In ovo exposure to polychlorinated biphenyls: Reproductive effects on second-generation American kestrels

The reproductive success of wild birds has been affected by exposure to mul tiple contaminants. Reproduction of captive American kestrels (Falco sparve rius) was suppressed when adult birds were exposed to dietary polychlorinat ed biphenyls (PCBs). In this study, the reproductive effects of in ovo expo sure to PCBs is explored, along with determining effects on reproduction in second-generation birds indirectly exposed to PCBs. Reproductive changes i n this subsequent generation are examined separately in male and female bir ds. Captive American kestrels (F. sparverius) were hatched from clutches wi th eggs containing environmentally relevant levels of total PCBs (34.0 mug/ g whole egg WW versus 0 mug/g controls); parent birds had been fed PCB-spik ed (Aroclor 1248:1254:1260) food (7 mg/kg BW day(-1)) for 100 days until th eir eggs hatched. In 1999, the second-generation PCB birds were paired with unexposed kestrels having reproductive experience. In ovo PCB exposure sup pressed egg laying completely in 25% of PCB females and resulted in delays in clutch initiation and smaller clutch sizes for PCB male and female pairs . There was no evidence in this study of in ovo PCB treatment effects on fe rtility or hatching success. The decline in reproductive success was also r eflected in the reduced hedging success and higher incidence of complete br ood mortality of PCB nestlings. Differences between in ovo-exposed PCB male s and females but not between controls were evident in reproductive success . in ovo PCB exposure appears to have had greater effects on female kestrel s until clutch completion, with a greater time lag between pairing and egg laying, reduced numbers of pairs laying eggs, and smaller clutches being la id. In ovo PCB exposure has greater effects later in the breeding season on male kestrels, which had poorer hatching and hedging success relative to t he PCB females. Possible behavioral and physiological mechanisms involved i n these reproductive changes are discussed.