From Chuck Knapp:

Here we report a nocturnal predation event on a subadult green iguana, Iguana iguana, by an adult spectacled owl, Pulsatrix perspicillata at the Iguana Verde Foundation located in the Gandoca-Manzanillo Wildlife Refuge in Costa Rica. Nocturnal predation events are observed rarely and to our knowledge this is the first account of a predation on I. iguana by any avian species in the family Strigidae and augments our knowledge of nocturnal predators of green iguanas.  

Bessier, E., J.A. Perla, E. Bonilla Diaz, D. Martinez, and C.R. Knapp. 2010. Iguana iguana. Predation. Herpetological Review. 41:224.