For example, areas such as Sanctuary Campground, Igloo Canyon, Porcupine, and Toklat have been occupied by merlins for at least five consecutive years. This clearly indicates that the specific nesting area is important to these falcons. These nesting areas, some of which are near roads or in campgrounds should be maintained as naturally as possible. All nesting areas that have been found east of the Toklat River are in spruce stands. The spruce stands that are regularly occupied by merlins invariably contain old blackbilled magpie (Pica pica) nests. In addition, merlins probably require a constant supply
1989 PROGRESS REPOR1 9 of new magpie nests from which they can select a nest site because merlins seldom reuse a nest. As such, nesting merlin populations in the eastern portion of our study area may be limited by the distribution of magpie nests. Spruce stands are less common west of the Toklat River along the road corridor and magpies do not nest in areas such as around Wonder Lake. Magpies are seldom encountered in the vicinity of Wonder Lake (P. and G. Pederson, pers. comm.). Mertins nest on the ground under shrubs on south-facing slopes in these areas. A helicopter flight on 29 May, over the Muldrow Glacier- Wonder Lake area confirmed the thought that south facing slopes are snow-free and vegetation leaf-out occurs earlier. on these slopes. This provides earlier nesting opportunities with adequate cover than sites with less favorable exposures. In 1989, we began collecting information on the types of magpie nests used as a nest substrate (Table 4). Nests built by magpies contain a stick dome over the top along with a mud-filled nest cup. As the nests deteriorate over the years the mud cup and dome may be lost. Most of the magpie nests used by merlins contained both a mud cup and a dome. Even if the nests did not have a dome overhead, they were usually against the trunk of the spruce tree and concealed from above by branches. Therefore, we conclude that concealment of the nest itself may be important to merlins, coupled with adequate perch trees and sufficient open-flight access around the nest tree. Table 4. Attributes of merlin nest sites in Denali National Park and Preserve, 1989. Name/Location Substrate Height a DBH b mud cup I dome Carlo Creek live spruce/magpie 7.2 33 mud cup + dome Permafrost live spruce/witch brm 15.8 39 Upper Upper Savage live spruce/magpie 6.9 42 mud cup I no dome Lower Upper Savage live spruce/magpie 9.5 49 mud cup +dome Savage Bridge dead spruce/magpie 3.8 27 mud cup + 1/4 dome Sanctuary Narrows live spruce/magpie 5.3 27 mud cup +dome Sanctuary Campground live spruce/magpie 7.5 35 mud cup + dome Teklanika live spruce/magpie 4.5 26 mud cup I no dome Upper Igloo/Tattler willow/magpie c 3.8 16 mud cup + dome Lower East Fork live spruce/magpie 7.8 25 not recorded Upper East Fork live spruce/magpie 2.0 25 mud cup + dome Porcupine live spruce/magpie 3.3 24 not recorded Toklat live spruce/magpie 6.2 30 not recorded Grassy Pass(Thorofare ground Delta Abba ground W. L. Water Tank ground W. L. Ranger Station ground a Nest height in meters b Diameter breast height in centimeters c Nest tree feltleaf willow (Salix alaxensis)
1989 PROGRESS REPORT 10 This was the first year that we located a pair of merlins using a black-billed magpie nest located in a willow. In this instance, the nest was in an exposed and highly visible location in contrast to amy magpie nests in willows that are well-concealed. The male at this nest site used nest sites located in live spruce trees in the previous two years. Population Ecology of Adults High-quality data continues to be acquired by capturing as many adults as possible at nest sites. Most adults continue to be easy to capture with our non-evasive procedure. This was the first year that we have not been able to capture all adult females. This exception was at the Lower East Fork, where a previously banded adult female would not become aggressive towards the owl lure. This female was very aggressive and she repeatedly struck the climber during banding, yet she ignored the owl, suggesting a learned behavior. Males proved to be more difficult to capture partly because they were less aggressive, but mainly because they were not in attendance or they perched too far from the nest tree to see the owl. Some marked birds were not captured (Table 5). For example, a marked adult female merlin was observed at the ground nest behind the Wonder Lake Ranger Station, but this nest failed prior to our trapping attempt. Six of the adults captured this year were previously marked (Table 5). Four were marked as adults and two were marked as nestlings. Of 28 adults captured in 1988, we encountered only two or 7% of them in 1989. Although most nest sites are occupied in consecutive years, the rate of return for adults is very low. In 1988 and 1989, we captured or observed all adults at nine nesting areas that produced young in both years. At four of these nine sites complete turnover occurred whereby a different pair occupied the site in two consecutive years. Complete turnover of pairs occurred at the Upper Savage, Sanctuary Campground, Porcupine, and Toklat sites. Nesting areas such as Sanctuary Campground have been occupied for three consecutive years by different pairs. This turnover rate is surprisingly high; most adult birds of prey exhibit low mortality and high philopatry once a breeding attempt has been made at a site. In 1988, two male nestlings banded in 1986 were captured as breeding adults at locations away from their natal nest sites. Neither of these birds were encountered in 1989. For example, at the Upper Upper Savage and Lower Upper Savage sites an unmarked male were present in 1989, even though a two-year old male nested at this site in 1988. At the Upper East Fork site, the nest site was found late in the season and the male was never seen. Two males banded as nestlings in 1987 were captured in 1989. Interestingly, one of the males was banded as a nestling at Toklat in 1987 was breeding at Porcupine. In 1989, he was mated with his mother, who had shifted her nesting area to Porcupine.
1989 PROGRESS REPORT 11 The Delta Abba ground-nesting area was active in both 1987 and 1989. The actual nest sites were only about 100m apart between years. Despite the fact that this site was occupied by a different pair, they used the same perches and plucking locations as the previous pair that we monitored. This was the first year that we captured an immature breeding falcon. A one-year old male captured at the Wonder Lake Water Tank nest site was paired with an adult female at least two years of age. One merlin was captured at the commencement of its annual southward migration on 24 September 1989. Carol Mcintyre captured an adult male merlin while conducting banding studies at Dry Lake, near Delta, Alaska. This individual was banded as a nestling on 16 July 1986 on the East Fork River approximately lkm downstream from the bridge. Table 5. Resights and recaptures of banded merlins, 1989. RE-SIGHT/CAPTURE BANDING YEAR AGE AT SEX LOCATION LOCATION BANDED BANDING Savage Bridge unknown Adult Male Upper Upper Savage East Fork I 1987 Nestling Male Sanctuary Narrows Sanctuary Narrows 1988 Adult Female Igloo/Tattler lgloo/u pper Igloo 1987, 1988 a Adult Male Lower East Fork East Fork II 1987 Adult Male Lower East Fork unknown Adult Female Porcupine Toklat 1987 Adult Female Porcupine Toklat 1987 Nestling Male Toklat b unknown 1988 Nestling Male W.L. Ranger Station unknown Adult Female a This male was first captured in 1987 and recaptured in 1988. b This immature male merlin was banded "yellow-right" and was present at the nest site for part of the season. Productivity Mean clutch size in 1989 ( 4.8, n = 9, SD = 0.44) was within the range from previous years. Fifty-two nestlings were banded in 1989, which is fewer than in 1988. Productivity was also lower than in 1988, with three complete nest failures and eight addled eggs, resulting in five young reaching bandable age at only four nests (Table 1). The number of young banded per pair in 1989 (3.3, n = 16, SD = 1. 11) was lower than in 1988, but is within the range found for the previous six years (Table 6).
1989 PROGRESS REPORT 12 Table 6. Productivity of merlin nests in central Alaska, 1983-1989, based on the number of young reaching banding age, for all nests where the outcome was known. YEAR 1983 1984 1985 1986 1987 a 1988 1989 PAIRS FOUND 7 10 10 10 14 16 17 YOUNG BANDED I PAIR 3.3 3.8 2.8 3.6 2.8 4.1 3.3 (n=16) a One egg was removed from each nest in 1987. Environmental Contaminants Three addled eggs were collected in 1988 and analyzed during the past year. The results of the analyses are shown in Table 7. Table 7. Contaminants found in 3 addled merlin eggs collected in 1988 in Denali National Park and Preserve, Alaska (parts per million, uncorrected wet weight). SAMPLE SAMPLE SAMPLE COMPOUND ME-88-01 ME-88-02 ME-88-03 HCB 0.03 0.02 0.02 Oxychlordane 0.14 0.13 0.12 Heptachlor Epoxide 0.10 0.08 0.09 Nonachlor 0.13 0.06 0.03 PCB (Total) 1.3 2.3 2.5 DOE 9.5 6.1 7.0 DOD 0.14 ND 0.09 DDT ND ND 0.03 Dieldrin 0.25 0.07 0.05 Mirex 0.05 0.43 0.21 Sample weight (gr) 15.7 17.2 15.5 Moisture (%) 84.4 83.6 79.7 Lipid(%) 4.8 6.2 7.6 ND - not detected
.. 1989 PROGRESS REPORT 12 Table 6. Productivity of merlin nests in central Alaska, 1983-1989, based on the number of young reaching banding age, for all nests where the outcome was known. YEAR 1983 1984 1985 1986 1987 1988 1989 PAIRS FOUND 7 10 10 10 14 16 17 YOUNG BANDED I PAIR 3.3 3.8 2.8 3.6 2.8 4.1 3.3 (n=16) a One egg was removed from each nest in 1987. Environmental Contaminants Three addled eggs were collected in 1988 and analyzed during the past year. The results of the analyses are shown in Table 7. Table 7. Contaminants found in 3 addled merlin eggs collected in 1988 in Denali National Park and Preserve, Alaska (parts per million, uncorrected wet weight). SAMPLE SAMPLE SAMPLE COMPOUND ME-88-01 ME-88-02 ME-88-03 HCB 0.03 0.02 0.02 Oxychlordane 0.14 0.13 0.12 Heptachlor Epoxide 0.10 0.08 0.09 Nonachlor 0.13 0.06 0.03 PCB (Total) 1.3 2.3 2.5 DDE 9.5 6.1 7.0 DDD 0.14 ND 0.09 DDT ND ND 0.03 Dieldrin 0.25 0.07 0.05 Mirex 0.05 0.43 0.21 Mercury 0.52 0.42 0.26 Sample weight (gr) 15.7 17.2 15.5 Moisture (%) 84.4 83.6 79.7 Lipid(%) 4.8 6.2 7.6 ND - not detected
1989 PROGRESS REPORT 13 These concentrations are within the ranges observed in past years. The concentration of DDE in the three samples is high enough to cause shell thinning, but not enough to cause the complete failure of the clutch of contaminated eggs. The occurrence of DDD and DDT in some samples suggest that exposure was fairly recent and, most likely, within the area where the chemicals were applied. Otherwise, only the stable breakdown product DDE would have been observed. ARLIS Alaska Resources Library & Information Services Anr horarlp Alnska