North Brigantine Natural Area experimental closure to study shorebirds

31 October, 2010

Written by Larry Niles

Two weeks ago the New Jersey Department of Environmental Protection’s Division of Parks and Forestry and the City of Brigantine, New Jersey gave the green light to a new project to temporarily close about one half of North Brigantine Natural Area (NA) to all use. The closure will provide an opportunity to experimentally test the effect of disturbance on  migratory shorebirds. North Brigantine NA, at the north end of Brigantine Beach, is recognized as one of the most important Atlantic coast beaches on the US east coast for southbound migrant shorebirds, and this is the first effort of it kind in New Jersey to help these birds.


Signs at the point of closure on Brigantine Natural Area. © Larry Niles

The shorebirds using North Brigantine NA come from the Arctic and leave for wintering areas spanning the entire hemisphere — from Cape Hatteras, North Carolina, to Tierra del Fuego, Chile. Many shorebirds stay at North Brigantine NA to build fat reserves then jump off on trips that would frighten the most intrepid traveler. One red knot we tracked (via geolocator data) left NJ into the jaws of a storm and flew for six days before reaching land.  Other red knots come to Brigantine and stay for longer periods — up to 70 days — while they molt flight feathers before continuing south to wintering areas. Both groups need places that are productive (for invertebrates like small surf clams, marine worms and mussels) and provide relative safety from the horde of hawks that migrate south at the same time.  North Brigantine Natural Area provides both.


Shorebirds roosting on North Brigantine Natural Area. © Larry Niles

So why are we experimenting with a closure? There are only a  few good southbound stopovers in the mid Atlantic Coast that include enough area and diversity of habitat to accommodate the needs of migrating shorebirds. Nearly all beaches in this area of the Atlantic are intensively used for recreation — sunbathing in the late summer and off-road vehicle use in fall and winter. What does this mean to a shorebird?


Young Peregrine falcon flying low in dunes at No. Brigantine NA. © Larry Niles

You have to think like a shorebird to understand why. Most often you’ll find your food at the water’s edge –on the beach or mudflat — often out in the open where you can be attacked by a passing peregrine falcon, merlin, or Cooper’s hawk. You also need to rest or roost; most shorebirds at Brigantine spend nearly one half of their time digesting food or roosting during high tides. Staying close to cover would be a mistake, not only because of low flying raptors hidden in the low dunes, but also because of the many nighttime ground predators like foxes, feral cats, even coyotes. The best strategy is to be in a flock, where “many eyes” will quickly spot an approaching predator, and in a location with a good visibility in all directions. Most often shorebirds prefer wide open beaches or a sandy peninsula. North Brigantine has all of these attributes which is why it is so valuable for shorebirds.


Peregrine stooping on shorebird flock at North Brigantine NA. © Larry Niles

We closed the beach because on most days of the migratory period- late July to November – North Brigantine NA is used by fishermen, dog walkers, joggers, sunbathers and people who ride the beaches in sport utility vehicles (SUV’s). Red knots, sanderlings, dunlins, black bellied plovers, piping plovers, western sandpipers, short-billed dowitchers, declining species all, must continually dodge and fly from people. What is the effect: birds stop molting, they leave when they should stay, they fail to gain the weight they need.


Tracks left by off road vehicle traffic on North Brigantine NA just prior to the beach closure. © Larry Niles

 The closure was one week long ending last Thursday (October 21). Until recently, the needs of shorebirds have been poorly understood. But with the growing awareness of their needs, staff from North Brigantine NA, City of Brigantine and representatives of New Jersey Beach Buggy Association are supporting a scientific basis for management of this unique natural area.  This is important because the problem for shorebirds is larger than North Brigantine NA; the same lack of protection occurs in most  coastal areas leaving shorebird fewer and fewer places to go.  Coastal development, recreation and the use of SUV’s on beaches has increased exponentially over the last thirty years in areas important to shorebirds.


This red knot stopped molting after completing growth of 8 of its 10 flight feathers (see light brown outermost flight feathers). This condition, known as arrested molt, usually indicates stress in the stopover, lack of food, or frequent disturbance etc. © Larry Niles

To help with this problem, Dr. Joanna Burger of Rutgers and I are creating three closure experiments, one in North Brigantine NA and two in similar places in Florida, to test the effect of beach closures on both people and birds. Will shorebirds use the areas more, are people really resistant to helping the birds? This is what we will learn:


Red knots, black-bellied plovers and sanderlings feeding during the close period on North Brigantine NA. © Larry Niles


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