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Aim Knowledge of broad‐scale biogeographical patterns of animal migration is important for understanding ecological drivers of migratory behaviours. Here, we present a flyway‐scale assessment of the spatial structure and seasonal dynamics of the Afro‐Palaearctic bird migration system and explore how phenology of the environment guides long‐distance migration. Location Europe and Africa. Time period 2009–2017. Major taxa studied Birds. Methods We compiled an individual‐based dataset comprising 23 passerine and near‐passerine species of 55 European breeding populations, in which a total of 564 individuals were tracked during migration between Europe and sub‐Saharan Africa. In addition, we used remotely sensed primary productivity data (the normalized difference vegetation index) to estimate the timing of vegetation green‐up in spring and senescence in autumn across Europe. First, we described how individual breeding and non‐breeding sites and the migratory flyways link geographically. Second, we examined how the timing of migration along the two major Afro‐Palaearctic flyways is tuned with vegetation phenology at the breeding sites. Results We found the longitudes of individual breeding and non‐breeding sites to be related in a strongly positive manner, whereas the latitudes of breeding and non‐breeding sites were related negatively. In autumn, migration commenced ahead of vegetation senescence, and the timing of migration was 5–7 days earlier along the Western flyway compared with the Eastern flyway. In spring, the time of arrival at breeding sites was c . 1.5 days later for each degree northwards and 6–7 days later along the Eastern compared with the Western flyway, reflecting the later spring green‐up at higher latitudes and more eastern longitudes. Main conclusions Migration of the Afro‐Palaearctic landbirds follows a longitudinally parallel leapfrog migration pattern, whereby migrants track vegetation green‐up in spring but depart before vegetation senescence in autumn. The degree of continentality along migration routes and at the breeding sites of the birds influences the timing of migration on a broad scale., + Publisher's Statement: This is the peer reviewed version of the following article: Briedis, M, Bauer, S, Adamík, P, et al. Broad‐scale patterns of the Afro‐Palaearctic landbird migration. Global Ecol Biogeogr. 2020; 29: 722– 735, which has been published in final form at https://doi.org/10.1111/geb.13063. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.

Migratory species form an important component of biodiversity; they link ecosystems across the globe, but are increasingly threatened by global environmental change. Understanding and mitigating threats requires knowledge of how demographic processes operate throughout the annual cycle, but this can be difficult to achieve when breeding and non-breeding grounds are widely separated. Our goal is to quantify the importance of variability in survival during the breeding and non-breeding seasons in determining variation in annual survival using a single population and, more broadly, the extent to which annual survival across species reflects variation in probability of surviving the migratory period. We use a 25-year dataset in which individuals of a long-distance migratory bird, the alpine swift Tachymarptis melba, were captured towards the beginning and end of each breeding season to estimate age- and season-specific survival probabilities and incorporate explicit estimation of the correlations in survival between age-classes and seasons. Monthly survival was higher during the breeding period than during the rest of the year and strongly affected by conditions in the breeding season; effects that remained apparent in the following non-breeding season, but not subsequently. Recruitment of juveniles was dependent on the timing of breeding, being higher if egg-laying commenced before the median date, and substantially lower if not. Across migratory bird species, variation in annual survival largely reflects variation in the probability of surviving the migratory period. Using a double-capture approach, even within a single season, provides valuable insights into the demography of migratory species, which will help understand the extent and impacts of the threats they face in a changing world.

In many taxa, the most common form of sex-biased migration timing is protandry—the earlier arrival of males at breeding areas. Here we test this concept across the annual cycle of long-distance migratory birds. Using more than 350 migration tracks of small-bodied trans-Saharan migrants, we quantify differences in male and female migration schedules and test for proximate determinants of sex-specific timing. In autumn, males started migration about 2 days earlier, but this difference did not carry over to arrival at the non-breeding sites. In spring, males on average departed from the African non-breeding sites about 3 days earlier and reached breeding sites ca 4 days ahead of females. A cross-species comparison revealed large variation in the level of protandry and protogyny across the annual cycle. While we found tight links between individual timing of departure and arrival within each migration season, only for males the timing of spring migration was linked to the timing of previous autumn migration. In conclusion, our results demonstrate that protandry is not exclusively a reproductive strategy but rather occurs year-round and the two main proximate determinants for the magnitude of sex-biased arrival times in autumn and spring are sex-specific differences in departure timing and migration duration.

In many migratory birds, males precede females during migration and arrival at the breeding sites. Three proximate mechanisms are proposed to explain this phenomenon of protandry: males 1) winter closer to breeding sites, 2) start spring migration earlier, and/or 3) migrate faster than females. So far, the relative contribution of these mechanisms to protandry is unknown. The present study investigated the importance of each of the 3 proximate mechanisms of protandry for a songbird migrant wintering in Africa, the northern wheatear (Oenanthe oenanthe). Two subspecies co-occur in Europe on migration, of which the leucorhoa northern wheatears breeding from Iceland to Canada have to cross the North Atlantic, whereas the nominate form breeding in Europe does not face any significant sea barrier. We show that the leucorhoa subspecies had a significantly higher degree of protandry at stopover sites across Europe than the oenanthe subspecies (−6 vs. −2 days). Leucorhoa northern wheatear’s higher degree of protandry was associated with a larger age effect, in which old males preceded young males, and greater sex-specific differences in wing shape and refueling yielding higher migration speeds in males than females. In oenanthe northern wheatears, light-level geolocators revealed that males did not winter closer to the breeding sites or migrate faster than females, but initiated spring migration earlier. Our results demonstrate that the significance of the mechanisms causing protandry can differ between related taxa and highlight the importance of the advancement in male arrival date with age as a potential factor shaping the degree of protandry.

Social information, information acquired from other individuals, is used in a wide range of behavioral decisions in many taxa. In nature, individuals usually have access to social information from several species sharing the same habitat, yet social information use from multiple tutor (social information source) species is insufficiently understood. Earlier studies on collared flycatchers (Ficedula albicollis) have piecemeal reported use of both conspecific and heterospecific social information in nest site choices, making it an ideal species to study simultaneous use of conspecific and heterospecific information. Here, we used a previously successful experimental design with abstract geometric symbols as surrogates for tutors’ nest site choices to test the relative importance of intraspecific versus interspecific social information for decision making in collared flycatchers and intraspecific social information use in tits (great and blue tits; Parus major, Cyanistes caeruleus). Due to manipulation and divergent timing of nest site choices, flycatchers were faced with conflicting nest site choices of conspecific and heterospecific (tit) tutors, whereas tits only had access to the choices of tit tutors. In flycatchers, early settling pairs copied even earlier settled heterospecific choices when few conspecific tutors were around, whereas late-settling pairs copied conspecifics when conspecific tutors were numerous in relation to heterospecific tutors. In great tits, pairs with an old male tended to copy the choices of their conspecifics. Our study indicates that birds use flexibly social information from both conspecifics and heterospecifics in different situations, suggesting that perceived niche overlap with potential tutor species affects social information use.

Dispersal costs can be classified into energetic, time, risk and opportunity costs and may be levied directly or deferred during departure, transfer and settlement. They may equally be incurred during life stages before the actual dispersal event through investments in special morphologies. Because costs will eventually determine the performance of dispersing individuals and the evolution of dispersal, we here provide an extensive review on the different cost types that occur during dispersal in a wide array of organisms, ranging from micro-organisms to plants, invertebrates and vertebrates. In general, costs of transfer have been more widely documented in actively dispersing organisms, in contrast to a greater focus on costs during departure and settlement in plants and animals with a passive transfer phase. Costs related to the development of specific dispersal attributes appear to be much more prominent than previously accepted. Because costs induce trade-offs, they give rise to covariation between dispersal and other life-history traits at different scales of organismal organisation. The consequences of (i) the presence and magnitude of different costs during different phases of the dispersal process, and (ii) their internal organisation through covariation with other life-history traits, are synthesised with respect to potential consequences for species conservation and the need for development of a new generation of spatial simulation models.

Sex-specifi c dispersal behavior has been documented in a wide range of diff erent species. Avoidance of inbreeding and kin competition as well as diff erent benefi ts of philopatry have been invoked as explanations for these patterns. All of these factors have, however, focused on explaining why dispersal behavior diff ers between the sexes. In this paper, we make the case that dispersal causes an increase in spatial variability in the sex ratio which can reduce the local availability of mates, and thus feed back to infl uence the evolution of sex-specifi c dispersal and lead to more, rather than less, similar dispersal behavior in the sexes. We investigate this mechanism in two diff erent models, fi rst in a conceptually simple case showing why the coevolutionary eff ect arises, second in an individual-based model where we model a population in explicit space with dispersal implemented as dispersal kernels. While our mechanism is not expected to completely remove sex-bias in dispersal, it can act alongside other selection pressures to reduce such biases. Our model thus shows that dispersal of one sex can have an eff ect on the selective pressures on the opposite sex, without implementing inbreeding avoidance or differential benefi ts or costs of dispersal. Th e evolution of dispersal is driven by every organism ’ s need to adjust their distribution in space in response to environmental fl uctuations. Fluctuations of biotic or abiotic condi