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 fall seasons of 2012-2015, we fit satellite tracking units to thirteen female and nine male Peregrine Falcons. We were interested in determining where they overwintered, where they came from, which migratory routes and habitats they used throughout their migration, and the extent to which they used proposed offshore wind energy areas in the Mid-Atlantic U.S. Falcons fitted with transmitters on Block Island, RI, and Monhegan Island, ME, were successfully linked to wintering areas throughout the Caribbean and Central and South America (see Map 1). The majority of migrant peregrines initiated trans-oceanic flights from a stretch of shoreline spanning between Cape Charles, VA, and Cape Fear, NC, and tracked peregrines revealed several other fascinating habits such as barge-riding in the mid-Atlantic and iceberg-riding in Hudson Bay (see Map 2).

After their first winter, several individuals were tracked to Saskatchewan, Manitoba, northern Quebec, Ontario, and Greenland (see Map 3). We also established fall and spring migration routes of Merlins, whose habits during migration are poorly understood (see Map 4). Many of these satellite-tracked raptors continue to provide information important to our understanding of migration ecology, which is critical to conservation efforts.

BRI researchers have been measuring mercury exposure and impacts in birds for more than two decades. Mercury, 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.

Traditionally, toxicologists focused on evaluating contaminant exposure in fish-eating birds such as Bald Eagles. Recent studies, however, show that birds feeding in terrestrial food webs, such as songbirds (and thus their predators), are at equal or greater risk to mercury effects. Due to increased concerns that global mercury emissions are rising, researchers are interested in measuring current mercury exposure across species and regions.

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.

Peregrine tracking data was a component of BRI’s Mid-Atlantic Baseline Study, which aims to improve our understanding of wildlife use patterns relative to wind energy facilities proposed in the Mid-Atlantic U.S.

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. We will continue banding and collecting biological samples from raptors to evaluate their exposure to mercury as well as other contaminants. And, we will use the Block Island Raptor Research Station to conduct educational outreach efforts focusing on raptors, conservation, and environmental issues. 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.