Table 1 Overview and order of statistical analyses, including observations per data set.

Are all species motivated to participate?^A

 1

GLMM (binomial)

Species-level (AG: 120 obs, BHM: 105 obs, E: 75 obs, G: 180 obs)

Landings on receiver perch in motivational trials/total trials (all sessions)

Sex + Condition * Session

(1+Conditon + Session|Bird ID)

–

Do parrots sustain food provisions across sessions?

 2

GLM (poisson)

Species-level (AG: 5 obs, BHM: 5 obs, E: 5 obs, G: 5 obs)

Food provided (all sessions)

Session

–

–

Do they land according to task’s contingencies?^A

 3

Chisq-Tests (individual level)

All birds tested in Phase IV & V (32 obs)

Individual number of landings on provider perch in Phase IV & V (S4 & S5)

–

–

–

What explains species differences?

 4

GLM (zero-inflated, negative binomial)

All birds tested in Phase IV & V (32 obs)

Sum landings on provider perch in test condition (Phase IV—S4 & S5)

Cooperation + Nesting + Social Tolerance

–

Trial number

To whom do birds provide food?

 5

GLMM (negative binomial)

Dyadic-level (N = 424 obs)

Food provided in S4&5

Species * (Kinship + Sex + Affiliation)

(1|Provider: Dyad) + (1 + Affiliation|Provider)

Trial number