Physiological stress responses to nonmimetic model brood parasite eggs : Leukocyte profiles and heat-shock protein Hsp70 levels

Obligate avian brood parasites lay their eggs in the nest of other bird species, known as hosts. Brood parasitism often imposes severe fitness costs on hosts, selecting for the evolution of effective antiparasitic defences, such as recognition and rejection of brood parasite eggs. Glucocorticoids have been recently found to mediate host physiological and behavioral adjustments in response to brood parasite eggs; however, it remains unclear whether brood parasitism triggers a general response involving multiple physiological elements. In this study, we experimentally investigated whether a salient brood parasitic stimulus (the presence of a nonmimetic model egg in the nest) causes physiological adjustments in adult Eurasian blackbirds (Turdus merula) at immune (leukocyte profiles) and cellular (heat-shock protein Hsp70 synthesis) level. Also, we explored whether these physiological changes are mediated by variations in corticosterone (CORT) levels. We found that experimental brood parasitism caused an increase in heterophils and a decrease in lymphocytes, leading to higher heterophils and lymphocytes ratios in parasitized birds. Nevertheless, we did not find tradeoffs between immune function and CORT levels. Hsp70 synthesis was not affected by our experimental manipulation. Our findings provide evidence that brood parasite eggs trigger a general stress response in egg-rejecter hosts, including changes in cellular immune profiles.Peer reviewe

Multiparasitism and repeated parasitism by the great spotted cuckoo Clamator glandarius on its main host, the magpie Pica pica: effects on reproductive success, nest desertion and nest predation

This work was supported by the research project PID2020-1159506BI00 financed by MCIN/AEI/10.13039/501100011033. Permits - The research was conducted according to relevant Spanish national (Real Decreto 1201/2005, de 10 de Octubre) and regional guidelines. All necessary permits were obtained from the Consejeria de Medio Ambiente y Ordenacion del Territorio de la Junta de Andalucia (Spanish Regional Government). Field work was licensed by the Andalusian authority for wildlife protection (DGGMN; ref.: SGYB/FOA/AFR/CFS 15/03/2012).Brood parasites are expected to lay only one egg per parasitized nest, as the existence of several parasitic nestlings in a brood increases competition and can lead the starvation of some of them. However, multiparasitism (laying of two or more eggs by one or more parasitic females in a single host nest) is surprisingly frequent. Here, we study multiparasitism by different females or by the same female (repeated parasitism) in the great spotted cuckoo Clamator glandarius, a non-evictor brood parasite that mainly parasitizes the magpie Pica pica, and whose chicks may be raised together with host nestlings in the same nest. We used a total of 262 magpie nests found during four breeding seasons. Multiparasitism and repeated parasitism are very frequent because this brood parasite is less virulent than other cuckoo species and magpie hosts can successfully raise more than one parasitic nestling per nest. The total number of cuckoo chicks fledged was higher in multiparasitized nests than in single- or double-parasitized magpie nests. Magpie breeding success (i.e. the proportion of eggs that produce young that leave the nest) did not differ between single-, double-, and multiparasitized magpie nests. These results suggest that multiparasitism is an adaptation in the great spotted cuckoo. The intensity of parasitism (number of cuckoo eggs per nest), after controlling for the potential effect of year, did not affect nest desertion or nest predation rate, neither during the incubation nor the nestling periods. This implies that nest concealment does not affect the susceptibility of one nest being parasitized and predated, as nest predation rate was similar regardless of the intensity of parasitism. Predation rate during the nestling phase did not vary according to intensity of parasitism, which does not support either the 'mutualism' hypothesis or the 'predation cost of begging' hypothesis.MCIN/AEI/10.13039/501100011033 PID2020-1159506BI00Spanish national 1201/200

Fecal sacs attract insects to the nest and provoke an activation of the immune system of nestlings

Background: Nest sanitation is a widespread but rarely studied behavior in birds. The most common form of nest sanitation behavior, the removal of nestling feces, has focused the discussion about which selective pressures determine this behavior. The parasitism hypothesis, which states that nestling fecal sacs attract parasites that negatively affect breeding birds, was proposed 40 years ago and is frequently cited as a demonstrated fact. But, to our knowledge, there is no previous experimental test of this hypothesis. Results: We carried out three different experiments to investigate the parasitism hypothesis. First, we used commercial McPhail traps to test for the potential attraction effect of nestling feces alone on flying insects. We found that traps with fecal sacs attracted significantly more flies (Order Diptera), but not ectoparasites, than the two control situations. Second, we used artificial blackbird (Turdus merula) nests to investigate the combined attraction effect of feces and nest materials on arthropods (not only flying insects). Flies, again, were the only group of arthropods significantly attracted by fecal sacs. We did not detect an effect on ectoparasites. Third, we used active blackbird nests to investigate the potential effect of nestling feces in ecto- and endoparasite loads in real nestlings. The presence of fecal sacs near blackbird nestlings did not increase the number of louse flies or chewing lice, and unexpectedly reduced the number of nests infested with mites. The endoparasite prevalence was also not affected. In contrast, feces provoked an activation of the immune system as the H/L ratio of nestlings living near excrements was significantly higher than those kept under the two control treatments. Conclusions: Surprisingly, our findings do not support the parasitism hypothesis, which suggests that parasites are not the main reason for fecal sac removal. In contrast, the attraction of flies to nestling feces, the elevation of the immune response of chicks, and the recently described antimicrobial function of the mucous covering of fecal sacs suggest that microorganisms could be responsible of this important form of parental care behavior (microbial hypothesisPeer reviewe

Light received by embryos promotes postnatal junior phenotypes in a seabird

Light is a salient and variable ecological factor that can impact developmental trajectories of vertebrate embryos, yet whether prenatal light environment can act as an anticipatory cue preparing organisms to cope with postnatal conditions is still unclear. In asynchronous birds, last-laid eggs are particularly exposed to sunlight as parental incubation behavior becomes intermittent after the hatching of senior chicks. Here, we explore whether natural variations in prenatal light exposure shape the distinctive phenotype showed by last-hatched chicks of a semi-precocial seabird, the yellow-legged gull (Larus michahellis), potentially preparing them to cope with the postnatal competitive context. To do this, we manipulated the amount of light received by last-laid eggs (within a natural range) during last stages of embryonic development. Prenatal exposure to light cues promoted the development of the resilient “junior phenotype” exhibited by last-hatched gull chicks, characterized by accelerated hatching, increased begging behavior and a slower growth rate. These developmental and behavioral adjustments were accompanied by down-regulation of genes involved in metabolism and development regulation (SOD2 and TRalpha), as well as changes in the HPA-axis functioning (lower baseline corticosterone and robust adrenocortical response). Junior chicks exposed to light cues during the embryonic development showed longer telomeres during the early postnatal period, suggesting that light-induced adjustments could allow them to buffer the competitive disadvantages associated with hatching asynchrony. Our study provides evidence that postnatal junior phenotypes are, at least in part, prenatally shaped by light cues that act during a critical temporal window of developmental sensitivity.Agencia Estatal de Investigación | Ref. PGC2018-095412-B-I00Agencia Estatal de Investigación | Ref. FJC2018-037157-

Egg-recognition abilities in non-incubating males:Implications for the evolution of anti-parasitic host defenses

In the field of brood parasitism, it has been traditionally assumed that only the incubating sex rejects parasitic eggs, but this assumption has been rarely explored despite its important implications for the evolutionary relationship between brood parasites and hosts. Here, we used information on previous egg-rejection experiments to explore the recognition abilities of both males and females of Eurasian blackbirds Turdus merula towards experimental eggs with a variable degree of mimicry. We found that both sexes recognized non-mimetic eggs, supporting the idea that visits to the nest can favor the evolution of rejection abilities. In contrast, only females recognized mimetic eggs, indicating that although recognition abilities can evolve in both sexes, they are subsequently refined in females probably due to their more frequent interaction with parasitic eggs. Clutch size affected nest attendance since females, but not males, spent more time at the nest and visited it more frequently in larger clutches. Finally, our recordings showed that blackbird males are able not only to recognize, but also to eject parasitic eggs. Our results provide new insights into the main anti-parasitic defense in birds, egg rejection, and highlight the need of considering the role of the non-incubating sex in egg-rejection studies.Significance statementGiven the high costs associated to avian brood parasitism, both sexes are expected to evolve anti-parasitic defenses. However, in those species in which only females incubate, females have traditionally been assumed to be the responsible for egg rejection. Here, using the Eurasian blackbird (Turdus merula), we investigated the existence of egg-rejection abilities in non-incubating males and compared them to those exhibited by females. We found that males can recognize non-mimetic eggs, although their recognition abilities were less fine-tuned compared to females, who also recognized mimetic eggs. Even though females were the responsible for most documented egg-ejection events, recordings confirmed that males could also be involved in egg ejection, which could have important implication for the evolution of anti-parasitic defenses in host populations

A transformational creativity tool to support chocolate designers

A new formulation of the central ideas of Boden's well-established theory on combinational, exploratory and transformational creativity is presented. This new formulation, based on the idea of conceptual space, redefines some terms and includes several types of concept properties (appropriateness and relevance), whose relationship facilitates the computational implementation of the transformational creativity mechanism. The presented formulation is applied to a real case of chocolate designing in which a novel and flavorful combination of chocolate and fruit is generated. The experimentation was conducted jointly with a Spanish chocolate chef. Experimental results prove the relationship between appropriateness and relevance in different frameworks and show that the formulation presented is not only useful for understanding how the creative mechanisms of design works but also facilitates its implementation in real cases to support creativity processes.Postprint (author's final draft

Creativity Support System for cake design

In this paper, a new formulation of Creativity is presented in the context of Creativity Support Systems. This formulation is based on the central ideas of the theory of Boden. It redefines some concepts such as appropriateness and relevance in order to allow the implementation of a support system for creative people. The approach is based on the conceptual space proposed by Boden and formalized by other authors. The presented formulation is applied to a real case in which a new chocolate cake with fruit is design. Data collected from a Spanish chocolate chef has been used to validate the proposed system. Experimental results show that the formulation presented is not only useful for understanding how the creative mechanisms of design works, but also facilitates its implementation in real cases to support creativity processes.Peer ReviewedPostprint (published version

AoL: Action Learning: A methodology to capture expertise in adjustment tasks

It is well known that some people can perform a task with greater precision and accuracy than others: they are experts. In the past, experts were interviewed to find out why they have this expertise, but this was not always completely effective because often experts "don't know what they know". In this paper we propose a model of the process of making decisions performed by experts in the final adjustment of products task. Based on this model, we also propose a system based on a machine learning module that facilitates the capture of these expert skills. We give an example to illustrate the process proposed.Postprint (published version

A Transformational creativity tool to support musical composition

In this paper we use the idea of conceptual space introduced by Boden and redefine some properties such appropriateness and relevance that facilitate the computational implementation of the transformational creativity mechanism. While appropriateness can only be evaluated by an expert, relevance can be objectively measured for any spectator. Computational creativity is based on the relationship between appropriateness and relevance of a concept, and therefore a computational system can be used to support this task. The paper analyses this relationship in the field of music in order to obtain a computer tool to support the musical composition task.Peer ReviewedPostprint (published version

Functional explanation of extreme hatching asynchrony: Male Manipulation Hypothesis

Hatching asynchrony in birds is considered an adaptation to facilitate brood reduction because under conditions of food scarcity, the smallest nestling usually dies soon after hatching, thereby minimizing parental effort. However, in species with extreme hatching asynchrony, the last hatchlings paradoxically experience a very low probability of survival and death can take so long that it can hardly be considered an adaptation. Here, we propose and experimentally tested a new adaptive hypothesis explaining the brood reduction paradox, namely the “Male Manipulation Hypothesis”. Our hypothesis suggests that by inducing asynchronous hatching, females increase the feeding requirements of the brood, which will induce males to increase provisioning effort. In addition, females may extend the period of male manipulation by feeding the smallest nestling just enough to sustain life. Our study showed that male common blackbirds (Turdus merula) increased their effort (i.e., number of food items per hour) in experimental asynchronous broods compared to synchronous broods, while females reduced their contribution, as predicted by the hypothesis