Breeding latitude leads to different temporal but not spatial organization of the annual cycle in a long‐distance migrant

Abstract

The temporal and spatial organization of the annual cycle according to local conditions is of crucial importance for individuals' fitness. Moreover, which sites and when particular sites are used can have profound consequences especially for migratory animals, because the two factors shape interactions within and between populations, as well as between animal and the environment. Here, we compare spatial and temporal patterns of two latitudinally separated breeding populations of a trans-Equatorial passerine migrant, the Collared Flycatcher Ficedula albicollis, throughout the annual cycle. We found that migration routes and non-breeding residency areas of the two populations largely overlapped. Due to climatic constraints, however, the onset of breeding in the northern population was approximately two weeks later than that of the southern population. We demonstrate that this temporal offset between the populations carries-over from breeding to the entire annual cycle. The northern population was consistently later in timing of all subsequent annual events -autumn migration, non-breeding residence period, spring migration and the following breeding. Such year-round spatiotemporal patterns suggest that annual schedules are endogenously controlled with breeding latitude as the decisive element shaping the timing of annual events in our study populations.

Cold spell en route delays spring arrival and decreases apparent survival in a long-distance migratory songbird

“…Recent tracking studies confirm these findings, showing that breeding site arrival date in pied flycatchers largely depends on the onset of spring migration, rather than birds making adjustments en route [23]. In the closely related collared flycatcher F. albicollis , spring arrival at different breeding sites is related to local phenology, and timing of the onset of spring migration seems to be less important [24]. This coincides with our findings in semi-collared flycatchers.…”

Timing avian long-distance migration: from internal clock mechanisms to global flights

“…Generally, as explained above, circannual time programs prevent longdistance migrants from developing reproductive competence in the winter quarters [29][30][31] , explaining for example "why Bobolinks don't breed in Brazil" 30 . Instead, these programs trigger breeding migrations, sometimes at population-specific times and from sites where related species begin to breed [18][19][20] We hope to have shown that the spatiotemporal challenges birds are facing when globally tracking fluctuating resources are formidable, in particular at times when environments undergo rapid change, but that birds have also evolved enormous diversity in how they tackle these challenges as exemplified by our three case studies.…”

“…Species differ greatly in how they balance flexibility and consistency across their annual cycle. Recent studies have highlighted remarkable individual consistency of migratory timing in extremely punctual species, for example, bar-tailed godwits Limosa lapponica and 8 collared flycatchers Ficedula albicollis 18,20 . In contrast to their individual consistency, conspecifics differed widely amongst each other in departure timing at the exact same wintering areas further indicating robust individual-or population-specific patterns.…”

“…Substantial north-south-movements, including an equator crossing, on the other hand, will involve substantial changes of day length and of movement patterns of celestial bodies across the sky 144 , as well as a shifted geomagnetic inclination by migration. These routes probably offer more suitable habitats for refuelling after the desert crossing than the more direct routes from African wintering sites 20,147,148 , and possibly also favourable winds, resulting in a longer but energetically more economical route 149 . In this way, being at the right time at the right place, the birds would be able to use the temporarily available resources, despite the disadvantage of needing to travel further.…”

Resource tracking within and across continents in long-distance bird migrants

“…Part of this could be explained by the uncertainty in our tracking data or the if no seasonal resources were available in some seasons. Furthermore, the considerable variation in breeding altitude for many species leads to considerable variation in timing of events even within species ( 58 ), and the importance of optimal timing of important life history events, such as breeding, could constrain timing of other events such as migration ( 27 ). Alternatively, a more consistent lack of fit for shorter periods may result because the current migration schedules arose during variable climate and seasonality in the past hundreds or even thousands of years and are not necessarily perfectly adapted to the climate during the past decade.…”