Survey for anticoagulant rodenticides in raptors from New York City, 2012-15

In the first 3 months of 2012 we examined 3 red-tailed hawks (Buteo jamaicensis), from New York City with necropsy and analytical findings consistent with fatal hemorrhage facilitated by anticoagulant (AC) rodenticide... [ view full abstract ]

In the first 3 months of 2012 we examined 3 red-tailed hawks (Buteo jamaicensis), from New York City with necropsy and analytical findings consistent with fatal hemorrhage facilitated by anticoagulant (AC) rodenticide exposure. To better assess the general level of exposure of raptors to ACs in this part of New York State we analyzed liver samples from all raptors received from this area from January 2012 to early April 2015 regardless of diagnosis. Of 54 raptors examined, ACs were detected in 84 %, either singly (18%) or in combination. In birds with detections, difethialone was found in 71 %, brodifacoum in 69%, and bromadiolone in 44%). Diphacinone was detected in only 3 birds (6%), and only at low levels (0.01 - 0.06 ug/g). One-third [16 red-tailed hawks, 1 red-shouldered hawk (Buteo lineatus), 1 snowy owl (Nyctea scandica)] were judged to have died from AC exposure. In this subset, total AC loads ranged from 0.16 ug/g to 0.95 ug/g averaging 0.45 ug/g. In the 34 birds for which ACs were not suspected as a mortality factor at necropsy, ACs were detected in 74%, with total AC loads ranging from 0.02 ug/g to 0.52 ug/g, averaging 0.17 ug/g (S.D. = 0.13), and exceeding 0.1 ug/g in 38%. This survey highlights the considerable threat of secondary AC rodenticide poisoning to red-tailed hawks in an urban setting and the growing prominence of difethialone in these poisonings.