Interspecific Conflicts Research Articles

Interspecific competition among anemonefishes: pink anemonefish engage in hostile takeovers of sea anemones occupied by clown anemonefish

AbstractUnderstanding drivers of species co-existence on coral reefs is important to predict community responses to environmental change. Here, we present, for the first time, observations of takeovers of anemones occupied by one species, Amphiprion percula, by another species, A. perideraion, and ask if habitat characteristics, fish characteristics, or environmental conditions predict these occurrences. Comparing survey data from multiple years, we find that takeovers occur at a frequency of 0.48–6.84 per 100 groups/year and that this does not depend on disturbances (anemone bleaching) in the population. Takeovers are not predicted by depth, anemone size, A. percula rank 1 size or the number of A. percula in the original group. Instead, we hypothesize that proximity of the A. percula group to the A. perideraion group is a key predictor. Our study demonstrates how long-term observations of tagged individuals and groups could reveal the drivers and consequences of interspecific conflicts on coral reefs.

PAT: a comprehensive database of prokaryotic antimicrobial toxins.

Antimicrobial toxins help prokaryotes win competitive advantages in intraspecific or interspecific conflicts and are also a critical factor affecting the pathogenicity of many pathogens that threaten human health. Although many studies have revealed that antagonism based on antimicrobial toxins plays a central role in prokaryotic life, a database on antimicrobial toxins remains lacking. Here, we present the prokaryotic antimicrobial toxin database (PAT, http://bioinfo.qd.sdu.edu.cn/PAT/), a comprehensive data resource collection on experimentally validated antimicrobial toxins. PAT has organized information, derived from the reported literature, on antimicrobial toxins, as well as the corresponding immunity proteins, delivery mechanisms, toxin activities, structural characteristics, sequences, etc. Moreover, we also predict potential antimicrobial toxins in prokaryotic reference genomes and show the taxonomic information and environmental distribution of typical antimicrobial toxins. These details have been fully incorporated into the PAT database, where users can browse, search, download, analyse and view informative statistics and detailed information. PAT resources have already been used in our prediction and identification of prokaryotic antimicrobial toxins and may contribute to promoting the efficient investigation of antimicrobial toxin functions, the discovery of novel antimicrobial toxins, and an improved understanding of the biological roles and significance of these toxins.

Intra- and interspecific competition resulting from spatial coexistence among larvae of closely-related caddisflies from the genus Hydropsyche.

Caddisfly larvae commonly inhabit freshwater ecosystems, where they often create multi-species aggregations. However, while several strategies have been developed to avoid or reduce inter- and intraspecific interactions, most species choose the same time to seek a suitable place for pupation, which can increase competition. The current study assesses the competitive interactions among larvae (5th instar) of three co-existing Hydropsyche species, viz. H. contubernalis, H. pellucidula, and H. modesta, analysing their direct one-on-one interaction and various morphological features, such as size, weight, and mandibles. More than half of the interspecific conflicts ended with a draw, and 80% of intraspecific interactions with a decisive outcome. In fights between species, H. pellucidula was the most successful, and H. modesta the weakest. Our results confirm that among the larvae, competitive interactions were usually decided by body size, especially that of the head capsule. Although wider head capsule and higher weight were advantageous for ~60% of winning larvae, there were no distinct winning species. The chewing mouthpart turned out to be supportive in the fight: regardless of the species, longer and wider mandibles were significant for winning specimens, but not the distance between mandibles. Hence, acquiring a suitable place for pupation is determined by the possession of certain features enhancing the fighting potential of individual larvae, which does not exclude any species from the possibility of closing the life cycle. Future studies on interactions among caddisfly larvae could include experience in fights, volitional features and stridulation (not tested).

Answer to Caravaggi et al. (2021)

We understand and share the same concerns raised by Caravaggi et al. (2021), since we are all scientists, and we take scientific rigour seriously in our work. The paper published by Araujo et al. (2021) had authorization for scientific activities issued by SISBIO/ICMBio/MMA (no. 46031-4) and it was approved by two Ethics Committee on Animal Use (Federal University of Mato Grosso do Sul, no. 727/2015, and Federal University of Viçosa, no. 79/2015). Such authorizations were amended to the Acknowledgements in the version paged on 27 November 2020, before been assigned to an issue. In this way, the paper not only did not neglect ethics but was approved by three recognized research institutions. The authors of the questioned paper have been working for two or more decades generating data from free-living captures for conservation. Data on animal welfare, degree of injury, use of baits or attractants, response time, degree of risk to the animal and the team, among others, are systematically collected by experienced researchers from our group. Such data were part of the original manuscript but were removed when transformed into Practical Tools. We look forward to the opportunity of MEE to present this data in full, as our right of reply to Caravaggi et al. (2021) is limited to 3,000 characters. Some of the questions probably came from people with extreme theoretical knowledge. The statement that ‘Foot snares can pose a greater risk of injury to animals than cage traps’ clearly demonstrates little experience in the field. Cage traps are no longer the golden method to capture large felids due to low efficiency, higher costs, and risks of teeth and claw injuries. Araujo et al. (2021) describe several modifications and procedures that reduce the risk of injuries by foot snare traps. All the capture methods were evaluated not only by our researchers but also by Ethics Committees and Brazilian government agencies and were not neglected in this manuscript. Unfortunately, questions that come from theoretical extrapolations with no connection to the field reality can delay the conservation efforts and go against the One Conservation concept described by Pizzutto et al. (2021). Access to threatened species is the best way to generate data that allow a real diagnosis of the species in situ and suggests policies for its conservation. In the case of the jaguar, the greater the number of captures, the greater the chances of making the right decisions, and the greater the number of individual genetics collected and stored in germplasm banks. The isolation of populations and the extremely low number of jaguars in biomes such as the Caatinga and the Atlantic Forest justify the urgency of capturing. Fish broth and/or roar device were used as an attractant in 40 captures. In only one there was any injury to the animal: paw oedema, immediately treated by veterinarians and without compromising its health. The safety of the team is also a concern but taking some precautions such as not entering the area of imminent risk and paying attention to the presence of other animals reduces the chances of accidents to almost zero. Regarding animal welfare, the discussion should be based on the five domains model for animal welfare assessment and monitoring (Mellor et al., 2020), and foot snare traps do not compromise any physical/functional domains. Therefore, they do not promote negative mental experiences, as the rare, mild transient oedema in the paws does not compromise the ability to walk. The injury is much lighter than those that occur due to intraspecific and interspecific conflicts in nature. Furthermore, the anaesthetic protocol produces retrograde amnesia for the pre-anaesthetic period—eliminating negative mental experiences of the foot snare—and anterograde amnesia for the post-anaesthetic period (Gruber & Reed, 1968). Another strategy that reduces animal injuries and distress is frequent remote monitoring—at least every hour—allowing access to the animal within a maximum of 3 hours of capture. Finally, we believe that technical training combined with practical experience allows researchers to develop the intuition inherent in science. None of the authors have any conflicts of interest to declare. The peer review history for this article is available at https://publons.com/publon/10.1111/2041-210X.13706.

Altered Food Habits? Understanding the Feeding Preference of Free-Ranging Gray Langurs Within an Urban Settlement.

Urbanization affects concurrent human-animal interactions as a result of altered resource availability and land use pattern, which leads to considerable ecological consequences. While some animals have lost their habitat due to urban encroachment, few of them managed to survive within the urban ecosystem by altering their natural behavioral patterns. The feeding repertoire of folivorous colobines, such as gray langur, largely consists of plant parts. However, these free-ranging langurs tend to be attuned to the processed high-calorie food sources to attain maximum benefits within the concrete jungle having insignificant greenery. Therefore, besides understanding their population dynamics, the effective management of these urbanized, free-ranging, non-human primate populations also depends on their altered feeding habits. Here, we have used a field-based experimental setup that allows gray langurs to choose between processed and unprocessed food options, being independent of any inter-specific conflicts over resources due to food scarcity. The multinomial logit model reveals the choice-based decision-making of these free-ranging gray langurs in an urban settlement of West Bengal, India, where they have not only learned to recognize the human-provisioned processed food items as an alternative food source but also shown a keen interest in it. However, such a mismatch between the generalized feeding behavior of folivorous colobines and their specialized gut physiology reminds us of Liem's paradox and demands considerable scientific attention. While urbanization imposes tremendous survival challenges to these animals, it also opens up for various alternative options for surviving in close proximity to humans which is reflected in this study, and could guide us for the establishment of a sustainable urban ecosystem in the future.

Venom Use in Eulipotyphlans: An Evolutionary and Ecological Approach.

Venomousness is a complex functional trait that has evolved independently many times in the animal kingdom, although it is rare among mammals. Intriguingly, most venomous mammal species belong to Eulipotyphla (solenodons, shrews). This fact may be linked to their high metabolic rate and a nearly continuous demand of nutritious food, and thus it relates the venom functions to facilitation of their efficient foraging. While mammalian venoms have been investigated using biochemical and molecular assays, studies of their ecological functions have been neglected for a long time. Therefore, we provide here an overview of what is currently known about eulipotyphlan venoms, followed by a discussion of how these venoms might have evolved under ecological pressures related to food acquisition, ecological interactions, and defense and protection. We delineate six mutually nonexclusive functions of venom (prey hunting, food hoarding, food digestion, reducing intra- and interspecific conflicts, avoidance of predation risk, weapons in intraspecific competition) and a number of different subfunctions for eulipotyphlans, among which some are so far only hypothetical while others have some empirical confirmation. The functions resulting from the need for food acquisition seem to be the most important for solenodons and especially for shrews. We also present several hypotheses explaining why, despite so many potentially beneficial functions, venomousness is rare even among eulipotyphlans. The tentativeness of many of the arguments presented in this review highlights our main conclusion, i.e., insights regarding the functions of eulipotyphlan venoms merit additional study.

Aggressive Behaviors of Adult Male Atlantic Spotted Dolphins: Making Signals Count during Intraspecific and Interspecific Conflicts

Some species exhibit behavioral plasticity by altering their aggressive behavior based on their opponent. Atlantic spotted dolphins (Stenella frontalis) and bottlenose dolphins (Tursiops truncatus) are two sympatric species resident to the northern Bahamas. We examined whether groups of adult male spotted dolphins demonstrated behavioral plasticity during two different types of aggressive interactions. We described and compared the types of aggressive behaviors used during intraspecific aggression and interspecific aggression with bottlenose dolphins. Between the years 1991-2004, twenty-two aggressive encounters (11 intraspecific (spotted only), 11 interspecific (spotted vs. bottlenose)) were behaviorally analyzed. Twenty-three specific aggressive Behavioral Events, further grouped into three Behavioral Types, were examined throughout these encounters. Similarities and differences in the use of the Behavioral Types occurred during intra- and interspecific aggression. Groups of male Atlantic spotted dolphins altered their behavior during aggressive encounters with male bottlenose dolphins. Spotted dolphins increased their use of the Pursuit Behavioral Type and did not use the Display Behavioral Type significantly more than the Contact Behavioral Type during interspecific aggression. The increased use of a more overt and energy intensive Behavioral Type, Pursuit, suggests that Atlantic spotted dolphins altered their behavior during aggressive encounters with bottlenose dolphins to compensate during fights with a larger species and/or to effectively communicate with a different species.

Threat, Signal or Waste? Meaning of Corpses in two Dulotic Ant Species

Ant corpses, besides representing threat of infection by pathogens and parasites, can also be used during interspecific conflicts to inhibit the activity of the attacked colony, or they can be consumed as food. In the view of the former, the signal properties of corpses can be manifold. Besides discriminating nestmates and foes, the corpses of different ant species may act as cues for foragers, signaling the presence of other rival species, and triggering appropriate responses (e.g., alarm, retreat or foraging). In our study, we examined the responses of the facultative slave-maker Formica sanguinea and those of the obligate Polyergus rufescens towards corpses of nestmates, non-nestmate conspecifics, heterospecific slave-makers and their slaves, and corpses of non-enslaved host species under laboratory conditions. Both dulotic species responded differently to corpses of different origin. In F. sanguinea, the most intensive response was elicited by the corpses of P. rufescens and its slave, but also the corpses of non-nestmate conspecifics and their slaves elicited many adverse responses. In P. rufescens, the corpses of non-nestmate conspecifics and their slaves elicited the most adverse response. Both dulotic species distinguished corpses of their slaves from corpses of non-enslaved hosts. Based on our results, ant corpses are not meaningless objects scattered in the field, but cues carrying information that trigger different behavioral responses, and in F. sanguinea they can even represent an important food source.

A scientific note on the use of external feeders for the Amazonian stingless bee Melipona flavolineata (Apidae, Meliponini)

Artificial feeding of stingless bee colonies is widely applied in meliponiculture to maintain colonies in good conditions during periods of natural food scarcity. Traditionally, most stingless beekeepers tend to adopt the individual feeding of colonies, to avoid conflicts among colonies or competition with feral species. We trained foragers from Melipona flavolineata colonies to collective feeders containing sugar syrup, and showed they are useful for the management of this species, since they did not cause significant intra and interspecific conflicts, and thus, worker losses. Besides, most colonies from the meliponary frequented the feeder, showing that collective feeding in this species is possible and can be recommended to keep colonies in good condition during periods of natural food dearth or after honey harvesting.

Reduction of female copulatory damage by resilin represents evidence for tolerance in sexual conflict.

Intergenomic evolutionary conflicts increase biological diversity. In sexual conflict, female defence against males is generally assumed to be resistance, which, however, often leads to trait exaggeration but not diversification. Here, we address whether tolerance, a female defence mechanism known from interspecific conflicts, exists in sexual conflict. We examined the traumatic insemination of female bed bugs via cuticle penetration by males, a textbook example of sexual conflict. Confocal laser scanning microscopy revealed large proportions of the soft and elastic protein resilin in the cuticle of the spermalege, the female defence organ. Reduced tissue damage and haemolymph loss were identified as adaptive female benefits from resilin. These did not arise from resistance because microindentation showed that the penetration force necessary to breach the cuticle was significantly lower at the resilin-rich spermalege than at other cuticle sites. Furthermore, a male survival analysis indicated that the spermalege did not impose antagonistic selection on males. Our findings suggest that the specific spermalege material composition evolved to tolerate the traumatic cuticle penetration. They demonstrate the importance of tolerance in sexual conflict and genitalia evolution, extend fundamental coevolution and speciation models and contribute to explaining the evolution of complexity. We propose that tolerance can drive trait diversity.

Diurnal Activity Pattern of Golden Jackal (Canis aureus Linn.) in an Urban Landscape of Kolkata, India

The Golden jackal is known to have a wide distribution range and has been put under “Least Concern” category in the IUCN (ver 3.1) Red Data Book. However, the species once quite common along with the Bengal Fox in the eighteenth and nineteenth century of Kolkata has faced serious challenge due to land use and land cover changes in their urban habitats. As such, the Golden jackal has become “locally endangered” in the city of Kolkata, India. Kolkata, one of the largest cities in India, with population density of 14,112,536 is one such example where the land use change is profound. The Tollygunge Club, Kolkata is a social club with restricted entry at the heart of the city of Kolkata and harbours a healthy breeding population of the Golden jackal (Canis aureus Linn.). The present study focuses on the adaptability of the jackals to human proximity and its capacity to switch to natural food (fruits and leaves of available plants in the club, molluscs etc.) present in the club when the club refuse is not available. Their diurnal activity has been studied. These animals show diurnal activity in the open terrains of the club as they are least threatened by the humans. Only few intraspecific and interspecific (with the stray dogs in the club premises) conflicts have been noticed. In is interesting to note that at the heart of a city, in an urban area, such social clubs with restricted entry can provide suitable habitat to sustain a healthy breeding populations of the animals which are showing constant decline in their population due to change in land use pattern.

Cues or meaningless objects? Differential responses of the ant Formica cinerea to corpses of competitors and enslavers

Group living involves major health risks, since it facilitates the spread of pathogens and parasites among members. To counteract this negative effect, social insects, such as ants, adopt several social defensive strategies, one of the most widespread being the collective disposal of corpses often outside the nest, which represent potential sources of infection. Corpses might even be used during interspecific conflicts to inhibit the activity of the attacked nest or they could be consumed as food. As intra- and interspecific relationships are manifold and often vary in terms of fitness consequences for the interacting species, it can be hypothesized that responses to corpses of different origin can vary. Scattered or piled up corpses of different ant species could act as cues for foragers, signalling the presence of other species, and triggering appropriate responses: alarm, retreat or foraging. We examined the reactions of the ant Formica cinerea under natural conditions to corpses of co-occurring Formica species. Formica cinerea responded differentially to corpses of different origin. Those of the territorial Formica polyctena and the slave-maker Formica sanguinea elicited more aggression and their corpses were removed sooner than other dead bodies. The majority of corpses were carried inside the nest, with the exception of Formica fusca corpses, which may signify the lack of specific interest in this species. The removal of nestmate and foreign conspecific corpses could be explained through social prophylaxis, and that of superior competitors additionally by conflict avoidance and/or by food supplementation. Based on our results, for ants corpses are not meaningless objects scattered around ant nests, but cues that carry information that trigger different behavioural reactions.

Activity and competitive behaviour of invasive Neogobius melanostomus and Ponticola kessleri (Gobiidae) from the River Rhine, Germany

Behavioural experiments were conducted to gather information on how competitive behaviour between the invasive gobies Ponticola kessleri and Neogobius melanostomus may affect the development of populations in the River Rhine. Short-term experiments that were designed to measure activity could not discern any consistencies, neither between species nor based on gender. Although both species needed time to adapt to laboratory shelters, N. melanostomus hid conspicuously more often than P. kessleri. Few directly competitive interactions between species were observed. However, when such interactions were observed, N. melanostomus was stronger and won most inter-specific conflicts, even when it was the smaller opponent. It was also revealed in long-term feeding experiments that N. melanostomus preferred gammarids over fish during direct competition, while the opposite was true for P. kessleri. Behavioural results of the present study show these two species to exhibit different strategies, giving some evidence that P. kessleri and N. melanostomus may occupy different niches that enable them to coexist in the River Rhine.

The evolution of species recognition in competitive and mating contexts: the relative efficacy of alternative mechanisms of character displacement

Sympatric divergence in traits affecting species recognition can result from selection against cross-species mating (reproductive character displacement, RCD) or interspecific aggression (agonistic character displacement, ACD). When the same traits are used for species recognition in both contexts, empirically disentangling the relative contributions of RCD and ACD to observed character shifts may be impossible. Here, we develop a theoretical framework for partitioning the effects of these processes. We show that when both mate and competitor recognition depend on the same trait, RCD sets the pace of character shifts. Moreover, RCD can cause divergence in competitor recognition, but ACD cannot cause divergence in mate recognition. This asymmetry arises because males with divergent recognition traits may avoid needless interspecific conflicts, but suffer reduced attractiveness to conspecific females. Therefore, the key empirical issue is whether the same or different traits are used for mate recognition and competitor recognition.

Structure of multi-species ant assemblages (Hymenoptera, Formicidae) in the Mountain Crimea

The multi-species ant assemblages were studied in the Crimea Mountains, in 9 types of plant associations in the plateau pastures as well as on the southern and northern slopes of the Main Range. A list of 18 ant species with data on their distribution in biotopes and also layers and the structure of their foraging territories is given. The hierarchical organization of multi-species ant assemblages and different strategies of nest location of the influents depending on the dominant species and its territoriality were investigated. Territoriality of each dominant species was determined by the frequency of foraging areas without nests of other species. Depending on dominant territoriality and the number of dominant species, the following classification of multi-species assemblages is proposed. (1) Monodominant assemblages with weakly expressed territoriality of the dominant species. Low density of the workers of Camponotus aethiops in the foraging territory determines weak interactions with influent species. The settling pattern of the influents shows no evident dependence on the dominant. Weakly expressed territoriality of the dominant allows non-territorial species to exist on the dominant’s territory. Such species were not found in other types of ant assemblages. (2) Monodominant assemblages with strongly expressed territoriality of the dominant species. The settling pattern of the influents shows the subordinate species to avoid those of higher ranks in the hierarchy, thus decreasing the probability of conflicts. The influents settle in the neutral zones as well as in the foraging territory of the dominant, so as to reduce competition with the subdominant species Formica cunicularia. Such a strategy reduces the probability of interspecific conflicts in biotopes with fewer vegetation layers than in the forests. (3) Bidominant assemblages with a variable dendrobiont dominant are typical among forest assemblages. Coexistence of two dominant species is possible when foraging of one of them is completely or partly restricted to one vegetation layer. The subdominant species avoid settling in the foraging territory of the dominant that occupies the same layer. When the dendrobiont dominant Crematogaster schmidti drops out of the assemblage, it (and its role in the assemblage) is replaced by other dendrobiont species Lasius emarginatus which otherwise acts as the 1st order subdominant in C. schmidti assemblages. (4) Polydominant assemblages are characterized by the presence of as many as 3 dominant species, namely Crematogaster schmidti, Camponotus aethiops, and Plagiolepis tauricus. The coexistence of the dominants is possible due to use of different layers (one species is a dendrobiont, the other two are herpeto-hortobionts), different activity periods (round-the-clock in Crematogaster schmidti, night in Camponotus aethiops, and daytime in P. tauricus), and different size classes of the workers (3rd, 5th, and 1st, respectively). The different size classes of workers reduce competition for food. Thus, when the number of dominant species in the assemblage increases, so does the number of mechanisms facilitating their coexistence.

Low intraspecific aggressiveness in two obligate plant-ant species

Little is known about the aggressiveness of plant-ants typically living in isolated trees nor about how that aggressiveness varies based on this isolation. Here, we examine intra- and interspecific aggressiveness between workers of two Allomerus species associated with two different myrmecophytes. In both cases, the level of intraspecific aggressiveness is very low whatever the distance separating the tested nests, while interspecific conflicts are always violent. Similar patterns of aggressiveness have been reported in various ant species, but the strictly arboreal life of Allomerus ants associated with the isolation of their adult colonies highlight different ecological conditions that might explain the lack of aggressiveness between conspecifics.

Behavioural mechanisms of conflict avoidance among shrews

Stable co-existence of similar species should be facilitated by mechanisms impairing, besides exploitative, interference competition. We investigated avoidance of intra- and interspecific conflicts in a four-species community of shrews [Sorex minutus Linnaeus, 1766,S. araneus Linnaeus, 1758,Neomys anomalus Cabrera, 1907, andN. fodiens (Pennant, 1771)], using the method of dyadic encounters in a neutral arena. We tested whether the use of passive (habituation, reduction of mobility, increase of inter-individual distance, and stillness) and active (‘to-and-fro’ and ‘keeping distance’ behaviours) forms of conflict avoidance depends on species, size or domination rank. The duration of conflicts was positively correlated with mobility and negatively with inter-individual distance, whereas it was unrelated to time of stillness and the active forms. The repertoire of conflict avoidance mechanisms was not species-specific and the display of these mechanisms depended rather on the size and domination rank of animals participating in a given interaction. In contrast to rodents, shrews did not avoid conflicts by the most passive forms: freeze and stillness reactions. All other forms were used with a higher or lower efficiency by all species. However, consistent with our predictions, large shrews (asN. fodiens) used mainly the passive mechanisms of conflicts avoidance (‘wait-and-see’ strategy), whereas small shrews (asS. minutus) invest proportionally more time in active forms (‘escape’ strategy).

Wars of attrition: colony size determines competitive outcomes in a guild of African acacia ants

Territorial aggression is a primary mode of population regulation among ants, and frequently leads to the formation of linear dominance hierarchies. However, few experimental studies have investigated the proximate mechanisms that underlie these hierarchies. In this study I examine the mechanisms underlying dominance relationships in interference competition for nest sites in a guild of acacia ants residing on Acacia drepanolobium. I show that (1) interspecific conflicts are fought as simple wars of attrition, with mortality ratios among combatant species approximating 1:1, (2) interspecific competitive outcomes, both within and between habitats, closely parallel differences in estimated average colony size among the four acacia ant species, and (3) experimental manipulation of colony size effectively reverses the dominance hierarchy. This is the first study to demonstrate experimentally that size asymmetries underlie dominance relationships in an entire guild of competitors. These results also highlight the contingent nature of ecological dominance in this community. Because dominance is dictated by characteristics of a trait shared by all ant species (colony size), interspecific competitive outcomes may vary if species differ in growth and/or mortality responses to factors such as disturbance or environmental conditions. Contingencies in competitive outcomes among these acacia ants may play an important role in promoting coexistence in this intensely nest-site-limited community.

Redstart Phoenicurus phoenicurus and black redstart P. ochruros in a mosaic urban environment: neighbours or rivals?

Redstart and black redstart inhabit different types of habitats under natural conditions. However, they come into close contact in a mosaic urban environment. Mechanisms enabling their local coexistence were looked for. We found that: 1) The two species occupied exclusive territories of different habitat compositions. 2) Territories differed in the proportion of trees and buildings. 3) Within their territories, the two species used the same foraging techniques, but with different frequencies. 4) Prey size was similar, but the proportions of taxonomic groups differed. 5) Spontaneous interspecific conflicts were observed. Interspecific aggression was confirmed in playback experiments. The black redstart was dominant in both natural and simulated encounters. We conclude that the main mechanism enabling coexistence of the two redstarts in a mosaic urban environment is different habitat selection with the proportion of trees as a key parameter. This proportion was always below 26% in black redstart territories, and above 27% in redstart territories. This is consistent with the habitat preferences these two species show in non‐urban conditions. This pattern is compared to the other cases of coexistence of congeneric bird species such as chickadees Poecile or Sylvia warblers. As the two redstart species are able to hybridise in the wild, the observed interspecific aggression may operate as a pre‐copulation barrier.

Observations on a newly detected breeding site of Bonelli’s Eagle, Hieraaetus fasciatus, in south-eastern Anatolia

In spring 2003, a pair of Bonelli’s Eagle (Hieraaetus fasciatus) reared a young near Hasankeyf, Batman province, Turkey. The site shows very similar habitat properities to the only known breeding site in the region. Observations on the nest structure, feeding, courtship dancing flight, and on interspecific conflicts are described.