Newcastle disease virus (NDV) and avian influenza virus (AIV) are pathogens of major economic and social importance, and the diseases they cause are often devastating, particularly in domestic poultry. Both viruses are naturally found in a wide variety of wild birds, particularly aquatic species, where asymptomatic infection typically occurs. Wild birds are therefore considered to be a natural reservoir for both viruses. Wild birds kept in captivity are in an environment that promotes transmission of infection with both influenza and Newcastle disease viruses. This report describes a survey for the detection of antibodies against Newcastle disease and avian influenza A viruses using the hemagglutination inhibition test in samples from 88 wild birds from 38 species in four Bulgarian zoos. Samples with positive results against NDV were also tested against avian paramyxovirus type 3 (APMV-3). Real-time reverse-transcriptase PCR was also performed to detect viral RNA of NDV and AIV among 127 wild birds from 57 species from the same zoos. In 13 samples from seven avian species (ten birds from the family Phasianidae, two from the family Numidae, and one from the family Columbidae), antibodies against APMV-1 were detected. Seven birds, whose sera were APMV-1 positive, had been vaccinated. The other six birds (five Phasianidae representatives and one of the Columbidae family) had no immunization history. No antibodies against both H5 and H7 AIV and against APMV-3 were detected, and no RNA of NDV and AIV were detected.