Basic Information
Common Name: Northern Harrier
Scientific Name: Circus cyaneus
Species Code: CIRCYA
Management Category: SO (significant occurrence at risk of loss)
Occurrence Map
Table of Occurrences
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Species Information

MSP Species Background

Goals and Objectives

Goal: Protect, enhance, and restore northern harrier occupied and historically occupied habitat to create resilient, self-sustaining populations that provide for persistence over the long-term (>100 years).

regional NFO 2019 SO
MON-SURV-SPEC CIRCYA-1

Management units: 1, 3, 4, 5, 6, 7, 8

In 2019, conduct a survey for northern harrier and other associated raptors to document the harrier's current distribution and abundance and to assess habitat and threats at survey sites. Prepare site-specific management recommendations based on survey results and habitat assessments.

Action Statement Action status Projects
SURV-1 Submit monitoring data and management recommendations to MSP web portal Available for implementation
Criteria Deadline year
Northern Harrier Surveys and Reports Completed by 2020 2021
Threat Name Threat Code
Human uses of the PreservesHUMUSE
Invasive plantsINVPLA
Pesticides
Urban developmentURBDEV
local NFO 2017, 2018, 2019, 2020, 2021 SO
MON-IMP-IMG CIRCYA-2

Management units: 1, 3, 4, 5, 6, 7, 8

From 2017 to 2021, annually inspect the existing nesting occurrences of northern harrier, taking precautions to avoid disturbance, to identify necessary management actions in order to support the expansion of the occurrence to self sustaining levels.

Action Statement Action status Projects
IMP-1 Conduct regional IMG monitoring protocol survey locations and habitat, assess status, and quantify potential threats. Available for implementation
IMP-2 Based upon threat evaluation, determine if routine management or more intensive management is warranted. Available for implementation
IMP-3 Submit monitoring data and management recommendations to MSP web portal Available for implementation
Criteria Deadline year
Surveys Completed Annually with management recommendations 2021
Threat Name Threat Code
Human uses of the PreservesHUMUSE
Invasive plantsINVPLA
Pesticides
Urban developmentURBDEV
local NFO 2017, 2018, 2019, 2020, 2021 SO
MGT-IMP-IMG CIRCYA-3

Management units: 1, 3, 4, 5, 6, 7, 8

From 2017-2021, perform routine management activities such as protecting nesting occurrences from disturbance through fencing, signage, and enforcement.

Action Statement Action status Projects
IMP-1 Perform management activities protecting occurrences from disturbance through fencing, signage, and enforcement. Available for implementation
IMP-2 Submit project metadata and management data to MSP web portal. Available for implementation
Criteria Deadline year
Management Completed as Needed Based Upon Monitoring Recommendations 2021
Threat Name Threat Code
Human uses of the PreservesHUMUSE
Invasive plantsINVPLA
Pesticides
Urban developmentURBDEV
regional NFO 2020 SO
MGT-PRP-MGTPL CIRCYA-4

Management units: 1, 3, 4, 5, 6, 7, 8

In 2020, prepare a management plan for northern harrier that prioritizes management actions to protect nesting sites from disturbance and enhances habitat using data from annual IMG monitoring.

Action Statement Action status Projects
PRP-1 Prioritize management actions, focusing on reducing threats and expanding occurrences in areas most likely to remain viable over the long-term in the context of future land development. Available for implementation
PRP-2 Develop a management plan for northern harrier that prioritizes management actions for the next five years. Available for implementation
PRP-3 Submit management plan to MSP web portal Available for implementation
Criteria Deadline year
Management Plan for Northern Harrier prepared by 2021 2021
Threat Name Threat Code
Human uses of the PreservesHUMUSE
Invasive plantsINVPLA
Pesticides
Urban developmentURBDEV
regional and/or local NFO 2021 SO
MGT-IMP-MGTPL CIRCYA-5

Management units: 1, 3, 4, 5, 6, 7, 8

Beginning in 2021, implement the highest priority management actions for northern harrier on Conserved Lands.

Action Statement Action status Projects
IMP-1 Management actions to be determined by the management plan. waiting for precedent action
IMP-2 Submit project data and management actions to MSP web portal waiting for precedent action
Criteria Deadline year
Management actions implemented for Northern Harrier 2021
Threat Name Threat Code
Human uses of the PreservesHUMUSE
Invasive plantsINVPLA
Pesticides
Urban developmentURBDEV
regional and/or local NFO 2021 SO
MON-IMP-MGTPL CIRCYA-6

Management units: 1, 3, 4, 5, 6, 7, 8

Beginning in 2021, monitor the effectiveness of management actions implemented for northern harrier on Conserved Lands

Action Statement Action status Projects
IMP-1 Submit monitoring data and reports to MSP web portal waiting for precedent action
Criteria Deadline year
Monitoring completed and data and report submited within 1 year of management actions being completed. 2021
Threat Name Threat Code
Human uses of the PreservesHUMUSE
Invasive plantsINVPLA
Pesticides
Urban developmentURBDEV
Northern Harrier (Circus cyaneus) Surveys
Northern harrier is a species that has disappeared as a breeding resident from many areas in southern California. Once abundant and widespread in San Diego County, there are few known breeding populations remaining in marshes and grasslands on Conserved Lands. In 2021, AECOM surveyed for northern harriers at historic and recently documented breeding sites and in other suitable habitat to determine if harriers are present during the breeding season, and to estimate population size and breeding status. AECOM used an SDMMP protocol to evaluate habitat quality and threats at each suitable habitat site, even those without northern harriers. SDMMP will use these data, and data from subsequent surveys, for the development of management priorities.
SR 94 Wildlife Infrastructure Plan
Proposed road improvements to SR 94 provide an opportunity to mitigate the potential barrier effects of the highway. This project identifies where improvements to existing infrastructure on SR-94 could improve connectivity across the South County preserves, using Best Management Practices from the scientific literature; recommends wildlife movement monitoring to identify where new crossings are needed; and identifies where additional conservation would enhance the integrity of South County linkages. The review prioritizes infrastructure improvements of 35 existing undercrossings inspected by wildlife experts in the field along 14.6 miles of SR-94 where the highway bisects conserved lands. The majority of the recommendations for infrastructure improvement focus on increasing the diameter, and thus the openness ratio (cross-sectional area divided by length), of the undercrossing itself, removing vegetation and debris blocking the undercrossing, restoring habitat in the approach to the undercrossing, and installing fencing to both (1) keep animals off the highway and (2) funnel wildlife to the undercrossings.

Current Distribution Rangewide

Breeding range from northern Alaska and Canada (mostly south of tundra) south to northern Baja Peninsula, Mexico and east to southern Nevada, northern Arizona, southern Utah, northern New Mexico, and northern Texas (references in Smith et al. 2011). Winters primarily from southern Canada south through conterminous U.S., Central America, and Caribbean islands.

List Status

None.

Habitat Affinities

During breeding seasons, uses open wetlands; wet, lightly grazed pastures; old fields; freshwater and brackish marshes, and tundra; also dry uplands, including upland prairies, mesic grasslands, drained marshlands, croplands, cold desert shrub-steppe, and riparian woodland [1]. In winter, may occur in a variety of open habitats dominated by herbaceous cover, including deserts, coastal sand dunes, pasturelands, croplands, dry plains, upland and lowland grasslands, old fields, estuaries, open-habitat flood plains, and salt- and freshwater marshes (references in Smith et al. 2011)

Taxonomy and Genetics

Two subspecies recognized. C. c. hudsonius breeds from western Alaska east across Canada and south, coastally, to northwest Baja California and southern Great Basin east across n. Oklahoma and s. Illinois to Chesapeake Bay; winters from southern portion of breeding range (largely south of Canada) south through Middle America to Colombia and Venezuela [1].

Seasonal Activity

Relatively few observations of nesting during surveys for Bird Atlas suggests that lay eggs at least from 1 April to 1 May [2]. Winter visitors occur mainly from September to March [2]. Reported as fairly common winter visitant to open marshes and fields throughout southern California but scarce and local as a breeder [3].

Life History/Reproduction

Like most other harriers, nests on ground, usually in tall, dense clumps of vegetation, either alone or in loose colonies [1]. Rears one brood per season. Reported as nesting at mouth of Tijuana River and in vicinity of Camp Pendleton [3]. Size of local breeding population in S.D. County expected to vary relative to rainfall and abundance of prey; estimated to be ~25-75 pairs [2]. Important known and/or potential breeding areas include Camp Pendleton and Tijuana River estuary and valley, including Border Field State Park. Additional nesting areas include Carlsbad, Los Peñasquitos Canyon, Otay Mesa, and various locations in southwestern S.D. County.

Diet and Foraging

In summer consumes small- and medium-sized mammals (primarily rodents), birds, reptiles, and frogs; in winter in southern part of range feeds on mammals and birds [1].

Dispersal

Offspring reported as having essentially no fidelity to natal area [1].

Threats

Previously common breeding resident (references in Unitt 2004). Current rarity as a breeder believed to due to loss of most habitat from urbanization. Loss of foraging areas and disturbance of nest sites likely contributors. Ground-nesting behavior creates particular vulnerability. Smith et al. (2011) identified threats as including: (1) ongoing elimination of freshwater and estuarine wetlands in the U.S. (threatens breeding and wintering populations); (2) conversion of native grassland prairies for farming; increase in mechanized agriculture and early mowing in upland areas (threatens nests); (3) overgrazing and the advent of larger crop fields and fewer fence rows; (4) widespread use of insecticides and rodenticides have reduced prey availability.

Special Considerations:

Population estimates and estimates of reproductive success may be difficult to make due to ground-nesting behavior (i.e., difficult to census). In one study of nesting in managed versus non-managed grasslands (4), northern harriers located their nests in fields not disturbed by recent (within previous 12 months) management activities, and nest placement was not influenced by whether fields were dominated by native or nonnative grasses. Generally avoids urban areas, but has been reported to forage along roadsides (5, 6). In New England, Northern Harriers leave wintering areas with potentially suitable nesting habitat presumably in part because of heavy use of coastal areas by humans (Serrentino 1992 in Smith et al. 2011). See Smith et al. (2011; “Conservation and Management”) for lengthy review of management of grasslands (e.g., mowing, burning, grazing), wetlands, and croplands.

Literature Sources

[1] Smith, K.G., S. R. Wittenberg, R. B. Macwhirter and K. L. Bildstein. 2011. Northern Harrier (Circus cyaneus), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/210

[2] Unitt, P. 2004. San Diego County Bird Atlas. El Cajon, CA: Sunbelt Publications. 766 pp.

[3] Garrett, K., and J. Dunn. 1981. Birds of southern California. Los Angeles Audubon Soc. 408 pp.

[4] Herkert, J. R., S. A. Simpson, R. L. Westemeier, T. L. Esker, and J. W. Walk. 1999. Response of northern harriers and short-eared owls to grassland management in Illinois. Journal of Wildlife Management 63: 517-523.

[5] Hager, S. B. 2009. Human-related threats to urban raptors. Journal of Raptor Research 43(3):210-226.

[6] Serrentino, P. 1992. Northern harrier, Circus cyaneus. Pages 89-117 in Migratory nongame birds of management concern in the northeast. (Schneider, K. J. and D. M. Pence, Eds.) U.S. Fish Wildl. Serv. Newton Corner, MA.