BRI biologists established a raptor research station on Block Island during the autumn seasons of 2012 and 2013 with the help of The Nature Conservancy. From that station, we captured, banded, and collected blood and feather samples from migrating raptors.

In the first two seasons, we captured 263 individuals of 8 different raptor species; the most commonly observed and captured being Merlins and Peregrine Falcons. We encountered Northern Harriers, Cooper’s Hawks, and Sharp-shinned Hawks with moderate frequency, and rarely captured American Kestrels, Red-tailed Hawks, and Northern Goshawks.

The suite of species we encountered on Block Island was expected because their body design (wing shape and bird weight) influences their willingness and ability to embark upon large open water journeys to offshore islands.

Scientists have been using raptors as barometers of ecosystem health for decades. Their distribution and abundance are closely tied to the food webs that support them. Raptors often sit at or near the top of those food webs and tend to accumulate contaminants from prey; their tissues (blood, feather, or eggs) are regularly used to monitor contaminants in our environment.

Several raptors, such as Bald Eagles, Peregrine Falcons, and others, were nearly extirpated due to contaminant exposure and other factors. As a result, these species’ natural histories are closely intertwined with some of the most important landmark environmental policies in U.S. history, such as the banning of DDT and the Endangered Species Act.

Some raptors such as Peregrine Falcons have been observed over a thousand miles offshore, but such movements were poorly documented until recently. Recent advances in animal tracking technology have allowed researchers to collect information on the migratory patterns of birds at a scale that was previously unthinkable: globally.

By fitting birds with small backpack-mounted tracking units, we can study their daily and annual movements, flight altitude, and other information. This information is critical in providing background information critical to numerous management and conservation issues, such as evaluating the potential conflicts between migrant raptors and offshore wind energy facilities.

Over the 2010 through 2023 season at Block Island, our researchers have fitted satellite telemetry transmitters on Peregrine Falcons and Merlins (below).

• Preliminary patterns suggest that males captured during our stud may use more southerly wintering areas than females, including the Bahamas, Central and South America (Map 1).
• The majority of spring migrating Peregrine Falcons traveled through the central U.S., west of the Great Lakes (Map 2).

BRI researchers have been measuring mercury exposure and impacts in birds for more than two decades. Mercury (Hg), a naturally occurring element, is released into the environment through a wide variety of industrial processes, such as coal burning and gold mining. Mercury is persistent and quickly accumulates in organisms, magnifying up food webs, placing top predators at risk. Species have different sensitivity levels to mercury exposure, and mercury’s potential effects on some populations remain poorly understood.

Since the fall of 2021, an outbreak of avian influenza, or “bird flu” has increased dramatically in numerous organisms across broad geographic regions. The severity of disease varies in accordance with the species infected, and the virus strain. Infection with Low Pathogenic Avian Influenza (LPAI) strains typically do not elicit symptoms, while the Highly Pathogenic Avian Influenza (HPAI) has a high mortality rate in some bird species, particularly in domestic poultry, waterfowl, and some raptors.

During the fall seasons of 2022 and 2023, we collected samples from migrant raptors to evaluate the prevalence of avian influenza infection in raptor migrants using the Atlantic flyway. None of the 162 fall migrant raptors during 2022 or 2023 seasons produced a positive result for avian influenza.

The Block Island Raptor Research Station is the northernmost and furthest offshore on the Atlantic coast. These characteristics, coupled with the unique migration patterns of raptors there, make this island valuable to the scientific community for its research and monitoring potential.

The station has enabled BRI researchers to gather one of the most comprehensive datasets on migration routes used by Peregrine Falcons along the Atlantic Flyway. Information on migration patterns helps us better understand the migratory ecology of species and has a wide variety of conservation and management applications, such as linking breeding and wintering populations and identifying important stopover habitats.

Continued wildlife disease monitoring, specifically for avian influenza, is important in both migratory and non-migratory raptors given their high susceptibility to infection, limited overall monitoring in “healthy” wild populations, and the role they play in the geographic patterns of disease transmission. Additionally, future sampling and exploration of PFAS and Hg analyses will contribute to our understanding of potential contaminants and their impacts to wildlife.

We are building our sample size of satellite-tracked Peregrine Falcons and further expanding tracking efforts to focus on other species such as Merlins and Northern Harriers, both of which are poorly studied. Sustaining operation of this research station will enable further development of other studies with additional partners to maximize overall conservation benefits of this work.

Download our Science Communications Brochure:
Desorbo, C. R. 2014. Raptor Research on Block Island. Biodiversity Research Institute. Portland, Maine. Science Communications Series BRI 2013-23. 6 pp.