Blog #350 Ospreys as a Sentinel Species

Orpheus flying over Salt Point, courtesy of Karel and Cindy Sedlacek. 

Canaries have been used for centuries as sentinels or early warnings to the exposure of  toxic buildup of carbon monoxide in coal mines; the birds are more sensitive to the  odorless gas than humans. Osprey, as top or apex predators in many aquatic  environments, are the modern sentinels or canaries for shoreline communities. Ospreys  make excellent environmental sentinels as they readily habituate to living among  humans, especially in industrial and municipal sites where water contamination may be  severe 

Ospreys are long-lived (25 years), breed globally, and have strong nest fidelity and a restricted home range, returning annually to the same or a nearby nest. Their aquatic  diet is >99+% fish, and they hunt and feed within a few miles of their nests. Fish species  captured can be identified based on prey remains at nest sites, direct observations, and nest cameras. 

Osprey nests are highly visible and easily located, and nesting pairs will tolerate short term nest disturbances for banding and blood tests. Ospreys are sensitive to many  contaminants, especially lipophilic contaminants, which accumulate over time in the  bird’s fat. These Osprey traits, together with a well-known biology and natural history,

Fledgling Olan eating a fish in a cottonwood, courtesy of Karel and Cindy Sedlacek. 

have been instrumental in understanding their population distribution, abundance, and  changes over time; the effects of various contaminants on their reproductive success;  and how contaminants in fish contribute to their biomagnification and concentration in  

eggs. These features contribute to making Ospreys a powerful watch dog in the local  environment. 

Thousands of chemical compounds have been introduced into our environment since  the early 1900s, polluting the air, soil, water, and biota, and many are still with us. Once  hailed as a miracle, DDT (dichlorodiphenyl-trichloroethane) saved crops and combated  malaria across the world. Although banned in the U.S. in 1972, DDT is so stable that it  continues to poison the environment and be a part of the food chain.  

When DDT accumulates in the food chain’s apex bird, this calcium blocker weakens egg shells causing mass breakage. It took the near extinction of key prized sentinels—

One of thousands of disintegrating barrels of DDT found off the coast of  

Santa Catalina Islandin California, courtesy of Scripps Institution of Oceanography. 

Ospreys, bald eagles, and peregrine falcons—to make Americans realize how toxic  DDT was in the environment. 

The problem continues: significant amounts of DDT-related compounds are still leaking  from old metal drums illegally dumped off Catalina, an island off the California coast.  How do we know there is a problem? Because the sentinel species are sick. DDT is bio accumulating in Southern California dolphins and is causing an aggressive cancer in  sea lions. 

Ospreys are sensitive other polyhalogenated aromatic hydrocarbons. These include  organochlorine pesticides [OCs], polychlorinated biphenyls [PCBs], dioxins [PCDDs],  polychlorinated dibenzofurans [PCDFs], brominated flame retardants [PBDEs],  perfluorooctane sulfonates [PFOSs]), 2,3,7,8-tetrachlorodibenzo-p-dioxin [TCDD] and  p,p'-dichlorodiphenylethylene (DDE). These lipophilic toxic compounds resist  environmental or metabolic breakdown. Long-lived piscivores and other top predators  atop aquatic food webs are also at greatest risk for elevated methylmercury (MeHg)  exposure, accumulation and toxicity. These compounds bioaccumulate and bio-magnify  in animal fat tissues, traveling up the food web. Sound familiar? 

The physiological effects of harmful chemical contaminants on living organisms  depends on their bioavailability and toxicity, the concentration, and the duration of  exposure to the pollutant. Humans and Ospreys use the same environment and have  similar biochemical, molecular, and cellular responses to toxic agents, making it easy to  draw direct comparisons. Ospreys’ breeding in the small towns lining Cayuga’s  lakeshore signifies a healthy lake environment and a human community that cares and  protects it’s water quality.

Eyes to the sky!  

Candace  

Candace E. Cornell  

Friends of Salt Point  

Lansing, NY  

cec222@gmail.com 

EYES ONOSPREYS 

WATCH! 

Salt Point Osprey Nest Cam 2021 

READ! 

On Osprey Time—A Blog on the Ospreys of Salt Point 

VISIT! 

Cayuga Lake Osprey Trail

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