A COMPARATIVE-ANALYSIS OF SOME LIFE-HISTORY TRAITS BETWEEN COOPERATIVELY AND NONCOOPERATIVELY BREEDING AUSTRALIAN PASSERINES

Comparative analyses were carried out for some life-history traits of cooperatively and non-cooperatively breeding Australian Corvida (i.e. old-endemic passerines). Multivariate statistical analyses at the fami ly and genus levels revealed no significant differences between cooper ative and non-cooperative breeders. A matched-pairs analysis between c ongeneric species showed that cooperatively breeding species lay small er clutches than non-cooperatively breeding congenerics. Preliminary r esults also suggest that cooperative breeders have higher probabilitie s of rearing a second brood in the season and lower probabilities of s urvival than do non-cooperative breeders. However, the result for surv ival was significant in only one out of three tests. We conclude that cooperatively and non-cooperatively breeding Australian Corvida cannot be separated into distinct groups showing K- and r-selected life-hist ory traits, respectively. Some life-history traits follow the predicti on of the r-K selection model, others show evidence of co-adaptation i nstead, whereas still others show evidence of trade-offs.