Bald Eagles Fly the Garden State
Relocated from Canada in the 1980’s to Dividing Creek, NJ, Bald Eagles are now seen throughout the State. WATCH VIDEO
Trenton, NJ: New Jersey Bald Eagle Project, 2018 Prepared by: Larissa Smith and Kathleen E. Clark. Larry Herrighty, Director John Heilferty, Chief Endangered and Nongame Species Program NJDEP report –
The Division of Fish and Wildlife’s Endangered and Nongame Species Program (ENSP) biologists, Conserve Wildlife Foundation (CWF) staff, and volunteer observers located and monitored bald eagle nests and territories. Two hundred-four nest sites were monitored during the nesting season, of which 185 were documented to be active (with eggs) and 19 were territorial or housekeeping pairs. Thirty new eagle pairs were found this season, 20 in the south, nine in central and one in the north. One hundred-twenty-one nests (66%) of the 182 known outcome nests produced 172 young, for a productivity rate of 0.94 young per active/known outcome nest. The failure rate was well above average with 61 nests (33%) failing to produce. The Delaware Bay region remained the state’s eagle stronghold, with roughly half of nests located in Cumberland and Salem counties and the bayside of Cape May County. The state’s eagle population would not be thriving without the efforts of the dedicated eagle volunteers who observe nests, report sightings, and help protect critical habitat. Introduction Historic records are incomplete, but one study indicated New Jersey hosted more than 20 pairs of nesting bald eagles in the Delaware Bay region of the state (Holstrom 1985). As a result of the use of the pesticide dichloro-diphenyl-trichloroethane, commonly known as DDT, the number of nesting pairs of bald eagles in the state declined to only one by 1970 and remained there into the early 1980s. Use of DDT was banned in the United States in 1972. That ban, combined with restoration and management efforts by the Division of Fish and Wildlife’s Endangered and Nongame Species Program (ENSP), resulted in population increases to 23 pairs by 2000, 48 pairs by 2005, 82 pairs by 2010, and 150 pairs by 2015. ENSP recovery efforts – implemented since the early 1980’s – have resulted in a steady recovery as New Jersey’s eagle population has rebounded from the edge of extirpation. Recovery efforts were multifaceted. In 1982, after New Jersey’s only remaining nest (located in Cumberland County’s Bear Swamp) had failed at least six consecutive years, ENSP biologists removed the egg for artificial incubation at Patuxent Wildlife Research Center in Maryland, and fostered the young nestling back to the nest. As a result of residual DDT contamination, the Bear Swamp eggs were too thin to withstand normal incubation. Artificial incubation and fostering chicks continued with success until 1989, when the female of the pair did not return and a new, younger female was able to hatch eggs without intervention. New Jersey Bald Eagle Project Report, 2018 4 Increasing the production from a single nest, however, was not enough to boost the state’s population in a reasonable period of time. Mortality rates are high in young eagles (as high as 80%), and eagles do not reproduce until about five years of age. ENSP instituted a hacking project in 1983 that resulted in the release of 60 young eagles in NJ over an eight-year period (Niles et al. 1991). These eagles contributed to the increase in nesting pairs observed after 1990. Bald eagles nesting in NJ face many threats, with disturbance and habitat loss the greatest threats in our state. In addition, contaminants in the food web may negatively affect the eagles nesting in some areas of NJ. Disturbance is defined as any human activity that causes eagles to change their behavior, and takes many forms, including mere presence of people in nesting or foraging areas. In general, people on foot evoke the strongest negative reaction (Buehler 2000). When eagles change their behavior in reaction to people, they cease doing what is best for their survival and the well-being of their eggs and young. Ultimately, that reduces the survival of individuals and the population. ENSP biologists work to manage and reduce disturbance in eagle habitats, especially around nest sites. A corps of experienced volunteer observers, as well as education and safe viewing areas, are essential to this effort. Viewing eagles from safe distances, where eagles continue to act normally, is best for eagles and satisfies our natural desire to see them. Biologists also protect habitat in a variety of ways, including working with landowners, land acquisition and management, and applying the state’s land use regulations. ENSP has a history of investigating the impacts of organochlorines and heavy metals in eagles and other raptors nesting in the Delaware Bay region. Bald eagles, ospreys, and peregrine falcons nesting in the region have exhibited some reproductive impairment relative to other areas (Steidl et al. 1991, Clark et al. 1998), but recent research indicates problems may be limited to very local areas of contamination (Clark et al. 2001). ENSP biologists collect samples that allow monitoring of contaminants in eagles during the nesting season, and monitoring nest success is an integral part of this research. ENSP biologists, with the Division’s Bureau of Law Enforcement staff and project volunteers, work year round to protect bald eagle nest sites.
However, with increasing competition for space in the most densely populated state in the nation, it is clear that critical habitat needs to be identified and, where possible, protected. Critical habitat for eagles includes areas used for foraging, roosting and nesting, and is included in the program’s Landscape Project mapping of critical wildlife habitats. Landscape Project mapping is identifies suitable habitat that is associated with nests, foraging areas, and documented communal roosts. The population of wintering bald eagles has grown along with the nesting population, especially in the last ten years. The NJ Eagle Project discontinued Mid-winter eagle surveys, but has expanded surveys to document important roosting areas in winter and year-round. The federal government removed the bald eagle from its list of Endangered Species in August, 2007, in recognition of the national resurgence in the eagle population in the lower 48 states. The U.S. Fish and Wildlife Service oversees a 20-year monitoring period (through 2027) to watch for and investigate any problems that could compromise the eagle recovery. In addition, a revised version of the Bald and Golden Eagle Protection Act remains in effect to protect nest and New Jersey Bald Eagle Project Report, 2018 5 roost sites for bald eagles nationwide. The bald eagle’s official New Jersey status remains state endangered for the breeding season and state-threatened for the non-breeding season, and state regulatory protection remained unchanged by the federal action. Objectives of the New Jersey bald eagle program: 1) monitor the recovery of the bald eagle in the state by documenting the status, distribution, and productivity of breeding bald eagles in NJ; 2) enhance nest success by protecting bald eagles and their nest sites; 3) monitor wintering areas and other concentration areas and plan for their protection; 4) document locational data in the Biotics database and apply it to identify critical habitat using the Landscape Project mapping; 5) provide information and guidance to landowners and managers with regard to bald eagles on their properties; 6) increase our understanding of bald eagle natural history in New Jersey. Methods Nest Survey All known nest sites are monitored January through July or through fledging. Volunteer observers watch most nests from a distance of 1,000 feet, using binoculars and spotting scopes, for periods of two or more hours each week. Observers record all data including number of birds, courtship or nesting behaviors, incubation, feeding, and other parental care behaviors that provide essential information on nesting status. ENSP or CWF staff contact volunteers weekly with an update and are available to discuss observer questions and data. Dates are recorded for incubation, hatching, banding, fledging, and, if applicable, nest failure. A nesting territory is considered “occupied” if a pair of eagles is observed in association with the nest and there is some evidence of recent nest maintenance. Nests are considered “active” if a bird is observed in an incubating position or if eggs or young are detected in the nest. Observers report other bald eagle sightings to ENSP or CWF biologists, who review the information for clues to potential new nest locations. ENSP staff and volunteers investigate territorial bald eagles for possible nests through field observations. When evidence suggests a probable location, biologists may conduct aerial surveys of the region to locate a nest. Following guidance from the US Fish and Wildlife Service’s post-delisting monitoring plan (USFWS 2009), we maintain a list of occupied nests and territories for population monitoring. When necessary, nests are protected from disturbance with barriers or posted signs. Staff works in partnership with landowners and land managers to cooperatively protect each nest. Volunteers notify ENSP staff immediately if any unusual or threatening activities are seen around the nest site. The Division’s Bureau of Law Enforcement conservation officers act to enforce protection measures as needed, and provide routine assistance as well. At select sites, ENSP biologists enter the nest site to band young when nestlings are between five and eight weeks old. A biologist climbs the tree and places nestlings into a large duffel bag and New Jersey Bald Eagle Project Report, 2018 6 lowers them, one at a time, to the ground. A team records measurements (bill depth and length, eighth primary length, tarsal width, and weight) and bands each eaglet with a federal band and a green state color band with an alpha-numeric code. A veterinarian examines each bird and takes a blood sample for contaminant analysis. Blood is collected and stored following techniques in Bowerman et al. (1994). Samples are stored frozen pending analysis by a technical lab. Nest trees are generally not climbed the first season to avoid associating disturbance with the new site. Winter and Roost Surveys In recent years, we in New Jersey did not participate in the National Mid-Winter Eagle survey held in January. As eagle numbers have increased in NJ we found that the standardized count no longer covered all important eagle areas, and that volunteer efforts could be put to better use. Biologists asked eagle project volunteers to search for locations where eagles roost and otherwise concentrate in the winter months of January and February. In 2018, volunteers conducted surveys at a dozen known roosts on a quarterly basis, to confirm roost locations and measure eagle use at different times of the year. Those results will be part of the Biotics database documentation. Results Nest Survey The statewide population increased to 204 territorial pairs in 2018, a slight increase from 178 last year. One hundred eighty-five pairs were known active (meaning they laid eggs), thirty-two more than last year (Figure 1); 19 pairs maintained nest territories but did not lay eggs. One hundred twenty-one nests (66%) were known to be successful in producing 172 young, for a productivity rate of 0.94 young per known-outcome/active nest, which is in the range of 0.9 to 1.1 young per nest for population maintenance. Sixty-one (33%) nests failed to fledge young, a rate that is above average for New Jersey. We documented nest failures and brood loss that occurred as 194 chicks were reported at active nests, but only 172 fledged. The number of young lost could be higher as monitors can’t always see the number of chicks in the first few weeks. Most nests were located in the southern portion of the state, particularly within 20 km of Delaware River and Bay (Figure 2). The majority of nests were located on private land, while the rest were on state, federal, county, and conservation-dedicated lands. Disturbance was a management issue at many nests, and posting and regular surveillance by staff and nest observers remained essential to increase the chance of success. All documented nests and significant dates of the nesting season are listed in Table 1. Excluded from our nest table are 42 previously documented nest sites that were unoccupied and where no new nest could be found, or search effort was lacking (Table 2). MORE: