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Bird parents may choose among various breeding strategies. From an evolutionary point of view the outcome of their choice is believed to provide the highest reproductive success in a given environment. However, some of the mechanisms underlying parental reproductive decisions are still poorly understood, for example the phenomenon of hatching asynchrony. Resultant age and size hierarchy among nest mates often lead to competitive disadvantages, starvation and death of last-hatched siblings. Although synchronised broods generally result in higher fledging success, altricial bird species typically hatch asynchronously. Various hypotheses were proposed and tested to explain this strategy. A quarter of a century has passed since the last review of research on hatching asynchrony. In the meantime the number of studies investigating the issue has considerably grown, same as the array of hypotheses. Our aim is to present a comprehensive synthesis of the research on 20 hypotheses presented until recently as well as to indicate the blind spots in the reviewed area—9 out of 20 formulated hypotheses still lack any experimental approach that would confirm or reject the assumptions.

The RNA world concept1 is one of the most fundamental pillars of the origin of life theory2–4. It predicts that life evolved from increasingly complex self-replicating RNA molecules1,2,4. The question of how this RNA world then advanced to the next stage, in which proteins became the catalysts of life and RNA reduced its function predominantly to information storage, is one of the most mysterious chicken-and-egg conundrums in evolution3–5. Here we show that non-canonical RNA bases, which are found today in transfer and ribosomal RNAs6,7, and which are considered to be relics of the RNA world8–12, are able to establish peptide synthesis directly on RNA. The discovered chemistry creates complex peptide-decorated RNA chimeric molecules, which suggests the early existence of an RNA–peptide world13 from which ribosomal peptide synthesis14 may have emerged15,16. The ability to grow peptides on RNA with the help of non-canonical vestige nucleosides offers the possibility of an early co-evolution of covalently connected RNAs and peptides13,17,18, which then could have dissociated at a higher level of sophistication to create the dualistic nucleic acid–protein world that is the hallmark of all life on Earth.

War has always brought millions of silent non-human victims but the scale of this suffering is often either unknown, neglected or difficult to quantify. Further, the complexities associated with long-term and large-scale monitoring of marine species make it difficult to assess the impacts of war and the mortality of cetaceans resulting from warfare has not been investigated. Here we propose the use of a modified form of citizen science, namely gathering the information from social media. Dolphin stranding is such a poignant incident for most people, that the probability of eyewitness posting information on social media appears high. We test this idea by collecting data on cetacean strandings along the Black Sea published on the Internet over the three months of Russia's invasion of Ukraine in 2022. We also validate this method with a small-scale scientific study on cetacean mortality during the same period of time, conducted in ‘Tuzlivski lymany’ Nature National Park in Ukraine. Our dual approach has produced similar results, indicating a dramatic increase in cetacean mortality due to war operations in the Black Sea. We advocate the future use of social media to bridge the knowledge gap on the impacts of war on animals, in particular cetaceans.

Halina Hila Marcinkowska, Wieczni tulacze. Powojenna emigracja polskich Żydow, Proszynski i S-ka, Warszawa 2019, ss. 424.

The RNA world concept

In my paper entitled "Seeking a return to Poland. The case of “Gomulka Aliyah” immigrants in Israel (1956–1960)" I describe the emigration of Polish citizens of Jewish origin to Israel in the second half of the 1950s. From October 1956, when Wladyslaw Gomulka came into power in Poland, it became possible for Polish Jews to relocate in to Israel. Leaving Poland was not obligatory for Jews in that period, but a rise in anti-Semitism and disappointment with the communist regime in Poland led a number of Polish citizens of Jewish origin to make the decision to emigrate. In the period of 1956 to 1960 approximately 50,000 Jews went to Israel. However, after few months of living in the New Homeland, some of the new immigrants from Poland were seeking to return. Difficult living conditions, an unfamiliar language, and unemployment led Polish Jews to request repatriation. That was in most of the cases impossible, as most of them had given up on Polish citizenship while immigrating to Israel.

Acoustic communication is an important part of behaviour in many bird taxa. In most woodpecker species drumming functions in mate attraction and territory defence. However, woodpeckers also produce calls, which function has been less studied to date. Unlike other woodpeckers, the Middle Spotted Woodpecker Dendrocoptes medius, which is the subject of our study, drums very rarely. Instead, it uses a number of calls, which functions have not been tested to date. We aimed our study at the identification of different calls and assessing their function, both by observation of spontaneous interactions between individuals and playback experiments. We distinguished three calls of different spectral characteristics and functions. Call-1 was mostly uttered by individuals sitting on the branch or a trunk. It was an initial response of territorial pairs to any disturbance within a territory. It signals general anxiety and/or arousal of territorial individuals. Call-2 was mostly uttered by the individuals during flight and it accompanied territorial conflicts and trials to remove the intruder from the territory. It warns the intruder about a territory owner’s readiness to a direct fight. Call-3, characteristic for floaters, was a persistent vocalisation without any obvious stimulus. Acoustic analyses of call-3 revealed that it was individually distinctive and the experimental approach confirmed that woodpeckers were able to distinguish between calling floaters. Thus, Call-3 functions as a vocal signature of unpaired individuals.

In its sexual stage, the fungus Epichloe typhina (Ascomycetes: Clavicipitaceae) is a pathogen that causes choke disease in many grass species. It forms stromata on developing inflorescences, resulting in reductions in flowering and seed production in the infected plants. As a result of fungal infection, economic losses in meadows and pastures have been reported. Unfortunately, there are no effective methods for reducing the spread of E. typhina. One potential solution is the use of hyperparasites as biocontrol agents, for example, the fungus Trichoderma harzianum, known for its ability to parasitize other parasites. We investigated the effects of T. harzianum on E. typhina (strain CBS 122147) in Petri dishes containing PDA medium using two methods: a dual-culture method and a precolonized plate method. Three strains of E. typhina of different origins were used. These experiments showed that: (1) E. typhina mycelium grew slower in the presence of T. harzianum and could be overgrown by hyperparasite mycelium, and (2) all strains of E. typhina responded similarly to T. harzianum. The results indicate that the presence of T. harzianum has an inhibitory effect on the growth of mycelium in E. typhina. Therefore, this hyperparasite can be used to develop safe methods of limiting the spread of choke disease.

Social monogamy with bi-parental care is the most common breeding pattern in birds, yet cooperation between mates has not been intensively studied to date. In this study we investigate synchronisation of parental behaviours in the blackcap Sylvia atricapilla, a species characterized by bi-parental care and high nest predation. We test the hypothesis that mates synchronize their behaviours to decrease total activity at the nest, which is known to affect predation rate in birds. We examine if blackcap parents synchronise their feeding trips more when nestlings are at the poikilothermic stage, and they may be more vulnerable to nest predation due to their inability to escape and survive outside the nest without parental brooding. We also investigate the alternation of feeding trips by parents. We show that blackcap parents synchronise the majority of their feeding trips during the whole nestling period, and the level of parental synchrony is higher before nestlings develop endothermy. The alternation of male and female feeding trips was much higher than would be expected by chance and was positively related to parental synchrony. We have demonstrated that synchronisation of parental feeding trips significantly decreased parental activity at the nest, and nest survival time increased with the synchrony of parental feeding trips.

The paper presents a method of numerical modeling of binary alloy solidification process in a permanent mold in a two-dimensional area. The model takes into account the influence of the gas gap of variable width existing between the mold and the casting on the rate of solidification process. The numerical model is based on the finite element method (FEM) with independent spatial discretization of the casting and the mold. The displacements of these regions resulting from a thermally dependent changes of their volumes are also taken into account. The adopted approach involves the use of two separated meshes, where the temporary temperature fields are obtained. The thermal interaction between the casting and the mold is described by the appropriate boundary condition. The solution is obtained sequentially in each time step independently for the each region.

The paper presents an approach of numerical modelling of alloy solidification in permanent mold and transient heat transport between the casting and the mold in two-dimensional space. The gap of time-dependent width called "air gap", filled with heat conducting gaseous medium is included in the model. The coefficient of thermal conductivity of the gas filling the space between the casting and the mold is small enough to introduce significant thermal resistance into the heat transport process. The mathematical model of heat transport is based on the partial differential equation of heat conduction written independently for the solidifying region and the mold. Appropriate solidification model based on the latent heat of solidification is also included in the mathematical description. These equations are supplemented by appropriate initial and boundary conditions. The formation process of air gap depends on the thermal deformations of the mold and the casting. The numerical model is based on the finite element method (FEM) with independent spatial discretization of interacting regions. It results in multi-mesh problem because the considered regions are disconnected.

During solidification process the phenomenon of shrinkage cavity is often observed. It has negative impact on the structure and physical properties of the final product. To minimize the negative effect of shrinkage cavity the riser is commonly introduced to the solidifying system. If the riser is properly designed shrinkage cavity rather appears within its volume than in the other parts of the casting. It makes possible to obtain defect-free main part of the casting. Presented work shows the impact of the different shapes of the riser on the localization of the shrinkage cavity. The results are obtained with the use of an original computer program based on the finite element method (FEM). They are presented for three-dimensional case of solidification of three types of the riser. The comparison of the results is discussed in details.

The numerical approach based on the finite element method (FEM) for modeling of mechanical interaction between three-dimensional objects is presented in the paper. The model of contact is based on the assumption that the nodes of the region which is the source of contact cannot overlap with the nodes of the region being the target. The procedure of the detection of collision between surfaces of the source and the target is discussed in details. The behaviour of surfaces being in contact depends on their rigidity and is numerically modeled in the case of perfectly rigid source and deformable target. Each modeled object has an independent mesh of finite elements. These meshes can be freely moved relative to each other. Example of calculation using original program written in C++ is presented and discussed.

Global warming has the potential to affect many animal species, in particular temperature-dependent insects with their short generation times and high reproductive rates which facilitate adaptations to long-term climatic fluctuations. Aphids are the model species in studying the association of insect biology with large-scale climate fluctuations because they multiply only within a certain range of temperatures and their rate of development directly depends on temperature. Here, we investigate the effect of climate warming on phenology and voltinism of the juniper aphid (Cinara juniperi De Geer 1773), a native species of a temperate climate zone in Poland. We also experimentally test for the temperature optimum of the study species. Our study demonstrated that environmental conditions significantly affected phenology of juniper aphid. The timing of larval emergence depended on mean temperatures in March, and in warmer years larvae appeared earlier. The emergence of the sexual generation was related to mean...

Nest predation is a major source of reproductive failure in birds and thus it can exert selection on both parental and offspring strategies. Begging calls are known to be a powerful component of parent–offspring communication but these calls can also increase predation risk. Here we demonstrate a sophisticated strategy for the development of begging vocalization in a species under high nest predation. Blackcap Sylvia atricapilla nestlings spend most of their nesting period silent, and develop begging calls just before they are able to fledge. The onset of begging vocalization matches the onset of endothermy, which enables Blackcap chicks to leave the nest. We demonstrate experimentally that begging calls function as a signal of the increased needs of homeothermic nestlings. Playback of begging calls conducted in nests with silent nestlings resulted in a significant increase in feeding rates and a decrease in brooding. Development of begging calls only at the age of endothermy allows species under high nest predation to keep the risky period of begging vocalizations and frequent feeding to a minimum. This strategy may constitute an evolutionary solution to high predation pressure in some open nesting passerines. This is the first study to demonstrate the existence of silent begging in a passerine.

Ant-aphid mutualism has been investigated by many authors but it is unknown if anti-predator protection provided by ants is the main benefit for aphids. The aim of our paper is to analyse the ant-aphid interactions in the absence of predators. Based on video recordings we distinguish ant behaviours in interactions with attended aphids and we present ant time-budget at different times of the day. We also test if an aphid colony can survive without ant attendance in an environment free from predators and we inquire how much ant attendance is needed to maintain an aphid colony in good condition. Our study shows that, despite the lack of predation pressure, aphids of the species Cinara tujafilina were not able to survive without ant attendance and the extinction was caused by the excessive honeydew that covered aphids and their surroundings. We also found that ants cleaning aphids was the most frequent and time-consuming activity in ant-aphid interactions. However, in general, ants interacted with aphids only...

Mathematical and numerical models of Fe-C alloy solidification process based on the finite element method (FEM) are presented in the paper. The phenomenon of the defect called "shrinkage cavity" is introduced to the model. It is very important aspect of presented work which makes possible the prediction of the location and shape of mentioned defect depending on the geometry of the casting and cooling condition of the process. An original computer program using Visual C++ environment has been written in order to simulate described process. The results of computer calculations of the three-dimensional solidification problem of the casting with riser are presented and discussed in details.

We studied the effect of ectoparasitism by hematophagous larvae of the blow fly of the genus Protocalliphora on nestling blackcaps Sylvia atricapilla in southeast Poland. Approximately 81% of blackcap nests left by nestlings contained Protocalliphora larvae; however, mean parasite load was only 1.8 larvae per nestling. Nestling mass and tarsus length measured just before fledging did not differ significantly with parasite load. This finding might have resulted from several factors. First, the number of larvae per nestling was very low, which may be connected with the structure of blackcap nests. Second, the time of exposure of nestlings to parasitic larvae in the studied species is relatively short as fledglings are able to leave a nest when they are 9 days old. The combination of the open lacework structure of blackcap nest and a very short nestling period may constitute an evolutionary adaptation that enables blackcap nestlings to escape the cost of Protocalliphora parasitism.