DANIEL PAREJO-PULIDO / CONFERENCES
Conferences
12 contributions · 2017–2025
01 / ORAL PRESENTATIONS
* Oral presentation delivered by Daniel Parejo-Pulido.
Dynamic begging displays as partly informative signals of nestling hunger*
Parejo-Pulido D, Pérez-Rodríguez L, Ruiz AM, Redondo T
XIX National Conference and XVI Ibero-American of Ethology and Evolutionary Ecology. Seville (Spain), 2–5 September 2025.Costly signalling models of nestling begging regard it as a rich source of information that allows parents to obtain accurate information about their offspring's level of need or hunger. These models typically focus on a single type of honest signalling equilibrium —the separating equilibrium— in which each condition state produces a unique, distinct signal intensity in a gradual manner. However, communication between relatives could evolve into alternative equilibria, such as pooling equilibria—in which hunger states overlap across different begging intensities—or mixed equilibria—in which some random, but directional, variation occurs in how begging intensity varies with hunger and how parents respond. In this study, we combined observations of spotless starling nestling begging and parental feeding in natural broods with a laboratory deprivation experiment to revisit the concept of begging honesty, exploring theoretical alternatives to separating-equilibrium models. First, we assessed whether postural begging displays function as graded signals by analysing their fine temporal structure. We then tested whether such variation predicted intermediate levels of food deprivation. Second, we measured the efficacy and consistency of postural and vocal begging as indicators of hunger using both traditional correlational methods with random regression and novel information-theory measures. Our results suggest that postural begging does not function as a graded, information-rich signal, as predicted by separating-equilibrium models. Postural displays efficiently encoded extreme, but not intermediate, hunger levels and showed a bimodal pattern. The most informative component of the postural display was the duration at maximum intensity, while other postural or acoustic variables conveyed little or no information. We also found substantial random variation in the relationship between food deprivation and signal intensity, as well as in parental responses to these signals. This random variation departed from pure noise in ways predicted by mixed-equilibrium models. These findings suggest that begging may align more closely with the predictions of partly informative pooling and mixed-equilibrium models. This study highlights the need to reconsider the strict reliance on separating equilibria in models of parent-offspring communication, suggesting that alternative equilibria may offer a more accurate framework for explaining natural observations.
Still begging for answers: Nestling signals revisited
Redondo T, Pérez-Rodríguez L, Parejo-Pulido D
XIX National Conference and XVI Ibero-American of Ethology and Evolutionary Ecology. Seville (Spain), 2–5 September 2025.Nestling begging has become a model for understanding animal communication. Elaborate and seemingly costly behaviours such as calling, posturing, and gape colouration have traditionally been explained through signalling theory, particularly Godfray’s (1991) model, which treats begging as an honest and costly signal of cryptic need. While widely adopted, this framework is now being challenged both theoretically and empirically.
Begging may convey information—but what kind? While it is well established that begging reflects nestling hunger, this is not exactly what theory predicts. Whether begging also informs parents about long-term condition, beyond short-term hunger, remains unresolved—and difficult to test. Moreover, begging varies with many other factors, including sex, temperature, size, social environment, and experience. Is this complex blend of traits the message of interest to parents? How should we understand such high plasticity? In most studies, this variation is dismissed as noise, yet it aligns with recent models predicting low-cost, partly informative signals. Although there is broad consensus that begging is highly informative (and therefore must be costly), this assumption remains untested.
On the receiver side, parents do respond to begging—but often inconsistently. Their decisions are influenced by non-begging traits and frequently show substantial intra- and inter-individual variation that classical begging theory overlooks. However, this variation is crucial to alternative explanations of begging as a cheaper, less informative signal. Also, after almost half a century of research, we still lack consensus on how parents decide which chick to feed—and this seemingly minor detail has major theoretical consequences.
Begging is widely assumed to be costly, yet evidence for the direct costs proposed by traditional costly models—such as increased predation risk or physiological stress—remains elusive. Some possibilities, however (such as differential or out-of-equilibrium costs), remain unexplored.
The field now needs models that allow for receiver inattention, integrate variation in both hunger and long-term reproductive value, and incorporate learning and plasticity. Crucially, traditional models treat begging as a purely competitive trait, overlooking cooperative behaviour among siblings driven by both indirect and direct shared benefits. Despite decades of work, nestling begging remains a rich field with major unanswered questions and exciting research opportunities.
Reglas de cebas de padres de estornino negro en escenarios ecológicos contrastados* [Feeding rules of spotless starling parents in contrasting ecological scenarios]
Parejo-Pulido D, Casquero S, Redondo I, Gómez-Llanos E, Fusté R, Ruiz AM, Crespo-Ginés R, Gil D, Redondo T, Pérez-Rodríguez L
XXVI Spanish Ornithology Conference. Valencia (Spain), 12–16 February 2025.In broods containing multiple nestlings, parents must decide how to distribute food resources to maximise their reproductive success, taking into account both their own physical condition and environmental conditions. Previous studies suggest that, when food is abundant, parents distribute food equitably on the basis of their nestlings’ signals of need. Under conditions of scarcity, however, parents tend to feed the most viable nestlings, taking signals of quality or size into account to optimise their investment. This study tested these hypotheses using the spotless starling (Sturnus unicolor), a bird that produces two clutches during the breeding season, each subject to different ecological conditions. The first clutch occurs early in the season, under optimal conditions, whereas the second, towards the end of the season, is characterised by less favourable conditions, greater brood reduction through nestling mortality and poorer nestling condition, probably because high-quality food is less available. We found that second clutches were smaller and females reduced their feeding rate compared with first clutches, whereas males maintained a constant level of effort in both. Feeding preferences also differed between the sexes. Males maintained the same pattern across clutches, feeding the larger nestlings, those that begged first, occupied more favourable positions and displayed more intense postures. Females, by contrast, showed more complex patterns. In first clutches, they favoured nestlings showing signals associated with greater nutritional need (intense begging postures), while discounting their competitive ability, as indicated by begging first or occupying better positions. In second clutches, however, they prioritised nestlings that begged earlier or occupied more favourable positions in the nest. Parental feeding strategies therefore varied between these contrasting environmental scenarios. In first clutches, females actively and carefully assessed nestling signals; in second clutches, they adopted strategies that were less time-consuming, responding instead to nestlings that begged earlier or passively occupied favourable positions. Males, by contrast, used this latter strategy consistently, irrespective of environmental conditions.
Efectos del consumo de fungicidas triazoles sobre la salud y el sistema inmunológico del gorrión común (Passer domesticus) [Effects of triazole fungicide consumption on the health and immune system of the house sparrow (Passer domesticus) infected and non-infected with avian malaria]
Jiménez-Peñuela J, Martínez-Solera I, Peiró-Triguero PL, Camarero-Abella PR, Fernández-Tizón M, Bolívar P, Santamaría-Cervantes C, Parejo-Pulido D, Casquero S, Andrés-Esteso M, González-López S, Ortiz-Santaliestra ME, Mateo R
XXVI Spanish Ornithology Conference. Valencia (Spain), 12–16 February 2025.Granivorous birds in agricultural environments find a major food source in cereal seeds sown during autumn and winter. However, these seeds are generally coated with triazoles, currently the most widely used fungicides in agriculture. Recent experimental studies have reported substantial adverse effects on avian physiology following triazole exposure. These fungicides affect sterol synthesis, altering endogenous cholesterol levels and the regulation of steroid hormones. The most concerning and widely studied effect is reduced reproductive success in birds. However, despite the well-known interactions between steroid levels and immunocompetence, little is known about the impact of triazoles on the immune system or their possible interactions with pathogens. In this study, we conducted an experiment in which house sparrows naturally infected or uninfected with avian malaria consumed wheat seeds coated or uncoated with difenoconazole for 10 days. The birds’ body mass was measured and blood samples were collected before treatment (day 0), during treatment (day 11) and after treatment (day 21). Blood smears were used to measure white blood cell composition and avian malaria parasitaemia; telomere length and the birds’ oxidative status were measured using the remaining blood. Preliminary results show that infected birds consuming treated seeds lose weight. We predict a reduction in antioxidant enzyme activity and telomere length in infected birds exposed to the treatment, both during and after exposure. We also expect increased avian malaria parasitaemia and a change in white blood cell composition in birds exposed to the triazole. These results could provide a more integrated approach to assessing the environmental risk of these pesticides, as well as contribute to understanding the transmission dynamics of infectious pathogens and the evolution of host–parasite interactions in agricultural habitats.
Global overview of the flower visits of velvet ants (Hymenoptera: Mutillidae and Myrmosidae) as a case of study on neglected pollinators
Robla J, Díaz-Calafat J, Parejo-Pulido D
21st edition of the Annual Meeting of the Floral Ecology Working Group – EcoFlor. Coimbra (Portugal), 1–2 February 2024.Plant-animal interactions constitute a recurrent and central focus in ecological research, with pollination representing one of its most extensively studied aspects. While certain insect orders have traditionally received considerable attention due to their abundance and efficiency, it is undeniable that the significance of other less popular flower visitors in pollination processes cannot be overlooked. Therefore, further research is imperative to gain insights into the floral interactions of these often neglected groups. In this regard, focusing on velvet ants (Hymenoptera: Mutillidae and Myrmosidae) as a case study, we conducted a comprehensive global review of their floral visitation patterns using citizen science data, literature records and unpublished data and explored the potential role of this wasp group as pollen vectors. Our analysis revealed that velvet ants visited almost 40 plant families worldwide, and that the plant species visited differed between male and female velvet ants, with regional variations among bioregions. The availability of plants and the different biology of both sexes could play an important role in explaining such differences. Furthermore, approximately 43% of the documented photographic records (likely an underestimation) indicate that these insects carry pollen in the same way as other arthropods. Nevertheless, there remains ample scope for ongoing investigation to comprehensively assess the importance of numerous arthropods, not only as floral visitors but also as potential pollinators.
Interactions among siblings: how are begging signals influenced by nestmates?*
Parejo-Pulido D, Pérez-Rodríguez L, Redondo T
XVIII National Conference and XV Ibero-American of Ethology and Evolutionary Ecology. Badajoz (Spain), 31 October–3 November 2023.Early theoretical models for the evolution of offspring begging have largely focused on competitive interactions among siblings. Some of these models predict that a nestling will escalate its begging effort in response to more intense begging by a needier nestmate. However, nestlings in multi-chick broods also share genes and common interests (e.g. ensuring adequate food provisioning for the whole brood), and recent models allow for different nestling responses depending on the function of specific begging components (competitive allocation vs. cooperative solicitation). In this study, we investigated how begging by spotless starling nestlings of different rank (core vs. marginal) was affected by the behaviour of a deprived nestmate. We focused on two distinct begging components that may influence different aspects of parental care: postural intensity (affecting competitive food allocation) and begging duration (related to cooperative food provisioning for the whole brood). We analysed the behavioural change of a focal nestling (core or marginal) before and after sharing the nest with a hungry core sibling. We found that core nestlings did not change their postural intensity in response to a hungry sibling. By contrast, marginal nestlings that had not received food at the previous feeding event reduced their postural intensity in proportion to the time their hungry core sibling had spent begging at that event. Regarding the cooperative component, core nestlings reduced their begging duration when their hungry sibling had begged for longer at the previous feeding event, while marginal nestlings showed no change. These results suggest a scenario of mild sibling rivalry: we found no evidence of escalation in the food-allocation component, but rather a decrease in begging effort compatible with more cooperative scenarios. More realistic theoretical models for the evolution of offspring signalling should incorporate a wider array of mutualistic interactions between family members.
Immune challenge modulates nestling begging behavior in the spotless starling*
Parejo-Pulido D, Pérez-Rodríguez L, Redondo T
International Society for Behavioral Ecology Congress. Stockholm (Sweden), 28 July–2 August 2022.Empirical evidence for an immunological cost of nestling begging behaviour has been reported in different bird species. These studies have found a reduced local, cell-mediated immune response to an antigen (phytohaemagglutinin) after nestlings were experimentally induced to beg at higher rates. However, differential stimulation of nestlings may affect their stress response, providing an alternative explanation for their reduced immune performance. In this study, we tested the hypothesis that begging signals incur an immunological cost by manipulating the nestlings’ immune response and measuring the effect of this manipulation on their begging behaviour. We exposed six-day-old spotless starling nestlings (Sturnus unicolor) to an immune challenge (an injection of bacterial lipopolysaccharide, LPS) that simulates a bacterial infection, and assessed its effects on postural begging intensity and call structure under controlled food-deprivation conditions in the laboratory. We recorded begging components before and after the LPS injection, at 30, 60 and 90 minutes after the nestlings had been fed to satiety. We found that the LPS injection had strong effects on postural begging intensity but much weaker effects on call structure. LPS-injected nestlings begged with less extended postures and spent less time begging. They emitted begging calls with higher and more variable peak frequencies and lower energy dispersion (entropy). The LPS injection did not affect other call parameters, such as latency to call or call duration. Our results are consistent with immunological costs modulating begging intensity as a reliable indicator of hunger, offspring quality or both, although different signal components may convey different information.
Need and quality in parent-offspring communication in pied flycatcher broods*
Parejo-Pulido D, Pérez-Rodríguez L, Abril-Colón I, Potti J, Redondo T
ASAB Summer Virtual Conference. Belfast (United Kingdom), 23–25 August 2021.In the context of parent-offspring communication, three hypotheses have been proposed to explain the nature of the information encoded by begging behaviour: the Signal of Need (SoN), Signal of Quality (SoQ) and Signal of Hunger (SoH) hypotheses. Compared with the SoN/SoH hypotheses, the SoQ has received less empirical support, given the difficulty of teasing apart cryptic and non-cryptic (e.g. chick size) components of nestling quality. In this study, we experimentally induced variation in nestling cryptic quality by supplementing pied flycatcher (Ficedula hypoleuca) nestlings with either an antioxidant (vitamin E, VitE) or a coconut-oil vehicle (controls). We measured nestling behaviour and appearance, as well as parental feeding responses, at natural nests. VitE enhanced nestling growth but had no effect on mouth colouration or begging behaviour (probability of gaping, latency to beg, postural intensity and rate of changing spatial positions); however, it increased the probability that a nestling positioned itself in a favourable nest location. The main predictor of begging performance was the duration of food deprivation, consistent with the SoN/SoH hypothesis. Male and female parents followed different feeding rules. Males fed nestlings according to their spatial location and begging latency, apparently following a time-saving, passive allocation mechanism. Females also relied on these cues, but were additionally affected by an interaction between treatment and postural intensity: they favoured VitE-treated over control nestlings when both begged with high postural intensity. These results fit reasonably well with a SoN scenario in which parents maximise their fitness returns by responding to nestling signals and cues conveying information about offspring prospective fitness, integrating signals of need (hunger) and nestling cryptic quality.
02 / POSTER PRESENTATIONS
Efecto del estrés de captura sobre los recuentos leucocitarios en aves [Effect of capture stress on leukocyte counts in birds]
Serrano-Jiménez A, Parejo-Pulido D, Fusté R, Crespo-Ginés R, Peiró-Triguero PL, Gil D, de la Peña E, Pérez-Rodríguez L
XIX National Conference and XVI Ibero-American of Ethology and Evolutionary Ecology. Seville (Spain), 2–5 September 2025.In behavioural ecology, certain physiological variables—known as biomarkers—can be very useful for quickly and easily assessing specific aspects of the physical state, condition or other key characteristics of the study animals. Leucocyte counts are one such measure and can provide valuable information about an organism’s immune status and stress levels. However, various external factors, including those associated with blood sampling, can introduce bias, affect results and compromise our conclusions. One of the main sources of bias may be the stress caused by capturing and handling animals, which can alter biomarker levels.
The aim of this study was to identify the effect of this stress on leucocyte counts in birds. We worked with two study models: wild adult spotless starlings (Sturnus unicolor) and adult male red-legged partridges (Alectoris rufa) from a captive population. In both cases, the birds underwent a standard capture-and-handling protocol, and blood samples were collected at different times after capture. Blood smears were prepared from these samples and used to obtain total and differential leucocyte counts.
Our results show that the longer the interval between capture and blood sampling, the lower the total number of blood leucocytes and the higher the heterophil-to-lymphocyte ratio—two parameters closely associated with the acute stress response. Minimising handling and blood-sampling time is therefore essential to avoid alterations in physiological measurements and ensure reliable, comparable data. In conclusion, assessing and controlling the potential impact of the sampling protocol itself should be standard practice in all studies involving key biomarkers.
El estrés de captura y la manipulación reducen los niveles de testosterona en sangre: evidencias en adultos de estornino negro [Capture and handling stress reduce blood testosterone levels: evidence in adult spotless starlings]
de la Peña E, Casquero S, Parejo-Pulido D, Gil D, Pérez-Rodríguez L
XXVI Spanish Ornithology Conference. Valencia (Spain), 12–16 February 2025.Testosterone is a steroid hormone that plays a central role in vertebrate sexual selection, regulating courtship behaviour, territorial defence and the development of sexual traits. Testosterone also modulates sperm production and quality, which are closely linked to male reproductive success. Sources of variation in plasma testosterone levels are well established and include social context, time of day and season. However, the most common method for quantifying individual levels of this hormone—blood sampling—involves capturing and handling individuals, which could itself introduce bias into the measurements. Few studies have investigated the magnitude and direction of this potential effect of capture stress on plasma testosterone levels. In this study, we explored whether capture and handling could influence blood testosterone levels in male and female spotless starlings (Sturnus unicolor) at the beginning of the breeding season. We captured wild adults and collected a blood sample at capture and again after a set interval. We carried out this procedure at different times of day and after different handling periods, ranging from 10 minutes to 3 hours. We quantified plasma testosterone levels and found a significant decline after handling in both male and female starlings, regardless of the time of day at which they were captured. These results show that stress is an important source of variation in testosterone levels measured from blood samples in free-living passerines. The main practical implication is that such samples should be collected as soon as possible after capture and that the elapsed time should be recorded systematically.
Efecto de la malaria aviar en la cría cooperativa del rabilargo ibérico (Cyanopica cooki) [Effect of avian malaria on cooperative breeding of the Iberian magpie (Cyanopica cooki)]
Parejo-Pulido D, Magallanes S, Valencia J, De la Cruz C, Marzal A
XXIV Spanish Conference and VII Iberian Conference of Ornithology. Cádiz (Spain), 13–17 November 2019.Bird adaptations for combating parasites, including those mediated by the immune system, are energetically costly. Because energy is a limited resource for living organisms, there is a trade-off between the energy allocated to immune defence and that available for other activities, such as reproduction. To minimise the costs associated with reproduction and maximise reproductive performance, animals have evolved different reproductive strategies, including cooperative breeding systems in which the breeding pair may be assisted by helpers. The balance between immune function and reproductive activities can be affected by various factors, including infection by malarial parasites. The workload of infected individuals could therefore be compromised. In this study, we used a population of the Iberian Azure-winged magpie (Cyanopica cooki), a cooperative breeder, and measured feeding rates for each status group (helpers, breeding males and breeding females) in relation to their level of infection by the malarial genus Leucocytozoon. The results showed that malaria infections significantly reduced feeding rates in breeding individuals, while no significant effect was found in helpers. Among infected individuals, mixed infections had a greater negative effect than single infections. However, this reduction in feeding rate did not appear to be related to poorer physical condition, as infected individuals did not differ significantly in condition from uninfected individuals. In conclusion, there may be a trade-off between allocating resources to reproduction and maintaining a competent immune system in the Iberian Azure-winged magpie, with the effect being more pronounced in individuals with greater energy expenditure during the breeding period.
Carga parental de los ayudantes en el Rabilargo ibérico: una cuestión de procedencia (Nativos vs Foráneos) [Parental effort of helpers in the Iberian magpie: a question of origin (Native vs. Foreign)]
Parejo-Pulido D, Morán A, Castillo JF, Valencia J, De la Cruz C
XXIII Spanish Ornithology Conference. Badajoz (Spain), 2–5 November 2017.In cooperative breeding, individuals other than the breeding pair (helpers) participate in parental care of the offspring. In the Iberian Azure-winged magpie (Cyanopica cooki), helpers can be of two types according to their origin: native individuals, born in the colony (previously ringed as nestlings in nests within our study area), and foreign individuals, which arrive after post-fledging dispersal from their respective natal colonies. In this study, we investigated, first, the probability that natives and foreigners would act as helpers or breeders during their first breeding season and, second, the parental care provided by each type of helper. Among natives, there was no difference in the proportion acting as breeders and helpers, whereas foreigners showed a greater tendency to act as breeders. Regarding parental care, colony-born helpers fed more frequently than foreign helpers. This difference arose because native helpers significantly increased their feeding rate as the chicks grew older, whereas foreign helpers maintained their parental care regardless of offspring age. Both types of helper increased their feeding rate when more chicks were present in the nest; however, as the breeding season progressed, both decreased their feeding rate. Foreigners’ lower probability of acting as helpers and the lower level of parental care they provided when they did so may be explained by their more distant or absent family relationship with the breeders, which probably prevents them from gaining direct benefits from helping. This contrasts with natives, which usually cooperate with one or both parents.