Abstract
Food availability is known to influence parental care and mating systems in passerine birds. Altricial chicks make uni-parental care particularly demanding for passerines and parental investment is known to increase with decreasing food availability. We expect this to limit uni-parental passerines to habitats with the most consistent food availability. In passerine birds, species having uni-parental care are primarily female-only parental care (female-only care) and most passerine birds with female-only care are frugivores. We predict that frugivorous passerines with female-only care should be restricted to the most stable habitats characterized by longer fruiting season length. At a global scale, female-only care frugivores were distributed in areas with significantly longer fruiting seasons than non-female-only care frugivores. Female-only care species richness had a stronger spatial relationship with longer fruiting season than non-female-only care species richness. Verifying the lack of a phylogenetic signal driving this pattern, our findings indicate that the geographic distribution of female-only care, a geographically and phylogenetically widespread parental care system, is restricted by an extrinsic factor: fruiting season length. This reinstates the importance of food availability on the evolution and maintenance of parental care systems in passerine birds.
Highlights
Parental care is a crucial life-history strategy in birds
The greatest concentration of the 561 frugivorous passerine species occurred in the tropics (Fig 1A)
Frugivorous passerine species with female-only care were limited to the equatorial regions of tropical Central and South America, Southeast Asia and Australia with the curious exception of Africa (Fig 1B)
Summary
Parental care is a crucial life-history strategy in birds. Bi-parental care, where the male and female raise chicks together is the most common strategy 81% of all species) [1]. Other parental care systems such as multi-parental care and uni-parental care are widespread [1]. Multi-parental care and uni-parental care are phylogenetically labile and have evolved independently in birds multiple times [1,2]. Mating systems in birds with altricial chicks, which depend on adults for food, are strongly associated with parental care [3]. All cooperative breeders show multi-parental care, bi-parental care is seen in socially monogamous and promiscuous species, while uni-parental care is almost exclusively found in polyandrous or polygynous species [4]
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