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The great reed warbler Acrocephalus arundinaceus is a common migrant through the Western Palearctic. However, its migration strategy, especially the spatiotemporal pattern of accumulation and utilisation of energy stores en route, is poorly known. Using ringing data collected at distant stopover sites located from Central Europe to Asia Minor, we observed that pattern in juvenile great reed warblers migrating along the eastern European flyway in autumn. We analysed body condition and stopover duration and estimated potential flight ranges for this species, taking into account two large ecological barriers – the Mediterranean Sea and the Sahara Desert – which it crosses during its southward migration. In Central and South-Eastern Europe the seasonal trends in body condition were similar and non-linear, with low values in August (i.e., during intensive migration of Acrocephalidae), and then a significant increase from the beginning of September until the end of the month. Estimated potential flight ranges showed that individuals migrating through Central and South-Eastern Europe might generally reach only the northern coast of the Mediterranean Sea. On the other hand, those flying from Asia Minor were able to reach the northern edge of the Sahel zone, crossing two large ecological barriers without refuelling. Therefore, it seems that great reed warblers change their autumn strategy en route: first, they migrate in short steps with low energy reserves through continental Europe; and then, after intensive refuelling before the Mediterranean Sea, they reach sub-Saharan Africa in a long flight. Based on the analysis of ringing data from several stopover sites, we show the complex pattern of how a long-distance migratory species accumulates and utilises its energy stores en route.

We studied the advancement of the spring migration in a 28-year period in two groups of blackcaps (Sylvia atricapilla) differing in wing length, which is known to be a proxy for migration distance. We related this advancement to the numbers of captured blackcaps. Short-winged birds (short-distance blackcaps), in the period preceding their increase in numbers (1982–1989), advanced their spring passage more and arrived 5 days earlier at their stop-over site than long-winged individuals (long-distance blackcaps). In the second period (1994–2009) characterised by a marked increase in numbers of blackcaps, advancement of spring migration was less pronounced and in this period all blackcaps arrived at the stop-over site at the same time. We suggest that the difference in the magnitude of the response of short- and long-winged birds resembles that found between short- and long-distance migrants. Shorter distance to the breeding grounds and earlier departure from their European wintering grounds may strongly affect spring migration phenology of the former group.

Recent climate change has a major impact on the sizes and distribution of bird populations, the phenology of their breeding/migration and migratory behaviour (migration distance, migration strategy). We documented changes in the numbers of juvenile Blackcaps migrating in autumn through the S Baltic that were paralleled by changes in wing length of captured individuals during a 43-year study period (1967–2009). We suggest that the observed trends may indicate changing population composition of migrating birds. In the Blackcap, wing length distinguishes among different populations and increases with increasing migration distance of a given population. Available published data show that long-distance and short-distance Blackcaps pass the study region. Hence, we assumed that shorter-winged birds are short-distance migrants wintering in the southern Europe, and that longer-winged individuals are long-distance migrants wintering in the sub-Saharan region. It seems that in 1967–1980 most Blackcap populations declined, but, as wing length slightly increased, the rate of this decline has been higher in the shorter-winged/short-distance Blackcaps. Over the subsequent 24 years alongside with rapidly growing numbers of birds, we noted a remarkable decrease in wing length. This indicates a pronounced increase in the number of short-distance individuals compared to long-distance migrants. Both groups may benefit from improved conditions at their breeding grounds, but the shorter migration route and favourable conditions at wintering sites north of Sahara could favour short-distance migrants over the longer distance and longer-winged Blackcaps.

Related species showed different strategies when migrating south towards wintering grounds in the Sahel and southern Africa: the garden warbler steadily increased fuel reserves along the migration route, the blackcap showed mixed fattening strategy with high fat reserves just before the Sahara crossing, the common whitethroat accumulated large fat reserves well in advance (North Mediterranean) before crossing this barrier, while the lesser whitethroat starting from the northern part of the Mediterranean showed a stable level of fat reserves. Results of this study support the hypothesis that species-specific ecology, rather than phylogenetic relationships, plays the major role in the evolution and form of bird migration. There were also population-specific differences in the strategy of species based on migration distance (blackcap), as well as individual differences where some individuals of the same species were potentially able to cover larger distance than conspecifics (blackcap, common whitethroat).

Migratory animals have adapted to life in multiple, sometimes very different environments. Thus, they may show particularly complex responses as climates rapidly change. Van Gils et al. show that body size in red knot birds has been decreasing as their Arctic breeding ground warms (see the Perspective by Wikelski and Tertitski). However, the real toll of this change appears not in the rapidly changing northern part of their range but in the apparently more stable tropical wintering range. The resulting smaller, short-billed birds have difficulty reaching their major food source, deeply buried mollusks, which decreases the survival of birds born during particularly warm years. Science, this issue p. 819; see also p. 775Reductions in body size are increasingly being identified as a response to climate warming. Here we present evidence for a case of such body shrinkage, potentially due to malnutrition in early life. We show that an avian long-distance migrant (red knot, Calidris canutus canutus), which is experiencing globally unrivaled warming rates at its high-Arctic breeding grounds, produces smaller offspring with shorter bills during summers with early snowmelt. This has consequences half a world away at their tropical wintering grounds, where shorter-billed individuals have reduced survival rates. This is associated with these molluscivores eating fewer deeply buried bivalve prey and more shallowly buried seagrass rhizomes. We suggest that seasonal migrants can experience reduced fitness at one end of their range as a result of a changing climate at the other end.

Stêpniewska K., O¿arowska A. 2012. The Eurasian Reed Warbler (Acrocephalus scirpaceus) breeding in Egypt - a new evidence? Ring 34: 45-50. To date, the documented breeding range of the Eurasian Reed Warbler in Egypt is limited to the Nile Delta. In March and September 2001 two females with brood patches were caught in the Wadi El Rayan Protected Area (30°19’E, 29°12’N) in the Western Desert of Egypt. These records, if accepted, might shift the southern border of the breeding range of Reed Warblers in Egypt west of the Nile Delta. The two individuals were the only records of breeding Reed Warblers in Wadi El Rayan, suggesting that the breeding population is small. It is possible that the population has been established recently because artificial lakes were created in Wadi El Rayan in 1973. The studies during the breeding season are essential to determine if such probable breeders demonstrate a new, but permanent breeding population or only ephemeral incidents, as well as to collect the data on the number, breeding biology and biometrical characteristics of such local populations at the southern limit of the world breeding range of the Reed Warbler.

Four ringing stations of the SE European Bird Migration Network in Egypt (at the coasts of the Mediterranean and Red seas, in the Nile Valley, and at the northern edge of the Sahara) provided data on birds resting in adequate habitats. At three stations more birds per day were caught in spring than in autumn. Deviating geographical conditions induced high capturing numbers at the Red Sea coast, particularly in autumn. Differences between spring and autumn may indicate loop migration and/or seasonally differing flight or resting strategies. Wing-length distribution may indicate passage of different populations through Egypt. In autumn, birds with low fat scores were caught in high proportion after the crossing of the Mediterranean Sea, while average fat scores increased in birds approaching the edge of the Sahara.

Directional behaviour of the Sedge Warbler (Acrocephalus schoenobaenus) studied in two types of orientation cages during autumn migration - a case study Migratory directions of Sedge Warblers tested in the Emlen funnel and Busse's flat cage during autumn migration in the Balkan region were studied. Some methodological aspects of orientation data analysis were discussed as well. According to orientation data at least two populations of the Sedge Warbler migrate in NE Bulgaria: one in SW direction via Greece, crossing the Mediterranean Sea to Libya, and then Central Africa and second one through Turkey, (Cyprus?) and the Middle East to the eastern parts of winter quarters (SE direction). This pattern is clear when a calculation method that assumes reverse and axial behaviour of birds (i.e. reversing vectors from northern sectors) is applied. Nature of "reverse migration" is still not well recognised and seems to be very interesting for further studies.

Summary Circular orientation cages have been used for several decades to record the migratory orientation of passerine migrants, and have been central when investigating of the functional characteristics of the biological compasses used for orientation. The technique offers unique possibilities to study the migratory behaviour of songbirds, but suffers from statistical limitations to evaluate the directions of the activity recorded in the cages. The migratory activity has been reported to vary, including complex multimodal orientation of migratory passerines tested in orientation cages irrespective of species studied. The currently applied circular statistical methods fail to describe orientation responses differing from unimodal and axial distributions. We propose for the first time a modelling procedure enabling the analyses of multimodal distributions either at an individual or group level. In this paper we compare the results of conventional methods and the recommended modelling approach. Migratory routes may be more complex than a simple migratory direction and multimodal behaviour in migratory species at the individual and population levels can be advantageous. Individuals may select the expected migratory direction, but may also return to more safe sites en route, i.e. sites already known, which provide food and/or shelter in reverse directions. In individual birds several directions may be expressed in the same test hour. At the species level multimodal orientation may give an opportunity to expand the range or may refer to differential migration route preferences in different populations of birds. A conflicting experimental situation may also result in different preferential orientation. In this paper we suggest a statistical solution to deal with these types of variations in orientation preferences.

Avian predation is one of the most probable factors maintaining polymorphism of shell coloration in Cepaea nemoralis. This assumption is justified by the fact that birds frequently forage on snails and their prey choice varies with morph coloration. However, in all preceding studies, the conspicuousness of morphs was determined only by using human vision which is significantly different from birds’ visual perception. In this study, we assessed how birds perceive colors of four Cepaea nemoralis morphs using physiological models of avian color vision. We calculated combined chromatic and achromatic contrast between shells and three habitat background types as a measure of shell conspicuousness. The degree of background color matching in Cepaea nemoralis depended on both shell morph and habitat type. On average, banded morphs were more conspicuous than unbanded morphs. Morphs were the most cryptic against dry vegetation and the most conspicuous on bare ground. We also found a significant interaction between habitat type and color morph. The relative conspicuousness of shell morphs depended on habitat and was the most variable against green vegetation. Our study provides the first insight into how potential avian predators view Cepaea nemoralis morphs. The results are discussed in light of multiple hypotheses explaining selective predation on Cepaea nemoralis morphs.