Reproduction success of American kestrels exposed to dietary polychlorinated biphenyls

While reproduction of wild birds is adversely affected by multiple environm ental contaminants, we determined that polychlorinated biphenyls (PCBs) alo ne alter reproduction. Captive American kestrels (Falco sparverius), fed PC B-spiked (Aroclor((R)) 1248:1254:1260) food (7 mg/kg body weight/d) prior t o and during the first breeding season only (100 d) laid eggs with environm entally relevant levels of total PCBs (34.0 mug/g whole egg wet wt vs 0 mug /g for controls). Reproduction changed during, not after, PCB exposure in t his two-year study. The PCB-exposed pairs laid smaller clutches later in th e season and laid more totally infertile clutches. Hatching success was red uced in PCB-exposed pairs, and 50% of PCB nestlings died within 3 d of hatc hing, Nearly 60% of PCB-exposed pairs with hatchlings failed to produce fle dglings. Higher levels of total PCB residues and congeners were associated with later clutch initiation and fewer fertile eggs, hatchlings, and fledgl ings. We suggest that nonpersistent PCB congeners have a greater influence on reproduction than do persistent congeners.