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

Abstract

In 2010, the Deepwater Horizon oil spill released an estimated 4.9 million barrels of oil into the Gulf of Mexico, damaging coastal ecosystems. Seaside Sparrows (Ammospiza maritima)—a year-round resident of Gulf Coast salt marshes—were exposed to oil, as shown by published isotopic and molecular analyses, but fitness consequences have not been clarified. We monitored nests around two bays in Plaquemines Parish, Louisiana, USA from 2012–2017 to assess possible impacts on the nesting biology of Seaside Sparrows. A majority of nests failed (76% of known-fate nests, N = 252 nests, 3521 exposure-days) during our study, and predation was the main cause of nest failure (~91% of failed nests). Logistic exposure analysis revealed that daily nest survival rate: (1) was greater at nests with denser vegetation at nest height, (2) was higher in the more sheltered bay we studied, (3) decreased over the course of the breeding season in each year, and (4) was not correlated with either sediment polycyclic aromatic hydrocarbon concentrations or estimated predator abundance during the years for which we had those data. Although the Deepwater Horizon spill impacted other aspects of Seaside Sparrow ecology, we found no definitive effect of initial oiling or oiled sediment on nest survival during 2012–2017. Because predation was the overwhelming cause of nest failure in our study, additional work on these communities is needed to fully understand demographic and ecological impacts of storms, oil spills, other pollutants, and sea-level rise on Seaside Sparrows and their predators.

Observations of mixed parentage and male-biased primary sex ratio in Seaside Sparrow (Ammospiza maritima) nests along the Gulf of Mexico

“…Study plots (25 ha; 50 × 500 m along marsh edge) were established in areas initially oiled ( n = 4) and areas not initially impacted ( n = 3) by the Deepwater Horizon event. Nests were found as part of a study examining nest survival following the oil spill; nest search effort was equal across plots within years (Hart et al 2021).…”

“…Predation pressure may also influence EPP (e.g., Teru and Itsuro 2016, Abbey-Lee et al 2018). In our study area, Seaside Sparrow nest survival is higher in more sheltered contexts (Hart et al 2021), so we asked if EPP was less prevalent in our more sheltered sites. Statistical tests were performed in R 4.1.1 (R Core Team 2021).…”

“…In this paper we describe mixed parentage and nestling sex ratios from Seaside Sparrow broods in southeastern Louisiana in 2012–2017. This work was part of a larger study of effects of the 2010 Deepwater Horizon oil spill (see, e.g., Bergeon Burns et al 2014, Bonisoli-Alquati et al 2016, Olin et al 2017, Perez-Umphrey et al 2018, Bonisoli-Alquati et al 2020, Hart et al 2021, Snider et al 2022), allowing us to consider whether patterns of EPP and nestling sex ratios were associated with oiling status, relative sparrow abundance, clutch size, or seasonality.…”

Sex and habitat drive hantavirus prevalence in marsh rice rat populations impacted by the Deepwater Horizon oil spill

“…Site‐level vegetation data were collected as part of another, concurrent study (Hart et al, 2021); GoMRI https://doi.org/10.7266/n7-w5g6-e664). Ground cover was quantified for a 5 m radius around randomly selected points ( n = 200; total).…”

“…A principal component analysis (PCA) was first used to evaluate structure in ground cover characteristics ( ggbiplot; Vu, 2011). Based on the results of the PCA (Figure 2) and Hart et al (2021), which found substantial overlap in PCA space for vegetation  treatment, it was more informative to investigate the site-specific relationship between ground cover characteristics and prevalence rather than group data points by treatment. The mean plot scores of PC1 and PC2 (Fischer et al, 2018;Kitagawa et al, 2020) for each site were used in analyses (described below) to evaluate whether prevalence was related to a site's ground cover characteristics.…”