Evaluation of a novel feather scoring system for monitoring feather damaging behaviour in parrots

Feather damaging behaviour is common in captive psittacine birds and there is a need for reliable methods to evaluate the efficacy of therapeutic and preventive interventions. This study compared the inter- and intra-observer reliabilities of a novel feather scoring system with an existing system to assess the plumage of grey parrots (Psittacus erithacus). Regions of the body were photographed separately at 1 week intervals and shown at random to 35 examiners (avian veterinarians and veterinary students), who used the two scoring systems to assess plumage. Since the quality of the photographs was insufficient to allow accurate assessment of the individual flight and tail feathers, the novel scoring system was only evaluated for its reliability regarding covert and down feathers. Inter- and intra-observer reliabilities were determined using the intra-class correlation coefficient. Bland-Altman analysis was performed to determine absolute reliabilities for both systems. Correlation coefficients were 0.90 and 0.95 for intra-observer reliability and 0.83 and 0.89 for inter-observer reliability for the existing and novel feather scoring systems, respectively. When using the novel system, a change in plumage condition of ≥10% was needed to ensure that the change reflected a real difference in 95% of cases, while a change of ≥15% was needed for the existing system. Since it may take from 4 weeks (covert or down feathers) to over 1 year (flight or tail feathers) for feathers to regrow, sufficient time should be allowed to elapse between two scoring sessions to reliably evaluate the efficacy of preventive or therapeutic interventions for feather damaging behaviour.