Ducks diligently care for their young, guiding them from hatching through early development. Mother ducks provide warmth, protection, and lead their offspring to foraging areas. Ducklings are precocial, able to swim and find food soon after hatching, but rely on their mother for guidance and safety.
The Phenomenon of Brood Amalgamation
Ducks “adopt” ducklings that are not their biological offspring. This behavior is formally known as “brood amalgamation” or “creching.” It describes a situation where ducklings from different broods merge and are cared for by a female who may not be their genetic mother. This phenomenon occurs in two ways: pre-hatch, when eggs are laid in another female’s nest, or post-hatch, when ducklings join an existing brood.
Brood amalgamation is common among waterfowl, observed in at least 41 species of ducks, geese, and swans. These combined groups can become quite large, with some common eider creches containing as many as 60 ducklings under the care of one or more adult females.
Factors Contributing to Duckling Adoption
Duckling adoption, or brood amalgamation, results from environmental and behavioral factors rather than a deliberate choice. Pre-hatch amalgamation results from nest parasitism, where a female lays eggs in another duck’s nest. This strategy is more prevalent in species nesting in cavities or dense colonies. Post-hatch mixing can happen accidentally, especially in crowded nesting areas or places with limited suitable habitat.
Sudden disruptions, such as aggressive encounters or predator attacks, can scatter ducklings, leading to their regrouping with incorrect or multiple broods. Some ducklings may become abandoned or lost and join another female’s brood. Occasionally, a female with strong maternal instincts, sometimes termed “super broody,” might actively attract and accept ducklings, including those left by other females.
Outcomes for Ducklings and Adoptive Mothers
The impact of brood amalgamation on ducklings and their adoptive mothers varies. For ducklings, survival rates in amalgamated broods show mixed results. Some studies suggest larger groups offer enhanced protection through predator dilution. However, other observations indicate duckling mortality might be higher in creches compared to smaller family broods, especially if ducklings are older when they join. Ducklings within larger creches may also experience faster growth.
For the adoptive mother, taking on additional ducklings may not always impose a significant energetic cost, as ducklings are precocial and can forage independently soon after hatching. While some research finds no clear benefits or drawbacks for the host female, others point to potential advantages of larger broods, such as improved predator detection. Females in better physical condition are more likely to care for amalgamated broods for extended periods. Ducklings face inherently low survival rates in the wild during their initial weeks, with estimates ranging from 10% to 70%. Ducks’ tendency to lay large clutches may compensate for these high early mortality rates.