The bald eagle has been a symbol of freedom and power in American culture, representing the resilience and strength of our nation. However, despite their population recovery in recent decades, these majestic birds are facing new challenges present-day, due to the impacts of climate change. Upstate New York, home to a significant bald eagle population, has experienced notable changes in its climate patterns, with rising temperatures and shifting precipitation patterns altering the landscape of the region. The effects of climate change have created numerous challenges for the bald eagle population, including a decrease in available food source, changes in migration patterns, and concentrations of mercury in their habitat. The impact of climate change on bald eagles is a serious issue, as these birds play a vital role in the ecosystem of the region, and their decline could have implications for the entire food chain.
Range and Habitat
Bald eagles are North American birds. Their range extends from the Mexican border across the United States and into Canada (National Wildlife Federation). Throughout New York State, they breed in areas with large bodies of water that support high fish populations (New York Natural Heritage Program). They are known to perch on branches of either deciduous or coniferous trees, usually outside areas of human activity (New York Natural Heritage Program). Tall pine, spruce, fir cottonwood, oak, poplar or beech trees near water are where large, heavy nests are built (New York Natural Heritage Program).
The Upstate New York region is exposed to various hazards directly related to climate change (Evers et al. 2020). Due to global warming, terrestrial and aquatic species are migrating into new regions, causing habitat changes and the reshuffling of communities (Wu et al. 2023). The bald eagle’s main food source: freshwater fish, are shifting in a poleward and upward direction (IPCC, 2022). The shortage of their primary food source may result in bald eagles having no choice but to seek alternative sources of nutrition which may not provide adequate nutrition or energy (Desorbo et al. 2020).
Global lake summer surface temperature has warmed by 0.34°C per decade on average (Wu et al. 2023). Freshwater fish communities that have limited dispersal available, such as lakes, experience at least half of their geographic range being threatened by projected climate extremes (Barbossa et al. 2021).
Freshwater fish species are sensitive to thermal changes such as:
- mortality rates
- reproductive processes
As a result, breeding populations cannot establish in regions beyond their limits, thus suggesting severe implications for the future of freshwater fish in North America (Wu et al. 2023). Rising temperatures can lead to the distribution and abundance of freshwater fish populations, further highlighting the challenges faced by bald eagles in finding an adequate food source (Desorbo et al. 2020).
Mercury (Hg) pollution continues to be a prominent environmental problem in New York State that adversely affects the health of ecosystems at local, regional, and global scales (Evers, et al. 2020). In different regions of New York State, freshwater fish species are known to contain concentrations of mercury (Desorbo et al. 2020). The Adirondack and Catskills are two areas of New York State where mercury concentrations exceed the human and ecological risk thresholds (Evers et al. 2020).
According to the sixth assessment of the IPCC, climate change is responsible for changes in runoff and rainfall patterns as well as the frequency of extreme weather events to increase in different regions such as:
Extreme weather events impact the prevailing west to east wind patterns which facilitate the short and long distance of airborne pollutants, such as mercury, across Upstate New York (Desorbo et al. 2020). The Adirondacks contain sportfish with mercury concentrations due to acid deposition- precipitation with acidic components in the region (Razavi et al. 2020).
Streams and rivers in forested watersheds are among the most mercury sensitive habitats identified in New York State (Evers et al. 2020). In a statewide assessment of mercury concentrations in sportfish, the New York State Department of Environmental Conservation (NYSDEC) found that mercury concentrations in the fish from lakes in the Adirondack and Catskill preserves were higher than freshwater areas from other regions in New York State (Desorbo et al. 2020).
Bald eagles foraging in the Catskills, Adirondacks, and large rivers in New York are at the greatest risk of exposure to mercury concentrations (Desorbo et al. 2020). Regional and elevational factors also influence mercury exposure in bald eagles, with those in the Delaware-Catskill region and higher elevations having a greater exposure (Desorbo et al. 2020). Samples of nestling bald eagle individuals contained lower concentrations of mercury than those located inland on freshwater rivers and reservoirs (Kramar et al. 2019).
Climate change is altering the energy requirements and food availability for bald eagles, which have a similar phenological shift with chum salmon (Rubenstein et al. 2018). Changes in the flow of rivers and temperatures due to climate change affect the abundance and accessibility of salmon, a primary food source for bald eagles (Harvey et al. 2012)
Extreme weather events are also affecting the local abundance of bald eagles (Desorbo et al. 2020). The migration patterns of bald eagles are also changing, with a decreased distance between winter and breeding centers of abundance (COA) due to northward winter shifts in COA and southward shifts in breeding COA (Curley et al. 2020).
Adaptation & Resilience
In order to ensure that these majestic birds can adapt and survive in the face of these challenges, it is important for humans to implement adaptation strategies that can help support their populations. Humans can help reduce the impacts of climate change on bald eagles and ensure that these important species continue to thrive in the region. Such efforts not only benefit the bald eagle, but can also positively impact other species and the overall health of the ecosystems in which they live. By taking action now, we can help ensure that future generations will be able to enjoy the beauty and majesty of the bald eagle in upstate New York.
During the non-breeding periods of the bald eagle’s life cycle, eagles gather in communal roosts which are designated as an area where eagles shelter overnight or in extreme weather conditions repeatedly over the course of a season (Mojica et al. 2022). The US Fish and Wildlife Service (USFWS) and state wildlife agencies are responsible for protecting communal roosting sites, however, it is only effective if the roost is known to agencies (U.S. Fish and Wildlife Service). The location of potential roosting areas are difficult to locate due to their remote locations and primary usage by eagles at night and during extreme weather conditions (Mojica et al. 2020).
Banding eagles and using satellite-tracking data is a potential method for identifying communal roosts for the effort of conserving the bald eagle population in Upstate New York (U.S. Fish and Wildlife Service). However, the bald eagle is not currently listed as a species in risk of a decline (U.S. Fish and Wildlife Service). This creates challenges for the conservation of the bald eagle due to limited funding resources for a species not in risk of decline (Mojica et al. 2020).
Public and Private Land
Private property makes the act of applying endangered policies difficult due to the fact that equitable balance needs to be met between species protection and civil liberties (Watts and Byrd 2022), meaning that private property owners have certain civil liberties that are protected by law, such as the right to use their property for economic purposes. At the same time, endangered policies are designed to regulate land use or protect endangered species to ensure they minimize impacts to the species (Mojica et al. 2020).
A study on the social burden of applying nest management standards for the bald eagle was examined in Chesapeake Bay over a forty year period (1976-2016) (Watts and Byrd 2022). The results found that after the size of the protected land expanded over private property, not only did the bald eagle population average an annual increase of 8.7%, but the private property value on the protected land increased by more than 900 times its original value over the 40 year period (Watts and Byrd 2022). The results from the study demonstrate that the implementation of management standards for the bald eagle can benefit both landowners and conservation initiatives (Watts and Byrd 2022).
The State of New York is 61 percent forested (18.6 million acres) with much of the land being privately owned (Department of Environmental Conservation). The U.S. Fish and Wildlife Service could potentially make efforts to expand areas of protected land for the conservation of the bald eagle. However, successful recovery of imperiled species will depend on maintaining a public-private trust between landowners and conservation efforts (Watts and Byrd 2022).
- Wu, T., Imrit, M. A., Movahedinia, Z., Kong, J., Woolway, R. I., & Sharma, S. (2023). Climate tracking by freshwater fishes suggests that fish diversity in temperate lakes may be increasingly threatened by climate warming. Diversity & Distributions, 29(2), 300–315. https://doi.org/10.1111/ddi.13664
- Curley, S. R., Manne, L. L., & Veit, R. R. (2020). Differential winter and breeding range shifts : Implications for avian migration distances. Diversity and Distributions, 26(4), 415–425.
- Seggos, B., & COLYER-PENDAS, T. (2022). NEW YORK’S ENVIRONMENTAL COMMITMENT - Addressing the Climate Change Threat. New York State Conservationist, 76(4), 5–9.
- Evers, D. C., Sauer, A. K., Burns, D. A., Fisher, N. S., Bertok, D. C., Adams, E. M., Burton, M. E. H., & Driscoll, C. T. (2020). A synthesis of patterns of environmental mercury inputs, exposure and effects in New York State. Ecotoxicology, 29(10), 1565–1589. https://doi.org/10.1007/s10646-020-02291-4
- DeSorbo, C. R., Burgess, N. M., Nye, P. E., Loukmas, J. J., Brant, H. A., Burton, M. E. H., Persico, C. P., & Evers, D. C. (2020). Bald eagle mercury exposure varies with region and site elevation in New York, USA. Ecotoxicology, 29(10), 1862–1876. https://doi.org/10.1007/s10646-019-02153-8
- Razavi, N. R., Halfman, J. D., Cushman, S. F., Massey, T., Beutner, R., Foust, J., Gilman, B., & Cleckner, L. B. (2020). Mercury concentrations in fish and invertebrates of the Finger Lakes in central New York, USA. Ecotoxicology, 29(10), 1673–1685. https://doi.org/10.1007/s10646-019-02132-z
- Kramar, D.E., Carstensen, B., Prisley, S. et al. Mercury concentrations in blood and feathers of nestling Bald Eagles in coastal and inland Virginia. Avian Res 10, 3 (2019). https://doi.org/10.1186/s40657-019-0142-0
- IPCC, 2022: Climate Change 2022: Impacts, Adaptation, and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [H.-O. Pörtner, D.C. Roberts, M. Tignor, E.S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem, B. Rama (eds.)]. Cambridge University Press. Cambridge University Press, Cambridge, UK and New York, NY, USA, 3056 pp., doi:10.1017/9781009325844.
- Harvey, C.J., Moriarty, P.E. and Salathé Jr., E.P. (2012), Modeling climate change impacts on overwintering bald eagles. Ecology and Evolution, 2: 501-514. https://doi.org/10.1002/ece3.204
- Barbarossa, V., Bosmans, J., Wanders, N. et al. Threats of global warming to the world’s freshwater fishes. Nat Commun 12, 1701 (2021). https://doi.org/10.1038/s41467-021-21655-w
- Fownes, J. R., and S. B. Allred, 2019: Testing the Influence of Recent Weather on Perceptions of Personal Experience with Climate Change and Extreme Weather in New York State. Wea. Climate Soc., 11, 143–157, https://doi.org/10.1175/WCAS-D-17-0107.1.
- RUBENSTEIN, M. A.; CHRISTOPHERSEN, R.; RANSOM, J. Trophic implications of a phenological paradigm shift: Bald eagles and salmon in a changing climate. Journal of applied ecology, [s. l.], v. 56, n. 3 p.769–778, p. 769–778, 2019. DOI 10.1111/1365-2664.13286. Disponível em: https://search.ebscohost.com/login.aspx?direct=true&db=agr&AN=IND606316750&site=eds-live&scope=site. Acesso em: 4 abr. 2023.
- U.S. Fish and Wildlife Services, (2006). Bald Eagle Haliaeetus leucocephalus
- Mojica, E. K., Clark, K. E., Smith, L., & Frank, C. (2022). Improving Confidence in Remotely Delineated Bald Eagle Roosts to Trigger State Agency Habitat Protection. Northeastern Naturalist, 29(3), 311–320. https://doi.org/10.1656/045.029.0301
- Watts, B. D., & Byrd, M. A. (2022). Policy and the social burden of bald eagle recovery. Conservation Science and Practice, 4( 9), e12764. https://doi.org/10.1111/csp2.12764
- Forests. Forests - NYS Dept. of Environmental Conservation. (n.d.) https://www.dec.ny.gov/lands/309.html
- New York Natural Heritage Program. 2023. Online Conservation Guide for Haliaeetus leucocephalus. Available from: https://guides.nynhp.org/bald-eagle/