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New Jersey Endangered and Threatened Species Field Guide


Image of A ruddy turnstone searches for food on a Delaware Bay beach.Zoom+ A ruddy turnstone searches for food on a Delaware Bay beach. © Mark Peck

Ruddy turnstone

Arenaria interpres

Species Group: Bird

Conservation Status

State: Other Classification

 


IDENTIFICATION

A small (about 9 inches in length), hefty sandpiper, ruddy turnstones are completely unique among New Jersey’s shorebirds and are nearly unmistakable. Adult birds have a black, U-shaped “bib,” white belly, and orange legs in all plumages. During the summer, males have a completely white head with a bright, reddish-brown wash on their back and wings, while females have some brown on the top of the head and considerably browner backs and wings. Winter plumage is similar but duller, with the back, head, and wings completely brown in both sexes. In flight, ruddy turnstones have conspicuous white stripes on their wings and back.

Image of Range of the ruddy turnstone in New Jersey.Zoom+ Range of the ruddy turnstone in New Jersey.

DISTRIBUTION AND HABITAT

Like most of New Jersey’s shorebird species, ruddy turnstones are migratory, breeding in the northern Arctic and wintering further south. Small numbers can be found in New Jersey nearly year-round, as a few members of the eastern population will spend the winter as far north as Long Island; most of the population, however, winters in northern Brazil or at other locations in Central and South America.There are believed to be five total populations of ruddy turnstones worldwide, with other populations wintering in Scandinavia, China, Japan, Australia, Africa, and more.

Ruddy turnstones prefer sandy coastlines and mudflats during winter, but will also utilize rocky beaches, wetlands, and other similar areas. In the Arctic, either rocky coastal areas or tundra is preferred. During their northward migration in mid-May, large numbers of ruddy turnstones can be found on Delaware Bay beaches, where they consume high-protein horseshoe crab eggs to refuel before continuing their migration north.

DIET

The ruddy turnstone’s diet varies seasonally due to the different habitats they live in. During the summer breeding season, they eat mainly invertebrates such as insects, though some have been observed eating plant materials, bird eggs, or even carrion if they arrive in the Arctic before insect prey is available. During migration and winter, their diet shifts to mainly marine invertebrates, such as crustaceans and mollusks. Opportunistic feeders, they also will take advantage of temporary but highly abundant food sources on their migration, the most notable example being horseshoe crab eggs in Delaware Bay.

The name “turnstone” is derived from their feeding habits. Turnstones are highly skilled at using their bills to turn over rocks and other debris in search of prey. They can also probe through vegetation, soil, or sand, and even dislodge and open prey such as barnacles and clams.

LIFE CYCLE

Ruddy turnstones reach their Arctic breeding grounds in late May or early June. They are monogamous, with mated pairs rejoining each other at the same territory every year. The nest is a shallow depression in the ground lined with grass, moss, or other vegetation. 2-5 greenish-olive eggs (usually 4) are laid, usually within a few days, though this may be delayed if not enough insect prey is available. Both parents will incubate the eggs, but the majority is done by the female, while the male stands guard. Incubation averages about three weeks, with the eggs hatching within a day or two of one another in mid-July. The young are able to walk and find food within hours of hatching, and the family will abandon the nest within a day of the final egg hatching.

Both parents will aggressively guard the young during these first days. The female leaves midway through the hatchling period, while the male remains to guard the chicks until they fledge, approximately three weeks after hatching. The chicks, which at this point are nearly adult-size, will leave on their first migration south just a few days later, at about 21-23 days old.

The young will remain on their wintering grounds for the first year after hatching. While most begin breeding at age 2, this may be delayed until 3 or even 4 years old for some individuals. The average lifespan is about seven years, while the oldest recorded wild individual was 19.7 years.

CURRENT THREATS, STATUS, AND CONSERVATION

Due to their large population size and worldwide distribution, ruddy turnstones are not listed as a threatened species by any major conservation authority. However, they are at risk from many of the same factors that have reduced shorebird populations worldwide.

Continued coastal development and subsequent habitat destruction continue to place increased pressure on remaining acceptable sites. Similarly, global climate change could have as-yet unseen effects on ruddy turnstones, whose far-northern breeding territories make them especially vulnerable. And lastly, the recent decline of traditionally hyper-abundant food resources such as horseshoe crab eggs, a critical part of their migrations, greatly reduce the odds of successful breeding by limiting the fitness of adult birds arriving in the Arctic.

Harvesting horseshoe crabs has been banned in New Jersey since 2007, an attempt to reduce this unnecessary source of pressure on shorebird populations, but to date it has not resulted in increased horseshoe crab (or shorebird) numbers. While at present ruddy turnstones are in a more secure position than many other shorebirds, close observation and careful action need to be taken to prevent them from experiencing a similar decline in the future.


Text written by Matthew Danihel in 2013.



REFERENCES

  • Dewey, Tanya. "Arenaria interpres". 2009. Animal Diversity Web. University of Michigan. Accessed: July 31, 2013. Available at: http://animaldiversity.ummz.umich.edu/accounts/Arenaria_interpres/.
  • Nettleship, David N. "Ruddy Turnstone (Arenaria interpres)". Ithaca, NY, 2000. The Birds of North America Online (A. Poole, Ed.).Cornell Lab of Ornithology. Accessed: July 30, 2013. Available at: http://bna.birds.cornell.edu/bna/species/537.
  • Stokes, Donald, and Lillian Stokes. Field Guide to Birds: Eastern Region. New York, NY: Little, Brown and Company, 1996.

Scientific Classification

Kingdom: Animalia
    Phylum: Chordata
       Class: Aves
          Order: Charadriiformes
             Family: Scolopacidae
                Genus: Arenaria
                   Species: A. interpres

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