Crops modify habitat quality beyond their limits

Edge effect is a strong driver of change in fragmented landscapes. In the last few decades, agricultural land-use intensity at field scale has increased and, consequently, the edges between crops and natural vegetation matrix have sharpened. Interspersed crops produce now negative effects not only by direct habitat destruction, but also by inputs of agrochemicals that may spread their effects on the surroundings. These processes are taking place worryingly in steppe habitats in Iberian Peninsula where the high diversity of bird communities and other taxa they hold is at risk. The aims of this study were to evaluate the edge effect of crops on i) the microhabitat quality of a natural landscape matrix and ii) the space use of a threatened habitat-specialist steppe bird, the Dupont's lark (Chersophilus duponti). We carried out microhabitat sampling and bird surveys within and around crops interspersed in a typical Iberian shrub-steppe matrix during spring and autumn 2016 and spring 2017. Microhabitat quality was measured by sampling vegetation structure and arthropod biomass (as proxy of food availability) within and at increasing distances (1, 10 and 50 m) to seven crops. The intensity of space use by the Dupont's lark was estimated applying a Kernel density function on the spatial point pattern of the males’ territories. Vegetation structure variables were summarized by Principal Components Analysis. Linear Mixed Models and model averaging were used to test for effects of distance to crop on microhabitat quality and space use by the Dupont's lark. Distance to crop significantly affected microhabitat quality. A patchy structure of herbaceous and shrub was found outside crops in all sampling dates, with more shrub cover and less herbaceous cover as the distance to crops increased. Biomass of hypogeous arthropods significantly decreased when the distance to crops was lower than 50 m. The intensity of space use by Dupont's lark varied according to the sampling date, being higher in spring, and as the distance to crops and the biomass of hypogeous arthropods increased. Negative effects of crops on the space use of this bird species might be shaped both by the effect of the crop itself and by its edge effect on hypogeous arthropods. Our results point to an edge effect of crops of 10–50 m on natural vegetation structure, arthropod availability and use of space by the Dupont`s lark, which suggests that the effective area of optimal habitat available for true steppe species could be overestimatedThis study was supported by the Education, Youth and Sport Bureau (Madrid Regional Government, Spain) and the European Social Fund for the Youth Employment Initiative (Spain) [PEJ15/AMB/AI-0059], the European Commission (Spain) [Life-Ricotí project LIFE15-NAT-ES-000802] and the BBVA Foundation (Spain) [BBVA-Dron Ricotí project 026107]. This is a contribution to the Excellence Network Remedinal 3CM (Spain) (S2013/MAE2719), supported by Comunidad de Madri

Alondra ricotí – Chersophilus duponti (Vieillot, 1820)

Aves - Orden Passeriformes - Familia Alaudidae en la Enciclopedia Virtual de Vertebrados Españoles, http://www.vertebradosibericos.org/.A comprehensive review of the natural history of the Dupont’s Lark Chersophilus duponti in Spain.Peer reviewe

Évaluation du comptage des détections pour estimer la densité d'oiseaux à l'aide d'un suivi sonore passif : recommandations pour estimer un taux de détections fiable

Cue counting is a method developed for estimating vocally active wildlife density by dividing the density of cues (number of cues per unit area surveyed per unit time) by the average cue rate (ACR) at which individuals vocalize. It has been used successfully to estimate whale density using passive acoustic monitoring, but its efficacy has had limited testing in birds. We tested whether cue counting can be used to infer bird abundance using autonomous recording units and estimated the minimum effort required to obtain a reliable cue rate at individual and population levels. We recorded Dupont's Lark (Chersophilus duponti) vocalizations at 31 sites where traditional field censuses were also performed. We estimated the ACR using three methodologies: directional recordings, recordings from an online database of bird sounds (xeno-canto), and behavioral field studies. The ACRs estimated using directional recordings and behavioral field studies were similar, and bird numbers were over and underestimated by 0.8 and 10%, respectively (74–77% of the sampling sites were well estimated). However, the ACR estimated using xeno-canto recordings was much higher than those estimated using the other two methods, and bird numbers were underestimated by 41%. We also performed a cost-effectiveness assessment of the number of individuals and recording durations needed to optimize the estimation of a reliable ACR. We found that ACR estimates were more efficient if long (25 min) recordings were used when < 4 males were recorded, whereas 5-min recordings were more efficient for ≥ 20 males. We conclude that cue counting can be useful to infer bird density around recorders but requires an accurate measure of the ACR. Further research should evaluate the effectiveness of passive cue counting on a large number of species and under different circumstances.Le comptage des détections est une méthode qui a été élaborée pour estimer la densité de la faune active vocalement en divisant la densité de détections (nombre de détections par unité de surface étudiée par unité de temps) par le taux moyen de détections (TMD) auquel les individus chantent ou crient. Cette méthode a été utilisée avec succès pour calculer la densité des baleines à l'aide d'un suivi sonore passif, mais son efficacité a peu été testée chez les oiseaux. Nous avons testé si le comptage des détections pouvait être utilisé pour déduire l'abondance des oiseaux en utilisant des enregistreurs automatisés et avons calculé l'effort minimum requis pour obtenir un taux de détections fiable au niveau des individus et des populations. Nous avons enregistré les manifestations sonores du Sirli de Dupont (Chersophilus duponti) sur 31 sites où des recensements traditionnels ont également été effectués. Nous avons calculé le TMD de trois façons : à partir d'enregistrements directionnels, d'enregistrements provenant d'une base de données de cris et de chants d'oiseaux accessible en ligne (xeno-canto) et d'études comportementales sur le terrain. Les TMD calculés à l'aide d'enregistrements directionnels et d'études comportementales étaient similaires, et le nombre d'oiseaux était surestimé et sous-estimé de 0,8 et 10 %, respectivement (la mesure de 74-77 % des sites d'échantillonnage était juste). Cependant, le TMD calculé à l'aide d'enregistrements de xeno-canto était beaucoup plus élevé que ceux obtenus au moyen des deux autres méthodes, et le nombre d'oiseaux était sous-estimé de 41 %. Nous avons également réalisé une évaluation coût-efficacité du nombre d'individus et des durées d'enregistrement nécessaires pour optimiser le calcul d'un TMD fiable. Nous avons constaté que la mesure du TMD était meilleure si des enregistrements longs (25 min) étaient utilisés lorsque < 4 mâles étaient enregistrés, tandis que des enregistrements de 5 min étaient plus efficaces pour ≥ 20 mâles. Nous concluons que le comptage des détections peut être utile pour calculer la densité d'oiseaux autour des enregistreurs, mais une mesure précise du TMD doit d'abord être effectuée. D'autres recherches devraient se pencher sur l'évaluation de l'efficacité du comptage passif des détections dans le cas d'un grand nombre d'espèces et dans différentes circonstances.This study was supported by the Programa de Investigación y Conservación del Zoo de Barcelona within the project “Nuevas tecnologías para viejos trabajos: Uso de grabadores automáticos para la detección y censo de especies raras y amenazadas: El caso de la alondra ricotí en Lleida y otras poblaciones pequeñas”; the Education, Youth and Sport Bureau (Madrid Regional Government); and the European Social Fund for the Youth Employment Initiative (PEJ15/AMB/AI-0059 and PEJ1D-2018-PRE/AMB-8063). This work is a contribution to the Excellence Network Remedinal 3CM (S2013/MAE2719), supported by Comunidad de Madrid; and to the projects “Census of Dupont’s Lark in Guadalajara 2017 (SSCC/046/2017)”, supported by Junta de Comunidades de Castilla-La Mancha; LIFE Ricotí (LIFE15-NAT-ES-000802), supported by the European Commission, and “BBVA-Dron Ricotí”, funded by the BBVA Foundation

Selecting the best: Interspecific and age-related diet differences among sympatric steppe passerines

Parental food provisioning is crucial for the growth and survival of offspring. Growth rate depends on food quality and food supplied to offspring may differ from what adults use for their own. In the case of steppe passerine birds, detailed characterization on nestling dietary composition, as well as prey choice and resource partitioning among species, is a pending subject. Dietary differences between nestlings and adults remain also largely unexplored. By using faecal DNA metabarcoding, we described the diet of nestlings and adults of five shrub-steppe passerine species over the 2017–2019 breeding seasons in central Spain. We also monitored arthropod availability in the field to assess dietary selection. We expected interspecific dietary differences to limit competition for food resources among sympatric species, as well as parental selection of high quality prey for nestlings. We also predicted age-related differences, with nestlings being fed nutrient-rich prey more frequently than adults. The main arthropod orders provisioned to nestlings were Orthoptera, Julida, Araneae and Lepidoptera. Nestlings of the different species showed high interspecific diet overlap, indicating both a coincidence in growth needs among bird species and no or little limitation of the most profitable resources during the breeding season. Adults of all species showed higher diet richness than nestlings, and age-related differences in prey composition were mainly driven by the selection of the most easily digestible, larger protein- and calcium-rich prey for nestlings, which may favour their rapid growth, and avoiding highly sclerotized and less nutritional prey such as ants. Our study sheds light on the basic ecology and conservation of these declining steppe birds, indicating that interspecific competition may not be a major factor during the breeding season. Given the current global decline of arthropods, further long-term research would be necessary, along with the implementation of effective conservation measures that ensure a sufficient availability of resources identified as key prey in the diet of steppe bird nestlings.This study was supported by the European Commission LIFE Ricotí (LIFE15-NAT-ES-000802) and LIFE Connect Ricotí (LIFE20-NAT-ES-000133) projects. This is a contribution to the Excellence Network Remedinal TE-CM (S2013/MAE2719). JG-C is funded by a Margarita Salas postdoctoral fellowship (CA4/RSUE/2022–00205) provided by the Spanish Ministry of Universities and Universidad Autónoma de Madrid (Spain). CPG acknowledges support from Ministerio de Educación y Formación Profesional through the Beatriz Galindo Fellowship (Beatriz Galindo-Convocatoria 2020) and JZ acknowledges support from Ministerio de Universidades through the predoctoral FPU fellowship program

Prey choice in insectivorous steppe passerines: New insights from DNA metabarcoding

Food availability plays a key role affecting almost every aspect of bird ecology, including bird population, distribution, reproduction, and behavior. Understanding the functional relationship between prey availability and insectivorous birds’ diet is important in the current scenario of habitat loss and declining of insect and bird populations. We used a fecal metabarcoding approach coupled with prey availability sampling (arthropod abundance and biomass) to test for evidence of selective foraging in a shrub-steppe passerine assemblage over the 2017–2019 breeding seasons in semi-natural steppes of central Spain. The results showed that the six bird species selected specific arthropod taxa. Heteroptera, Orthoptera, Araneae, Lepidoptera and some Coleoptera families were the main selected prey taxa, while Formicidae appeared to be avoided, suggesting that shrub-steppe passerines tend to select prey items providing essential nutrients and energy during the breeding season, while poor quality ones are neglected. Our findings highlight the utility of metabarcoding dietary data to assess prey selection patterns in insectivorous passerines and provide valuable information for the development of conservation and management programs to ensure the long-term availability of crucial food resources for shrub-steppe birds and other insectivores.This study was supported by the European Commission LIFE Ricotí (LIFE15-NAT-ES-000802) and LIFE Connect Ricotí (LIFE20-NAT-ES-000133) projects. This is a contribution to the Excellence Network Remedinal TE-CM (S2013/MAE2719). JG-C is funded by a Margarita Salas Postdoctoral Fellowship (CA4/RSUE/2022-00205) provided by the Spanish Ministry of Universities and Universidad Autónoma de Madrid (Spain)

Interactions in shrubsteppes: Implications for the maintenance of a threatened bird

The interactions between ecosystem components and their implications on birds have been poorly studied, especially in shrubsteppes. In this work, we evaluate the interactions between vegetation structure, arthropods availability and the use of space by the Dupont's lark (Chersophilus duponti) in important areas for the species in the Iberian Peninsula. To that end, between 20152018 springs, bird censuses and microhabitat samples were carried out in suitable areas for the species, which should be taken as a reference for habitat restoration tasks. The intensity of space use by the species was calculated by a kernel density function, which defines the probability of finding a territory from the spatial pattern of observations. The habitat quality was determined by sampling vegetation structure and food availability. Habitat structure variables were summarized by principal component analysis. Linear mixed models (LMMs) were adjusted to evaluate the relationships between variables. Shrub cover was positively and significantly related to total epigeous biomass and Coleoptera biomass, and positive but marginally significant with hypogeous biomass (mainly arthropods larvae). The biomass of order Araneae was positively and significantly related to the use of space by Dupont's lark, while total epigeous biomass and Coleoptera biomass were positively but marginally related to the use of space by Dupont's lark. This work provides new results about habitat and its quality for Dupont's lark in optimal habitat for the species, and it highlight the fundamental role of arthropod availability for the maintenance of the species which has to be taken into account in carrying out restoration actions for the speciesEste trabajo se ha realizado gracias a la Oficina de Educación, Juventud y Deporte (Comunidad de Madrid) y el Fondo Social Europeo para la Iniciativa de Empleo Juvenil (PEJD-2018-PRE/AMB-8063); el proyecto Life-Ricotí (LIFE15-NATES-000802), otorgado por la Comisión Europea; el proyecto BBVADron-Ricotí, otorgado por la Fundación BBV

Comparative assessment of satellite- and drone-based vegetation indices to predict arthropod biomass in shrub-steppes

Arthropod biomass is a key element in ecosystems functionality, and basic food item for many species, which must be estimated through traditional costly field sampling in normally just a few sampling points. Arthropod biomass and plant productivity should be narrowly related, as a great majority of arthropods are herbivorous, and others depends on these. Quantifying plant productivity with satellite or aerial vehicles imagery is an easy and fast procedure already tested and implemented in agriculture and field ecology. However, the ability of satellite or aerial vehicles imagery for quantifying arthropod biomass and its relationship with plant productivity has been scarcely addressed. Here, we used Unmanned Aerial Vehicle (UAV) and satellite Sentinel-2 (S2) imagery to establish relationship between plant productivity and arthropod biomass estimated through ground-truth field sampling in shrub-steppes. We UAV sampled 7 plots of 47.6-72.3 ha at 4 cm pixel resolution, and afterwards downscaling spatial resolution to 50 cm resolution. In parallel, we used S2 imagery from same and other dates and locations at 10 m spatial resolution. We related several vegetation indices (VI) with arthropod biomass (epigeous, coprophagous, and four functional consumer groups: predatory, detritivore, phytophagous and diverse) estimated in 41-48 sampling stations for UAV flying plots, and in 67-79 sampling stations for S2. VI derived from UAV were consistently and positively related with all arthropod biomass groups. Three out of seven, and six out of seven S2-derived VI were positively related with epigeous and coprophagous arthropod biomass, respectively. BNDVI and ENDVI showed consistent and positive relationships with arthropod biomass, regardless of the arthropod group and the spatial resolution. Our results point out that UAV and S2-VI imagery data may be a viable and cost-efficient alternative to quantify arthropod biomass at large scales in shrub-steppes. The relationship between VI and arthropod biomass is probably habitat-dependent and thus, future research should address this relationship including several habitats to validate vegetation indices as proxies of arthropod biomass.This study was partially supported by the European Commission (Life Ricotí project LIFE15-NAT-ES-000802 and Life Connect Ricotí project LIFE20-NAT-ES-000133) and the BBVA Foundation (BBVA-Dron Ricotí project). This paper contributes to project REMEDINAL-3 from CAM

Comparative assessment of satellite- and drone-based vegetation indices to predict arthropod biomass in shrub-steppes

Arthropod biomass is a key element in ecosystem functionality and a basic food item for many species. It must be estimated through traditional costly field sampling, normally at just a few sampling points. Arthropod biomass and plant productivity should be narrowly related because a large majority of arthropods are herbivorous, and others depend on these. Quantifying plant productivity with satellite or aerial vehicle imagery is an easy and fast procedure already tested and implemented in agriculture and field ecology. However, the capability of satellite or aerial vehicle imagery for quantifying arthropod biomass and its relationship with plant productivity has been scarcely addressed. Here, we used unmanned aerial vehicle (UAV) and satellite Sentinel-2 (S2) imagery to establish a relationship between plant productivity and arthropod biomass estimated through ground-truth field sampling in shrub steppes. We UAV-sampled seven plots of 47.6–72.3 ha at a 4-cm pixel resolution, subsequently downscaling spatial resolution to 50 cm resolution. In parallel, we used S2 imagery from the same and other dates and locations at 10-m spatial resolution. We related several vegetation indices (VIs) with arthropod biomass (epigeous, coprophagous, and four functional consumer groups: predatory, detritivore, phytophagous, and diverse) estimated at 41–48 sampling stations for UAV flying plots and in 67–79 sampling stations for S2. VIs derived from UAV were consistently and positively related to all arthropod biomass groups. Three out of seven and six out of seven S2-derived VIs were positively related to epigeous and coprophagous arthropod biomass, respectively. The blue normalized difference VI (BNDVI) and enhanced normalized difference VI (ENDVI) showed consistent and positive relationships with arthropod biomass, regardless of the arthropod group or spatial resolution. Our results showed that UAV and S2-VI imagery data may be viable and cost-efficient alternatives for quantifying arthropod biomass at large scales in shrub steppes. The relationship between VI and arthropod biomass is probably habitat-dependent, so future research should address this relationship and include several habitats to validate VIs as proxies of arthropod biomassBBVA Foundation, BBVA Dron Ricoti project; European Commission, Grant/ Award Number: LIFE15-NAT-ES-000802; REMEDINAL-3 from CAM; European Comission, Grant/Award Number: LIFE20-NAT-ES-00013

European population trends and current conservation status of an endangered steppe-bird species: the Dupont’s lark Chersophilus duponti

Background Steppe-birds face drastic population declines throughout Europe. The Dupont’s lark Chersophilus duponti is an endangered steppe-bird species whose European distribution is restricted to Spain. This scarce passerine bird could be considered an ‘umbrella species’, since its population trends may reveal the conservation status of shrub-steppes. However, trends for the Spanish, and thus European, population of Dupont’s lark are unknown. In this work, we evaluated Dupont’s lark population trends in Europe employing the most recent and largest compiled database to date (92 populations over 12 years). In addition, we assessed the species threat category according to current applicable criteria (approved in March 2017) in the Spanish catalogue of threatened species (SCTS), which have never been applied to the Dupont’s lark nor to any other Spanish species. Finally, we compared the resulting threat categories with the current conservation status at European, national and regional levels. Methods We fitted switching linear trend models (software TRIM—Trends and Indices for Monitoring data) to evaluate population trends at national and regional scale (i.e. per Autonomous Community) during the period 2004–2015. In addition, the average finite annual rate of change ($\overline \lambda$λ¯) obtained from the TRIM analysis was employed to estimate the percentage of population size change in a 10-year period. A threat category was assigned following A1 and A2 criteria applicable in the SCTS. Results Trends showed an overall 3.9% annual decline rate for the Spanish population (moderate decline, following TRIM). Regional analyses showed high inter-regional variability. We forecasted a 32.8% average decline over the next 10 years. According to these results, the species should be listed as ‘Vulnerable’ at a national scale (SCTS). At the regional level, the conservation status of the species is of particular concern in Andalusia and Castile-Leon, where the species qualifies for listing as ‘Endangered’. Discussion Our results highlight the concerning conservation status of the European Dupont’s lark population, undergoing a 3.9% annual decline rate. Under this scenario, the implementation of a wide-ranging conservation plan is urgently needed and is vital to ensuring the conservation of this steppe-bird species. The role of administrations in matters of nature protection and the cataloguing of endangered species is crucial to reverse declining population trends of this and other endangered taxa

First documented case of Tawny Pipit Anthus campestris nest parasitism by common cuckoo Cuculus canorus in Spanish steppes

Primo caso documentato di parassitismo di un nido di calandro Anthus campestris da parte del cuculo Cuculus canorus nelle steppe spagnole. Il parassitismo interspecifico della covata o del nido è un comportamento riproduttivo relativamente comune negli uccelli. Attraverso questa tattica riproduttiva, i parassiti di cova evitano i costi associati all’allevamento e al mantenimento dei pulcini deponendo le uova nei nidi della specie ospite nella quale sono specializzati. Il cuculo (Cuculus canorus) segue questa strategia di parassitismo di cova. Le femmine di cuculo depongono le uova nei nidi di altre specie di uccelli, imitando la forma, le dimensioni e il colore delle uova della specie ospite. In questo lavoro riportiamo il primo caso documentato di parassitismo di nidi di calandro da parte del cuculo in habitat steppici spagnoli, dove finora non sono stati registrati casi di parassitismo su questa speci