Migratory connectivity describes to which degree different breeding populations have distinct (non-overlapping) non-breeding sites. Uncovering the level of migratory connectivity is crucial for ...effective conservation actions and for understanding of the evolution of local adaptations and migratory routes. Here we investigate migration patterns in a passerine bird, the great reed warbler Acrocephalus arundinaceus, over its wide Western Palearctic breeding range using geolocators from Spain, Sweden, Czech Republic, Bulgaria and Turkey. We found moderate migratory connectivity: a highly significant spatial structure in the connections between breeding and sub-Saharan non-breeding grounds, but at the same time a partial overlap between individual populations, particularly along the Gulf of Guinea where the majority of birds from the Spanish, Swedish and Czech populations spent their non-breeding period. The post-breeding migration routes were similar in direction and rather parallel for the five populations. Birds from Turkey showed the most distinctive migratory routes and sub-Saharan non-breeding range, with a post-breeding migration to east Africa and, together with birds from Bulgaria, a previously unknown pre-breeding migration over the Arabian Peninsula indicating counter-clockwise loop migration. The distances between breeding and sub-Saharan non-breeding sites, as well as between first and final sub-Saharan non-breeding sites, differed among populations. However, the total speed of migration did not differ significantly between populations; neither during post-breeding migration in autumn, nor pre-breeding migration in spring. There was also no significant relationship between the total speed of migration and distance between breeding and non-breeding sites (neither post- nor pre-breeding) and, surprisingly, the total speed of migration generally did not differ significantly between post-breeding and pre-breeding migration. Future challenges include understanding whether non-breeding environmental conditions may have influenced the differences in migratory patterns that we observed between populations, and to which extent non-breeding habitat fluctuations and loss may affect population sizes of migrants.
Billions of nocturnally migrating songbirds fly across oceans and deserts on their annual journeys. Using multisensor data loggers, we show that great reed warblers (
) regularly prolong their ...otherwise strictly nocturnal flights into daytime when crossing the Mediterranean Sea and the Sahara Desert. Unexpectedly, when prolonging their flights, they climbed steeply at dawn, from a mean of 2394 meters above sea level to reach extreme cruising altitudes (mean 5367 and maximum 6267 meters above sea level) during daytime flights. This previously unknown behavior of using exceedingly high flight altitudes when migrating during daytime could be caused by diel variation in ambient temperature, winds, predation, vision range, and solar radiation. Our finding of this notable behavior provides new perspectives on constraints in bird flight and might help to explain the evolution of nocturnal migration.
Through new tracking techniques, data on timing and routes of migration in long‐distance migrant birds are accumulating. However, studies of the consistency of migration of the same individuals ...between years are still rare in small‐sized passerine birds. This type of information is important to understand decisions and migration abilities at the individual level, but also for life history theory, for understanding carry over effects between different annual cycle stages and for conservation. We analysed individual repeatability of migration between years in great reed warblers Acrocephalus arundinaceus; a medium‐sized European songbird migrating to sub‐Saharan Africa. In seven males, with geolocator data from 2–4 yr per bird, we found low to moderate (non significant) repeatability in timing of migration parameters (R ≤ 0.41), but high (and significant) repeatability for most spatial parameters, i.e. autumn route (R = 0.64) and stopover sites (R = 0.59–0.87) in Europe, and wintering sites (R = 0.77–0.99) in sub‐Saharan Africa. This pattern of high spatial but low temporal within‐individual repeatability of migration between years contrasts other tracking studies of migrating birds that generally have found consistency in timing but flexibility in routes. High spatial consistency of migration in the great reed warbler may be due to it being a specialist in wetlands, an unevenly distributed habitat, favouring a strategy of recurrence at previously visited sites. Low temporal repeatability may be caused by large between‐year variation in carry‐over effects from the breeding season, high flexibility in decision rules during migration or high sensitivity to environmental factors (weather, wind) during migration.
Maternal and genetic factors determine early life telomere length Asghar, Muhammad; Bensch, Staffan; Tarka, Maja ...
Proceedings - Royal Society. Biological sciences/Proceedings - Royal Society. Biological Sciences,
01/2015, Letnik:
282, Številka:
1799
Journal Article
Recenzirano
Odprti dostop
In a broad range of species—including humans—it has been demonstrated that telomere length declines throughout life and that it may be involved in cell and organismal senescence. This potential link ...to ageing and thus to fitness has triggered recent interest in understanding how variation in telomere length is inherited and maintained. However, previous studies suffer from two main drawbacks that limit the possibility of understanding the relative importance of genetic, parental and environmental influences on telomere length variation. These studies have been based on (i) telomere lengths measured at different time points in different individuals, despite the fact that telomere length changes over life, and (ii) parent–offspring regression techniques, which do not enable differentiation between genetic and parental components of inheritance. To overcome these drawbacks, in our study of a songbird, the great reed warbler, we have analysed telomere length measured early in life in both parents and offspring and applied statistical models (so-called ‘animal models') that are based on long-term pedigree data. Our results showed a significant heritability of telomere length on the maternal but not on the paternal side, and that the mother's age was positively correlated with their offspring's telomere length. Furthermore, the pedigree-based analyses revealed a significant heritability and an equally large maternal effect. Our study demonstrates strong maternal influence on telomere length and future studies now need to elucidate possible underlying factors, including which types of maternal effects are involved.
The coevolutionary process among avian brood parasites and their hosts involves stepwise changes induced by the antagonistic selection pressures of one on the other. As long‐term data on an ...evolutionary scale is almost impossible to obtain, most studies can only show snapshots of such processes. Information on host behaviour, such as changes in egg rejection rates and the methods of rejection are scarce. In Hungary there is an interesting case between the common cuckoo Cuculus canorus and the great reed warbler Acrocephalus arundinaceus, where the level of parasitism is unusually high (around 50%). We compared host rejection rates and methods of rejection from within our own project to that of an early study carried out and published almost 70 yr ago in the same region. Our comparisons revealed high and stable rates of parasitism (range: 52–64%), and marked fluctuations in the ratio of multiply parasitized nests (range: 24–52%). No difference was revealed in egg rejection rates after 7 decades (34–39%). Linear mixed‐effects modelling revealed no year effect on the type host responses toward the parasitic egg(s) during the years of study (categorized as acceptance, ejection, burial, and nest desertion). Cuckoo egg rejection was primarily affected by the type of parasitism, as more cuckoo eggs were rejected during single parasitism than from multiply parasitized nests. Our comparison did not reveal any directional changes in this cuckoo–host relationship, except a slight decrease in the frequency of multiple parasitism, which is likely to be independent from coevolutionary processes.
Avian interspecific brood parasitism is an excellent system for studying coevolutionary processes in nature because brood parasites directly affect host reproductive success. Most research on avian ...brood parasitism has, therefore, focused primarily on specific host anti-parasite behaviours and parasite counter-adaptations. However, the population-level consequences of brood parasitism for host species are poorly understood. This study investigated the effect of Common Cuckoo (Cuculus canorus) parasitism on the productivity of a local population of the Great Reed Warbler (Acrocephalus arundinaceus) host in south-western Slovakia. A total of 495 females nesting at the studied site successfully fledged 1321 of their own young and 63 young of the Common Cuckoo over the course of 15 years (2008–2022), and the annual rate of successful parasitism ranged from 18% to 44% over this period. As predicted, higher rates of successful cuckoo parasitism significantly reduced the annual productivity of the local Great Reed Warbler population, and its contribution to decreased host reproductive success was at about the same rate as overall nest failure caused by predation and other environmental factors. Such a heavily parasitized population was probably maintained by immigrants from other populations and density-dependent selection, which is also consistent with source–sink dynamics. However, further long-term studies monitoring parasitized populations are required to confirm these findings.
Capsule Brood parasitic Common Cuckoo Cuculus canorus chicks hatch earlier than the nestlings of their Great Reed Warbler Acrocephalus arundinaceus hosts, but hatching priority is less consistent ...when Cuckoo eggs are laid after the onset of host incubation. Aim To reveal by field observations what the optimal stage is for Cuckoos to lay their eggs in relation to the host laying cycle to ensure prior hatching of the parasitic chicks. Methods We monitored the hatching of Cuckoo chicks in relation to the hosts’ laying stage at which the Cuckoo eggs appeared and also monitored host incubation behaviour. Results Great Reed Warblers incubated more on day 5 after the host's onset of laying relative to day 3. All Cuckoo eggs hatched earlier than hosts when they were laid prior to the onset of host incubation (day 4). Cuckoo eggs also maintained hatching priority in about 2/3 of the nests when laid on days 5–6. Conclusions Most Cuckoo eggs are laid prior to the onset of host incubation and this, together with other adaptive mechanisms, ensures the prior hatching of Cuckoo eggs. Cuckoo eggs laid after the onset of incubation lose the advantage of prior hatching in approximately 30% of nests.
Avian brood parasites pose a serious threat to hosts, substantially reducing their fitness, which selects for the evolution of host defences. A classic example of a host frontline defence is mobbing, ...which frequently includes contact attacking of brood parasites. Here, we investigated how the nest defence of a very aggressive host, the Great Reed Warbler Acrocephalus arundinaceus, influences the speed of egg‐laying and egg‐removing behaviour of its brood parasite – the Common Cuckoo Cuculus canorus. We video‐recorded 168 brood parasitic events at 102 active host nests and found that Cuckoos avoided host mobbing in 62% of cases. If hosts spotted the Cuckoo at their nests, they almost always attacked it (91 of 104 cases; 88%); however, such attacks only rarely and temporarily prevented Cuckoos from parasitizing (11 additional cases). When attacked, Cuckoos parasitized host nests significantly faster and left them immediately after laying. However, when not attacked, Cuckoos frequently stayed at or near the nest, suggesting that host aggression, rather than the risk of being spotted, influences the speed of brood parasitism in this species. Further, we found that Cuckoos performed egg‐removing behaviour in all parasitic events without regard to host aggression. As a result, Cuckoos removed at least one egg during all brood parasitism events except those when the egg slipped from their beaks when they were attacked by hosts and, thus, remained in the nest (in nine of 82 cases when they were attacked; 10.9%). This indicates that egg‐removing behaviour is not costly for the Common Cuckoo and is an essential part of its parasitism strategy, widening our understanding of this elusive behaviour.
Recent technological advancements now allow us to obtain geographical position data for a wide range of animal movements. Here we used light-level geolocators to study the annual migration cycle in ...great reed warblers (Acrocephalus arundinaceus), a passerine bird breeding in Eurasia and wintering in sub-Saharan Africa. We were specifically interested in seasonal strategies in routes and schedules of migration. We found that the great reed warblers (all males, no females were included) migrated from the Swedish breeding site in early August. After spending up to three weeks at scattered stopover sites in central to south-eastern Europe, they resumed migration and crossed the Mediterranean Sea and Sahara Desert without lengthy stopovers. They then spread out over a large overwintering area and each bird utilised two (or even three) main wintering sites that were spatially separated by a distinct mid-winter movement. Spring migration initiation date differed widely between individuals (1-27 April). Several males took a more westerly route over the Sahara in spring than in autumn, and in general there were fewer long-distance travels and more frequent shorter stopovers, including one in northern Africa, in spring. The shorter stopovers made spring migration on average faster than autumn migration. There was a strong correlation between the spring departure dates from wintering sites and the arrival dates at the breeding ground. All males had a high migration speed in spring despite large variation in departure dates, indicating a time-minimization strategy to achieve an early arrival at the breeding site; the latter being decisive for high reproductive success in great reed warblers. Our results have important implications for the understanding of long-distance migrants' ability to predict conditions at distant breeding sites and adapt to rapid environmental change.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
One group of commonly found parasites in birds, for which fitness consequences and effects on life history traits have been much debated are Haemosporidian blood parasites. In a long term study ...population of great reed warblers Acrocephalus arundinaceus in Sweden, previous studies have shown that the Haemosporidian blood parasites are in their chronic phase during the breeding season and that the fitness of infected and non‐infected birds are similar. In the present study, we quantified parasite intensity (parasitemia) in 718 adults great reed warblers sampled between 1987 and 1998 for the three most common parasite species; Haemoproteus payevskyi (lineage GRW1), Plasmodium ashfordi (GRW2) and Plasmodium relictum (GRW4). We verified that the q‐PCR method is accurately quantifying Haemoproteus payevskyi (GRW1) as it was highly correlated with the number of parasites seen under microscope. Frequency of mixed infections with two lineages was significantly higher than expected based on the prevalence of each of the three parasite lineages. The mean level of parasitemia was significantly different for the three lineages and individual birds had repeatable parasitemia levels between years. Females tended to have a higher parasitemia than males for all three parasite lineages combined. Females with higher GRW1 parasitemia tended to arrive later in spring to their breeding sites. There was a negative correlation between parasitemia and number of fledged offspring for GRW1, and a tendency for a negative correlation between GRW2 parasitemia and the proportion of recruiting offspring. Overall our results demonstrate that chronic Haemosporidian infections can have slight but significant effects on host life history traits, and therefore may act as important selective agents in wild bird populations.
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