Around half of all parrots (a highly threatened order) live in captivity. Here, some species thrive. Others, however, breed poorly or display stereotypic behaviours indicating stress. Using data on the prevalence of three types of stereotypic behaviour in pet (50 species; 1,378 individuals) and aviculture hatch rates (115 species; 10,255 breeding pairs), we applied Phylogenetic Comparative Methods (PCMs) to test hypothesised causes of this variation (relating to species’ rarity and constraints on natural behaviour). In the first empirical evidence that high intelligence increases vulnerability to poor captive welfare, species with large relative brain sizes were found to be most at risk of oral and whole-body stereotypic behaviour. This suggests that if they are to be kept in private homes, such parrots must be offered substantially more cognitive stimulation. Self-harming behaviours involving feather damage were predicted by naturally relying on food items that require substantial handling, highlighting inadequacies in captive diets (often highly processed); while relatively low hatch rates in aviculture were predicted by small captive population sizes, potentially due to genetic bottlenecks, inbreeding, and/or low availability of compatible mates. These novel findings should help advance captive parrot husbandry, and inspire further research applying PCMs to understand and improve animal welfare.

Outcome variable data collection

Stereotypic behaviour 

Prevalence of three types of stereotypic behaviours (feather-damaging behaviour; other non-feather related oral stereotypic behaviour; and whole-body forms) were calculated from survey responses made by pet owners between April 1^st 2012 and July 1^st 2013 (www.parrotsurvey.com). These responses related to 1,378 parrots representing 50 species (meeting our inclusion criterion of n ≥ 5 birds/species). Using the same survey, we also collected detailed information on parrots’ living and rearing conditions. We calculated 10 species-typical demographic and husbandry characteristics, which could potentially act as confounds during analyses.

Captive hatch rates

We obtained captive hatch rates from the Psittacine Captive Breeding Survey, a 1991 census of over 31,000 parrots in 1,183 private breeding collections by TRAFFIC USA. These breeding records enabled us to calculate chicks hatched/breeding pair/year for 115 species (meeting our inclusion criterion of n ≥ 3 breeding pairs/species). To control for species differences in life history, data on natural fecundity (product of the median eggs/clutch and clutches/year) were also obtained for inclusion in subsequent models.

Predictor variable data collection

We collated species-level data on sociality in the wild (maximum feeding group size when foraging; presence or absence of communal roosting when sleeping; reliance on extensive foraging behaviour in the wild (inferred from the percentage of the natural diet requiring prolonged food search and handling); and generalism/behavioural plasticity (habitat and diet niche breadth, feeding innovation rate, relative brain size). Our two measures of rarity were endangeredness according to IUCN Red List categories (www.iucnredlist.org), and captive population sizes in aviculture.

Missing values are coded as NA.

 

Description of variables

Species_name: Species scientific name 

English: Species common name

 

Outcome variables

FDB: Prevalence of feather-damaging behaviour

OSB: Prevalence of oral stereotypic behaviour   

BSB: Prevalence of whole body stereotypic behaviour    

Hatch_rate: Captive hatch rates (chicks hatched/breeding pair/year)

 

Wild biology predictor variables

Max_feed_size: Maximum feeding group size    

Communal_roost: Presence/absence of communal roosting when sleeping (yes v no)            

Communal_roost_code: As above, but coded 1 = yes, 0 = no

Food_search: Percentage diet requiring extensive food search             

Food_handling: Percentage diet requiring extensive food handling                          

Habitat_breadth: Count of main habitat types in the native range   

Diet_breadth: Count of main food types in the native range             

Innovation: Total number of feeding innovations reported in the literature (relating to specific geographic regions)    

Inn_region: Whether/not a species’ native range includes one of the geographic regions mentioned above (1 = yes, 0 = no)

Brain_vol: Species’ average endocranial volume (ml)

IUCN_code: Status in the International Union for Conservation of Nature Red List of Threatened Species (ranked 1-5): Least Concern, Near Threatened, Vulnerable, Endangered, Critically Endangered.

Hatch_n_breed_pairs: Number of breeding pairs contributing to calculation of captive hatch rates

Nat_fecund: Natural fecundity (product of the median eggs/clutch and clutches/year)

Body_mass: Species’ average body mass (g)       

Research_effort: Research effort (number of published papers)

 

Pet parrot population characteristics    

Prop_adult: Proportion of a species’ population which is adult (v pubescent)   

Prop_known: Proportion of a species’ population which is of known sex (v unknown)

Prop_female: Proportion of a species’ population which is female (v male)

Human_reared: Proportion of a species’ population which has been entirely human-reared (v some parental rearing)   

Stand_cage: Proportion of a species’ population housed in a standard-sized cage (v larger)    

Prop_isolated: Proportion of a species’ population housed in conspecific social isolation (v some social contact)

Short_feed: Proportion of a species’ population with short captive feeding times (v long [>2hrs])

Cap_diet_div: Count of main food types in diet 

Early_EE: Early (rearing) enrichment diversity    

Current_EE: Current enrichment diversity