Table 2.
Species-level predictors of behavioural and reproductive problems in captive parrots. Summary of key results from hypothesis-testing PCM models. Each partial R2 shown is calculated from the median values for the term's t-statistic (over the tree block); its associated degrees of freedom is also reported, with + and – denoting the direction of the relationship (in brackets if non-significant). Significant (p < 0.05) results are shown in bold. Full model results are shown in electronic supplementary material, table S6. ED = enrichment diversity; prop. = proportion.
| Hypothesis: behavioural and reproductive problems in captivity reflect… | predictor: | SB results |
hatch rate resultsd | |||
|---|---|---|---|---|---|---|
| captive population characteristic(s) controlled forc | whole-body SB | FDB | oral SB | |||
| … constraints on natural social interaction | maximum feeding group size | (+) R2 = 0.03 | – R2 = 0.10 | (–) R2 < 0.01 | (+) R2 = 0.02e | |
| communal roosting (yes versus no) | current ED | (–) R2 < 0.01 | (+) R2 < 0.01 | (+) R2 < 0.01 | (–) R2 = 0.01 | |
| early ED | ||||||
| … restriction of natural foraging behaviours | % natural diet needing extensive search | prop. standard cage | (+) R2 = 0.02 | (+) R2 = 0.01 | (+) R2 < 0.01 | (–) R2 = 0.03f |
| captive diet diversity | ||||||
| % natural diet needing extensive handling | prop. adult | (+) R2 = 0.01 | + R2 = 0.16 | (+) R2 = 0.06 | (–) R2 = 0.01 | |
| prop. female | ||||||
| prop. standard cage | ||||||
| … habitat and dietary generalism | diet breadth (1–5, count of main food types) | (+) R2 = 0.04 | (–) R2 < 0.01 | (+) R2 = 0.02 | (+) R2 = 0.01 | |
| habitat breadth (1–7, count of main habitat types) | (+) R2 = 0.04 | (+) R2 = 0.10g | (–) R2 < 0.01 | (+) R2 = 0.02 | ||
| … being intelligent or innovative | innovation rateb (number reported) | prop. hand-reared | (–) R2 = 0.02 | (+) R2 = 0.02 | (+) R2 < 0.01 | (–) R2 = 0.01 |
| brain volumea (ml) | prop. standard cage | + R2 = 0.19 | (+) R2 = 0.02 | + R2 = 0.26 | (–) R2 < 0.01 | |
| … being rare/threatened | IUCN Red List category (1–5, where 1 is Least Concern and 5 is Critically Endangered) | (+) R2 < 0.01 | (+) R2 = 0.01 | (+) R2 = 0.01 | (–) R2 = 0.03 (see main text for additional analyses) | |
| no. of pairs in aviculture dataset | N/A | N/A | N/A | + R2 = 0.08 | ||
The following controls were included (see text and electronic supplementary material for more details):
aBody mass included in all models to control for allometry;
bResearch effort included in all models to control for this potential influence on observed innovation rates;
cSpecies-typical attributes of pet populations controlled for where these covaried with a predictor variable;
dNatural fecundity included in all models to control for life-history traits.
In some models, the following correlated predictors were also included because collinear with the predictor under investigation (see electronic supplementary material, table S5):
eIUCN Red List category.
fBrain volume.
gMaximum feeding group size.