A Trans-Hemispheric Migratory Songbird Does Not Advance Spring Schedules or Increase Migration Rate in Response to Record-Setting Temperatures at Breeding Sites

Abstract

The decline of long distance migratory songbirds has been linked to an increasing mismatch between spring arrival date and timing of food availability caused by climate change. It is unclear to what extent individuals can adjust migration timing or en route rate in response to annual variation in temperature at breeding sites. We tracked the ca. 7300 km spring migration of 52 purple martins Progne subis from the Amazon basin to two breeding sites in eastern North America. Spring 2012 was the warmest on record in eastern North America, but contrary to predictions, this did not result in earlier departure, faster migration, or earlier arrival at breeding areas compared with earlier years. Temperatures and rainfall in the Amazon basin at the time of departure were not higher in 2012, and conditions along migration routes did not give consistent signals of a warmer spring at the breeding site. Once in North America, individuals likely had limited opportunity to speed up their migration because this final portion of the journey was already very rapid (570 km/d; 4–5 d in duration). Migration timing over the entire journey was best predicted by breeding latitude and sex and was not sensitive to ecological cues (temperature and rainfall amount) at departure from South American overwintering sites or en route, in contrast to recent studies of other songbirds. Our results provide the first direct evidence for a mismatch between higher spring temperatures at breeding sites and departure schedules of individual songbirds, and suggest phenotypic responses to short-term climatic warming may be limited for some species. Further direct-tracking data with greater geographic and temporal scope is needed to test for individual plasticity in response to temperature and rainfall along migratory routes for this, and other, species.

Combining direct and indirect tracking techniques to assess the impact of sub-Saharan conditions on cross-continental songbird migration

“…Additional data were thus analysed following the same procedure to ensure comparability among tracks. Geolocator positions were estimated from light-level recordings using the software BASTrack (Fox 2010). To define sunrise and sunset times we used a light-level threshold value of two, corresponding to the sun being below the horizon.…”

Fitness consequences of different migratory strategies in partially migratory populations: A multi‐taxa meta‐analysis

“…Rising temperatures have been linked to poleward range shifts in migratory species (Breed, Stichter, & Crone, ; La Sorte & Thompson, ), shorter migration distances (Heath, Steenhof, & Foster, ; Visser, Perdeck, Balen, & Both, ), earlier arrival times (Jonzén et al, ; Usui, Butchart, & Phillimore, ) and earlier breeding times (Both et al, ; Tomotani et al, ). Furthermore, the capacity of migratory species to adapt to climate change is not universal (Fraser et al, ; Robinson et al, ), and inability to do so has been linked to population declines (Møller, Rubolini, & Lehikoinen, ). Partial migration may confer some resilience to environmental change, since some individuals are not exposed to the threats posed by migration (Chapman et al, ); indeed, partial migration has been shown to be a positive predictor of population trends in European birds (Gilroy et al, ).…”

Repeatability in Spring Arrival Dates in Pied Flycatchers Varies Among Years and Sexes

“…However, the closer that individuals get to their destination, the more they can anticipate the specific conditions in that year (Marra et al 2005). Individual flexibility to between-year variation in breeding site phenology thus likely arises through incorporating variation during the latter part of the migratory journey (but see Fraser et al 2013 for lack of adjustment to a warm spring). At the population level, correlations between arrival date and circumstances en route have indeed been found (Ahola et al 2004, Both et al 2005, Marra et al 2005, Jonzén et al 2006, and in a few cases this was shown to be caused by phenotypic plasticity (Saino et al 2007, Balbontín et al 2009.…”