Accumulation Features of Persistent Organic Pollutants in Neotropical Migratory Songbirds

Migratory songbirds have seen significant population declines over the last several decades. One threat to songbird populations may be due to adverse health effects of legacy contaminants such as organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs). Migratory songbirds spend the vast majority of their annual cycle either migrating or on their wintering grounds in Latin America; due to their annual movements they may be exposed to a wide variety of contaminants. The major aim of this dissertation was to examine accumulation features of persistent organic pollutants (POPs) in migratory songbirds. The specific objectives were to 1) examine seasonal variation of contaminant accumulation in migrant and resident songbirds, 2) determine what ecological factors, through the use of stable isotopes (δv13C, δv15N, and δv2H), best explain contaminant levels and 3) determine the current state of the research on POPs levels for birds in Latin America. In general, no significant accumulation of contaminants during migration was observed for migratory songbirds. Resident birds from Texas were significantly more contaminated with €DE and €PBDEs compared to resident species from wintering areas (Yucatán and Costa Rica). Residents from Costa Rica also had the lowest levels of €PCBs. Stable isotopes revealed that there were only minor differences (≤ 2‰) in mean liver δ13C and δ15N values between migrants and residents, indicating similar diets. Results from linear regression models showed that δ15N was only useful in explaining €PCBs concentrations in resident birds from Texas and in songbirds from Yucatán. A significant relationship was found between δ13C and DDE and €PBDEs in residents from Texas; birds from College Station were more enriched in ^13C and had elevated levels of POPs suggesting proximity to urban environments as a source of contaminant exposure. Significant temporal decreases in POPs levels was observed in birds from 1980 – 2018. DDE was the most frequently reported contaminant, followed by €PCBs. Levels of contaminants were generally below those known to cause adverse health effects. The regional distribution of the data is currently uneven with most studies coming from Mexico, followed by Brazil, and centered on coastal regions and aquatic species