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Understanding natural populations trends has emerged as a key objective to bend the curve of biodiversity loss. Of particular concern are the impacts of stressors at the local scale, which are not necessarily reflected in the current global conservation assessments. As a hotspot of biodiversity, the Iberian Peninsula is an area of special interest for conservation. Here, we aim to synthesise the current knowledge about the population trends of marine, terrestrial and freshwater Iberian vertebrates. To that aim, we performed an extensive review, with more than 5000 scientific manuscripts screened and grey literature. From this initial review, and after applying data quality checks, we obtained 1500 population time series of Iberian vertebrates. Once we obtained this global database, we analysed their population trends using two-step modelling process: (i) first we applied state-space models to derive the population trend of each population time series; (ii) we then used multilevel Bayesian models to determine the factors influencing the population trends. Overall, we found that Iberian vertebrate populations display a disparity of trends, with both declines and increases, with fishes being the only taxa showing clear signs of declines. We identified major gaps in the monitoring data across the Iberian peninsula, with amphibians and reptiles being highly underrepresented in our dataset, despite being among the most threatened taxonomic groups. Overall, our approach will help to bridge the gap in our knowledge between the global and local scale conservation status of wild Iberian populations and help to focus the attention of future conservation policies.

Understanding and identifying the impacts of multiple stressors on natural populations has become a key objective for post-2020 biodiversity conservation. Of particular concern are the impacts of stressors at the local scale, which are not necessarily reflected in current global conservation assessments. As a hotspot of biodiversity, the Iberian Peninsula is an area of special interest for conservation, but it is currently facing myriad environmental problems. Yet, a synthesis of the impacts of multiple stressors on the Iberian faunal populations is glaringly missing. To contribute to this challenge, we join our efforts in an Early Career Researchers project funded by SIBECOL, which aims to synthesise current knowledge on population trends of Iberian marine, terrestrial and freshwater vertebrates, and, eventually, to identify the most common stressors for Iberian fauna populations, and their differences between major taxonomic groups and ecosystems. Here, we will present the results of the first phase of this project, whose objective was to describe the trends of Iberian vertebrate populations and identify knowledge gaps related to taxonomic groups and ecosystems. To that aim, we conducted an extensive literature review, with more than 5,000 scientific manuscripts and grey literature screened. From this initial review, and after applying data quality controls, we obtained > 1,000 population time series of Iberian vertebrates across marine, terrestrial, and freshwater ecosystems. Once we compiled this database, we analysed the population trends using a two-step modelling process: (i) first, we applied state-space models to derive the population trend of each population time series; and (ii) second, we used multilevel Bayesian models to determine the factors influencing these population trends. Overall, we found that Iberian vertebrate populations display a disparity in trends, with both declines and increases, with fishes (both marine and freshwater) being the taxa s

In many species of cooperative breeding birds, breeders and helpers participate in the parental care with different food provision rules. Normally, helpers feed nestlings less frequently and with smaller quantities of food than breeders. But studies analysing the reaction of feeders to nestling demand are scarce and rarely measure the quantity of food that is actually delivered. In this study, we analysed the provisioning effort of breeders and helpers in the Iberian Magpie, Cyanopica cooki, and how this effort varies with brood demand. We did so by measuring the nestling feeding rate and the biomass supply of each individual. In this way, we obtained a more accurate measurement of the investment assumed by each individual belonging to each status. We found that breeding males visited the nest more often than both breeding females and helpers (mean = 2.24; 0.85 and 1.58, respectively). Furthermore, breeding males delivered more biomass in each feeding visit to the nest than those from other statuses. Breeders, both male and female, increased their parental effort (i.e., provisioning rate and biomass) when brood demand was higher (i.e., more siblings and older nestlings), whereas helpers contributed differently to the nest, but depending on the two types of helpers occurring in this species. Differences in the possible benefits obtained by breeders and helpers may explain these different strategies. In addition, male and female breeders (but not helpers) reduce the feeding rate throughout the breeding season. Thus, in the Iberian magpie, breeders and helpers reveal different patterns of investment depending on nestling food demand.

Human activities are altering ecosystems and threatening the well-being of wildlife. The study of the stressful effects of human disturbances on animal distribution, physiology and behaviour can provide fundamental insights for wildlife conservation. Here, we assess how two declining birds, the European Roller Coracias garrulus and the European Scops Owl Otus scops, cope with alteration by human activities in farming habitats of the south of Spain. We studied nest distribution, quantified nestling physiology (corticosterone levels in plasma and feathers and body weight close to fledgling) and parental behaviour (feeding rates) of both species along a human alteration gradient. Rollers and Scops Owls used the same type of habitat and their spatial distribution was not determined by individual quality. In Rollers, nestlings raised in scrubland areas had high stress-induced corticosterone levels, possibly due to high predation risk in this habitat. In addition, Rollers and Scops Owls showed opposite relationships with farming activity and human disturbance. Nestling Rollers showed the highest corticosterone levels in feathers, weight and parental feeding rates in areas with intense farming activity. These results suggest that despite the disturbance produced by farming activities, inducing a higher stress in these areas, cultivated areas may, simultaneously, provide parents with a higher abundance of prey which would trigger increased feeding rates and, hence, higher nestling weights. Furthermore, nestling Scops Owls showed the highest stress-induced corticosterone levels in areas close to roads, suggesting that they would be affected by human disturbance due to infrastructures that disturb also at night when Scops Owls are active. Therefore, susceptibility to human disturbance may vary between species, probably due to variation in the daily pattern of human activities and the species' activity rhythm, buffering or exacerbating the effects, which should be considered i

Studying demographic parameters and how they may influence population growth is critical to the development of meaningful conservation actions for endangered species. The European Roller Coracias garrulus has experienced a drastic decline through its breeding distribution range, but very little is known about its demography (i.e. dispersal and survival). Here, we investigated the apparent survival, population growth and breeding site fidelity in a Roller population in the south of Spain over a period of 8 years. We used capture–recapture histories of 202 ringed adults and 369 fledglings to estimate annual survival, and studied factors affecting site fidelity in 56 adults found breeding over two consecutive years. Adult male and female apparent survival overlapped widely and was similar to that found in other similar migratory species. However, juvenile apparent survival, which was markedly lower than adult survival, was low relative to that found for other birds. Population growth was nearly stable during the study period. Regarding site fidelity, males raising more fledglings one year were more prone to be faithful the following year. In females, however, we did not find any factor influencing either site fidelity decisions or distance between consecutive breeding sites. Concerning settlement decisions, males, but not females, moved to nest-boxes where density of Rollers was lower than that at the nest-box of origin. Altogether, our results suggest that the low productivity and a potential decrease in immigration might be compromising the viability of the population.

Avian brood parasites impose large fitness costs on their hosts and, thus, brood parasitism has selected for an array of host defensive mechanisms to avoid them. So far most studies have focused on antiparasite defenses operating at the egg and chick stages and neglected defenses that may work prior to parasite egg deposition. Here, we experimentally explore the possibility that hosts, as part of a front-line defense, might minimize parasitism costs through informed nest site choice based on perceived risk of cuckoo parasitism. We conducted a large-scale manipulation of visual and auditory cues potentially informing on the risk of great spotted cuckoo Clamator glandarius parasitism during the nest site choice period of the magpie Pica pica host to investigate its effect on host’s nest settlement and individual year to year site fidelity. Early breeding magpies preferentially placed their nests in safe areas (i.e., in sites of low perceived risk of parasitism), and, this effect diluted with time elapsed since risk of parasitism was manipulated. Site fidelity of individual magpies decreased with risk of cuckoo parasitism, for those that were not parasitized in the previous year. Our results constitute the first strong evidence showing that hosts can minimize the costs of cuckoo parasitism through informed nest-site choice, calling for future consideration of defenses potentially operating prior to parasite egg deposition to achieve a better understanding of cuckoo-host coevolution.

Avian brood parasites impose large fitness costs on their hosts and, thus, brood parasitism has selected for an array of host defensive mechanisms to avoid them. So far most studies have focused on antiparasite defenses operating at the egg and chick stages and neglected defenses that may work prior to parasite egg deposition. Here, we experimentally explore the possibility that hosts, as part of a front-line defense, might minimize parasitism costs through informed nest site choice based on perceived risk of cuckoo parasitism. We conducted a large-scale manipulation of visual and auditory cues potentially informing on the risk of great spotted cuckoo Clamator glandarius parasitism during the nest site choice period of the magpie Pica pica host to investigate its effect on host's nest settlement and individual year to year site fidelity. Early breeding magpies preferentially placed their nests in safe areas (i.e., in sites of low perceived risk of parasitism), and, this effect diluted with time elapsed since risk of parasitism was manipulated. Site fidelity of individual magpies decreased with risk of cuckoo parasitism, for those that were not parasitized in the previous year. Our results constitute the first strong evidence showing that hosts can minimize the costs of cuckoo parasitism through informed nest-site choice, calling for future consideration of defenses potentially operating prior to parasite egg deposition to achieve a better understanding of cuckoo-host coevolution.

Hosts can counteract parasites through defences based on resistance and/or tolerance. The mechanistic basis of tolerance, which involve defensive mechanisms minimizing parasite damage after a successful parasitic attack, remains poorly explored in the study of cuckoo-host interactions. Here, we experimentally explore the possibility that the risk of great spotted cuckoo Clamator glandarius parasitism may induce tolerance defences in magpie Pica pica hosts through plasticity in life-history traits. We predict that magpies exposed to auditory cues indicating high parasitism risk will more likely exhibit resistance and/or modify their life-history traits to minimize parasitism costs (i.e. tolerance) compared to magpies under low parasitism risk. We found that manipulating the perceived parasitism risk did not affect host resistance (i.e. rejection of parasitic eggs) nor host life-history traits. Unexpectedly, host's egg volume increased over the season in nests exposed to auditory cues of control non-harmful hoopoes Upupa epops. Our results do not provide support for inducible defences (either based on resistance or tolerance) in response to risk of parasitism in magpie hosts. Even so, we encourage studying plastic expression of breeding strategies in response to risk of cuckoo parasitism to achieve a better understanding of the mechanistic basis of tolerance defences.