Preventing local extinctions of tidal marsh endemic Seaside Sparrows and Saltmarsh Sparrows in eastern North America

Abstract

Globally limited to 45,000 km2, salt marshes and their endemic species are threatened by numerous anthropogenic influences, including sea-level rise and predator pressure on survival and nesting success. Along the Atlantic coast of North America, Seaside (Ammospiza maritima) and Saltmarsh (A. caudacuta) sparrows are endemic to salt marshes, with Saltmarsh Sparrows declining by 9% annually. Because vital rates and factors affecting population persistence vary for both species, local estimates are necessary to best predict population persistence in response to management actions. We used a metapopulation model to estimate the population viability of the breeding Seaside and Saltmarsh sparrow populations in coastal New Jersey over a 42-yr period. We incorporated empirical data on the vital rates and abundances of these populations and simulated the effect of low (0.35 m) and high (0.75 m) levels of sea-level rise. We found that the Seaside Sparrow population persisted under both sea-level rise scenarios; however, the Saltmarsh Sparrow population reached a quasi-extinction threshold within 20 yr. Using the same framework, we modeled potential management scenarios that could increase the persistence probability of Saltmarsh Sparrows and found that fecundity and juvenile survival rates will require at least a 15% concurrent increase for the local population to persist beyond 2050. Future field research should evaluate the feasibility and effectiveness of management actions, such as predator control, for increasing Saltmarsh Sparrow vital rates in order to maintain the species in coastal New Jersey.

Nest survival of Seaside Sparrows (Ammospiza maritima) in the wake of the Deepwater Horizon oil spill

“…Our daily nest survival estimates are low relative to other temperate passerines (e.g., [ 66 – 68 ]), but are within the range of other estimates for Seaside Sparrows [ 45 , 46 , 69 ]). Predation accounted for 91% of all known nest failures at our sites, in contrast to several studies on the Atlantic coast, where flooding is often the main cause of Seaside Sparrow nest failure [ 45 , 46 , 70 ] (but see also [ 71 , 72 ]). We documented marsh rice rat and American mink as 2 main nest predators.…”

Geographic Variation of Mercury in Breeding Tidal Marsh Sparrows of the Northeastern United States

“…Sea-level rise is the principal driver of tidal marsh sparrow population declines (Shriver et al 2007;Gjerdrum et al 2008), and could cause the extinction of the saltmarsh sparrow by mid-century (Correll et al 2017;Field et al 2017Field et al , 2018Roberts et al 2019). Concurrently, some tidal marsh sparrows may face challenges coming from industrial practices in terrestrial systems that expose them and other wildlife to potentially dangerous levels of Hg contamination.…”

“…Anthropogenic activities including coastal development, marsh fragmentation, and alteration of hydrology have all reduced habitat available for both saltmarsh and seaside sparrows (Greenlaw et al 2020;Post and Greenlaw 2020), and global sea-level rise threatens saltmarsh systems range-wide (Bayard and Elphick 2011;Field et al 2017;Greenlaw et al 2020;Post and Greenlaw 2020). The saltmarsh sparrow is considered "globally endangered" by the International Union for Conservation of Nature in response to rapid population declines (Birdlife International 2018), decreasing at 9% per year with over 70% of the global population lost since the 1990s (Correll et al 2017;Roberts et al 2019). Sea-level rise and increased tidal flooding risk are the major drivers of population loss for this species, as approximately 60% of all nest failures occur due to flooding events (Shriver et al 2007;Gjerdrum et al 2008), and are projected to cause extinction as early as 2035 (Field et al 2017(Field et al , 2018Roberts et al 2019).…”

“…The saltmarsh sparrow is considered "globally endangered" by the International Union for Conservation of Nature in response to rapid population declines (Birdlife International 2018), decreasing at 9% per year with over 70% of the global population lost since the 1990s (Correll et al 2017;Roberts et al 2019). Sea-level rise and increased tidal flooding risk are the major drivers of population loss for this species, as approximately 60% of all nest failures occur due to flooding events (Shriver et al 2007;Gjerdrum et al 2008), and are projected to cause extinction as early as 2035 (Field et al 2017(Field et al , 2018Roberts et al 2019). Because salt marshes and coastal estuaries are often impacted by polluted urbanized watershed runoff (Schwarzbach et al 2006), heavy metal contamination may present additional challenges to sparrow reproductive success and survival.…”

Mercury exposure of tidal marsh songbirds in the northeastern United States and its association with nest survival

“…In saltmarsh sparrows and tidal marsh-nesting Acadian Nelson's sparrows, high tides are the largest reported influence on nest survival (Gjerdrum et al 2005;Shriver et al 2007;Humphreys et al 2007), with the majority of nest failure occurring during astronomical high tide events that occur in a 28-day cycle. In fact, population viability models predict that saltmarsh sparrows will be extinct before 2060 due to reproductive failures driven by sea-level rise (Field et al 2017;Roberts et al 2019). It is unclear whether Hg exposure may alter this trajectory by further impacting fecundity because a direct link between Hg exposure and fecundity at the individual level has never been quantified in either taxon.…”