Local Temperature Fine-Tunes the Timing of Spring Migration in Birds

Abstract

Evidence for climate-driven phenological changes is rapidly increasing at all trophic levels. Our current poor knowledge of the detailed control of bird migration from the level of genes and hormonal control to direct physiological and behavioral responses hampers our ability to understand and predict consequences of climatic change for migratory birds. In order to better understand migration phenology and adaptation in environmental changes, we here assess the scale at which weather affects timing of spring migration in passerine birds. We use three commonly used proxies of spring-time climatic conditions: (1) vegetation "greenness" (NDVI) in Europe, (2) local spring temperatures in northern Europe, and (3) the North Atlantic Oscillation Index (NAO) as predictors of the phenology of avian migration as well as the strength of their effect on different subsets of populations and the dependence of correlations on species-specific migratory strategy. We analyze phenological patterns of the entire spring migration period in 12 Palaearctic passerine species, drawing on long-term data collected at three locations along a longitudinal gradient situated close to their northern European breeding area. Local temperature was the best single predictor of phenology with the highest explanatory power achieved in combination with NAO. Furthermore, early individuals are more affected by climatic variation compared to individuals on later passage, indicating that climatic change affects subsets of migratory populations differentially. Species wintering closer to the breeding areas were affected more than were those travelling longer distances and this pattern was strongest for the earliest subsets of the population. Overall, our results suggest that at least early subsets of the population are affected by local conditions and early birds use local conditions to fine-tune the date of their spring arrival while individuals arriving later are driven by other factors than local conditions e.g. endogenous control. Understanding what cues migratory organisms use to arrive at an optimum time is important for increasing our knowledge of fundamental issues like decision making in organisms during migration and is crucial for future protection of migratory organisms.

Exploratory analyses ofmigration timing andmorphometrics of the Song Thrush (Turdus philomelos)

“…The bulk of currently available ringing data is often derived from long-term projects carried out at permanent ringing stations where large amount of individuals of various species are trapped simultaneously . These projects generally apply standardized methodologies in trapping, handling and data collection, thus information derived from these sites is suitable for location-wise comparisons (Schaub & Jenni 2000, Marra et al 2004, Schaub et al 2008, Tøttrup et al 2010.…”

Birds in New York State Have Altered Their Migration Timing and Are Experiencing Different Thermal Regimes While Breeding or on Stopover from 2010 to 2015

“…Although long-distance migrants seem to be under endogenous control for the onset of spring migration [16], our study highlights that many of the species that were significantly affected by temperature changes and those that have altered their migration timing through the state of New York were long-distance migrants (Tables 1-4). Tøttrup et al [13] concluded that local spring temperatures in migratory route are the best predictors of bird phenology, despite whether the migrating specie is a short-or long-distance migrant. Similar patterns of shift in migratory strategy for long-distance migrants have been documented for birds on Helgoland [33] and birds in Scandinavia and southern Italy [12].…”

“…Generally, timing of migration is said to be adjustable prior to departure when physiologically challenging environmental conditions pose additional threats to the bird, or it can be altered mid-migration when improved environmental conditions at stopover sites can reduce the time required to refuel [13]. However, timing of migration can be further complicated by effects of climate change, weather en route, and population declines, as well as the rate at which birds can refuel during stopover [14,15].…”

Exploratory analyses of migration timing and morphometrics of the Common Nightingale (Luscinia megarhynchos)

“…The bulk of currently available data is often collected at permanent, long-term ringing stations where large amount of individuals of various species are trapped simultaneously . These projects generally apply standardized methodologies in trapping, handling and data collection, thus information derived from these sites is suitable for location-wise comparisons (Schaub & Jenni 2000, Marra et al 2004, Schaub et al 2008, Tøttrup et al 2010.…”