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The characteristics of young with respect to basic development factors greatly affect whether one parent is able to raise the young on its own and, hence, the flexibility of mating systems. In most bird species, the young hatch naked and helpless, and the extensive demand for care in relation to food availability, temperature, and predator defense has been suggested to favor the evolution of monogamy. Here, we examine the evolution of bird mating systems in relation to precociality and altriciality, defined as the capability or incapability of young to leave the nest depending on their locomotive development. The mating pattern of males and females, respectively, is classified into monogamy or polygamy according to whether less or more than 5% of the mated individuals in a species have more than one sexual partner. The social bond between the sexes is classified according to whether the bond dissolves before hatching or not. Our analyses show that the proportion of transitions to a short bond is significantly higher in lineages with precocial young than in lineages with altricial young. Transitions to polygamy in females are significantly more frequent in birds with precocial young compared to birds with altricial young. In males, however, there is no significant difference in the frequency of transitions to polygamy between birds with precocial young and birds with altricial young. |
