Why Tropical Birds Have Fewer Chicks Than Temperate Birds

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Tropical species like this Whitehead's Broadbill, endemic to Borneo, commonly only raise two young, whereas temperate species generally raise more. Thomas E. Martin

Researchers have long puzzled over why tropical songbirds have fewer offspring than temperate songbirds living at higher latitudes. According to a new Science study, clutch size is a function of chick growth and parental investment strategies in response to age-related mortality risk.