State of Delaware

Blue Hen Chicken
Birding Delaware

Delaware is 96 miles long and ranges from 9 to 35 miles across, totaling 1,954 square miles and making it the second-smallest state in the United States after Rhode Island. Delaware is bounded to the north by Pennsylvania; to the east by the Delaware River, Delaware Bay, New Jersey and the Atlantic Ocean; and to the west and south by Maryland. Small portions of Delaware are also situated on the far, or eastern, side of the Delaware River estuary, sharing land boundaries with New Jersey. The state of Delaware, together with the Eastern Shore counties of Maryland and two counties of Virginia, form the Delmarva Peninsula, which stretches south down the Mid-Atlantic Coast.

The definition of the northern boundary of the state is highly unusual. Most of the boundary between Delaware and Pennsylvania is defined by an arc extending 12 miles (19 km) from the cupola of the courthouse in New Castle. It is referred to as the Twelve-Mile Circle. This is the only true-arc political boundary in the United States. This border extends all the way east to the low-tide mark on the New Jersey shore, then continues south along the shoreline until it again reaches the twelve-mile arc in the south; then the boundary continues in a more conventional way in the middle of the main channel (thalweg) of the Delaware River Estuary. To the west, a portion of the arc extends past the easternmost edge of Maryland. The remaining western border runs slightly east of due south from its intersection with the arc. The Wedge of land between the northwest part of the arc and the Maryland border was claimed by both Delaware and Pennsylvania until 1921, when Delaware’s claim was confirmed.Delaware is subdivided into three counties: from north to south, New Castle, Kent County and Sussex.

Delaware is on a level plain; the highest elevation, located at Ebright Azimuth, near Concord High School, Wilmington, does not rise fully 450 feet above sea level. The northern part is associated with the Appalachian Piedmont and is full of hills with rolling surfaces. South of Newark and Wilmington, the state follows the Atlantic Coastal Plain with flat, sandy, and, in some parts, swampy ground. A ridge about 75 to 80 feet in altitude extends along the western boundary of the state and is the drainage divide between the two major water bodies of the Delaware River and several streams flowing into Chesapeake Bay in the west.

Since almost all of Delaware is a part of the Atlantic Coastal Plain, the climate is moderated by the effects of the ocean. The state is somewhat of a transitional zone between a humid subtropical climate and a continental climate. Despite its small size (roughly 100 miles from its northernmost to southernmost points), there is significant variation in mean temperature and amount of snowfall between Sussex County and New Castle County. The southern portion of the state has a somewhat milder climate and a longer growing season than the northern portion of the State. The transitional climate of Delaware supports a surprising variety of vegetation. At Trap Pond State Park in Sussex County, bald cypress grow — this is thought to be one of the northernmost stands of such trees. The vegetation in New Castle County, on the other hand, is more typical of that of the northeastern United States. All parts of Delaware have relatively hot, humid summers. While Sussex and Kent Counties are considered to fall in the humid subtropical climate zone, there is some debate about whether northern New Castle County falls in the humid subtropical climate zone or warm continental climate.

Number of Species
  • Number of bird species: 416

    (As at October 2018)

    State Bird - Blue Hen Chicken


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Useful Reading

  • Birding the Delaware Valley Region

    | (A Comprehensive Guide to Birdwatching in Southeastern Pennsylvania, Central and Southern New Jersey and North Central Delaware) | By John J Harding & Justin J Harding | 1980 | Temple University Press | 233 pages, site maps | ISBN: 9780877221821 Buy this book from
  • Birds of Delaware

    | By Gene K Hess, Richard L West, Maurice V Barnhill & Lorraine M Fleming | University of Pittsburgh Press | 1998 | Hardback | 655 pages, Illustrations, figures, tables, maps | ISBN: 9780822940692 Buy this book from
  • Birds of Delaware

    | By Marc Parnell | Naturalist & Traveler Press | 2022 | Paperback | 312 pages, colour photos | ISBN: 9781954228399 Buy this book from
  • Birds of Maryland & Delaware Field Guide

    | (includes Washington, D.C. & Chesapeake Bay) | by Stan Tekiela | Adventure Publications | 2023 | Edition 2 | Paperback | 392 pages, colour illustrations | ISBN: 9781647553708 Buy this book from
  • Birds of Maryland, Delaware, and the District of Columbia

    | By Bruce M Beehler | Johns Hopkins University Press | 2019 | Hardback | 504 pages, 684 colour photos, 2 maps | ISBN: 9781421427331 Buy this book from
  • Delaware Birds: A Folding Pocket Guide to Familiar Species

    | By James R Kavanagh & Raymond Leung | Waterford Press | 2003 | Unbound | 12 pages, colour illustrations | ISBN: 9781583552223 Buy this book from
Museums & Universities
  • Delaware Museum of Natural History

    The bird collection consists of approximately 67,000 study skins, 11,000 skeletons, and 36,000 clutches of eggs. We also maintain a small tissue collection containing samples from eastern North American taxa. The collection, worldwide in scope, has especially strong collections of Philippine and Central and South American birds. The holdings represent about 4,000 bird species. About 140 taxa are in the type collection. Extinct species are also represented. Formation of the collection began when the Museum was founded in 1957. Among the collections that can be found here are those of George Miksch Sutton, Allan R. Phillips, Olin S. Pettingill, T.D. Burleigh, D.S. Rabor, M. Hachisuka, Vivien Hewitt, and Sibley’s Yale-Peabody Expedition. We also maintain an archive that contains field notes and other documentation from some of these collectors.
  • DelMarVa Ornithological Society

    If you love birding, birds or bird conservation then the Delmarva Ornithological Society (DOS) is for you. You’ll find a community of people interested in observing and enjoying birds, whether in a back yard or at one the many excellent birding sites in the area. You’ll also find people dedicated to helping conserve birds and the habitats they depend on. There are many opportunities to learn and grow, whether through the engaging speakers at our monthly meetings, by attending one of our many field trips with expert leaders, or by participating in one of the society’s many citizen-science projects. Families are invited to join the Delaware Dunlins, where kids can meet others with similar interests and learn about birding. No matter what your interests, at DOS you’ll find a community of people with interests similar to yours.
  • Delaware Audubon Society

    ncorporated in 1977, the Delaware Audubon Society is a statewide chapter of the National Audubon Society. Delaware Audubon is dedicated to developing a better appreciation of our natural environment and working for species and habitat conservation.
  • Delaware Nature Society

    Delaware Nature Society’s mission is to connect people with the natural world to improve our environment through education, advocacy and conservation. We envision a healthy and sustainable environment. We envision a healthy and sustainable environment. Our mission is to connect people with the natural world to improve our environment through education, advocacy, and conservation.
  • Delaware Records Committee

    The Delaware Bird Records Committee is charged with maintaining the Delaware State List of Bird Species (Downloadable PDF) (updated September 2018), which consists of all bird species accepted as having been observed in Delaware. A subset of this list is the Delaware State Review List, which are extremely rare species for which the committee requests documentation from observers to document their presence in the state.
  • Delaware Shorebird Monitoring Program

    The purpose of the Annual Reports is to provide an account of shorebird monitoring work that has been conducted on the Delaware side of Delaware Bay. It is intended to provide a popular account of activities
  • Nature Conservancy in Delaware

    The Nature Conservancy in Delaware works with government agencies, private corporations, conservation organizations and our members to conserve the places on which people and wildlife depend. This has resulted in the conservation of more than 30,000 acres across Delaware since 1990.

Abbreviations Key

  • Fish & Wildlife Service - Delaware

    WebsiteSatellite View
    Locations of reserves etc.
  • IBA Delaware Bay Wetlands

    WebsiteSatellite View
    The Delaware Bay's shores are a critical stopover area for six species of migrating birds. The late May arrival of these birds coincides with the spawning of horseshoe crabs, producing one of the most dramatic natural phenomena anywhere in the world. Feeding on crab eggs, the birds refuel and continue their journey to Arctic breeding grounds. Unfortunately, there has been a dramatic decline in horeshoe crab numbers since 1991 and a corresponding decline in shorebird numbers.
  • IBA Great Cypress Swamp Conservation Area

    WebpageSatellite View
    The Great Cypress Swamp is one of the largest contiguous areas of forest on the Delmarva Peninsula. Located at the headwaters of the Pocomoke River, the swamp has 600ha in Worcester Co., Maryland and 4400 ha in Sussex Co., Delaware. This IBA also includes the floodplain forests flanking the Pocomoke River south of the swamp to Highway 50. The swamp, once dominated by Atlantic white cedar and bald cypress, is now dominated by seasonally flooded forest of loblolly and pond pine and hardwoods, including red maple, sweetgum, black tupelo and black gum. Wood Thrush, Prothonotary Warbler, Swainson?s Warbler, Kentucky Warbler and Prothonotary Warblers
  • NR Great Marsh Preserve

    Observatory WebsiteSatellite View
  • NR Little Creek Wildlife Area

    WebpageSatellite View
    The wildlife area consists of over 4,700 acres of natural area consisting of tidal marsh, forest and agricultural fields dedicated to wildlife management.
  • NWA Prime Hook

    WebpageSatellite View
    The refuge is an important stopover site for migratory birds as they travel up and down the Atlantic Flyway and provides protected breeding habitat for federally and State-listed threatened and endangered species, as well as many neo-tropical migrating bird species. Prime Hook’s habitat features include salt marsh, freshwater marsh, ponds and impoundments, wooded swamps and upland grasslands and forest. Hundreds of native plant and animal species thrive in this mosaic of these diverse cover types that provide habitat for 308 species of birds, 51 species of fish, 45 species of reptiles and amphibians, 37 species of mammals, and an array of rare insect and plant species.
  • NWR Bombay Hook

    WebpageSatellite View
    Bombay Hook NWR, located on the western shore of Delaware Bay 8 miles southeast of Smyrna, Delaware, was established in 1937 to provide habitat for migratory waterfowl. Objectives have since broadened to include other migratory birds, a diversity of other native wildlife species and wildlife-oriented public use.
  • SP White Clay Creek State Park

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    The land that is today known as White Clay Creek State Park includes parts of the boundary line made famous by Mason and Dixon, who began their historic survey at “a post mark’d west,” a location that lies within the park. Over 37 miles of trails lead explorers to historic sites and scenic vistas overlooking lush valleys and impressive rock outcrops. Hikers and mountain bikers enjoy the large number of easy-to-moderate trails throughout the park. Of special interest are those at Possum Hill and the Judge Morris Estate, along with the Pomeroy Rail-Trail, which runs alongside White Clay Creek.
Forums & Mailing Lists
  • ABA Delaware Bird News

    News by date
  • Delaware Birding

    Forum, News etc.
    Please use discretion if posting locations of rare, endangered, or sensitive species, especially nesting species. Posts with sensitive information may be removed at the discretion of the administrators.
  • E-Bird Delaware Rare Bird Alert

    The reports show observations of rare birds in Delaware. Includes both unreviewed and reviewed/approved observations.birders of all descriptions in Maryland, Virginia, Delaware and surrounding areas. The group will concentrate on local birding issues and events, such asinteresting sightings, advice on local birding hotspots, announcements of local bird club meetings, events and exhibitions, planning of days out and joint birding expeditions, etc. MARVADEL is open to all individuals with a sense of humor and an interest in wild birds in the mid-Atlantic region.
Guides & Tour Operators
  • Delmarva Birding Weekends

    The Delmarva Birding Weekends and other events are organized by Conservation Community Consulting, LLC, along with a host of other sponsors and partners. To learn more, contact us at:Jim Rapp – – (443) 614-0261Dave Wilson – – (443) 523-2201
Trip Reports

Click on WAND to see Fatbirder’s Trip Report Repository…

  • 2013 [09 September] - Mattias Ullman - Cape May, Delaware & Jamaica Bay

    PDF Report
    ...The trip was deliberately put early in the season, partly because waders were one of our main priorities. Still, we were lucky to get two days with plenty of wood warblers in Cape May, due to cold winds from northwest...
Other Links
  • Birding the Delaware Valley Region

    For those of us who live in the Delaware Valley Region and for those who are visiting this wonderful area, here is ALL THE BIRDING INFORMATION that you need to know in order to bird within a 75-mile radius of Philadelphia, with emphasis on the counties surrounding Philadelphia.
  • Delaware Birding Trail

    The creation of the Delaware Birding Trail was a one and a half year collaborative effort by Delaware Audubon, Delmarva Ornithological Society, the Delaware Department of Natural Resources and Environmental Control and the U.S. Fish & Wildlife Service. Its purpose is to educate, inform and encourage both instate and out of state birders to experience the wealth of birdlife Delaware has to offer.
  • Delmarva Birding

    The Delmarva Peninsula possesses an extensive variety of environments, including barrier islands, tidal wetlands, cypress swamps, upland fields and primeval forests. Our annual Delmarva Birding Weekends celebrate the amazing warblers, shorebirds, waterfowl and raptors that visit and live here on the peninsula.
Photographers & Artists
  • Delaware Bird Photography

    Facebook Page
    Delaware Bird Photography is a group for people to share photographs they have taken of wild Delaware birds. Feel free to post questions about equipment, methods, and strategy in photographing birds.
  • Photographer - Kevin Fleming

    A Delaware native, Kevin began his career as a newspaper photographer. He has covered the world as a photographer for National Geographic and has been recognized America’s Best Observer by Readers Digest. His assignments have taken him into war and famine in Somalia, to the Mediterranean for a re-creation of the voyage of Ulysses and put him on a dogsled crossing the Canadian arctic.

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