The Raritan River Basin and The Atlantic Flyway

A NextGen Blog post by Johanna Mitra, Stony Brook University.

Cover image © Joe Mish. All other photos © Alison M. Jones, unless otherwise noted.

This is the latest post to our NWNL NEXTGEN BLOG series. Since 2007, NWNL has supported watershed education with college internships and blogging opportunities. This NWNL NEXTGEN BLOG series posts students’ essays; sponsors a forum for our student contributors; and invites upper-level students to propose work focused on watershed values, threats and solutions.

Johanna Mitra is currently an undergraduate student at Stony Brook University. She is majoring in ecosystems and human impacts with a focus on wildlife conservation and minoring in geospatial science. This is the first in her series of blogs about migratory birds and the Flyways of the Americas. Read her earlier posts for NWNL: The Use of Photography in the American Conservation Movement, Macroinvertebrates in the Mississippi River and Cycles of Dependency.

Regardless of where you live in the northern hemisphere, at some point you might catch a glimpse of a migratory bird en route to its northern breeding ground or southern wintering ground. About 350 different species of neotropical birds migrate between North and South America yearly, some traveling thousands of miles each way.[mfn]Lockhart, Jhaneel[/mfn] As they make this exhausting and often dangerous journey, many will utilize freshwater resources such as rivers, wetlands and riparian zones as areas for rest and recuperation. Rivers and their bays and estuaries are critical to migratory birds. They provide a source of food and water, and also a means of orienting themselves along their journey, thus supplementing their existing natural migratory instincts.[mfn]Pharr, Lauren[/mfn]

Staten Island’s northern shore of the Raritan Bay

Additionally, wetlands – being incredibly abundant in resources due to their high levels of productivity – often serve as breeding grounds for some migratory birds. A few species in the U.S. are so reliant on certain wetlands for feeding and breeding that the destruction of any one of those critical marsh systems could devastate their entire population.[mfn]United States Environmental Protection Agency[/mfn] The riparian zone, or the vegetated area bordering a stream or river, is a region that approximately 80% of neotropical birds rely on for food during their migration.[mfn]American Rivers[/mfn] It is here that some bird species can so much as “double their body-weight…building fat stores that will sustain them as they fly thousands of miles.”[mfn]Rosenberg, Ken et al.[/mfn] Without such freshwater resources, annual migration would be an impossible feat and hundreds of bird species would be at risk of extinction.

The North American Atlantic Flyway

Rivers and other natural features including mountain ranges or coastlines often form boundaries of the distinct routes that birds use to fly between their breeding and wintering sites, also known as “flyways.” North America is home to four such flyways—the Atlantic, Mississippi, Central, and Pacific—each unique in their geographical location and migratory bird populations. Being able to identify these flyway boundaries is key to ensuring that crucial migratory stopovers are protected.

Flyways Map. Courtesy of U.S. Fish and Wildlife Service Headquarters and Creative Commons

However, across North America, the freshwater resources that prove so useful during migration season are threatened by widespread human activity. The most prevalent threat is commercial and industrial development which both fragments and pollutes bird habitats.[mfn]Tsipoura, Nellie et al[/mfn] In turn, this can negatively impact water quality to the point where the food sources that make rivers, wetlands, and riparian zones such attractive and critical stopovers, eventually decline in number.[mfn]Pharr, Lauren[/mfn] In particular, Atlantic Flyway habitats are especially prone to encroachment by human activity, with more than one third of the US’ population residing in and around it.[mfn]National Audubon Society[/mfn]

Migratory Birds in the Raritan River Basin

New Jersey’s Raritan River Basin, located within the Atlantic Flyway, has long played an important role for not only the state’s local wildlife but also for migratory birds. Its main rivers and their tributaries, which extend all the way down to where the Raritan River empties into the Raritan Bay before spilling into Hudson River. This bay provides vital breeding grounds, nesting sites and stopover points.[mfn]Tsipoura, Nellie et al.[/mfn]

Brown Thrasher in Raritan River Basin. Photo © Joe MIsh

The Audubon Society, with its numerous chapters across the US, works to protect North American birds and their habitats and keeps a list of “priority birds” and those which are in greatest need of conservation. Many such priority birds have been observed throughout the Raritan River Basin, which encompasses large grasslands in addition to its riverbanks and estuaries.[mfn]Tsipoura, Nellie et al.[/mfn] Examples include birds of prey like the bald eagle and osprey, as well as woodcocks, hummingbirds and songbirds like grasshopper sparrows and wood thrushes. (The latter cross the Gulf of Mexico in a single night en route to and from Central America!) Raritan waterway migrants also include certain species of gulls and herons.[mfn]National Audubon Society[/mfn],[mfn]Tsipoura, Nellie et al.[/mfn] One migratory shore bird on the Audubon’s list is the red knot, a prime example of how important New Jersey’s waterways are for birds during the migration season. During springtime, the red knot can be found on the shoreline refueling on a diet of horseshoe crab eggs, a food source limited in range to a small portion of the east coast. The eggs allow them to build up their energy reserves before completing their migration from the southernmost tip of South America to the Arctic Circle.[mfn]NJ Department of Environmental Protection[/mfn]

The recurring presence of these migratory birds year after year is not only a good indicator of the river basin’s health, but also signals the resumption of New Jersey’s bird-banding efforts and citizen science bird counts, growth in the state’s ecotourism industry and an increase in the number of eager new birdwatchers. Bird bands and bird counts allow researchers to monitor where migratory birds go each year and how far they could have flown, both of which are key to understanding how best to conserve at-risk populations.

Bald Eagle in Raritan River Basin. Photo © Joe MIsh

The Future of the Raritan River Basin in the Atlantic Flyway

Like other freshwater bodies in the U.S., the Raritan River Basin has dealt with the negative environmental effects of human activity – especially that from the past. Unfortunately for the red knot, a history of crab-fishing in the area and today’s changing water temperatures has led to a significant decline in the horseshoe crab population, putting the red knot at risk as well.[mfn]Hurdle, Jon[/mfn] New Jersey’s 18 Superfund sites and 60 sewage plants contaminated the waterways that other migratory species rely on with harmful chemicals, waste products and heavy metals.[mfn]Sierra Club[/mfn] However, ongoing efforts continue to remedy these damages through clean-up projects, habitat restoration, community awareness and activism.

(For further research and stewardship on this issue of the red knot see our blog, It’s Not Easy Being a Horeshoe Crab in New York Harbor by Joe Reynolds)

The presence of migratory birds in New Jersey brings a renewed sense of appreciation for its natural features and a desire to ensure that the Raritan River and New Jersey’s other freshwater resources remain accessible to the birds that depend on it most. Such sentiments fuel efforts by local organizations and communities to prevent contamination and habitat encroachment and will allow the Raritan River Basin to function as a key part of the Atlantic Flyway for many years to come.

Aerial of the Raritan Bay


“Flyways of the America: Atlantic Flyway.” National Audubon Society, n.d. Accessed Dec 26, 2020 by JM.

Hurdle, Jon. “Migration Numbers Plunge for the Red Knot, a Threatened Shore Bird.” The New York Times, June 11, 2020. Accessed on Jan 11, 2021 by JM.

Lockhart, Jhaneel. “9 Awesome Facts About Bird Migration.” National Audubon Society, Oct 11, 2012. Accessed Dec 26, 2020 by JM.’s%20big,to%20the%20tropics%20each%20fall

Pharr, Lauren. “Birds and Rivers: The Importance of a River Ecosystem.” Benton Soil and Water Conservation District, July 1, 2020. Accessed Dec 26, 2020 by JM.,from%20one%20landscape%20to%20another.&text=Precipitation%20patterns%20are%20also%20shifting,and%20agricultural%20areas%20into%20rivers

“Raritan River Contamination Fact Sheet.” Sierra Club, n.d. Accessed on Jan 11, 2021 by JM.

“Red Knot – An Imperiled Migratory Shorebird in New Jersey.” NJ Department of Environmental Protection, n.d. Accessed Jan 11, 2021 by JM.

Rosenberg, Ken et al. “Stopover Habitats and What Birds Need on Migration.” American Bird Conservancy, April 27, 2017. Accessed Dec 26, 2020 by JM.

Tsipoura, Nellie et al. “Connecting People to Urban Wetlands: Preserving Biodiversity in The Raritan River Watershed, New Jersey.” NJA Citizen Science Program, Sept 2012. Accessed Dec 26, 2020 by JM.

“Why are Wetlands Important?” United States Environmental Protection Agency, June 13, 2018. Accessed Dec 26, 2020 by JM.

“Why Do We Need Wild Rivers?” American Rivers, n.d. Accessed Dec 26, 2020 by JM.

2 thoughts on “The Raritan River Basin and The Atlantic Flyway

  1. Thanks, Judy. Such fun having Joe Mish’s photos available for this blog. And do stay tuned to the upcoming blogs in this series on migratory birds (along the Mississippi and Pacific Flyways)!

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