The use of nocturnal flights for barrier crossing in a diurnally migrating songbird

Abstract

Background The migration patterns of land birds can generally be divided into those species that migrate principally during the day and those that migrate during the night. Some species may show individual plasticity in the use of day or night flight, particularly when crossing large, open-water or desert barriers. However, individual plasticity in circadian patterns of migratory flights in diurnally migrating songbirds has never been investigated. Methods We used high precision GPS tracking of a diurnal, migratory swallow, the purple martin (Progne subis), to determine whether individuals were flexible in their spring migration strategies to include some night flight, particularly at barrier crossing. Results Most (91%) of individuals made large (sometimes > 1000 km), open-water crossings of the Caribbean Sea and the Gulf of Mexico that included the use of night flight. 32% of all water crossings were initiated at night, demonstrating that night flight is not only used to complete large crossings but may confer other advantages for diurnal birds. Birds were not more likely to initiate crossings with supportive winds, however crossings were more likely when they reduced travel distances. Our results are consistent with diurnal birds using night flight to help achieve time- and energy-savings through ‘short cuts’ at barrier crossings, at times and locations when foraging opportunities are not available. Conclusions Overall, our results demonstrate the use of nocturnal flight and a high degree of individual plasticity in migration strategies on a circadian scale in a species generally considered to be a diurnal migrant. Nocturnal flights at barrier crossing may provide time and energy savings where foraging opportunities are low in an otherwise diurnal strategy. Future research should target how diel foraging and refueling strategies support nocturnal flights and barrier crossing in this and other diurnal species.

Global positioning system (GPS) and platform transmitter terminal (PTT) tags reveal fine-scale migratory movements of small birds: A review highlights further opportunities for hypothesis-driven research

“…Separate from the biogeographical aspects of migration, the reviewed GPS and PTT studies have also yielded insights into behavioral strategies of migrating birds. For example, GPS data from diurnal purple martins ( Progne subis ) were used to evaluate hypotheses about the function of nocturnal flights; results supported the hypothesis that nighttime flights help birds conserve time and energy when crossing barriers and/or in areas where foraging opportunities are poor (Lavallée et al 2021). Other studies evaluated the relationship between environmental factors (e.g., wind speed/direction, temperature, and topography) and aspects of flight behavior like flight speed, altitude, and flight path (Senner et al 2018, Lopez-Ricaurte et al 2021).…”

Experimental manipulation of photoperiod influences migration timing in a wild, long-distance migratory songbird

“…Purple martins are aerial insectivores that breed in eastern North America and journey 10-20 000 km annually to overwintering locations mostly in the Amazon Basin in Brazil [15]. Spring migration starts in mid-April for our study population and the arrival and departure date at these latitudes is early May and mid-August, respectively [16,17]. To manipulate the photoperiod to test for its impact on the timing of fledge and post-breeding movements, we mounted programmable light units inside treatment nest-boxes.…”

Genomic architecture of migration timing in a long-distance migratory songbird

“…Ppfia2 has been linked to sleep and wakefulness in white-crowned sparrows 21 , and nts has been linked to sleep regulation in European mice 22 . While purple martins are primarily diurnal migrants, they can incorporate both day and night flights on spring migration 30 , and the former genes could play a role in these nocturnal flights. Epigenetic modifiers may play a role in migration timing, such as methylation on the polyglutamine repeat domain of the clock gene affecting phenology and breeding performance 31 .…”