Black-crowned Night-heron Minnesota Conservation Summary

Transcription

1 Credit Deborah Reynolds Black-crowned Night-heron Minnesota Conservation Summary Audubon Minnesota Spring 2014 The Blueprint for Minnesota Bird Conservation is a project of Audubon Minnesota written by Lee A. Pfannmuller (leepfann@msn.com) and funded by the Environment and Natural Resources Trust Fund. For further information please contact Mark Martell at mmartell@audubon.org ( ).

2 Black-crowned Night-Heron Priority for Minnesota s Bird Conservation Plan: Prairie Parkland: High Level Priority Prairie Hardwood Transition: High Level Priority Aspen Parklands: High Level Priority Other Status Classifications: Minnesota Species of Greatest Conservation Need Minnesota Audubon Action List USFWS Bird of Conservation Concern in BCR22 (2008) Focal Species for the Upper Mississippi Valley/Great Lakes Joint Venture United States Waterbird Conservation Plan: Moderate Concern; apparent population decline (PT = 4) Northern Prairie and Parkland Waterbird Region: Moderate Concern Upper Mississippi River and Great Lakes Waterbird Region: Moderate Priority in BCR12; High Priority in BCR22; and Moderate Priority in BCR23; Focal Species for Region-wide monitoring because it is a Conservation Priority species in the UMVGL Region Listed as Threatened in Canada Population Information: North American population estimate: >50,000 pairs (UMVGL Waterbird Conservation Plan) Population goal in the UMVGL JV region is 13,000; the current estimate is 8,700; the projected deficit is 4,300. No estimate available for species population in Minnesota Minnesota BBS Data: Yellow Level of Credibility : Decreasing trend (statistically significant) of -6.1; : Decreasing trend of -7.8 Minnesota does not have one of the highest centers of the species abundance; it supports about 1.87% of the species North American breeding range Minnesota Residency: Breeds locally S and W Habitat Requirements: Marsh Seasonal wetlands and wet meadows; shallow, semi-permanent marshes; deep-water marshes & open water, islands w/herbaceous or brushy veg; herbaceous wetlands w/associated forest/forested islands, riparian areas; Nesting numbers increase with availability of foraging habitat which includes swamps, streams, rivers, margins of pools, ponds, lakes, marshes, man-made ditches, canals, ponds, reservoirs, and wet agricultural fields (from Birds of North America) Often nests in trees on islands and in swamps associated with the Great Lakes; inland colonies are typically in large wetlands. Will nest on ground, in trees and shrubs, and in upper tree canopy, but often in lower portion of vegetation (<3 m). Intense searching is necessary to find nests of this species in dense vegetation. Flies up to 24 km to forage in shallow, weedy pond margins, creeks, marshes, rivers and also found in man-made ditches, canals, reservoirs, flooded agricultural fields. (UMVGL WCP). Migration: Temperate Black-crowned Night-heron Page 2 of 7 Audubon Minnesota

3 Climate Change Vulnerability: Low (0) Threats (from UMVGL WCP): Degradation/destruction of habitat Human disturbance Contaminants From 1984: Henderson report on Colonial Waterbirds in Minnesota: This species has been found nesting in 17 colonies in Minnesota, all in the southern half of the state except for two colonies in Marshall County at the Agassiz National Wildlife Refuge and at the Thief Lake Wildlife Management Area. Ten of these are mixed species colonies, all but one occurring in association with Great Blue Herons. The largest Black-crowned Night Heron colony in the state is the mixed species heronry at Pig s Eye Lake in Ramsey County, where several hundred nests of this species are found. From Heron Lake Report (by Susan Koster) In adult Black-crowned Night-Herons were found at Heron Lake In ,000 were found In were found In were found OVERALL MINNESOTA GOAL: Monitor large mixed species colonies where Black-Crowned Night-Herons occur on a regular schedule BEST MANAGEMENT PRACTICES From UMVGL JV Plan Maintain (protect) existing nesting habitat quantity and quality (e.g. prevent human disturbance) and add (restore/enhance): See specific conservation actions below Manage trees and shrubs to ensure consistent availability of optimal structure nesting habitat and focus at existing colonies, historic sites if still potentially suitable, and near large wetlands Design dredge-spoil or other created islands to assure site is suitable for a nest colony Consider localized control of competitors (e.g. Double-crested Cormorants) if determined to be displacing Black-crowned Night-Herons. From Birds of North America: Although certain Black-crowned Night Heron populations have suffered declines, on a continental basis the species is stable or increasing (Sauer et al. 2008); thus extensive management practices have generally not been deemed necessary. To buffer nesting sites from human disturbance, set-back distances of 100 m for wading bird colonies were recommended in a Florida study (Rodgers and Smith 1995) In the event of climate change resulting in sea level rise or changes in temperature and precipitation, breeding and wintering habitats may become less suitable for night-herons, necessitating increased management to conserve populations. This may be particularly true for islands built from dredged material. Sometimes, breeding colonies of herons and egrets near human populations create nuisance problems that need attention and control. Black-crowned Night-heron Page 3 of 7 Audubon Minnesota

4 MONITORING NEEDS From UMVGL WCP The Black-crowned Night-Heron is a focal species for monitoring (conservation priority). High priority for monitoring in the Great Lakes. Should be included in Great Lakes and local colonial waterbird monitoring efforts. In areas where declines are suspected, monitoring efforts should be focused to find and count nests of this species. Monitor numbers and distribution at important breeding sites shared with cormorants to determine if night-herons are affected by cormorant activities. From NPP WCP More accurately estimate population size, distribution and trend Identify and target high priority landscapes and habitat for conservation action From UMVGL JV Plan Surveyed by BBS but it likely does not adequately survey this species Surveyed by the Great Lakes Colonial Waterbird Survey (conducted every 10 years, scheduled for ) Surveyed in some states by the Marsh Monitoring Program Surveyed in some states by State Breeding Bird Atlases Recommendations: 1. The Great Lakes Colonial Waterbird Survey conducted every 10 years provides a status assessment of the region s Black-crowned Night-Heron population. More frequent surveys and surveys of inland sites would better measure population change and habitat management performance. Eliminating the population deficit in the UMVGL JV requires a 50% increase or an average of 3% annually over a 15 year period. Recommendation from UMVGL JV Plan: Information about the location, size, productivity and long-term viability of inland (away from Great Lakes shoreline) colonies is needed. Surveys of known and new nesting colonies conducted on a more regular basis (e.g. annually or every 3-5 years) would assist assessment of management efforts. CONSERVATION ACTIONS Identify and target high priority landscapes and habitats for conservation action (NPP WCP). Action: Identify Important Bird Areas that are a priority for this species in Minnesota Upper Mississippi Valley/Great Lakes Joint Venture Region: Adopt habitat objectives for the Yellow Rail and King Rail established by the UMGLJV Waterbird Habitat Conservation Strategy (Soulliere et al. 2007) to maintain and/or benefit this species (UMVGL WCP). Herbaceous wetland with shrub/forest Goals for the Black-crowned Night-Heron in Minnesota BCR Maintenance & Protection Restoration & Enhancement 11 No goal established by PPJV (see next targeted conservation action) No goal established by PPJV (see next targeted conservation action) acres 170 acres acres 240 acres Black-crowned Night-heron Page 4 of 7 Audubon Minnesota

5 Action: Work with UMVGL JV conservation partners on Minnesota IBAs that support significant populations of Least Bitterns in the UMVGL region to achieve established habitat goals. Prairie Pothole Joint Venture Region: Adopt the Minnesota Prairie Landscape Conservation Plan (2010) habitat and restoration goals that target wet meadow wetlands that benefit Least Bitterns. Wetland Goals for the Prairie Pothole Region of Minnesota (BCR11) Conservation Action Prairie Landscape Conservation Areas Specific Conservation Action Habitat Wetlands (all types) Wetlands & Grasslands Protection Core Areas Acquisition 62,621 acres Voluntary management or conservation contracts Corridor Areas (complexes & general corridors) 154,277 acres Acquisition 13,295 acres 13,150 acres Voluntary management or conservation contracts 131,825 acres Matrix Landscape Acquisition 177,074 acres Voluntary management or conservation contracts 1,243,927 acres Protection Total 75,916 acres 1,720,253 acres Restoration Core Areas 82,161 acres Corridor Areas (complexes & general corridors) Matrix Landscape 20,731 acres 26,428 acres 250,880 acres Restoration Total 102, ,308 Action: Use the Minnesota Prairie Landscape Conservation Plan (2010) to guide habitat protection and restoration goals by conservation partners within Minnesota s Prairie Pothole Landscape and by Minnesota Audubon and conservation partners within Important Bird Areas located within the Prairie Pothole Landscape. RESEARCH NEEDS From UM VGL JV Plan: Determine if habitat is limiting population growth and determine area requirements/colony. Need information on habitat requirements and productivity, such as patch or island size, vegetation age and species preferences, landscape context, and effects of predators and human disturbance. Black-crowned Night-heron Page 5 of 7 Audubon Minnesota

6 The potential impact of growing Double-crested Cormorant populations have on Black-crowned Night-Heron colonies should be explored. Because this species is a predator, periodic monitoring for contaminants is warranted. Specific Actions for Audubon Chapters: Help monitor local colonies Black-crowned Night-heron Page 6 of 7 Audubon Minnesota

7 MN DNR MN Breeding Bird Atlas Birds of North America Black-crowned Night-Heron Distribution Maps Birds of North America Birds of North America MNBBA 2014 Black-crowned Night-Heron Black-crowned Night-heron Page 7 of 7 Audubon Minnesota