Can long-distance migratory birds adjust to the advancement of spring by shortening migration distance? The response of the pied flycatcher to latitudinal photoperiodic variation

摘要

Many organisms use day length as a cue for synchronizing their life cycles with seasonal changes in environmental productivity. Under rapid climate change, however, responses to day length may become maladaptive, and photo-responsive organisms may only be able to evade increasingly unsuitable habitats if they can accommodate to a wide range of photoperiodic conditions. A previous experiment showed that the pied flycatcher, Ficedula hypoleuca, a Palaearctic-Afrotropical migratory bird, would strongly advance the timing of spring migration and reproductive maturation if it shifted its wintering area from sub-Saharan Africa to the Mediterranean region. However, it is unknown whether this marked response to latitudinal variation in photoperiodic conditions is continuous over the entire range of potential wintering areas, and if a shortening of migration distance would be an effective mechanism to adjust the timing of migration to rapidly changing climatic conditions. Here, we experimentally show that a moderate northward displacement of the pied flycatcher's current wintering grounds by 10 degree would result in a clear advancement of the termination of prenuptial moult and the initiation of spring migratory activity and gonadal growth. However, we found no further advancement under conditions simulating higher wintering latitudes, suggesting the existence of a critical photoperiodic threshold or a steep gradual response within a narrow geographical range between 10 degree and 20 degree northern latitude. Because habitat conditions in this area are deteriorating rapidly, the potential for pied flycatchers to adjust their life cycle to changing climatic conditions by shortening the migration distance may be limited in the future.