Savannah sparrow (princeps subspecies) management plan: chapter 4

MANAGEMENT

3.1 Goals and objectives

The management goals and objectives, and the strategies for achieving them, are derived from the updated COSEWIC status report (Horn 1999), draft monitoring plans of the Sable Island Preservation Trust (Horn et al. 2003b), the Sable Island conservation strategy (Beson 1998), work done on the Ipswich Sparrow since the updated status report (Horn et al. 2003a; Smith et al. 2003), and recent work on other grassland sparrow populations.

3.1.1 Goal

The specific goal of this management plan is to maintain the breeding population of Ipswich Sparrows at the current level

This population’s restricted distribution means that it probably should never be down-listed from its status of Special Concern. Its breeding range cannot be increased; as far as is known, the bird has always bred almost exclusively on Sable Island. Instead, management can be directed only towards preventing any need for up-listing. Up-listing to Threatened for this species would occur if the population declined to fewer than 1000 mature individuals (COSEWIC 2003).

As mentioned previously, there is some debate over the current size of the population, so it is not possible to set an actual population goal. One of the management actions outlined in this plan is to establish an accurate and precise census method for the species. Intensive studies of the Ipswich Sparrow from 1967 to 1979 suggested that its population fluctuated widely but over the long term was stable at approximately 2000–3000 breeding birds (Stobo and McLaren 1975; McLaren 1979; Horn 1999). The most recent (1998) census, however (Smith et al. 2003), using more sophisticated statistical techniques, estimated the population at about double the size previously estimated (about 6000 birds). The lowest population estimates for this species occurred following two winters of unusually harsh weather (McLaren 1979); the population did not dip below the 1000 individual mark and showed signs of rapid recovery (Ross and McLaren 1981).

3.1.2 Objectives

The objectives of this management plan are to:

                    i.           Maintain the breeding population at the current level, allowing that the population may decline below the target minimum following particularly harsh winters;

                   ii.           Maintain the current amount and composition of breeding habitat;

                  iii.           Remove or reduce threats to Ipswich Sparrows and their breeding and wintering habitat.

3.2 Management actions

Management of a population that appears stable over the long term and is not currently under threat requires approaches that maintain the status quo. Significant gaps in knowledge, most notably of true population size and winter habitat needs, however, require attention, as does coordination of management efforts at the Canadian breeding grounds and the American wintering grounds.

Along with limited distribution, one of the main reasons the Ipswich Sparrow is of Special Concern is its small, and likely variable, population size (Horn 1999). Small size in itself is a risk to a population, because chance fluctuations in size can lower the population below its minimum viable level (Lande 2002). Thus, any small population’s size and variability must be monitored closely.

Dune habitats, including those on Sable Island (Byrne and McCann 1995), are dynamic, and Sable Island is the sparrow’s only breeding site (apart from a few hybrid pairs on the mainland). Therefore, changes in habitat availability must be monitored and their causes understood. Concern over erosion of dunes worldwide has led to considerable experience with manipulations of dune habitat -- for example, through construction of barriers to wind-blown sand, revegetation, and exclusion or removal of grazing animals. There now is general recognition, however, that these efforts can backfire unless the dynamics of the particular site are well understood (Doody 2001). Thus, large-scale manipulation of habitat should be discouraged until habitat trends are better understood and their cause can be attributed to anthropogenic factors (see section 2.4, “Knowledge gaps”).

The protective status of the wintering range is complex and needs a thorough review that specifically focuses on Ipswich Sparrow habitat (for a general review, see Bernd-Cohen and Gordon 1998). Portions are protected under a variety of local, provincial, state, and federal designations -- for example, state or provincial parks, national wildlife refuges, national parks, and national seashores. Much of the range is under private ownership, however, where protection ranges from private refuges to a wide variety of state, provincial, and municipal regulations that affect dune habitat, especially dune erosion (Bernd-Cohen and Gordon 1998).

3.2.1 Monitor breeding population

Census the breeding population at appropriate intervals.As of the updated status report (Horn 1999), the number of Ipswich Sparrows nesting on Sable Island was thought to be, based on censuses conducted from 1967 to 1979 and in 1995, between 2100 and 3400, excepting dips to 1700 and 1250 birds in 1977 and 1978, respectively. A 1998 census, however, used more statistically rigorous methods to estimate a population of 5962 individuals (Smith et al. 2003). The large disparity between the estimates clearly throws doubt on our ability to accurately estimate the size and variability of the population.

An accurate and precise census method must be developed and then applied as needed until the population’s size and stability are confirmed. Censuses from 1967 to 1995 were done by flushing all birds within transects of varying size that contained representative habitat. Transects were chosen so that they could be easily recognized and be returned to from year to year, to allow even sampling of all habitats and precise estimation of yearly trends. Since sampling was not random, however, estimates may have been biased, and their variability could not be estimated (Smith et al. 2003). The 1998 census overcame this problem by randomly selecting count transects, but likely at the expense of representative, repeatable sampling.

Experience gained in these attempts and in successful grassland censuses elsewhere (e.g. Wiens 1985; Walters et al. 2000) should be applied to developing an improved census method for long-term modelling. Requisite features include 1) low year-to-year variance attributable to sampling error, 2) randomization that allows estimates of sampling error, and 3) estimation of observer error. Observer error can be measured by noting birds’ distance to transects during counts (Buckland et al. 1998), by repeatedly sampling some transects, and by censusing in areas where the true number of birds is known from territory mapping and banding studies (Walters et al. 2000).

These recommendations assume that transect flush counts will be used. Other methods should not be ruled out, but each has its drawbacks for this population. Specifically, point counts during singing season are the preferred method at some other study sites for surveying grassland sparrows (e.g. Curnutt et al. 1998), including Savannah Sparrows (e.g. Rotella et al. 1999). On Sable Island, however, the singing season is short (Reid and Weatherhead 1990), singing males are hard to hear in the windy conditions (pers. obs.), and the density of singing males may vary only weakly with population size (Reid and Weatherhead 1988). Mark–recapture banding programs can be highly accurate and yield valuable demographic information (Sillett and Holmes 2002), but they would require intensive effort across this sparrow’s particularly long breeding season.

Once a census method is developed, power analyses should be done to determine how often censuses must be performed if declines in the population are to be detected. Data on year-to-year variability in population size are needed to do this, as well as to estimate the risk of extinction through a chance downswing in numbers. Although the 1967–1979 censuses provide such data, recent indications that those data are unreliable (Smith et al. 2003) suggest that power analysis must await either a new series of yearly censuses or vindication of the earlier censuses. Population viability analysis (PVA) might then be applied to formally estimate the risk of extinction from variability alone, although infrequent catastrophes, such as storms, usually make PVA models overly optimistic for localized populations, even large ones (Pimm and Bass 2002).

3.2.2 Monitor breeding habitat

Estimate breeding habitat area and distribution. On the breeding ground, the area and distribution of vegetation across the island should be measured on a regular basis to detect changes across years. Aerial photography seems to be the most thorough and efficient way to do this (Freedman 1996; Desjardins 2002), although the use of satellite imagery to discern both vegetation (e.g. Mayer et al., no date) and topography (DeStoppelaire et al. 2001) should be explored. Certain habitats on Sable Island are difficult to discern from aerial photos (Z. Lucas, pers. commun.), so at first these surveys should be ground truthed. If the final design of the sparrow censuses (see section 3.2.1 above) requires or at least allows collection of data on vegetation distribution, such data might be used for ground truthing.

Surveys should be conducted often enough to detect not only changes in the total area of vegetated terrain, but also changes in the preponderance and continuity of low- and high-quality habitats for the sparrows -- marram- and heath-dominated terrain, respectively. A survey interval of 5–10 years, as recommended in the Sable Island conservation strategy (Beson 1998), seems realistic, given the high cost of surveys. It may also be adequate, because large-scale changes in habitat will presumably be slow. This interval should be reevaluated, however, as new data become available.

The Sable Island Preservation Trust is working with the Centre of Geographic Sciences (Nova Scotia Community College, Annapolis Valley Campus) to produce a digitized, georeferenced map that will greatly facilitate future censuses and vegetation surveys. A pilot comparison of aerial photos taken by this project in 2002 with provincial photos from 1996 and earlier data did not occur because of a funding shortfall; however, this project should be pursued (Desjardins 2002).

3.2.3 Examine conservation status of SableIsland

Strengthen legal protection of habitat.Sable Island is legally protected through the Sable Island Regulations of the Canada Shipping Act and theMigratory Bird Sanctuary Regulations of the Migratory Birds Convention Act, 1994. The former controls access to the island and regulates activities on it, while the latter prohibits disturbance of migratory birds and their nests. Neither protects habitat per se.

Critical habitat for Roseate Tern (Sterna dougallii) has been identified on Sable Island and will be protected under theSpecies at Risk Act. However, that critical habitat is centred on tern colonies and may only marginally overlap with Ipswich Sparrow habitat. Further steps should be taken to provide adequate protection.

3.2.4 Ensure regulatory compliance on SableIsland

Promote and ensure compliance with regulations on Sable Island. Sable Island’s isolation provides some protection, but its isolation will decrease as better and cheaper navigational aids make trips to the island easier. Most visits, whether project-related (e.g. maintenance of facilities, research) or more informal, are unlikely to affect the sparrow population. Nonetheless, they do carry a low risk of serious inadvertent or intentional damage to sparrow habitat -- for example, through fire, introduction of mammalian predators, or introduction of non-native plants. The latter two threats in particular have characterized the history of Sable Island’s biota.

Eliminating these threats requires close monitoring of all human activities on the island. Currently, visits to the island are very closely monitored. Except for persons in distress, permission to visit the island must be granted by the Canadian Coast Guard, to whom this authority was delegated by the Minister of Fisheries and Oceans Canada, pursuant to the Canada Shipping Act. All visitors are briefed on environmental protocol upon arrival and monitored throughout their visit by year-round resident staff.

3.2.5 Ensure precautionary approach to projects with potential impacts on Ipswich Sparrows

Critically examine projects for potential effects on Ipswich Sparrows and their habitat. Review of project proposals should always consider the potential for interactions with the Ipswich Sparrow and its habitat. Through application of environmental assessment processes, project alternatives should be identified, potential impacts avoided or minimized, uncertainties investigated, impact predictions verified, and mitigation effectiveness tested, taking into account the goals, objectives, and actions set out in the management plan. Throughout the breeding, migration, and wintering range of the Ipswich Sparrow, attention should be given to any project or activity that could result in 1) the loss or alteration of habitat, 2) the introduction of predators to Sable Island, or 3) direct mortality (e.g. collision with vertical structures, spills). A focus should be placed on assessing risk to habitat on Sable Island and ensuring that the management objective of maintaining available breeding habitat is respected.

Multiple projects and activities may have cumulative effects that are undetectable in the short term. Therefore, it is important that decisions on proposed projects that could interact with the Ipswich Sparrow and its habitats be informed by application of the precautionary principle, a consideration of potential contributions to cumulative effects, and a consideration of mitigation measures that could be taken to avoid or minimize adverse effects, including alternative means of carrying out the project. After a consideration of such factors, any approval that may be granted so as to allow a project to proceed should be accompanied by the requirement for an effects monitoring or follow-up program that is undertaken by personnel experienced with the Ipswich Sparrow and is sensitive enough to detect subtle cumulative effects. 

3.2.6 Conserve wintering IpswichSparrows and their habitat

Collaborate with U.S. authorities to identify Ipswich Sparrow as a priority species. The North American Bird Conservation Initiative (NABCI) is a coalition of government, academia, private organizations, and industry in Canada, the United States, and Mexico. The objective of NABCI is to advance bird conservation through evaluation, planning, and implementation. NABCI divides North America into Bird Conservation Regions (BCR) and assesses the conservation priority of species in each region.

The Ipswich Sparrow is listed as a “highest priority” landbird species in BCR 14 (Dettmers 2003), the region in which it breeds as well as winters in small numbers. Wintering Ipswich Sparrows are not currently addressed in either BCR 27 or BCR 30, regions that cover the vast majority of their wintering range. To identify and promote actions that will benefit wintering Ipswich Sparrows, discussions with planning personnel from BCR 27 and BCR 30 should occur.

The size of this bird’s breeding range is dwarfed by its wintering range, suggesting that the wintering population is spread thinly across the eastern seaboard. Within that range, however, the bird appears to have specific habitat requirements that have not been adequately assessed. Also, islands off Virginia may host the bulk of the wintering population, but have never been formally searched (Stobo and McLaren 1971). Interest in counting Ipswich Sparrows in winter has stayed low since the bird’s relegation to subspecies status (McLaren 1979); CBC totals remain low and hence unreliable (Horn 1999).

Repeat winter survey. The survey of Stobo and McLaren (1971) should be repeated, with the improvements they suggest -- namely, more objective assessment of habitat associations and formal surveys of the islands off Virginia. A study of the behaviour and ecology of the bird on its wintering grounds would be invaluable for understanding its habitat needs and thus choosing appropriate management options. Both tasks would of course be easier with the participation of university or government researchers from the mid-Atlantic states.

Changes in wintering habitat should also be monitored, but this will first require better identification of that habitat than we currently have. As a preliminary step, a literature search of data on dune habitat trends along the east coast of North America would be an invaluable tool for deciding whether protection of winter habitat should be a management priority.

3.2.7 Implement education and communication programs

Engage public and media. Public support for protection of Sable Island and especially wintering habitat will aid management efforts. The Ipswich Sparrow, as one of Canada’s only endemic songbirds, adds to the appeal of Sable Island as a special place for Canada. Publicizing this fact will be beneficial for public and, in turn, political and financial support of conservation of Sable Island and the sparrow. Interest in this particular bird may translate directly into better estimates of winter population trends and distribution, as more birders seek them out during CBCs. Interest and awareness can be increased via public talks, web postings, pamphlets, and feature articles, both in Canada and along the Atlantic seaboard. The Canadian Wildlife Service and researchers at Dalhousie University have conducted periodic radio and TV interviews and public lectures on Ipswich Sparrows, although no formal campaign has been launched.

3.3 Recommended approach/scale for managing the species

Ipswich Sparrows use a variety of habitats on Sable Island, so their conservation is consistent with conservation of the island as a whole but not coincident with management of any single habitat. Also, their combined need for the island for breeding and the entire Atlantic U.S. coastline for wintering is unique and requires an approach that targets the population, rather than the habitat or species associated with it.

3.4 Evaluation

Management will be successful over the long term if the breeding population and both breeding and wintering habitats remain stable. Evaluation of management success will be through long-term monitoring programs that assess trends in breeding habitat and breeding population size. Any indication that breeding habitat, especially heath habitat, is declining should trigger immediate reassessment of the management needs of the sparrow and the island. Ipswich Sparrow management should be part of an integrated management plan for the island.

3.5 Summary table: management strategies

Priority1 Objective Section Management action Specific steps Outcomes or deliverables
High i 3.2.1 Monitor breeding population Census the breeding population at appropriate intervals Determine population trends and detect changes
Moderate ii 3.2.2 Monitor breeding habitat Estimate breeding habitat area and distribution Detect breeding habitat changes
Moderate ii/iii 3.2.3 Examine conservation status of Sable Island Strengthen legal protection of habitat Protect breeding habitat
High All 3.2.4 Ensure regulatory compliance on Sable Island Promote and ensure compliance with regulations on Sable Island Minimize disturbance to breeding birds and breeding habitat
High All 3.2.5 Ensure precautionary approach to projects with potential impacts on Ipswich Sparrows Critically examine projects for potential effects on Ipswich Sparrows and their habitat

Minimize disturbance to birds and habitat

Protect birds and habitat

Low ii/iii 3.2.6 Conserve wintering Ipswich Sparrows and their habitat

Collaborate with U.S. authorities to identify Ipswich Sparrow as a priority species

Repeat winter survey

Determine necessary winter habitat

Protect winter habitat

Low All 3.2.7 Implement education and communication programs Engage public and media Increase awareness

1   Priorities are defined as follows: High = top priority action, without which population may decline irreversibly; Moderate = required to evaluate and guide recovery actions; Low = all other actions necessary to provide for survival.

3.6 Implementation schedule

Shaded boxes indicate the proposed year(s) of implementation.

Specific steps Section Lead1 Other1 2005 2006 2007 2008 2009
Census the breeding population at appropriate intervals 3.2.1 CWS University Specifically, develop census method, which will dictate timing of future surveys      
Estimate breeding habitat area and distribution 3.2.2 CWS

COGS

SIPT

       
Strengthen legal protection of habitat 3.2.3 CWS            
Promote and ensure compliance with regulations on Sable Island 3.2.4

CWS

MSC

DFO

  Ongoing
Critically examine projects for potential effects on Ipswich Sparrows and their habitat 3.2.5

CWS

EPB

  Ongoing
Collaborate with U.S. authorities to identify Ipswich Sparrow as a priority species 3.2.6 CWS

U.S. agencies

NABCI

 
Repeat winter survey 3.2.6

U.S. agencies

NABCI

CWS To be determined
Engage public and media 3.2.7 Various    

1 Acronyms are as follows:

COGS:      Centre of Geographic Sciences, Nova Scotia Community College, Annapolis Valley Campus

CWS:        Canadian Wildlife Service, Environmental Conservation Branch, Environment Canada

DFO:         Department of Fisheries and Oceans

EPB:          Environmental Protection Branch, Environment Canada

MSC:        Meteorological Service of Canada, Environment Canada

NABCI:    North American Bird Conservation Initiative

SIPT:        Sable Island Preservation Trust

 

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