Herbert Hoi

• University of Veterinary Medicine Vienna

The beginning of reproduction is usually accompanied by a series of decisions including where to establish a territory, attract a mate, to lay eggs or give birth. These decisions might be influenced by the quality of potential partners but also conspecific neighbours. In birds, the quality of an individual can be signaled by song features, like son...

Landscape changes and the intensification of agriculture in recent centuries were largely responsible for the dramatic decline in the biodiversity of farmlands. Rural settlements have also been subject to radical changes due to modernisation, but their impact on bird populations is poorly quantified. The Lesser Grey Shrike Lanius minor is a threate...

Song complexity has been identified as one song characteristic important in female choice, whereas its role in male-male interactions is less clear and not much is known which song characteristics are specifically important for territorial defense. In Acrocephalus warblers, males seem to increase song complexity towards females but reduce it during...

Wing design in birds is the result of different and potentially opposing natural selection pressures, such as those related to migration, predator avoidance and habitat type. Sexual selection for flight performance may also shape wing design via female preferences for superior performance of flight display. The black-headed bunting Emberiza melanoc...

Parasites are known to be a key driving force in mate choice and are important for the expression and evolution of ornaments and behavioural traits being used. However, there is little experimental evidence on how parasite’s burden of the choosing individual is integrated in the mate-choice process and how it affects decision-making, especially in...

In birds, male song is mainly driven by sexual selection, whereby several song characteristics have been demonstrated to be important. In this context, the number of syllables produced per time unit (syllable rate), which thus reflects the “speed” of a song, has been suggested as a reliable indicator of male quality. It has been also shown that syl...

Many songbirds produce song-flights; however, the function, vocal and motor characteristics, as well as the diel and seasonal variation of song-flight in songbirds remain not well understood. Here, we studied two types of song-flight in male Black-headed Buntings (Emberiza melanocephala), the Moth — a standard, i.e., perch song produced during a ho...

Air-borne chemicals are highly abundant sensory cues and their use in navigation might be one of the major evolutionary mechanisms explaining the development of olfaction in animals. Despite solid evidence for the importance of olfaction in avian life (e.g., foraging or mating), the importance of chemical cues in avian orientation remains controver...

Sibling cannibalism is relatively common in nature, but its evolution in birds and certain other vertebrates with extended parental care had been discarded. Here, however, we demonstrate its regular occurrence in two European populations of the Eurasian hoopoe (Upupa epops) and explore possible adaptive and non-adaptive explanations. Results showed...

In this study, we investigated the influence of different weather aspects on breeding performance, food supply and nest-space use in hoopoe offspring ( Upupa epops ). Camera recordings of 88 nests were used to examine how ambient environmental conditions influence food supply, offspring nest-space use and the trade-off nestlings face regarding the...

Bacteria are known to exert positive and negative influences on animals’ health and fitness. Bacteria, in particular those inhabiting the skin and inner organs of vertebrates, are horizontally or vertically transmitted. Specifically, mothers of bird species can transfer bacterial strains to their offspring when the egg is passing the reproductive t...

For most animals, the rearing environment is an important factor influencing early offspring development and behaviour. Also, in altricial birds, where the rearing environment (nest) is usually restricted, it is known that if sufficient nest space is provided, offspring show social interactions and a variety of other behaviours. In fact, the availa...

The performances of different social groups can depend on various characteristics, such as familiarity among their members or the presence of individuals with specific traits. However, it has rarely been investigated how groups perform during an encounter with other conspecifics, even if in the natural environment social groups often run into each...

Avian plumage colors and ornaments are excellent models to study the endocrine mechanisms linking sexually selected traits and individual parameters of quality and condition. Insulin-like growth factor 1 (IGF-1) is an evolutionarily highly conserved peptide hormone. Its regulatory role in cell proliferation and differentiation and its high sensitiv...

Interspecific territoriality can frequently be observed in the animal kingdom, including birds. One important factor driving the degree of interspecific territoriality is competition for resources. Other influential factors are, for instance, population density, phylogenetic relatedness, fighting asymmetries, and shared predation. Although the degr...

Avian malaria (caused by Plasmodium spp.) and avian malaria-like infections (caused by Haemoproteus spp.) are widespread and can seriously affect the health of their bird hosts, especially of immunologically naïve individuals. Therefore, these parasites have long been in the focus of bird-parasite studies. However, the species richness and diversit...

Avian plumage colors and ornaments are ideal models to study the endocrine mechanisms linking sexually selected traits and individual parameters of quality and condition. The insulin-like growth factor 1 (IGF-1), an evolutionarily highly conserved peptide hormone, represents a link between body condition and the individual capacity to grow elaborat...

Many organisms use inducible defenses as protection against predators. In animals, inducible defenses may manifest as changes in behavior, morphology, physiology, or life history, and prey species can adjust their defensive responses based on the dangerousness of predators. Analogously, prey may also change the composition and quantity of defensive...

Several functions have been proposed to explain eggshell colouration in birds. Eggshell colour may, for instance, signal female egg investment and hence the quality of the female and/or the egg. Such a covariation between eggshell colour and egg quality is supported by several studies, but what is related to eggshell colour is not necessarily consi...

A growing body of evidence suggests that birds can use olfactory cues to detect the presence of predators. We predicted that the ability to gather information about predator presence through chemical cues might be particularly important for ground-living and foraging bird species, since their main predators, namely mammals and reptiles, use chemica...

Background Exploratory behaviour is one of the best-investigated behavioural traits. However, little is known about how differences in familiarity, i.e. in the knowledge and previous experience with a companion can influence the exploration of a novel environment. However, to our knowledge, such a critical feature of the social environment has neve...

Fighting and flirting are the main evolutionary forces behind the development of bird song and both contribute to different song characteristics. By comparison of vocalisations throughout bird taxa, we can help to reconstruct the evolutionary history of the song. In this study, we provide the first detailed analysis of song structure and song type...

In the last decades increasing attention has been paid to olfactory perception in birds. As a consequence, a handful of avian species have been discovered to use olfaction in different contexts. Nevertheless, we still have a very limited knowledge about the use of odour cues in avian social life, particularly in the case of songbirds. Here, we inve...

In the last decades increasing attention has been paid to olfactory perception in birds. As a consequence, a handful of avian species have been discovered to use olfaction in different contexts. Nevertheless, we still have a very limited knowledge about the use of odour cues in avian social life, particularly in the case of songbirds. Here, we inve...

Environmental factors and genetic incompatibilities between parents have been suggested as important determinants for embryonic mortality and survival. The genetic set-up of the immune system, specifically the highly polymorphic major histocompatibility complex (MHC) may also influence individual resistance to infections. MHC proteins are important...

One way that parasites influence host survival and fitness is by competing with their hosts for resources that would otherwise be used for growth and immune system development. Thus resource availability, influenced by environmental conditions, may be particularly important during offspring development. This study examined the influence of a haemat...

Background One possibility suggested regarding female post-mating strategies is differential allocation into offspring investment. Female birds produce not only the largest, but also most colourful eggs of all oviparous taxa. Larger eggs provide space for bigger embryos, or more nutrition for their development, but the question why eggs are more co...

Analysis of egg position and egg volume

Background A well-functioning immune defence is crucial for fitness, but our knowledge about the immune system and its complex interactions is still limited. Major histocompatibility complex (MHC) molecules are involved in T-cell mediated adaptive immune responses, but MHC is also highly upregulated during the initial innate immune response. The ai...

Supplementary Methods: Immune tests; MHC - bioinformatics and data processing; Suppl. Tables 1-11; Supplementary literature

Researchers generally measure personality and many ecologically-related traits through standardised tests. Usually, these tests are conducted in small and simple environments in a matter of minutes. Nevertheless, a growing body of literature is pointing out caveats and pitfalls associated with common personality tests. Hence, we tried to shed some...

Parental care in birds consists of two major duties, namely, food provisioning and nest defence. Nest predation has a crucial impact on reproductive success in altricial birds and parents developed a manifold set of strategies to cope with predation threat. Indeed, behavioural plasticity allows individuals to respond to changes in predation risk, i...

While the function of ornaments shaped by sexual selection is to attract mates or drive off rivals, these signals may also evolve through social selection, in which the social context affects the fitness of signallers and receivers. Classical ‘mate choice’ experiments often reveal preferences for ornaments, but few studies have considered whether t...

Social foraging is thought to provide the possibility of information transmission between individuals, but this advantage has been proved only in a handful of species and contexts. We investigated how social connections in captive flocks of house sparrows (Passer domesticus) affected the discovery of (i.e. feeding for the first time from) two hidde...

Avian eggshell color seems to fulfill multiple functions, some of them being structural and others signaling. In this study, we tested whether or not eggshell coloration may play a role in sexual selection of Tree Sparrows (Passer montanus). According to the " Sexually selected eggshell coloration " hypothesis, eggshell coloration signals female, e...

Since most avian species have been considered anosmic or microsmatic, olfaction and associated behavioural patterns have hardly been investigated. Most importantly, empirical data on avian olfaction is not equally distributed among species. Initial investigations focused on species with relatively big olfactory bulbs because they were thought to ha...

This editorial accompanies the launch of BMC Zoology, a new open access, peer-reviewed journal within the BMC series that considers manuscripts on all aspects of zoology. BMC Zoology will increase and disseminate zoological knowledge through the publication of original research, methodology, database, software and debate articles. With the launch o...

Bird nests are designed to contain and protect parents, eggs and nestlings and to facilitate optimal safety and climatic conditions from egg-laying to fledging offspring. Bird nests also provide optimal conditions for a rich and diverse community of mainly invertebrates, who use nests as a foraging site, shelter, hiding place and reproduction and o...

Invasive alien predators (IAP) are spreading on a global scale and often with devastating ecological effects. One reason for their success may be that prey species fail to recognize them due to a lack of co-evolutionary history. We performed a comprehensive test of this ‘prey naiveté’ hypothesis using a novel approach: we tested whether predator-na...

The aim of the study is to get a representative picture of the diet composition of hoopoes in vineyards as specific man made habitats in Central Europe. Therefore diet composition and its interannual variability and the representativeness of two sampling techniques have been studied in hoopoe nestlings, Upupa epops during two breeding periods. Alto...

Both habitat changes and predation can cause population declines in farmland birds. Habitat changes may allow novel or invasive alien predators to establish populations in new environments, which can have major ecological consequences for native prey species. We studied effects of a novel avian predator, the Montagu's Harrier (Circus pygargus), on...

Amphibians are the most threatened vertebrates today, experiencing worldwide declines. In recent years considerable effort was invested in exposing the causes of these declines. Climate change has been identified as such a cause; however, the expectable effects of predicted milder, shorter winters on hibernation success of temperate-zone Amphibians...

Showy ornaments are considered as outcomes of sexual selection processes. They provide a “badge of status” to impress conspecific rivals or potential mating partners. Single ornaments may signal attractiveness or individual quality, yet many species display multiple ornaments. There are several hypotheses that explain the existence of multiple orna...

Female song is recognized to serve a similar function as male song and underlies sexual selection processes; yet certain patterns of the expression of female singing behaviour are not in line with traditional explanations known from male songbirds. In particular, in northern hemisphere songbirds, female singing behaviour is regarded to occur only r...

While it is well established that females prefer to mate with well-ornamented males, the influence of perceptive and cognitive processes on the expression of female mate choice is still poorly known. It has been suggested that the female perception of a male's attractiveness is not absolute, but depends on the other males with which he is compared...

Short introduction on avian olfactory perception. Here, we show some preliminary results on the use of smell in House sparrows (Passer domesticus).

There is growing evidence for active male choice of ornamented females, as well as for ornamental traitsassociated with condition and/or fighting ability and dominance. In bird species in which both the males and females are ornamented, could operate mutual mate choice on the same trait. We test this mechanism of mate choice in the Yellow-vented Bu...

A preliminary study on the olfactory capabilities of House sparrows. The individuals are exposed to the odours of hay and mouse urine.

Experimental study on the role of sociality during the exploration of a novel environment in House sparrows

Several studies have investigated how individuals’ social status or behavioural and physiological traits affect social organisation in group-living species, but the potential role of ornamental traits has been rarely studied. Here, we analysed initiator-follower interactions in relation to experimentally manipulated sexually selected ornaments in c...

Do parents defend their offspring whenever necessary, and do self-sacrificing parents really exist? Studies recognized that parent defence is dynamic, mainly depending on the threat predators pose. In this context, parental risk management should consider the threat to themselves and to their offspring. Consequently, the observed defence should be...

Bacteria play a central role in animal health. Yet, little is known about the acquisition of bacteria and the extent to which bacteria are acquired from different environmental sources. For example, bird nests host diverse bacteria associated with the eggs, nestlings and nesting material, but previous research has typically focussed on only a limit...

Food availability is generally considered to determine breeding site selection and therefore plays an important role in hypotheses explaining the evolution of colony formation. Hypotheses trying to explain why birds join a colony usually assume that food is not limited, whereas those explaining variation in colony size suggest that food is under co...

Habitat choice may have an important impact on survival and fitness of an individual. Besides an individual's intrinsic features, such as resource-holding potential, experience, age, and habitat characteristics like habitat heterogeneity may play a role. In line with this, we investigate the importance of vegetation type for habitat choice, reprodu...

There is growing empirical support for teaching in nonhuman animals. To unravel the evolutionary dynamics of teaching, we need to understand its costs and benefits. In superb fairy-wrens (Malurus cyaneus), females teach their embryos by calling to them: embryos learn a vocal password, and hatchlings incorporate the learned vocal password into their...

Experimental evidence suggests that reproductive interference between heterospecifics can seriously affect individual fitness; support from field studies for such an effect has, however, remained scarce. We studied reproductive interference in 25 natural breeding ponds in an area where two ranid frogs, Rana dalmatina and Rana temporaria, co-occur....

Forming foraging groups may help to improve protection from predators, foraging efficiency and exchange of information, but to benefit from these advantages, animals need to maintain group cohesion. Several studies have investigated how social status or behavioural and physiological traits promote leadership and followership in various species, but...

Maternal investment can play an important role for offspring fitness, especially in birds, as females have to provide their eggs with all the necessary nutrients for the development of the embryo. It is known that this type of maternal investment can be influenced by the quality of the male partner. In this study, we first verify that male song is...

Higher interclutch colour variation can evolve under the pressure of brood parasitism to increase the detection of parasitic eggs. Nest sanitation could be a prerequisite for the evolution of anti-parasite defence in terms of egg ejection. In this respect, we used nest sanitation behaviour as a tool to identify: i) motivation and its underlying fun...

Introduction Risk assessment occurs over different temporal and spatial scales and is selected for when individuals show an adaptive response to a threat. Here, we test if birds respond to the threat of brood parasitism using the acoustical cues of brood parasites in the absence of visual stimuli. We broadcast the playback of song of three brood pa...

In many socially monogamous species, both sexes seek copulation outside the pair bond in order to increase their reproductive success. In response, males adopt counter-strategies to combat the risk of losing paternity. However, no study so far has tried to experimentally prove the function of behaviour for paternity assurance. Introducing a potenti...

2013): Does egg colouration signal female and egg quality in reed warbler (Acrocephalus scirpaceus)?, Ethology Ecology & Evolution, 25:2, 129-143 This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution...

Higher interclutch colour variation can evolve under the pressure of brood parasitism to increase the detection of parasitic eggs. Nest sanitation could be a prerequisite for the evolution of anti-parasite defence in terms of egg ejection. In this respect, we used nest sanitation behaviour as a tool to identify: i) motivation and its underlying fun...

The widely accepted functions of complex bird song – to defend a territory or attract a mate, or both – have generally been tested in northern hemisphere species in which males produce the song and females choose the singer. In our study species, the Superb Fairy-wren (Malurus cyaneus), both males and females sing a solo song throughout the year. W...

There is growing interest in sperm senescence, both in its underlying mechanisms and evolutionary consequences, because it can impact the evolution of numerous life history traits. Previous studies have documented various types of sperm senescence, but evidence of post-meiotic intra-testicular sperm senescence in wild animals is lacking. To assess...

How do parents recognize their offspring when the cost of making a recognition error is high [1 • Davies N.B. Cuckoos, Cowbirds and Other Cheats. T. & A.D. Poyser, London2000 • Google Scholar , 2 • Lotem A. Learning to recognize nestlings is maladaptive for cuckoo Cuculus canorus host.Nature. 1993; 362: 743-745 • Crossref • Scopus (125) • Googl...

The differential allocation hypothesis (DAH) predicts that individuals should adjust their parental investment to their current mate's quality. Although in principle the DAH holds for both sexes, male adjustment of parental investment has only been tested in a few experimental studies, revealing contradictory results. We conducted a field experimen...

An individual's investment in mating or keeping a pair bond intact may be influenced not only by the attractiveness of its current mate, but also by that of other potential mates. In this study, we investigated the effect of relative attractiveness on pair-bond behaviour in bearded reedlings, Panurus biarmicus. We showed that mate attractiveness, i...

Males frequently signal their resistance against parasites by elaborate ornaments. By mating with more ornamented males, females may choose less parasitized partners, and benefit by reducing the probability of contagion of parasites with direct transmission. Chewing lice (order Phthiraptera) are parasites of birds that considerably harm hosts, even...

The theory of life history evolution assumes trade-offs between competing fitness traits such as reproduction, somatic growth, and maintenance. One prediction of this theory is that if large individuals have a higher reproductive success, small/young individuals should invest less in reproduction and allocate more resources in growth than large/old...

In order to understand habitat selection, it is important to consider the way individual animals assess the suitability of a future reproductive site. One way of investigating mechanisms (such as those involved in nest site selection) is to examine breeding success and habitat characteristics in terms of animals returning to a place where they have...

Animals frequently host organisms on their surface which can be beneficial, have no effect or a negative effect on their host. Ectoparasites, by definition, are those which incur costs to their host, but these costs may vary. Examples of avian ectoparasites are chewing lice which feed exclusively on dead feather or skin material; therefore, costs t...

Pair bond duration and age are suggested to be important determinants for reproductive success in long-term monogamous pair bonding. These two effects are generally difficult to separate, however, and experimental approaches are scarce. We experimentally examined the role of the extended pair bond period, controlling for age and experience, in the...

In a few bird species, dimorphism already exists in nestling and juvenile plumage coloration and these colour morphs are often attributable to different sexes. In this study we detected variation in nestling coloration among European Bee-eaters Merops apiaster. We identified two distinct colour morphs, namely nestlings with yellowish-brown and nest...

Optimal foraging strategies and food choice are influenced by various factors, e.g. availability, size and caloric content of the food type and predation risk. However, food choice criteria may change when food is not eaten immediately but has to be carried to a storage site for later use. For example, handling time in terms of harvesting and trans...

Several factors can influence the risk of cuckoldry through extra-pair paternity for male birds. The number of neighbouring males is thought to affect the chance of females engaging in extra-pair copulations, and species which breed both socially (colonially) and solitarily provide an ideal opportunity to test the effect of close proximity on extra...

In a few bird species, dimorphism already exists in nestling and juvenile plumage coloration and these colour morphs are often attributable to different sexes. In this study we detected variation in nestling coloration among European Bee-eaters Merops apiaster. We identi-fied two distinct colour morphs, namely nestlings with yellowish-brown and nes...

In birds, colourful and elaborate feathers are important traits in mate choice. Distinct tail white patches are present in many species of birds, but they remain little studied. Tail markings may indeed have a signal function because in many species males spread the tail offering a good view of these markings to females during courtship behaviour....

In many animal species ornaments and display behaviours are used together in intersexual communication. Few studies, however, have simultaneously explored how the static and dynamic components interact. We examined the significance of behaviour (e.g. dominance status) in comparison with beard length for the mate choice process in a bird species, th...

Male song is known to be important in the mate choice of birds, as different song features reflect different traits of the singer. The reason why song complexity, in this context, should reflect the quality of the performing individual is still under debate. Nevertheless, some studies show that song complexity may serve as an honest indicator of ma...

Females can potentially assess the quality of potential mates using their secondary sexual traits, and obtain "good genes" that increase offspring fitness. Another potential indirect benefit from mating preferences is genetic compatibility, which does not require extravagant or viability indicator traits. Several studies with mammals and fish indic...

While theoretical studies predict that inducible defences should be fine-tuned according to the qualities of the predator, very few studies have investigated how dangerousness of predators, i.e. the rate at which predators kill prey individuals, affects the strength of phenotypic responses and resulting benefits and costs of induced defences. We pe...

In contrast with house mice (Mus musculus musculus and Mus musculus domesticus), Mus spicilegus is seasonal in its reproduction. Thus overwinter survival seems to be an important factor for population dynamics. In autumn, the mice construct voluminous mounds made of plant material covered with soil, under which they overwinter without reproducing....

The Lesser Grey Shrike has suffered successive declines in population size and a marked contraction of its breeding range since the early 20th century, largely because of long-term agricultural intensification. This has resulted in a severely fragmented distribution in Western Europe, with isolated breeding nuclei in Spain, France and Italy and a m...