Removal of Alaskan Bald Eagles for Translocation to Other States Michael J. Jacobson U.S Fish and Wildlife Service, Juneau, AK Bald Eagles (Haliaeetus leucocephalus) were first captured and relocated from Alaska in 1981 when the state of New York requested eagles in an effort to re-establish a viable nesting population (Cain and Hodges 1981). As in most of the contiguous 48 states, New York's Bald Eagle populations had declined drastically and by the mid-1970s was reduced to a single unproductive nesting pair (Nye 1982). Suitable habitat remained and prey sources were present to support a growing population of Bald Eagles. An infusion of young birds was needed to become a viable population in the area. Alaska was selected as a reliable donor of young because of its abundance of eagles. Each year from 1981-1990 Southeast Alaska provided young Bald Eagles for translocation to one or more of the lower-48 states (Jacobson 1987). Over 300 eagles had been captured and relocated since 1980. The young eagles were removed from wild nests, transported to lower 48 states, reared in hacking towers (artificial nests on human-made towers) until capable of flight, usually at 11 or 12 weeks of age and then released into the wild. New York received the majority of Alaskan eagles, the remainder have gone to Missouri, Indiana, North Carolina and Tennessee. Study Area The project was designed to remove Bald Eagle nestlings from the same region each year. A study area was established in Southeast Alaska, west and southwest of Juneau along a portion of Lynn Canal and Chatham Strait (Figure 1). The shoreline habitat was composed of old-growth coastal rainforest dominated by Sitka spruce and western hemlock (Cain and Hodges 1981, Cain et al. 1982). The study area was divided into a removal (experimental) area and an adjacent control area where no young were removed (Figure 2). The removal area consisted of 211 km (131 miles) of shoreline and the control area totaled 84 km (52 miles) of shoreline. The entire study area was within the Tongass National Forest. The amount of eagle nesting habitat within the study area remained unchanged throughout the 1981-1990 period. In 1987 an additional 30 eaglets were removed from a location outside of the study area which contained similar habitat. This separate location was south of Juneau on the eastern side of Stephens Passage and Frederick Sound (Figure 1). 288
Methods Aerial surveys of the study area were conducted by helicopter in mid-may to find active nests. Follow-up surveys were flown in July to locate successful nests, determine the number of young, estimate the age of young and evaluate if the nest trees could be safely climbed. Active nests were defined as those with eggs or an adult in incubating position. Successful nests were those that contained one or more young at the time of the survey. The nest activity surveys were conducted from May 12 to May 18 and nest success surveys were flown between July 6 and July 18. Adult eagles were counted in July by fixed-wing aircraft. Two observers participated in each helicopter survey. The pilot also helped with the search for nests and birds. The primary observer (Jacobson) remained the same during all surveys from 1984 through 1990. The survey for active nests in May was conducted during two consecutive days and averaged nine hours of flight time; whereas the July survey was completed in a single day and averaged five hours. Only adult eagles with white head and tail were observed nesting. 289
Bald Eagle capture area, Couverden Islands and the Chilkat Peninsula. Photo by Mike Jacobsen. The usual procedure for capturing eaglets was to shuttle two capture crews of two to three people each to shore by skiff. Nest trees were climbed using climbing spurs, ropes and rappelling equipment. An average of 4 to 6 trees could be climbed daily by two crews depending on the distance between nests, difficulty of climbing and the weather conditions. When a climber reached a nest, an eaglet was placed in a padded nylon bag and carefully lowered to the ground. Young were 6 to 8 weeks of age when removed from nests. Eaglets were then taken by skiff to a larger vessel and placed in standard air kennels. While on the vessel, young were provided a constant supply of fresh fish and the kennels were cleaned daily. All eaglets were leg-banded and treated with anti- 290
ectoparasite powder following collection. Upon returning to Juneau, they were immediately flown to lower-48 states via private charter or commercial airline. Chip Grafe ascends and descends these Bald Eagle nesting trees to remove a young eaglet for relocation to Tennessee. Photos by Mike Jacobson. Results and Discussion A total of 279 eaglets (50% of available young) were removed from the original study area during 1981-1990. Table 1 summarizes the results of all surveys through the 10-year period. Productivity Surveys In the removal area, the number of active nests in May ranged between 36 and 89 with an average of 64 over all years. Successful nests ranged from 22 to 61 with an average of 38. Sixty-three percent of all active nests were successful in producing one or more young. Successful nests averaged 1.44 young, with a range of 1.16 to 1.69. No nest contained more than two young in the removal area during the entire 1981-1990 period. The control area, which contained 40% of the shoreline distance of the removal area, had a range of 15 to 47 active nests, with an average of 32. Successful nests varied between 10 and 33, with an average of 19. Sixty-two percent of all active nests successfully produced one or more young in the control area. Young per successful nest averaged 1.40, with a range of 1.20 to 1.69. Three young were seen in a single nest on only one occasion in the control area. 291
In both the removal and control areas, the years 1988, 1989 and 1990 showed a surge in the number of active and successful nests. Productivity reached a peak in 1989 with 96 young in the removal area and 50 young in the control, compared to an average of 56 and 28 respectively (Figure 3). The old-growth spruce/hemlock forest provided an abundance of Bald Eagle nesting habitat and the density of nests was high in the entire study area. The removal area averaged 0.82 nests per km (1.32 nests per mile) of shoreline, while the control area averaged 1.06 nests per km (1.71 nests per mile) of shoreline. Active and successful nest densities were somewhat higher in the control area. An average of one active nest could be found for every 3.3 km (2.0 mi.) of shoreline in the removal area and every 2.6 km (1.6 mi.) in the control area. An average of one successful nest was found for every 5.5 km (3.4 mi.) in the removal area and 4.4 km (2.7 mi.) in the control. Population Surveys Counts of adult Bald Eagles were conducted by fixed-wing aerial survey during seven years (1982, 1984-1989) in the removal area and six years (1984-1989) in the control area. The density of adult Bald Eagles was nearly identical in both the removal and control areas. The average number of adult eagles observed in the removal area was 217, or 1.03 adults per km (1.66/mi.) of shoreline. In the control area, the average number of observed eagles was 85 adults, or 1.01 per km (1.64/mi.) of shoreline. 292
Hansen and Hodges (1985) reported that many adult Bald Eagles in Southeast Alaska do not breed annually. Based on the seven years of July counts in the removal area, a minimum of 59% of adult Bald Eagles occupied nests and 35% of adults successfully raised young. The six years of census data in the control area showed an average of 75% of adults occupied nests and 45% of adults successfully raised young. The adult population, as counted by aerial survey in July, was highest in 1986 for both removal and control areas, but was variable throughout the study, no doubt due to such factors as weather and attraction to food sources. On warm sunny days eagles often soar on thermals at high elevations, so they can be missed during a low level aerial survey (Jacobson 1987). This also suggests that a single census on one day in July is not adequate to properly quantify the adult eagle population. The number of adult eagles recorded in July decreased after 1986. The reason for the reduction is not fully known but was common to both the removal and control areas. The percentages of active and successful nests and the number of young were highly correlated between the removal and control areas through the 10 year period of the study (Table 1). The proportion of all nests active in both the removal and control areas was identical (36%) and the proportion of all nests that were successful in both the removal and control areas was nearly identical (22% versus 21%). It was impossible to determine the reaction of specific pairs of adult eagles to the removal of their young. Eagles were not individually marked and it was impossible to identify breeding territories occupied by particular pairs from year to year. Rather than attempt to monitor individual eagles, surveys were conducted to monitor the population and reproductive trends. 293
Perhaps when young were taken from a pair of adults, that pair may have been more persistent in nesting the following year. Even if they were less likely to nest the following year, there was apparently an abundance of non-breeding adult eagles ready to "fill in" and become breeders, thus concealing any possible effects of removal of young during the prior year(s). Also, the study area is a relatively small part of an extensive coastal shoreline and forested region that supports a large population of Bald Eagles. Over 12,000 adult Bald Eagles are estimated to occur in Southeast Alaska (Jacobson 1989). This large pool of birds could have buffered the effect of removing young from nesting pairs in the study area because there were so many other eagles from the surrounding region to potentially fill any vacancies. Even though 50% of available young were taken from the removal area during this study, there was no indication of a detrimental affect on the Bald Eagle population. Productivity was not affected by the removal of a major portion of the young during the previous nesting season. Bald Eagle nestlings are placed in animal shipping containers. Photo by Mike Jacobsen. Lower 48 States The ultimate measure of success for this or any Bald Eagle translocation project is the establishment of a self-sustaining wild population in the region where they are released. New York pioneered the hacking of Bald Eagles on a small scale in 1976, then expanded the effort in 1981 with large numbers of eagles from Alaska. Of the 178 Alaska eagles taken to New York, 175 were successfully reared and released by hacking (P. Nye, pers. comm.). New York's interim goal was the establishment of 10 breeding pairs by 1990. 294
This goal was achieved in 1989 and enabled New York to end their hacking project that year. The long range goal is 40 breeding pairs by the year 2000. Some of the eagles released in New York have also successfully nested in adjacent states. Missouri began a Bald Eagle hacking project in 1981 with a small number of birds from Wisconsin (J. Wilson, pers. comm.). At that time Missouri had no nesting Bald Eagles and had not had an active nest since 1960. However, hacked Bald Eagles became established and augmented naturally occurring eagles in Missouri. In 1990 there were 4 successful nests that produced a total of 8 young. The first of 30 Alaska eagles were translocated to Missouri in 1986. A total of 29 Bald Eagles were reintroduced into North Carolina from 1983 to 1988. Of these, nine young were received from Alaska (in 1987), but only one survived after being released. Most of the Alaskan eagles died from avian malaria (T. Henson pers. comm.). When its reintroduction program began in 1983, North Carolina had no known nesting Bald Eagles. The last documented nesting pair failed to produce young in 1971. Even though eagles from Alaska did not fare well in North Carolina, some of the eagles reintroduced from other areas have survived. As of 1990, a total of 31 young had been produced from wild nests in North Carolina (7 young from 3 nests in 1990) and the number of breeding pairs continued to rise. Bald Eagle nestlings are placed in bags and slowly lowered to the ground. Photo by Mike Jacobsen. Indiana began reintroducing Bald Eagles in 1985, with the goal of establishing at least 5 breeding pairs in the state by the year 2000 (Castrale 1990). The final year of planned releases took place in 1989. A total of 73 eagles were released (36 from Alaska). In 1989 295
Indiana had its first nesting pair of eagles in over 90 years. Tennessee also reintroduced Bald Eagles and received 64 young eagles from Alaska during 1986-1990. Prior to 1983, a successful nestling pair of Bald Eagles had not been sighted in Tennessee since 1961. In 1990, 8 nests successfully produced 17 young. The goal was to have about 25 successful nests by the year 2000. Kentucky also benefited from Tennessee's hacking program as some of the eagles moved into Kentucky to nest (R. Hatcher, pers. comm.). The Bald Eagle is making a strong comeback in much of the contiguous United States and its numbers will likely continue to increase, due in part to translocation projects. Reintroduced young have survived and established themselves. They are reaching maturity and breeding successfully. The translocation of Alaskan Bald Eagles proved to be a successful method to reestablish viable breeding populations in other parts of the country. Editor's Note: The translocation of Bald Eagles; from Alaska ended in 1993. California was added to the group of states that received Alaskan eagles. From 1981 to 1993 a total of 394 Bald Eagle young were removed from nests in Alaska for translocation to lower 48 states (the study area at Lynn Canal and Chatham Strait provided 357 of the total). Bald Eagle numbers have greatly increased across the contiguous United States. In 1995 the Bald Eagle was reclassified under the Endangered Species Act from endangered to threatened in the lower 48 states. Hopefully, it will never again be necessary to translocate Bald Eagles from Alaska. Literature Cited Cain, S. L. and J. I. Hodges. 1981. Involvement of the U.S. Fish and Wildlife Service in the New York state Bald Eagle reintroduction project. Unpubl. rep., U.S. Fish Wildl. Serv., Juneau, Alas. 8pp. Cain, S. L., J. I. Hodges and P. Nye. 1982. The capture of Alaska Bald Eagles for translocation to New York and related productivity studies 1982. Unpubl. rep., U.S. Fish Wildl. Serv., Juneau, Alas. 6pp. Castrale, J. S. 1990. Bald Eagle restoration efforts in Indiana, 1989-1990. Indiana Dept. Nat. Resourc., Div. Fish Wildl., Mitchell. 6pp. Hansen, A. J. and J. I. Hodges. 1985. High rates of non-breeding adult Bald Eagles in Southeastern Alaska. J. Wildl. Manage. 49(2):454-458. Jacobson, M. J. 1989. A survey of the adult Bald Eagle population in Southeast Alaska. Unpubl. rep., U.S. Fish Wildl. Serv., Juneau, Alas. 6pp. Nye, P. E. Status, research and management of Bald Eagle nesting territories in New York. Federal Aid to Endangered Species New York Project E-1-6. Performance Rep. 11-2. Personal Communication Hatcher, R. 1991. Tennessee Wildl. Resourc. Agency, Henson, T. 1991. North Carolina Wildl. Resourc. Comm., Nye, P. 1990. New York State Dept. Environ. Conserv., Wilson, J. 1991. Missouri Dept. Conserv., Jefferson City. 296