Search

Transients can have a severe impact on demographic parameter estimates. For instance, the use of visual counts or number of captures at a ringing station to assess indices of abundance may result in biased over-estimates due to the presence of transients. With the aim of contributing to understand transient dynamics within the Eurasian breeding passerines, we used data collected at a ringing station (2010–2018) in a reed bed area of northern Spain designed to sample breeding reed warblers Acrocephalus scirpaceus. Specifically, we tested for the effect of season on the proportion of transients and explored for correlations of rainfall regimens at both the winter and breeding quarters on annual fluctuations of the proportion of transients. The proportion of transients was not constant across the season; it showed relatively small values until mid-June, coinciding with arrivals from Africa and the peak of the breeding period, and then increased very steeply (means > 60%) already in July, with even ca. 90% of transients captured during the second half of July, coinciding with an influx of birds that would be already passing through the area en route to winter quarters in Africa. Analyses to estimate population trends of breeding reed warblers should take this circumstance into account; otherwise, models may show odd patterns, due to a mixture of local and non-local population that might show dissimilar demographic trends. Limiting data analyses to the breeding sub-period having a lesser amount of transients is recommended. Annual fluctuations in the proportion of transients did not correlate with any of the rainfall values in Africa (winter quarters) or meteorological conditions in Europe (NAO index; rainfall values at a local level), though it might be that we did not choose the appropriate variable/period/location combination. Our data set was relatively small; hence, this may hamper us to detect weak linear trends. Future research should contribute to answer this question and deep into the factors driving transience dynamics in bird populations.

Las cajas-nido constituyen una herramienta muy útil para el desarrollo de diversos estudios en aves, pues permiten el diseño experimental y la comparación de muestras sometidas a distintos tratamientos o localizaciones. Igualmente, son útiles para la conservación de aves en hábitats con muy poco arbolado maduro, como ocurre en muchos parques urbanos. Con el fin de impulsar la biodiversidad en el ámbito urbano, la Sociedad de Ciencias Aranzadi inició en 2018 el proyecto Hirilife, entre cuyas acciones estaba la colocación de cajas nido para aves paseriformes insectívoras en arbolado en calles, paseos y parques urbanos de la ciudad de San Sebastián. Este artículo se presenta con el fin de (1) determinar la tasa de ocupación de estas cajas-nido; y (2) explorar los factores que condicionan esta ocupación, con el fin de establecer, a futuro, una guía de buenas prácticas orientada a optimizar su colocación. A lo largo de la primavera de 2020 se revisaron 202 cajas en total, de las 220 que se habían colocado. Se ocuparon un total de 91 (45%). La tasa de ocupación, no obstante, varió significativamente entre zonas. Las cajas en las que se pudo determinar la especie fueron ocupadas por dos especies de páridos: el herrerillo común Cyanistes caeruleus y el carbonero común Parus major. Se observa una dominancia del carbonero común (31 versus 10 cajas; el resto se corresponde con las que no se pudo determinar la especie). Según los modelos las cajas son ocupadas con más probabilidad cuando se sitúan en entornos con una gran cantidad de hábitat natural. Abstract: Nest-boxes constitute a very useful tool in ornithological studies, since they allow the development of experimental designs and permit comparisons to be made between samples subjected to different treatments and locations. Moreover, they are also useful for bird conservation in habitats with low amounts of mature trees, as occurs in many urban parks. The ‘Hirilife’ project, developed by the Aranzadi Sciences Society, was launched in 2018 with the aim of promoting biodiversity in urban areas. This project included actions oriented to install and monitor nest-boxes for insectivorous passerine birds in the streets, promenades and parks of the city of San Sebastian. As a result, in this article we (1) describe the nest-box occupation rate, and (2) examine those factors that determine this rate, with the aim of drawing up a good practice guide to optimize the installation of new nestboxes in the future. During the spring of 2020, 202 nest-boxes were surveyed. Overall, 91 were occupied (45%). The occupation rate, however, varied substantially between zones. The nest-boxes were occupied by two species: the blue tit Cyanistes caeruleus and the great tit Parus major. The latter species was dominant (31 versus 10 nest-boxes). According to the model of nest-box, these were more likely to be occupied when they were situated in areas close to/surrounded by a high amount of natural habitat.

espanolEn este trabajo se desarrollo un protocolo de censo a gran escala para obtener datos actuales de las aves nocturnas y que sirva de base para futuros trabajos. El area de estudio, Euskadi, se dividio en cuadriculas UTM de 5x5 km de las que se escogieron 65 que representaban todos los tipos de vegetacion. Dentro de cada cuadricula se seleccionaron 8 Unidades de Censo (UCs), separadas entre si por una distancia minima de 1 km. En cada UC se llevo a cabo un protocolo de censo dividido en tres fases: 5 min de escucha de voces espontaneas, 5 min de reclamo de una sola especie y 5 min de escuchas en silencio, que se repitio mensualmente desde enero hasta julio de 2018. Solo se utilizo el reclamo de una especie por censo, de acuerdo con los picos anuales especificos de respuesta al reclamo, y unicamente para las estrigiformes. El carabo comun resulto ser la especie mas abundante y ampliamente distribuida de Euskadi, siguiendole bastante lejos la lechuza comun, el autillo europeo y el mochuelo europeo; mientras que el buho chico y el buho real fueron escasos y con una distribucion localizada, y el buho campestre y el mochuelo boreal resultaron ser especies raras. El chotacabras europeo aparecio en el 31,1% de las UCs, mientras que no se detectaron chotacabras cuellirrojos, ni alcaravanes comunes, y tan solo tres machos de chocha perdiz en el periodo reproductor. Finalmente, las codornices comunes fueron detectadas en el 3,8% de las UCs y solo en el censo de julio EnglishWe developed a large-scale survey protocol to secure current data on nocturnal birds as well as to obtain a reliable method for future surveys. We surveyed nocturnal birds in 65 5x5 km UTM squares that represented all the vegetation types of the Basque Country. We selected eight Survey Points (SPs) in each square, considering a minimum distance of 1 km between SPs. In each SP we developed a three-phase survey protocol for censusing nocturnal species: a 5-min wait for spontaneous voices, a 5-min broadcast of recorded vocalisations of only one species, and a 5-min wait in silence, which was repeated on a monthly basis from January to July 2018. According to the annual maximum peak of response to playback broadcasts in our study area, we broadcasted recorded vocalisations of only one owl species per survey period. The tawny owl was the most abundant and widely distributed owl species in the study area, followed a long way behind by the barn owl, Eurasian scops owl, and little owl, whereas the long-eared owl and eagle owl resulted scarce and patchily distributed, and the short-eared owl and boreal owl were rare species. European nightjars appeared in 31.1% of the SPs, whereas no records of red-necked nightjars and stone-curlews were obtained and only three woodcocks were detected during the breeding season. Common quails were detected in 3.8% of the SPs and only in July euskaraLan honetan azalera handiko guneetan burutzen diren zenbaketen protokolo bat garatu da, gaueko hegaztien datu berriak lortzeko eta etorkizuneko lanen oinarri izateko. Ikerketa area, Euskadi, 5 x 5 km-ko UTM lauki sareetan banatu zen, landaredi mota guztiak ordezkatzen zituzten 65 lauki sare aukeratu zirelarik. Lauki sare bakoitzean zortzi Zenbaketa Unitate (ZU) hautatu ziren, bata bestetik kilometro bateko tartearekin. ZU bakoitzean hiru fasetan banatutako zenbaketa protokoloa gauzatu zen: 5 min hegaztien kantuak entzunez, 5 min espezie apeua erabiliz eta 5 min isilean entzunez, protokoloa hilean behin gauzatu zen 2018ko urtarriletik uztailera bitarte. Zenbaketa bakoitzean apeua espezie bakar batentzat erabili zen, betiere apeuaren erantzun espezifikorako urteko momentu egokiena baliatuz, eta soilik estrigiformeentzat. Urubi arrunta izan da Euskadi mailan ugariena, bai kopuruan nahiz banaketa arean, alde handiz hurrenak hontz zuria, apo-hontz europarra eta mozolo europarra; aldiz, hontz ertaina eta hontz handia nahiko eskasak, eta banaketa area nahiko mugatua erakutsi dute, eta espezie urrienak landako hontza eta elurretako mozoloa. Zata europarra ZUetako % 31,5ean azaldu zen; aldiz, ez dira topatu zata lepogorria, ez eta atalar arrunta, eta ugaltze garaia izanda soilik hiru oilagor ar. Amaitzeko, galeper arrunta soilik ZUetatik %3,8an antzeman zen eta uztaileko zenbaketan baino ez.

We describe red kite Milvus milvus nesting habitat in Gipuzkoa (Basque Country, northern Spain), a region under high human pressure where the traditional countryside has been extensively substituted by Monterey pine Pinus radiata plantations. All nests were 10–30 m up in Monterey pine stands 20–40 m tall. Forest patches were mono-specific and most comprised from 100 to over 1,000 trees. Vegetation cover around the nests was typical of the region, with a mosaic of meadows and forests, including exotic tree timber plantations. The fact that the red kite in Gipuzkoa breeds in Monterey pine plantations does not mean that this habitat constitutes a priority for its long-term conservation. However, its replacement by native forest should entail a gradual substitution of the old pine stands to guarantee the availability of sufficient tall, mature trees offering good conditions for red kite nests.

The illegal hunting of wild birds is still today a major threat to the conservation of biodiversity on a global scale. This activity jeopardizes the survival of several migratory species. Our aims in this work were to (1) determine the spatial and temporal distribution of illegal hunting activities affecting bird species with regard to the location of fixed hunting posts in particular, and (2) identify the most affected species in Gipuzkoa (north of Spain), situated in a bottleneck area within one of the main routes of migration between Europe and Africa. All of our data came from birds with firearm injuries that were admitted to the Gipuzkoa Wildlife Rehabilitation Center (WRC). Over a period of 8 years (2006–2013), 421 birds belonging to 53 species were registered. The number of shot birds was found to be greater in more highly populated areas and during the months coinciding with hunting periods. Moreover, shot birds were recovered close to fixed hunting posts, suggesting that the illegal shooting of birds took place near or directly from these posts. Although the figures were not comparable to the high numbers of migrants shot annually in some other southern European areas, our results show that, even in small areas like Gipuzkoa, increased levels of protection are necessary.

Capsule The effects of playback use on number of captures, recaptures, fuel load, and age and sex ratios, and so potential bias in stopover studies in migrant Bluethroats was investigated. Playback promoted biases in the number of captures (although this was site-dependent) and fuel load. We strongly advise against the systematic use of playback to sample Bluethroats at constant effort sites or other type of ringing station, especially if studying fuel loads.

Fennoscandian alpine tundra habitats support large numbers of breeding waders, but relatively little is known about their breeding ecology despite the fact that this habitat is threatened by climate change. We studied habitat selection, diet and prey availability of European (Eurasian) Golden Plover Pluvialis apricaria chicks at the Vindelfjallen Nature Reserve, Ammarnas, Sweden. Information from 22 chicks tracked using radio-transmitters was analysed. By analysing 149 faecal samples, four main prey taxa were identified, Coleoptera (40%), Bibionidae (31%), Hymenoptera (13%) and Tipulidae (10%). We found that chicks switched from feeding on Tipulidae to feeding on Bibionidae as they grew, and that this switch coincided with a shift from the use of the habitat where Tipulidae were abundant (alpine meadow/heathland) to the use of the habitat were Bibionidae were abundant (Willow shrub). Although chicks track food availability to some extent, the link between prey availability and habitat use was not perfect, indicating that additional factors other than food abundance, such as shelter from predators, determine habitat selection. Bibionidae are an important prey for Golden Plover chicks as it is the only prey group that has a late summer flush in abundance, in contrast to the general decline of total arthropod biomass during the chick-rearing period. However, Bibionidae imagoes only occurred in 2011 and were virtually absent in 2013, which relates to the species' ecology with 2- to 5-year cycles in mass occurrence. Extreme annual variation in an essential food source such as Bibionidae imagoes might have an important effect on the condition and survival of Golden Plover chicks, an important subject for future studies. The foraging conditions for Golden Plover chicks in Fennoscandia appear to be different to those in the UK, where the chicks rely mainly on a Tipulidae flush only.

28 páginas, 3 tablas, 2 figuras., research on the stopover ecology of migrant birds has examined the role of multiple factors, both intrinsic and extrinsic, on departure decisions. however, a single factor may influence stopover decisions differentially, depending on the relative geographic location of a stopover site within the flyway and the expectation of ecological challenges ahead. For instance, actual fuel load may have a decisive influence on departure decisions before a crossing of major geographical barriers, such as seas or deserts, but may be less important when crossing vast continental areas offering plenty of opportunities to refuel. the aim here was to test whether the relative influence of fuel load on departure decisions of the Common reed-warbler Acrocephalus scirpaceus, a long-distance migrant songbird, varies in relation to proximity to a geographical barrier: the sea expanse between Iberia and Africa. we expected that departure from southern Iberian stopover sites would be highly influenced by fuel load, since migrants would not fly to Africa until they had sufficient fuel to cross the sea. we used Cormack- Jolly-Seber (CJS) models to test for the effect of fuel load on emigration (departure) probability from a number of stopover sites situated in northern and southern Iberia during the autumn migration period. reed-warblers stopping over for longer than one day were more likely to depart if they were in northern Iberia than in southern sites. Moreover, large fuel loads promoted emigration from stopover sites in northern, but not in southern, Iberia. therefore, we found no evidence supporting the hypothesis that reed-warblers wait until they acquire large fuel loads before leaving their stopover sites near the edge of the barrier. this study shows that the same parameters may not act in the same way along migration route, in particular in relation to geographical barrier proximity, this research was funded by the Spanish Ministry of Education (pre-doctoral fellowship to MA),Spanish Ministry of Science and Innovation (project CGL2010-21933-C02-02; to EB), Basque Government and Gipuzkoa Administration.

The structure of a species assemblage at given sites constitutes a key ecological parameter to understand the dynamics of bird assemblages. The aim of this paper is to (1) quantify how variable is a passerine assemblage associated with an inter-tidal reedbed area at a main stopover site in the Atlantic flyway in northern Iberia and to explore potential factors explaining the variation, with emphasis on the vegetation productivity, and (2) to test whether inter-annual fluctuations reflect possible demographic trends. Migratory birds, especially those species which show high flexibility to stop over in some places or others using an opportunistic strategy, should be expected to land in larger numbers and stay for longer periods at given stopover sites in years with higher vegetation productivity, thus with a higher amount of insect prey, since this would permit achieving higher fuel deposition rates. We used ringing data collected at Txingudi marshlands during the autumn migration of 2007–2016. The assemblage had a relatively simple structure, because few species dominated in number over the rest. Reed Warblers Acrocephalus scirpaceus dominated the assemblage in nine out of ten study years, supporting the importance of the site for the species. As compared with the other two most abundant passerines (the Sedge and Willow Warblers, A. schoenobaenus and Phylloscopus trochilus, respectively), the ratio between these three warblers varied from year to year, with the Willow Warblers having much higher annual fluctuations than the other two species. This is likely linked to an opportunistic exploitation of the reed bed by this species, but we did not find significant effect of vegetation productivity (quantified by Normalized Difference Vegetation Index, NDVI) on the structure and diversity of the bird assemblage. Annual fluctuations in species' contribution to the assemblage did not vary linearly, except for the Bluethroat Luscinia svecica. Only for Bluethroats the proportion of captures and the mean number of captures declined from year to year. The structure and diversity of the assemblage did not seem to be affected by local conditions hence factors working at larger spatial scales or at the origin region of the migrants captured at Txingudi apparently may be more relevant at explaining the structural traits of the assemblage.