Falskläckor

Falskläckor is a term used in Swedish ornithology to describe brood parasitism, a reproductive strategy in which a bird species lays eggs in the nest of another species. The parasite’s eggs hatch and the young are raised by the host as if they were the host’s own offspring. The name emphasizes that the hatchlings are not the host’s genetic offspring, and that the host is often unknowingly supporting a “false” chick.

In brood parasitism, the parasite may lay eggs that resemble the host’s eggs in color and pattern to reduce the chance of detection. The parasite chick frequently outcompetes or even ejects the host’s eggs or young, gaining most or all of the parental care and food. Hosts respond in various ways, from egg rejection and nest abandonment to increased vigilance; some hosts eventually evolve improved discrimination or begging calls to differentiate between parasite and host offspring.

Notable examples include the common cuckoo (Cuculus canorus) in Europe and Asia, which lays eggs in the nests of a range of small passerines, and cowbirds (family Icteridae) in North America, which parasitize numerous species. The phenomenon is of interest to evolutionary biology because it drives coevolutionary dynamics between parasites and hosts, influencing egg appearance, nest structure, and parental behavior across species.

Falskläckor highlights an interaction where one species exploits the parental care of another, illustrating broader themes in ecology such as adaptation, deception, and the balance of costs and benefits in reproductive strategies.