Contributed by Marielle Grenade-Willis
Migration is a key element to survival for songbirds. According to the Cornell Lab of Ornithology, birds intuit when it is the best time to migrate based on a number of seasonal and sensory factors including: the position of the sun and stars, familiar landmarks, and the pull of the earth’s magnetic field. White-crowned sparrows are long distance migrants meaning their breeding range stretches over Canada and the Arctic while they return to portions of North and Central America to winter. Migration is so vital to this bird’s continuity that a study on a white-crowned sparrow subspecies found that, during migratory season, the sparrows were able to actually function on less sleep and still keep their cognitive function.
Most recently, an alarming new study in Nature, Eng et al._Insecticides Impair Migratory Abilities in Songbirds, found that agricultural pesticides like neonicotinoids have a disorienting effect on migratory birds like the white-crowned sparrow who may consume them during migration pitstops. “Birds that utilize agricultural landscapes may be exposed to insecticides through consumption of treated seeds, granules, or sprayed soils and prey items. Small migratory songbirds that regularly use farmland habitats as a stopover and refueling source may be particularly susceptible to exposure and the negative effects of neurotoxic insecticides.” Using two widely-used agricultural chemicals, the researchers found that the birds exposed experienced a loss in body mass as well as “significantly impaired orientation”. The consequences of neonicotinoids on migration patterns are still unknown, but “the energetic demands of long-distance flight and the negative fitness consequences of poor navigation and delays in arrival at the breeding grounds make migration one of the most vulnerable stages in a bird’s life cycle.” It is imperative that humans begin to recognize the repercussions of such harmful substances on other species’ movement capabilities like that of migrating birds.