Bald Eagle Nest-Tree Survey and Stewardship Program 2009
Twenty-six Bald eagle nest-trees were identified in a survey of Denman Island in 2009. Denman eagle nest-trees are large and probably greater than 200 years of age. All nests were in Douglas-fir old-growth veteran trees, except for one in a large cottonwood. All but one tree was alive and most trees were in reasonable condition, although 48% had broken tops. The diameter at breast height averaged 1.35m.
The 2009 DCA Bald eagle stewardship program offered nest-tree stewards a package consisting of the recent Hornby Island Eagle book, a wildlife tree sign and record-keeping materials, if they agreed in future years to conduct the minimum of 2 productivity surveys per year and to look after their nest-tree. Nine landowner stewards agreed to participate and 10 adoptive-stewards agreed to monitor the remaining nest-trees.
Monitoring by stewards is particularly important to obtain data from the 27% of nest-trees visible only from private land. Although data from the 2009 survey is insufficient to determine the overall eagle territory productivity for Denman, the nest-tree stewardship program should provide these data in future years.
Bald Eagle Nest-Tree Survey & Stewardship Program 2009
(Report Summary)
The Survey and Stewardship Program was conducted by Jennifer Balke R.P.Bio. ably assisted by volunteer mapping assistants Galen Malthouse and Elizabeth Chapman. Funding for the Survey was provided by DCA and the Wildlife Stewardship program of BC Nature.
Eagle Tree Survey
Twenty-six Bald eagle Haliaeetus leucocephalus nest-trees were identified in a survey of Denman Island in 2009. One of these trees blew down before the completion of this report. Fourteen former nest-trees were also assessed. Nine of these trees were dead, badly damaged or gone, some as a result of the winter hurricane of 2006, when many large Denman trees were lost. Sixty-five percent of the current nest-trees were located since 2002, suggesting that the majority were new, although some nests may have been missed in earlier surveys.
Eagles were seen or heard near 21 of the nests. Although the survey was not conducted within nest-monitoring periods, at least 10 eagle territories were noted. Overall, 8 juvenile eagles were observed fledging from 6 nests. The good condition of 7 other nests suggests that more juveniles may have been produced.
Denman eagle nest-trees are large and probably greater than 200 years of age. All nests were in Douglas-fir Pseudotsuga menziesii old-growth veteran trees, except for one in a large cottonwood Populus balsamifera. All but one tree was alive and most trees were in reasonable condition, although 48% had broken tops. The diameter at breast height (DBH) averaged 1.35m. In 1998, the average DBH of 20 nest-trees measured 1.99m, which suggests that available trees on Denman may be reduced in size.
Most of the nest-trees were within 100m of the ocean (62%); however, 19%, were on the central spine or ridge of Denman, an average 907m from the ocean. Most of the nest-trees were on or near cliffs greater than 10m (55%).
Seventy-seven percent of the Denman Island eagle nest-trees were on private land. Only 23% of nest-trees were in protected old-growth reserves. Five of these were in provincial parks and 1 was in a conservation covenant area held by the Denman Conservancy Association (DCA). One was on vacant Crown land and 8 % were in existing development permit areas (DPA).
The Stewardship Program
Monitoring and stewardship of Denman’s eagle nest-trees serve a key role in sustaining Bald eagle populations. Past monitoring records were incomplete, although more data may be collected from non-resident landowners over time.
The 2009 DCA Bald eagle stewardship program offered nest-tree stewards a package consisting of the recent Hornby Island Eagle book, a wildlife tree sign and record-keeping materials, if they agreed in future years to conduct the minimum of 2 productivity surveys per year and to look after their nest-tree. Nine landowner stewards agreed to participate and 10 adoptive-stewards agreed to monitor the remaining nest-trees.
Monitoring by stewards is particularly important to obtain data from the 27% of nest-trees visible only from private land. Although data from the 2009 survey is insufficient to determine the overall eagle territory productivity for Denman, the nest-tree stewardship program should provide these data in future years.
While provincial legislation exists to protect nest-trees, local land-use regulating bodies may have more success protecting these irreplaceable and threatened nest-trees within their communities. A reward-based incentive program for local protection is encouraged, but the designation of development permit areas for nest-trees is discouraged. The recruitment of future trees is also seen as a crucial component of eagle habitat stewardship. With second-growth trees a maximum of 100 year old, reserves need to be set-aside on Denman to provide future nest-trees 100+ years from now.
Stewardship Issues
Stewardship and monitoring of Bald eagle nest-trees, by private landowners, is essential to the survival and understanding Denman Island Bald Eagle populations. Currently 20 nest-trees are on private land and the well-being of these trees depends on the care given by landowners.
Seventeen of the 20 private nest-trees had no form of protection and of the remaining 9 nest-trees that are in parks, on Crown land or in a covenant, 5 were exposed to considerable public pressures along roads or beaches. Thus, the public’s sensitivity to, and support for the presence and behaviour of eagles is likely to enhance the productivity of eagle nest-trees.
Lastly, the participation of private landowner-stewards in collecting data is extremely useful, especially for the 7 nest-trees, which can only be seen from private land.
Activities near Nest-trees and Sensitivity to Disturbance
Bald eagles vary in their sensitivity to disturbance. Each pair tolerates the activities that they are familiar with, in the vicinity of their selected nest-tree, whether it is the constant drone of highway traffic, the labour-intensive gardening activities of the homeowner, or the passing of cougar and bear in the wilderness.
In general, heightened sensitivity usually arises when the levels or patterns of human activity near the nest-tree change. Thus, there may be increased stress with walkers on the highway, machinery in the home-yard or even distant humans in remote areas.
The most critical period, when disturbance should be avoided, is early in the nesting season, before adults have bonded with their chicks (pers. comm. I. Moul WiTS 2009). Disturbance at this time may have negative effects on nesting success. In general, the best stewardship approach is to avoid new activities and disturbance near the nest-tree during the nesting-period from March to August.
Care of Nest-trees
Living with a Bald eagle nest-tree can be both rewarding and frustrating. One can expect everything from fish or feces dropping on one’s head or possessions, to noisy disturbances at all hours. One also has the breathtaking pleasure of witnessing such majestic animals at relatively close quarters,being part of their lives and in essence soaring with the eagles. Similar to sharing space with any living thing, a harmonious existence requires effort and compromise. The eagles compromise is allowing human presence and human activities to be near the chosen nest-tree. The landowners contribution can be the care of that nest-tree!
Before deciding how to live with an eagle nest, observation of the eagles behaviour is helpful. Seeing which trees the eagles use as perches and where their flight routes are for seeking prey and defending their territory, demonstrates where potential conflict areas are located. Obviously, the eagles world is much more 3-dimensional that ours. After collecting data on what matters to the eagle, a life-sharing plan can be devised so that each party has their space and appropriate buffers.
The nest-tree will benefit from a healthy buffer zone. At least one and a half tree-lengths is recommended as a nest-tree buffer. If possible, this area should be free of vegetation removal, soil compaction, trails, equipment, buildings and other disturbances. The water inflows and drainage within this zone requires protection from changes and contaminants. The less soil and water disturbance that landowners can ensure, the more likely eagles will have a future on Denman Island. Visual barriers, such as other trees and large shrubs help to shield the birds from human activities and thus lessen the disturbance. The birds are particularly sensitive during the nesting season from March to the end of July, and new human activities, near the nest-tree, during this period, should be avoided.
Landowners, who take care of these nest-trees and limit their activities around them, ultimately benefit all of us, so all of us could contribute to eagle nest-tree conservation efforts. Community support for a nest-tree protection program can be generated more successfully through rewards and positive reinforcement. DCA encourages the Islands Trust to consider a reward-based stewardship approach for the conservation of the extremely valuable, irreplaceable and threatened Bald eagle habitat within their jurisdiction.
Nest-tree Recruitment
Recruitment of trees to replace existing nest-trees is also critical. With most nest-trees in the 200+ year age class and most second-growth less than100 years, the need for both protection of existing old-growth trees and encouragement of groups of older second-growth trees is essential.
Legal Nest-tree Protection
Due to their crucial importance and limited availability, Bald eagle nest-trees are protected under Section 34 of the Provincial Wildlife Act.
Landowner Privacy
Landowner privacy has been respected during the collection of the data for this report. While wildlife information, especially where protected by Provincial Legislation, is necessarily the purview of the Provincial agency responsible, there is a role for local community organizations, such as the Denman Conservancy Association (DCA), to mediate the potential disruption to landowner privacy. Thus, the DCA offers levels of landowner-confidentiality through its stewardship program. DCA encourages all eagle enthusiasts to use the DCA as a resource for eagle nest information and to completely respect the privacy of landowners.
