No abstract

Migration during spring is usually faster than during autumn because of competition for breeding territories. In some cases, however, the costs and benefits associated with the environment can lead to slower spring migration, but examples are quite rare. We compared seasonal migration strategies of the endangered Baltic population of the dunlin Calidris alpina schinzii using light‐level geolocator data from 26 individuals breeding in Finland. Autumn migration was faster, with individuals showing a ‘jump’ and ‘skipping’ migration strategy characterised by fewer stationary periods, shorter total stopping time and faster flight. Spring migration was slower, with individuals using a ‘skipping’ strategy. The duration of migration was longer for early departing birds during spring but not during autumn suggesting that early spring migrants are prevented from arriving to the breeding areas or that fueling conditions are worse on the stopover sites for early arriving individuals. Dunlins showed high migratory connectivity. All individuals had one long staging at the Wadden Sea in the autumn after which half of the individuals flew 4500 km non‐stop to Banc d’Arguin, Mauritania. The other half stopped briefly on the Atlantic coast on their way to Mauritania. One bird wintered on the coast of Portugal. Nine individuals that carried geolocators for two years were site faithful to their final non‐breeding sites. Based on the strategies during the non‐breeding period we identified, Baltic dunlin may be especially vulnerable to rapid environmental changes at the staging and non‐breeding areas. Consequently, the preservation of the identified non‐breeding areas is important for their conservation.

BackgroundSocial information use is usually considered to lead to ecological convergence among involved con- or heterospecific individuals. However, recent results demonstrate that observers can also actively avoid behaving as those individuals being observed, leading to ecological divergence. This phenomenon has been little explored so far, yet it can have significant impact on resource use, realized niches and species co-existence. In particular, the time-scale and the ecological context over which such shifts can occur are unknown. We examined with a long-term (four years) field experiment whether experimentally manipulated, species-specific, nest-site feature preferences (symbols on nest boxes) are transmitted across breeding seasons and affect future nest-site preferences in a guild of three cavity-nesting birds.ResultsOf the examined species, resident great tits (Parus major) preferred the symbol that had been associated with unoccupied nest boxes in the previous year, i.e., their preference shifted towards niche space previously unused by putative competitors and conspecifics.ConclusionsOur results show that animals can remember the earlier resource use of conspecifics and other guild members and adjust own decisions accordingly one year after. Our experiment cannot reveal the ultimate mechanism(s) behind the observed behaviour but avoiding costs of intra- or interspecific competition or ectoparasite load in old nests are plausible reasons. Our findings imply that interspecific social information use can affect resource sharing and realized niches in ecological time-scale through active avoidance of observed decisions and behavior of potentially competing species.

SummaryPopulations of several long-distance migratory songbirds in Eurasia are in peril, drastically illustrated by the recent range-wide population collapse in the Yellow-breasted Bunting Emberiza aureola. There are signals of a strong decline also in the Rustic Bunting E. rustica, but no range-wide assessment of population trends in this superabundant and widespread bunting species has yet been undertaken. The conservation status of Rustic Bunting is ‘Least Concern’ on the global IUCN Red List, but it has recently been upgraded to ‘Vulnerable’ on the European Red List. To assess the Rustic Bunting’s global conservation status we compiled, for the first time, population data across its breeding and wintering ranges. The analysis reveals a 75–87% decline in overall population size over the last 30 years and a 32–91% decline over the last 10 years. The trend estimates indicate that the long-term (30-year) range-wide population decline in the Rustic Bunting is of similar magnitude to two well-known examples of declining species within the same genus, the Yellow-breasted Bunting and the Ortolan Bunting E. hortulana. The magnitude of the range-wide population decline over the last 10 years suggests that the Rustic Bunting could be upgraded from ‘Least Concern’ to ‘Vulnerable’ or ‘Endangered’ on the IUCN global Red List. Agricultural intensification in the wintering range and intensified levels of disturbance, including logging and fire, in the breeding range could be important drivers of the range-wide population decline, and persecution could also contribute. Untangling threat factors and their interactions on Rustic Bunting is necessary for conservation, but hampered by our currently limited understanding of the relationships between population dynamics and different threats.

Using the behavior of others in guiding one's own behavior is a common strategy in animals. The prevailing theory predicts that young age and the inexperience of an individual are expected to increase the probability of adopting the behaviors of others. Also, the most common behavior in the population should be copied. Here, we tested the above predictions by examining social information use in the selection of nest-site features with a field experiment using a wild cavity nesting bird, the collared flycatcher (Ficedula albicollis). We used an experimental design in which geometric symbols depict nest-site features. By manipulating the apparent symbol choices of early settled individuals and monitoring the choices of later arriving birds, we can study social information use without bias from learned or innate preferences. Flycatchers were found to use social information in the selection of nest-site features, with about 60% of the population preferring the manipulated conspecific choices. However, age and experience as explanatory factors suggested by the social information use theory did not explain the choices. The present result, in concert with earlier similar experiments, implies that flycatchers may in some situations rely more on interspecific information in the selection of nest-site characteristics.