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Saltmarsh Sparrow Ammospiza caudacuta



Justification

Justification of Red List category
This species is declining at a rapid rate. It is therefore listed as Endangered.

Population justification
Recent population estimates suggest that the species may number 53,000 (37,000-69,000) individuals in the breeding range (Wiest et al. 2016). This population estimate was conducted to largely capture the breeding population (C. Elphick in litt. 2017) and so this may actually equate to the number of mature individuals. Whilst this species was previously thought to adopt a 60:40 sex ratio, recent findings found that this is likely a result of interannual variation and when measured across multiple years, the sex ratio is confirmed to be ~1:1 (Benvenuti et al. 2018). As a result, the population is placed in the band 37,000-69,000 mature individuals.

Trend justification
Correll et al. (2017) estimated that the species has undergone a 9.0% annual decline throughout its range since the 1990s. This equates to a 61.1% decline over a ten year period (placed here in the range 50-79%), which is considered likely to continue into the future.

Distribution and population

Ammospiza caudacuta is confined to a narrow Atlantic coastal strip of the U.S.A. from Maine southwards to the Delmarva Peninsula, with a southward shift in winter as far as Florida and north to Maryland and Massachusetts (Greenlaw and Woolfenden 2007, J. S. Greenlaw in litt. 2012). It is common to abundant in saltmarshes in the core of its range (J. S. Greenlaw in litt. 2012) and has been estimated to number c.250,000 individuals (Rich et al. 2003, P. Comins in litt. 2003); more recent estimates suggest that the species may number 53,000 (37,000-69,000) individuals in the breeding range (Wiest et al. 2016). Its highly fragmented range is c.20,000 km2, within which it occupies an area of less than 2,000 km2 of appropriate habitat (P. Comins in litt. 2003, C. Elphick in litt. 2003).

Ecology

Ammospiza caudacuta is found in tidal coastal marshes where there is dense cordgrass, blackgrass or saltmeadow grass. Home ranges preferentially include Spartina patens and Juncus gerardii cover (Shriver et al. 2010), and nesting success is positively correlated with the presence of the latter (Gjerdrum et al. 2008). Nesting takes place from mid May through to early September and males sing occasionally (C. Elphick in litt. 2012, K. O'Brien in litt. 2020) during this time. Nests are placed 6-15 cm above the ground and usually 3-5 greenish white to greenish blue eggs, speckled with reddish brown, are laid. They are not territorial and are not usually found in mixed species groups or flocks (Rising 1996), apart from with other tidal marsh sparrows during non-breeding periods (J. S. Greenlaw in litt. 2012, C. Elphick in litt. 2016, Greenlaw et al. 2020).

Threats

Localised populations have suffered throughout its range from the historical loss and fragmentation of marshes owing to urban development (Greenlaw and Rising 1994, Sibley 1996, C. Elphick in litt. 2003, 2012). Recent population declines are associated with the presence and number of downstream tidal restrictions (levees, roads, train tracks, etc.) that alter natural flow of tide waters in and out of marshes, although the mechanism behind this link is not well known (Correll et al. 2017). Further on-going threats include increased tidal flooding (e.g., due to sea level rise and increased storm surge frequency/magnitude), hybridization with Nelson’s Sparrows A. nelsoni (which may reduce fitness and limit the number of pure Saltmarsh Sparrow populations), degradation from chemical spills and other pollutants, and invasive species (particularly Phragmites, which makes the habitat completely unsuitable) (C. Elphick in litt. 2016). Predation also presents another notable threat to the species. Whilst the identity and relative impact of the primary predators is uncertain, predation is known to dramatically reduce nest and juvenile survival throughout the species's range, particularly in the southern portion (Roberts et al. 2017).

This species appears to be extremely vulnerable to a slight rise in sea-level, as nests are lost due to flooding (Bayard and Elphick 2011, Shriver et al. 2016, Field et al. 2017a). To date the species has not been recorded nesting outside of high marsh habitats; the implications of sea-level rise and loss of high marsh habitats are therefore extremely serious, with the potential for the species to go extinct in the near future (see Field et al. 2017a); already-low vitality rates, largely attributable to the impact of predation throughout the southern portions of this species's range, are also thought to be generating localised extinctions in the immediate future (Roberts et al. 2019). The amount by which sea level will rise owing to climate change remains uncertain but Spartina patens dominated marsh (high marsh) may disappear or be greatly reduced in size as the large amount of development along the coast means that there is limited scope for marshes to migrate inland; and vegetation within marshes is already changing in a manner that suggests marshes are getting wetter (Field et al. 2016). High precipitation during the breeding season is also known to be negatively associated with population growth in Saltmarsh Sparrow populations (Shriver et al. 2016) and given the increased frequency and intensity of rainfall and storm events being witnessed throughout the species's range, this will likely drive further ongoing population declines in the future (K. O'Brien in litt. 2020).

Conservation actions

Conservation Actions Underway
The Saltmarsh Habitat and Avian Research Program (SHARP) and their partners have conducted a number of recent studies to assess the species’ status.  These include a range-wide population survey (Wiest et al. 2016) and trend assessment (Correll et al. 2017), demographic studies (e.g. Field et al. 2017a,b), studies of changing habitat conditions (Field et al. 2016), as well as studies on many other aspects of the species’ biology. The species occurs within a number of protected areas supporting coastal habitat, and restoration of tidal marshes is on-going (C. Elphick in litt. 2012). Past efforts to restore tidal flow to marshes appear not to have benefitted saltmarsh sparrow (Elphick et al. 2015). Over the past few years, saltmarsh sparrows have become more central to coastal marsh planning within the species’ range and SHARP has begun investigating the effects of coastal management activities on the species (C. Elphick et al. in litt. 2016). This work includes investigations of potential methods to increase habitat area (including facilitation of marsh migration into upland habitats and creation of floating habitat structures) and systematic evaluation of a range of marsh management activities throughout the species’ range. Partners are working to identify historic and modern marsh manipulations to determine which ones are not healthy for salt marsh regeneration and working to restore areas which are water logged or holding back water. Novel approaches such as thin layer deposition, ditch remediation and re-vegetation are also underway (K. O'Brien in litt. 2020). The Atlantic Coast Joint Venture (ACJV) have developed a series of objectives to first stabilise, then increase Saltmarsh Sparrow populations, the focus of which centres on restoring and enhancing existing salt marsh patches and protecting adjacent inland areas that buffer existing salt marsh patches and provide corridors to allow marsh migration as sea levels rise in the future (ACJV 2020). Such plans comprise a primary focus of the ACJV's wider Salt Marsh Bird Conservation Business Plan (SMBCBP) for the Atlantic Flyway (ACJV 2019). 

Conservation Actions Proposed
Identify, protect and enhance high-elevation marsh suitable for breeding and less susceptible to flooding (C. Elphick in litt. 2016). Manage areas to reduce nest flooding on extreme high tides, and facilitate marsh migration at the upland edges of marshes (C. Elphick in litt. 2016).

Identification

13.5 cm. Well-marked and long-billed sparrow. Colourful orange, black and grey head pattern, grey crown and nape, and white streaks on back. Similar spp. Told from close relative Nelson's Sparrow A. nelsoni by its orange malar (brighter than breast), poorly defined white belly and the distinct black streaking on the breast and flanks. Voice Much softer song than A. nelsoni lacking distinctive final note of that species.

Acknowledgements

Text account compilers
Everest, J.

Contributors
Benstead, P., Benvenuti, B., Bird, J., Butchart, S., Butcher, G., Comins, P., Elphick, C., Greenlaw, J., Khwaja, N., Kovach, K., O'Brien, A., O'Brien, K., Olsen, B., Roberts, S., Rosenberg, K., Sharpe, C.J., Shriver, G., Symes, A., Wege, D., Wells, J. & Westrip, J.R.S.


Recommended citation
BirdLife International (2024) Species factsheet: Ammospiza caudacuta. Downloaded from https://datazone.birdlife.org/species/factsheet/saltmarsh-sparrow-ammospiza-caudacuta on 21/02/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org on 21/02/2024.