Coal Tit Research Articles

Association of Success in Interspecific Rearing of Nestlings with the Width of Trophic Niche of the Recipient Species in Hollow-Nesting Birds

The structure of the diet of passerine bird nestlings was analyzed in order to identify possible ways to reduce food competition between these species during the breeding period. We assumed that analysis of the effects of obtaining diets of heterospecific birds by nestlings in nature can help better understand their species-specific adaptations to living conditions, and we considered the case of joint nesting of the coal tit (Periparus ater (L. 1758)) (CT) and pied flycatcher (Ficedula hypoleuca (Pallas 1764)) (PF) in Moscow oblast as a key link. A PF male attracted a female to an artificial nest box, which has been already occupied by a CT pair. The females of both species incubated a mixed clutch sitting side by side. The CT nestlings hatched earlier than the PF nestlings, and the parents of both species began to feed them. The CT nestlings started to die one by one on the 4th day of joint feeding, and the last nestling died on the 11th day. This case encouraged us to compare the diets of nestlings from 22 broods of CTs and PFs in the same region. To compare the ratios of nestlings, we collected the portions of food that were delivered to nestlings by their parents and analyzed video recordings from the nests. The diet of PF nestlings was significantly more diverse than in CT nestlings (Berger–Parker reverse indices (1/d) were 3.01 and 2.11, respectively). Caterpillars and spiders (objects with a high content of carotenoids and taurine important for the development of nestlings) dominated in the CT diet. In PF feed, these objects occupied a much smaller portion. In addition to the above, compared with coal tits, PFs brought the following to nestlings: a significant number of objects with rough, highly chitinized covers (Coleoptera, Homoptera, etc.); objects with a sharp taste, such as true bugs (Heteroptera), ladybirds (Coleoptera, Coccinellidae), and millipedes (Diplopoda, Julidae); insects containing cantharidin toxin (soldier beetles, Coleoptera, Cantharidae). The nestlings developed successfully in PF nests to which parents brought such feed objects. The dimensional ranges of objects in the CT and PF diets completely overlapped. According to our opinion, the rougher, highly chitinized food and some poisonous insects (Cantharidae) in the PF diet make fundamentally important differences in the nutrition of PFs and CTs. Most likely, PFs have resistance to cantharidin and some other toxins that are contained in insects and therefore have a wider trophic niche.

Anthropogenic noise reduces avian feeding efficiency and increases vigilance along an urban–rural gradient regardless of species’ tolerances to urbanisation

Anthropogenic noise can adversely impact urban bird populations by interfering with vocal communication. Less research has addressed if anthropogenic noise masks the adventitious sounds that birds use to aid predator detection, which may lead to increased vigilance and reduced feeding efficiency. We test this hypothesis using a controlled playback experiment along an urban–rural gradient in Sheffield (UK). We also test the related predictions that anthropogenic noise has the greatest impacts on vigilance and feeding efficiency in rural populations, and on species that are more sensitive to urbanisation. We focus on six passerines, in order from most to least urbanised (based on how urbanisation influences population densities): blue tit Cyanistes caeruleus, robin Erithacus rubeculla, great tit Parus major, chaffinch Fringilla coelebs, coal tit Periparus ater and nuthatch Sitta europaea. We used play‐back of anthropogenic urban noise and a control treatment at 46 feeding stations located along the urban–rural gradient. We assess impacts on willingness to visit feeders, feeding and vigilance rates. Exposure to anthropogenic noise reduced visit rates to supplementary feeding stations, reduced feeding rates and increased vigilance. Birds at more urban sites exhibit less marked treatment induced reductions in feeding rates, suggesting that urban populations may be partially habituated or adapted to noisy environments. There was no evidence, however, that more urbanised species were less sensitive to the impacts of noise on any response variable. Our results support the adventitious sound masking hypothesis. Urban noise may thus interfere with the ability of birds to detect predators, reducing their willingness to use food rich environments and increase vigilance rates resulting in reduced feeding rates. These adverse impacts may compromise the quality of otherwise suitable foraging habitats in noisy urban areas. They are likely to be widespread as they arise in a range of species including common urban birds.

Best environmental predictors of breeding phenology differ with elevation in a common woodland bird species.

Temperatures in mountain areas are increasing at a higher rate than the Northern Hemisphere land average, but how fauna may respond, in particular in terms of phenology, remains poorly understood. The aim of this study was to assess how elevation could modify the relationships between climate variability (air temperature and snow melt‐out date), the timing of plant phenology and egg‐laying date of the coal tit (Periparus ater). We collected 9 years (2011–2019) of data on egg‐laying date, spring air temperature, snow melt‐out date, and larch budburst date at two elevations (~1,300 m and ~1,900 m asl) on a slope located in the Mont‐Blanc Massif in the French Alps. We found that at low elevation, larch budburst date had a direct influence on egg‐laying date, while at high‐altitude snow melt‐out date was the limiting factor. At both elevations, air temperature had a similar effect on egg‐laying date, but was a poorer predictor than larch budburst or snowmelt date. Our results shed light on proximate drivers of breeding phenology responses to interannual climate variability in mountain areas and suggest that factors directly influencing species phenology vary at different elevations. Predicting the future responses of species in a climate change context will require testing the transferability of models and accounting for nonstationary relationships between environmental predictors and the timing of phenological events.

“The tale of the three little tits”: Different nest building solutions under the same environmental pressures

Evolutionary selection pressures, and species-specific ecology and behavior, promote a great variability in the size and composition of nests. However, it would be expected that phylogenetically close species, with similar ecological needs, breeding at the same time in the same place, would also build similar nests. In contrast with this, previous studies have found differences in nest mass and composition among closely related sympatric species. These differences have been attributed to small differences in body size (smaller species building larger and/or more insulated nests), or to the different ways in which species perceive the environment (e.g. perceived predation risk). In this study, for the first time, we searched for differences between nest mass, composition, and importance of the different functional parts of the nest between Blue ( Cyanistes caeruleus), Great ( Parus major) and Coal tits ( Periparus ater) breeding under the same conditions. We found that smaller species built larger nests and/or include more thermoregulatory materials, probably having greater insulating capacity, which agrees with previous hypotheses. In particular, Blue Tits made greater use of bark, feathers and vegetable fiber, while Great Tits used wild boar hair in greater proportions. In addition, for the first time, we described in detail the nest composition of Coal Tits, which contained large amounts of fluff compared to the other two species. All these results are in line with previous hypothesis linking nest size and composition to the size of the birds, and the existence of species-specific characteristics in the selection of materials for nest building.

Other Species’ Alarm Calls Evoke a Predator-Specific Search Image in Birds

Many animals produce vocal alarm signals when they detect a predator, and heterospecific species sharing predators often eavesdrop on and respond to these calls [1]. Despite the widespread occurrence of interspecific eavesdropping in animals, its underlying cognitive process remains to be elucidated. If alarm calls, like human referential words, denote a specific predator type (e.g., "snake!"), then receivers may retrieve a mental image of the predator when hearing these calls [2-4]. Here, using a recently developed experimental paradigm [5], I test whether heterospecific alarm calls evoke a predator-specific visual search image in wildbirds. During playback of snake-specific alarm calls produced by Japanese tits (Parus minor), coal tits (Periparus ater) approach a wooden stick being moved in a snake-like manner. However, coal tits do not approach the same stick when hearing other call types or if the stick's movement is dissimilar to that of a snake. Thus, Japanese tit snake alarms cause coal tits to specifically enhance visual attention to snakelike objects. These results provide experimental evidence for the evocation of visual search images by heterospecific alarm calls, highlighting the importance of integrating cross-modal information in interspecific eavesdropping.

How generalist are these forest specialists? What Sweden’s avian indicators indicate

AbstractMonitoring of forest biodiversity and habitats is an important part of forest conservation, but due to the impossible task of monitoring all species, indicator species are frequently used. However, reliance on an incorrect indicator of valuable habitat can reduce the efficiency of conservation efforts. Birds are often used as indicators as they are charismatic, relatively easy to survey, and because we often have knowledge of their habitat and resource requirements. In the Swedish government’s environmental quality goals, there are a number of bird species identified as being associated with ‘older’ and ‘high natural value’ forests. Here we evaluate the occurrence of four of these indicator species using data from 91 production forest stands and 10 forest reserves in southern Sweden. The bird species assessed are willow titPoecile montanus, coal titPeriparus ater, European crested titLophophanes cristatusand Eurasian treecreeperCerthia familiaris. For the production stands assessed, these indicator species exhibited no significant preferences regarding forest composition and structure, indicating a wider range of habitat associations than expected. These species frequently showed territorial behavior in forest stands <60 and even 40 years of age; much younger than the 120‐year threshold for ‘older forest’ as defined by governmental environmental goals. As almost 80% of the production stands ≥10 years old included at least one of the four indicator species, this raises questions regarding the suitability of these species as indictors of forests of high conservational value in southern Sweden. Notably, besides the four species assessed here, none of the additional indicator taxa identified by the government, were recorded in the 10 reserves. This outcome may reflect the difficulties involved in finding bird indicator species indicative of high natural values in this region. Our results highlight the importance of coupling bird surveys with quantified assessments of proximate vegetation cover.

Biodiversity and Structure of Undisturbed Mountain Siberian Pine Taiga of the Idarsky Belogorye Ridge (East Sayan)

The structure of flora and fauna, which is a standard of the state and dynamics of the taiga forests in humid climatic facies of the Altai-Sayan mountain region, has been analyzed based on the example of the undisturbed mountain Siberian Pine taiga (Eastern Sayan mountains). The ecological–phytocenotic features and floristic and faunistic composition of the late succession stage are studied. The dominance of the green moss group of forest types is revealed across the topographic profiles. The forest stands have a complex age structure with the dominance of Pinus sibirica Du Tour. and are characterized by low productivity (quality classes IV–V prevail), high class of normality (from 0.5 to 1.0), and sufficient regeneration. A floristic, ecological–coenotic analysis of the herb–dwarf-shrub layer, the elements of undergrowth, and the moss cover indicates the dominance of humid taiga flora. The species of the taiga ecological–coenotic group (ECG) (Vaccinium myrtillus, Carex iljinii, Calamagrostis obtusata, Gymnocarpium dryopteris, Phegopteris connectilis, Oxalis acetosella, Aegopodium alpestre, Trientalis europaea, Linnaea borealis, Maianthemum bifolium, Stellaria bungeana, et al.), moss–bog ECG (Ledum palustre, Vaccinium uliginosum, Carex globularis et al.), and bor-taiga ECG (Vaccinium vitis-idaea, Pyrola rotundifolia, Lycopodium annotinum et al.) form the herb–dwarf-shrub layer in the prevailing forest types. Green mosses (Hylocomium splendens and Pleurozium schreberi with a mixture of Ptilium crista-castrensis and Rhytidiadelphus triquetrus) dominate in the moss layer. Polytrichum commune, P. strictum, Dicranum scoparium, D. polysetum, and Sphagnum sp. mosses are found in some sites. The increased role of higher spore plants characterizes the flora as well-preserved archaic features flora. The Siberian pine forest coenoflora consists of 224 species and belongs to the Cyperaceae type. In the structure of the geographical elements of the flora, the leading role belongs to the Palaearctic, European, and Siberian elements with an increased role of endemics. The species typical for the Siberia taiga complex compose the core of the fauna. The most diverse avifauna is represented by 102 species (Tarsiger cyanurus, Parus montanus, Parus ater, Luscinia calliope, Sitta europaea, Loxia curvirostra, Coccothraustes coccothraustes, Tetrastes bonasia, Phylloscopus proregulus, etc.).

Comparative analysis of hissing calls in five tit species

Nest predation often leads to breeding failure and is an important component of natural selection that affects the evolution of nest defense behavior in birds. Many tit species give a hissing call as nest defense, but there are few studies of interspecific variation in hissing calls, and whether these are related to nest predation and nesting success. In this study, we compared the hissing calls of five tit species including cinereous tits (Parus cinereus), marsh tits (Poecile palustris), varied tits (Sittiparus varius), willow tits (Poecile montanus), and coal tits (Periparus ater) in Saihanba National Forest Park in Hebei and Xianrendong National Nature Reserve in Liaoning. In Saihanba of Hebei, the proportion of cinereous, willow, and coal tit individuals giving a hissing call differed significantly but the rate of nest predation was similar. It was also true for the three tit species (cinereous, varied, and marsh tits) in Xianrendong of Liaoning. Cinereous and varied tits showed no differences in clutch size, date of the first egg, nest predation and nesting success between individuals that gave and those that did not give a hissing call. These results indicate that for tit species that breed in nest boxes distributed within the same area, there is interspecific variation in hissing calls but this variation is not significantly correlated with nest predation risk.

The Effect of Pine Forest Structure on Bird-Mobbing Behavior: From Individual Response to Community Composition

Pine-forest bird communities are affected by the forest structure and the density and composition of its understory vegetation. In this study, we focused on the combined effects of vegetation structure and caller identity on the mobbing behavior of birds in breeding and non-breeding seasons. We examined the effect of the understory structure and the density of three types of conifer forest habitats on bird behavior by broadcasting three different types of mobbing calls: Those of two all-year resident species in the state Israel (Sardinian warbler Sylvia melanocephala Gmelin and great tit Parus major L.) and one European species (coal tit Periparus ater L.), which is absent from these habitats. The mobbing call attracted 689 birds of 17 species, which represented 31% to 95% of the forest bird species that we detected in point counts at the same study plots. Bird reactions to mobbing calls were affected by the status and season, depending on forest type. Our results show that responses were stronger in forests with developed understory in comparison to forests with no understory, especially in winter. The highest number of responders and highest species richness of responders were observed in winter. P. major calls generated more interspecific than intraspecific responses, whereas S. melanocephala calls generated equal levels of inter- and intraspecific reactions. Both species generated different response patterns across the three forest habitat types. The response level of responders is higher when the mobbing calls are issued by local species rather than the P. ater. In winter, the response of non-resident species was higher than of resident species. Based on these results, we encourage the managers to maintain well-established understory vegetation, with special attention to the shrubs layer, to promote species diversity and rich behavioral responses of birds in the conifer forests in the eastern Mediterranean region.

Syntax manipulation changes perception of mobbing call sequences across passerine species

AbstractMany species approach predators to harass them and drive them away. Both the intensity of this antipredator strategy and its success are positively related to the size of the group that carries out this mobbing. To recruit individuals to the mob, members of prey species produce mobbing calls. In some songbirds—the Japanese tit, Parus minor, and the southern pied babbler, Turdoides bicolor—mobbing calls are structurally complex and it has been suggested that they convey information by means of compositional syntax, when meaningful items are combined into larger units. These two species combine alert and recruitment calls into an alert and recruitment sequence when attracting conspecifics to cooperate in mobbing a predator. Whether this rudimentary, two‐call, compositional structure is used by other bird species in mobbing calls and how it can alter the ability of heterospecifics to adequately recognize mobbing calls is not well understood. Heterospecifics’ responses to mobs are critical to the success of the mobbing strategy, so it is of great importance to understand whether and how syntax influences these responses. To address these questions, we conducted two playback experiments. Firstly, we investigated whether the great tit, Parus major, extracts different meanings from different individual motifs (i.e., component calls), and from combined motifs in both natural and artificially reversed order. We found that great tits extract different meanings from the two motifs involved in mobbing calls and that they also discriminate for motif order reversal in the mobbing call sequence. Secondly, we investigated whether heterospecifics (the coal tit, Periparus ater, and the common chaffinch, Fringilla coelebs) are sensitive to syntax alteration of great tit mobbing calls. While chaffinches did not respond to great tit mobbing calls, coal tits were sensitive to mobbing call sequence reversal although they did not react in the same way as conspecific subjects. Overall, whereas our results indicate that tits are sensitive to call reversal, this is not to say that tits actually use compositional syntax to increase the information content.

Stepping stones

PurposeLarge-scale urbanisation has become a significant barrier to the natural migration of tree species, which is being exacerbated by accelerated climate change. Within this context, improving the permeability of urban landscapes is expected to be an effective strategy to facilitate the process of forest migration through cities. The purpose of this paper is to develop a method to assess the permeability of urban green spaces as stepping stones for forest migration, from the perspective of seed dispersal.Design/methodology/approachThe proposed method combines a least-cost path (LCP) model and a graph theory-based approach. The LCP model is applied to map the potential pathways of seed dispersal at multiple spatial and temporal scales, based on which graph theory-based indices are used to quantify the accessibility of urban landscapes for seed dispersers. This method is demonstrated by a case study in the Greater Manchester area, UK. Eurasian jay, Eurasian siskin, coal tit and grey squirrel are selected as the main seed dispersers in the study area.FindingsThe results provide a comparison of the landscape permeability maps generated from different seed dispersers and identify key areas likely to facilitate the process of forest migration. Recommendations regarding landscape management for improving permeability are also discussed.Originality/valueThis method allows designers to re-visualise highly modified and fragmented urban landscapes as stepping stones for seed dispersal, which in turn allows for a more piecemeal form of landscape design to optimise urban landscapes for climate adaptation.

Using nest-boxes in pine stands of the Augustów Forest

Abstract In 2011–2014, the occupancy of nest-boxes by secondary hole-nesting birds and their breeding success was investigated in pine stands of the Augustów Forest (North-Eastern Poland). In the studied area of 12600 ha, the share of Scots Pine Pinus sylvestris L. in the stands was 92%. On average, birds occupied 54% and bats 3% of the 224–317 nest boxes controlled yearly. Nest boxes were also used by the Pygmy Owl Glaucidium passerinum L. as food caches. In total, broods of nine secondary hole-nesting species were observed, but only four bird species nested in each year of study. The most numerous species, occupying 53–60% of all boxes each year was the Pied Flycatcher Ficedula hypoleuca Pall. The Great Tit Parus major L. occupied 15–24% and the Coal Tit Periparus ater L. 10–12% of available nest-boxes, while the Redstart Phoenicurus phoenicurus L. used 2–7% of nest boxes. The yearly breeding success was highest for tits (Great Tit – 52–84%, Coal Tit – 50–72%) and strongly variable for the Pied Flycatchers – 38–78%. Broods were lost due to predation by martens Martes sp. (38%) and great spotted woodpeckers Dendrocopos major L. (6%) as well as nest competition (2%). The nest-boxes were occupied at a constant rate during the following four years after their exposition. Over 67% of the new nest-boxes were occupied annually which means new nest-boxes (up to 4 years) were occupied significantly more often than boxes older than 4 years.

The effect of urbanization on population densities of forest passerine species in a Central European city

Abstract Typical, but less common, passerine forest species were selected for this study, such as Lullula arborea, Anthus trivialis, Troglodytes troglodytes, Prunella modularis, Turdus philomelos, Turdus viscivorus, Phylloscopus sibilatrix, Regulus regulus, Regulus ignicapillus, Muscicapa striata, Ficedula albicollis, Ficedula hypoleuca, Parus cristatus, Parus palustris, Parus ater, Certhia familiaris, Certhia brachydactyla, Oriolus oriolus, Garrulus glandarius, and Corvus corax. M. striata and T. philomelos were the most numerous among the 20 investigated species, the former one nested in a density of 6.7 pairs per 100 ha of wooded area, while the later one at 5.1 pairs per 100 ha. Density of most other species was below 3 pairs per 100 ha of wooded area. A. trivialis, P. cristatus and P. modularis were unexpectedly rare (< 1 pair per 100 ha). Otherwise, relatively numerous were T. troglodytes (1.8 p./100 ha), R. regulus (1.8 p./100 ha) and P. palustris (1.4 p./100 ha). P. cristatus, L. arborea, and T. viscivorus were the rarest species investigated (below 0.1 p./100 ha). Several bird species nested in wooded areas only in the outer zone of the city. This group included A. trivialis, R. regulus, P. ater, and C. corax. Population density of T. troglodytes, T. philomelos and O. oriolus were significantly higher in outer than in inner zone, while the reverse was true in the case of M. striata and F. hypoleuca.

Long-term declines in winter body mass of tits throughout Britain and Ireland correlate with climate change.

The optimum body mass of passerine birds typically represents a trade‐off between starvation risk, which promotes fat gain, and predation pressure, which promotes fat loss to maintain maneuvrability. Changes in ecological factors that affect either of these variables will therefore change the optimum body masses of populations of passerine birds. This study sought to identify and quantify the effects of changing temperatures and predation pressures on the body masses and wing lengths of populations of passerine birds throughout Britain and Ireland over the last 50 years. We analyzed over 900,000 individual measurements of body mass and wing length of blue tits Cyanistes caeruleus, coal tits Periparus ater, and great tits Parus major collected by licenced bird ringers throughout Britain and Ireland from 1965 to 2017 and correlated these with publicly available temperature data and published, UK‐wide data on the abundance of a key predator, the sparrowhawk Accipiter nisus. We found highly significant, long‐term, UK‐wide decreases in winter body masses of adults and juveniles of all three species. We also found highly significant negative correlations between winter body mass and winter temperature, and between winter body mass and sparrowhawk abundance. Independent of these effects, body mass further correlated negatively with calendar year, suggesting that less well understood dynamic factors, such as supplementary feeding levels, may play a major role in determining population optimum body masses. Wing lengths of these birds also decreased, suggesting a hitherto unobserved large‐scale evolutionary adjustment of wing loading to the lower body mass. These findings provide crucial evidence of the ways in which species are adapting to climate change and other anthropogenic factors throughout Britain and Ireland. Such processes are likely to have widespread implications as the equilibria controlling evolutionary optima in species worldwide are upset by rapid, anthropogenic ecological changes.

Brood parasitism of rosefinches by cuckoos: suitable host or accidental parasitism?

The arms race between avian brood parasites and their hosts is a classic model of co-evolution. Parasitic breeding by the common cuckoo (Cuculus canorus) in the nests of the Chinese beautiful rosefinch (Carpodacus davidianus) was found from May to July 2017 in Saihanba National Forest Park, Heibei, China. To understand whether the rosefinch is a suitable host species for the common cuckoo, egg recognition, chick recognition, brood rearing, and brood diets were studied. The results showed that rosefinches fully accepted non-mimetic white model eggs and parakeet (Melopsittacus undulatus) eggs, and also did not reject the similar-looking eggs of cinereous tits (Parus cinereus). Chinese beautiful rosefinches did not demonstrate any ability to recognize or discriminate between parasitic eggs or nestlings, and provisioned nestlings of cinereous tit, coal tit (Periparus ater), dusky warbler (Phylloscopus fuscatus), and common cuckoo within their nests. However, Chinese beautiful rosefinches were unable to rear the parasitic nestlings; dissections of deceased nestlings revealed that the food provided by Chinese beautiful rosefinch parents was largely composed of plant seeds and young plant shoot materials. This suggested that the high cross-fostered nestling mortality was due to unsuitable food provisioning from the host parents to the parasitic chicks. Therefore, we concluded that the Chinese beautiful rosefinch is not a suitable host for the common cuckoo, and this parasitic breeding system does not represent a co-evolutionary relationship.

LEARNING AND RECIPROCITY IN COAL TITS PLAYING THE PRISONER’S DILEMMA GAME

Foraging tests of the Iterated Prisoner’s Dilemma (IPD) show animals defect, contrary to evolutionary models that predict cooperative animals will prevail and spread in populations. This contradiction could be due to IPD rules that could be too challenging to understand for most animals. We explored this hypothesis relaxing the payoff matrix of the IPD (T>R>P>S=0) to a weak payoff-matrix (T=R>P=S>0) and tested it with coal tits, which did not play one another; rather, each one played against a computer programmed to deliver food pellets according to the ‘Tit for Tat’ strategy. Despite the IPD was programmed with a weak payoff matrix, coal tits preferences to defect increased a 10% when playing the Game condition as compared to a previous Control condition. In the Control condition they foraged at random (48±11%) between two pellet dispensers that delivered food rewards at the same rate, while in the Game condition they increased the preference towards the defection option (58±10%). A sequential (trial by trial) analysis showed that these small birds defected regularly and cooperated at random.

Social structure of Coal Tits Periparus ater in temperate deciduous forest

Analysis of the impacts of social structure on the behaviour and life history of birds is a rapidly developing area of ornithology. Such studies commonly focus on the Paridae (tits and chickadees) as a model group, but detailed assessment of the basic social structure is lacking for many parids, particularly in the non-breeding season. Such baseline information is essential for understanding the organisation of bird populations, including associations between individuals within social and spatial networks. We assessed the non-breeding (autumn–winter) social structure and that during spring (i.e. the breeding season) for Coal Tits Periparus ater in broadleaved forest in southern Britain. Coal Tits were found to be resident and sedentary in this habitat, with birds remaining close to their spring territories during the non-breeding season and associating in small groups averaging 3–4 individuals. Associations were variable, however, with no evidence of stable flock membership, group territoriality or strong pair bonds during autumn–winter. The non-breeding social structure during a year of high population density did not differ from that during a year of low population density, being most similar to a ‘basic flock’ organisation. This contrasted with that predicted for a food-hoarding parid, highlighting the potential differences in social behaviour between different populations of bird species. Such variation in social behaviour can inform our understanding of the evolution of avian social structures and associated behavioural traits, such as food hoarding, and aid the interpretation of intra- and interspecific differences in behaviour.

Peripherally injected ghrelin and leptin reduce food hoarding and mass gain in the coal tit (Periparus ater).

In birds little is known about the hormonal signals that communicate nutritional state to the brain and regulate appetitive behaviours. In mammals, the peptide hormones ghrelin and leptin elevate and inhibit consumption and food hoarding, respectively. But in birds, administration of both ghrelin and leptin inhibit food consumption. The role of these hormones in the regulation of food hoarding in avian species has not been examined. To investigate this, we injected wild caught coal tits (Periparus ater) with leptin, high-dose ghrelin, low-dose ghrelin and a saline control in the laboratory. We then measured food hoarding and mass gain, as a proxy of food consumption, every 20 min for 2 h post-injection. Both high-dose ghrelin and leptin injections significantly reduced hoarding and mass gain compared with controls. Our results provide the first evidence that hoarding behaviour can be reduced by both leptin and ghrelin in a wild bird. These findings add to evidence that the hormonal control of food consumption and hoarding in avian species differs from that in mammals. Food hoarding and consumptive behaviours consistently show the same response to peripheral signals of nutritional state, suggesting that the hormonal regulation of food hoarding has evolved from the consumption regulatory system.

Gene flow in the European coal tit, Periparus ater (Aves: Passeriformes): low among Mediterranean populations but high in a continental contact zone

Gene flow in the European coal tit, Periparus ater (Aves: Passeriformes): low among Mediterranean populations but high in a continental contact zone

Mobbing calls: a signal transcending species boundaries

When they detect a predator, some prey exhibit mobbing behaviour and produce mobbing calls that quickly draw a mixed conspecific and heterospecific group against the predator. While the efficiency of this strategy is often linked to interspecific communication, it raises the question of how animals recognize these signals as mobbing calls. It is usually suggested that associative learning about a predator when heterospecific mobbing calls are heard plays a crucial role in communication among species. Alternatively, phylogenetic conservation or evolutionary convergence could also explain this communication process. To determine whether prior experience is required to express a mobbing response, we conducted playback experiments with four European passerine species: great tit, Parus major, blue tit, Cyanistes caeruleus, coal tit, Periparus ater, and common chaffinch, Fringilla coelebs. The aim of the study was to examine whether they would respond to the mobbing signals of several North American passerines. As expected, because natural selection might shape a strong response to conspecific mobbing calls, our focal species reacted more strongly towards their own mobbing calls than towards those of American species. Nevertheless, for the three European species of tit, prior experience of heterospecific mobbing calls was not required to elicit a response. Additionally, for great tit and chaffinch, we found that acoustic similarity could explain behavioural responses to allopatric species. In contrast, such similarity was probably not the main mechanism underlying the response for the other two European species. Heterospecific response to mobbing calls probably involved many different mechanisms. Further studies focusing on each of these should allow us to understand their relative contribution to heterospecific communication.