Assessment of Shorebird Migratory Fueling Physiology and Departure Timing in Relation to Polycyclic Aromatic Hydrocarbon Contamination in the Gulf of Mexico

Abstract

Shorebirds depend on staging sites in the Gulf of Mexico that are frequently subject to pollution by oil and its toxic constituents, polycyclic aromatic hydrocarbons (PAHs). It was hypothesized that PAH contamination lowers staging site quality for migratory shorebirds, with consequences for fueling and departure timing. Sediment total PAH concentrations were measured at six staging sites along the Texas and Louisiana Gulf Coast. Sites in Louisiana were expected to have higher total PAH concentrations as they were more heavily impacted by the Deepwater Horizon oil spill. From 2015 to 2017, 165 Sanderling (Calidris alba) and 55 Red knots (C. canutus) were captured at these same sites during their northward migration (late April to mid May). Mass, body morphometrics, and plasma metabolite measurements were taken to determine fuel loads and fueling rates, and a subset of birds (120 Sanderling and 39 Red knots) received a coded radio tag to determine departure dates using the Motus telemetry array. Compared to Texas sites, sediment in Louisiana had higher total PAH concentrations, dominated by heavier 6 ring indeno[1,2,3-cd]pyrene (48%). Plasma metabolite profiles suggested that fueling rates for Sanderling, but not Red knots, tended to be lower in Louisiana, and both species departed later than the study average from Louisiana. However, multiple factors, including migration patterns, food supply, and other contaminants, also likely influenced fueling and departures. PAH contamination in the Gulf of Mexico remains an ongoing issue that may be impacting the staging site quality and migration timing of long-distance migratory birds.

Differences in Migration Timing along the Midcontinental Flyway in Sanderling (Calidris alba) from Three Gulf of Mexico Staging Areas

“…1). We classified trapping sites in the GOM into three staging areas: (1) North Padre Island, Texas; (2) Bolivar Flats, Texas; and (3) Louisiana (composed of Elmer's Island, Grand Isle, and Port Fourchon) based on evidence that individuals did not make local movements between these three areas (Bianchini and Morrissey 2018a).…”

“…New World Sanderling can migrate up to 10,000 km annually between their wintering grounds in South and Central America and the Gulf of Mexico (GOM) and their breeding grounds in the Canadian Arctic (Macwhirter et al 2020). We recently found that departure dates vary among Sanderling trapped in different staging sites in the GOM, which is linked to individual condition and oil spill contaminant levels (Bianchini and Morrissey 2018a). Here, we investigated whether these individuals from different GOM staging sites continue to show differences in arrival and subsequent departure timing as they migrate farther north.…”

“…We tracked Sanderling as they travelled north using the Motus Wildlife Tracking System (Motus), an international array of automated radio-telemetry receivers (Taylor et al 2017). In a previous study, we found that individuals trapped in North Padre, Texas, departed earlier from the GOM than individuals trapped in Bolivar Flats, Texas, and Louisiana (Bianchini and Morrissey 2018a). Therefore, here we examined whether Sanderling departing from North Padre would continue to exhibit differences in travel times to and departure timing from Saskatchewan relative to individuals departing from the other GOM sites.…”

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

“…The most immediate impacts of oil are from physical contact or ingestion [ 15 ]; an estimated 600,000–800,000 birds were killed during the DWH spill [ 16 ]. Negative impacts on bird populations also result from long-term exposure to polycyclic aromatic hydrocarbons (PAHs) via multiple pathways [ 17 – 19 ], or from changes in habitat quality or resource availability due to oiling [ 4 , 13 ]. For example, following the Exxon Valdez spill in Alaska, Harlequin Duck ( Histrionicus histrionicus ) populations did not fully recover for at least 9 years post-spill [ 20 ], and experienced chronic exposure to oil for at least 20 years [ 17 ].…”

Antibacterial and anatomical defenses in an oil contaminated, vulnerable seaduck

“…In particular, demographic variables such as the proportion of nonbreeders and adult survival rates have been suggested to be severely affected by oil spills (Votier, Birkhead, et al., 2005 ; Votier, Hatchwell, et al., 2005 ; Wolfaardt et al., 2009 ). Finally, while several studies have focused on birds killed by oil pollution, fewer studies have examined the physiological and plumage consequences for individuals that survived oil spills (Alonso‐Alvarez et al., 2007 ; Bianchini & Morrissey, 2018 ; Champoux et al., 2020 ; Horak et al., 2017 , 2020 ).…”