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Variability in morphology and body size between populations of the same species is common and can be influenced by environmental conditions or differential migratory strategies. We focused on analysing body size differences between Yellow-legged gulls Larus michahellis from Mediterranean and Cantabrian-Atlantic Iberian colonies as previous studies have suggested that Cantabrian-Atlantic gulls are smaller than Mediterranean gulls. However, those analyses were based on small sample sizes or did not account for sexual dimorphism. Here we analyse an extensive biometric data set (> 1,500 adult individuals), separating males and females, from nine different sites in each region. Our results reveal a 7% (median) difference both between regions and sexes, for most morphometric variables, with Mediterranean gulls having longer legs (tarsi) and heads (cranium-bill) and thicker bills (bill-depth). This inter-regional difference was even larger for body mass, Mediterranean gulls being 11% (males) and 20% (females) heavier than Cantabrian-Atlantic gulls. In particular, we found that individuals from the Mediterranean populations were allometrically longer-winged than their northern counterparts. We suggest, after discarding other factors, that this wing allometry may be related to the sedentariness of the Cantabrian-Atlantic gulls, compared with the partially migratory strategy of Mediterranean gulls. We also suggest that the larger body size of Mediterranean gulls may help them compete better with resident gulls for food acquisition, once they coincide in the Cantabrian-Atlantic region. Finally, females from both populations were also found to be proportionately longer-winged than males. We hypothesise that this difference could allow smaller females to travel longer distances locally in search of food or to make use of different habitat types, avoiding foraging competition with the larger males.—Marcos Pacheco, M.L., Tavecchia, G., Igual, J.M., Alonso-Álvarez, C., Arizaga, J., Galarza, A., Oro, D. & Martínez-Abraín, A. (2023). Yellow-legged Gulls from the Mediterranean are not only larger but also allometrically longer-winged than those from the Cantabrian-Atlantic. Ardeola, 70: 225-240. La variabilidad en la morfología y el tamaño del cuerpo es común entre poblaciones de la misma especie y puede verse influenciada por las condiciones ambientales o por estrategias migratorias diferenciales. En este trabajo nos centramos en analizar las diferencias de tamaño corporal entre las gaviotas patiamarillas Larus michahellis del Mediterráneo y de las colonias ibéricas cántabro-atlánticas, ya que estudios previos sugirieron un tamaño más pequeño de las gaviotas del Cantábrico/Atlántico en comparación con las gaviotas mediterráneas. Sin embargo, esos análisis se realizaron empleando tamaños de muestra pequeños o no tuvieron en cuenta el gran dimorfismo sexual de la especie. Aquí, analizamos un extenso conjunto de datos biométricos (> 1,500 individuos adultos), separando machos y hembras, de nueve sitios diferentes en cada una de las dos regiones. Nuestros resultados revelaron una diferencia del 7% (mediana) tanto entre regiones como entre sexos, para la mayoría de las variables morfométricas, teniendo las gaviotas mediterráneas patas (tarsos) y cabezas (cráneo-pico) más largos y picos (altura de pico) más gruesos. Esta diferencia entre regiones fue aún mayor en el peso, siendo las gaviotas mediterráneas un 11% (machos) y un 20% (hembras) más pesadas que las gaviotas cántabro-atlánticas. Es importante destacar que los individuos de las poblaciones mediterráneas tuvieron alas alométricamente más largas que sus contrapartes del norte. Sugerimos que esta alometría alar puede estar relacionada con el sedentarismo de las gaviotas cantábrico-atlánticas, frente a la estrategia parcialmente migratoria de las gaviotas mediterráneas, tras descartar otros factores. También sugerimos que el mayor tamaño corporal de las gaviotas mediterráneas podría ayudarles a competir mejor con las gaviotas residentes por la adquisición de alimento, una vez coinciden en la región cántabro-atlántica. Finalmente, también se encontró que las hembras de ambas poblaciones tuvieron alas proporcionalmente más largas que los machos. Proponemos que esa diferencia podría permitir que las hembras (más pequeñas) viajen distancias más largas a nivel local en busca de alimento o hagan uso de diferentes tipos de hábitat, evitando la competencia de forrajeo con los machos más grandes.—Marcos Pacheco, M.L., Tavecchia, G., Igual, J.M., Alonso-Álvarez, C., Arizaga, J., Galarza, A., Oro, D. y Martínez-Abraín, A. (2023). Las gaviotas patiamarillas del Mediterráneo no sólo son más grandes que las cántabro-atlánticas sino que además tienen alas alométricamente más largas. Ardeola, 70: 225-240. [ABSTRACT FROM AUTHOR]

Wildlife conservation policies directed at common and widespread, but declining, species are difficult to design and implement effectively, as multiple environmental changes are likely to contribute to population declines. Conservation actions ultimately aim to influence demographic rates, but targeting actions towards feasible improvements in these is challenging in widespread species with ranges that encompass a wide range of environmental conditions. Across Europe, sharp declines in the abundance of migratory landbirds have driven international calls for action, but actions that could feasibly contribute to population recovery have yet to be identified. Targeted actions to improve conditions on poor-quality sites could be an effective approach, but only if local conditions consistently influence local demography and hence population trends. Using long-term measures of abundance and demography of breeding birds at survey sites across Europe, we show that co-occurring species with differing migration behaviours have similar directions of local population trends and magnitudes of productivity, but not survival rates. Targeted actions to boost local productivity within Europe, alongside large-scale (non-targeted) environmental protection across non-breeding ranges, could therefore help address the urgent need to halt migrant landbird declines. Such demographic routes to recovery are likely to be increasingly needed to address global wildlife declines. [ABSTRACT FROM AUTHOR]

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The article that first evidence of nocturnal flight overland was provided by satellite telemetry Osprey. Topics include an osprey reintroduction program was initiated at Urdaibai Biosphere Reserve for interconnecting small breeding population; use of raptors for avoiding associated risks such as starvation, dehydration, and disorientation; and collection of ospreys under license of the Scottish Natural Heritage.

The article discusses research on the dynamics and structure of the wintering population of reed bunting Emberiza schoeniclus in northern Iberia. The reed bunting is described as a common Palearctic songbird that tends to select Iberia as one of its main wintering grounds. It is noted that male reed buntings are expected to be more abundant during mid-winter because they prefer to remain close to breeding areas during the winter season. Details concerning sampling site selection, bird subject collection, and wing length recording are reported. It is also mentioned that flight-associated morphology tend to vary seasonally and between bird age classes and sexes.

The article discusses the findings of a study to determine whether or not Aquatic Warblers have the tendency to stop at suboptimal locations during poor weather. It notes that the research was conducted in the Jaizubia and Txingudi marshlands of northern Iberia where vegetation consisted mostly of reed beds. The results confirm that Aquatic Warblers are forced to land in Jaizubia's small habitats under rainy conditions, while optimal locations prove useful to them regardless of weather. The article mentions that Aquatic Warblers are endangered due to the loss of habitat.

The article provides information on a study which analyzed the potential variation in stopover behavior between dominant and subordinate individuals of the Northern Wheatear Oenanthe oenanthe, a territorial migrant bird species, at an offshore stopover area on the island of Helgoland, Germany. It also highlights the two strategies which subordinate birds could adopt in relation to their stopover duration. During their entire stopover in Helgoland, the behavior, individual features, and spatial distribution between subordinate and dominant Wheatears were compared. The researchers found that birds initiating an aggressive encounter were more likely to win.

The article presents a study on fuel load and potential flight ranges for common passerines that stopover at Txingudi marshlands in the western edge of the Pyrenees. The researchers used mist nets to capture the birds, which were ringed, aged and measured for subcutaneous fat scores, flight muscle and body mass. They also used the analysis of variance (ANOVA) to test whether fuel load differed between periods and species with different migration distances. They found that fuel load and flight ranges tended to be longer in autumn compared to spring.

The article focuses on a study which examined the migration strategy, specifically stopover duration and fuel load, of bluethroats Luscina svecica cyanecula in northern Iberia during the autumn migration period. Data were obtained in the reed bed Phragmites australis that surrounds the Badina de Escudera lagoon near Villafranca, Spain. Stopover duration was calculated by means of minimum stopover duration and Cormack-Jolly-Seber models. Findings reveal that the stopover duration was nearly 30 days and that adults were more fuel loaded than juveniles. The article notes that the results suggest that birds with long stopovers were not true fuelling migrants but wintering birds with balanced energy budgets.

The article focuses on the study which examines the migration strategies of goldfinches Carduelis carduelis as they pass through the western edge of Pyrenees. The study considered the species' time-associated variations in age and sex ratios and morphology. It was carried out through systematic sampling sessions during a specific period. After data analysis, it was revealed that spring migrants showed a shorter wing and tail and were more fuel loaded than birds from autumn and winter. Adults also tended to pass later than juveniles during the autumn season.

The article focuses on one study which examines the effect of haemosporidians on fuel deposition rate and fuel load in a population of population of migratory blackcaps Sylvia atricapilla in Loza lagoon, northern Iberia. Fuel deposition rate is defined as method that determines bird migration strategies. Blood samples were taken from recaptured birds and were analyzed to determine haemospiridian content. The results revealed that these birds' mass deposition rate, fat score and body mass remain the same if compared with non-infected birds. They suggested that infected birds are unable to migrate south from their breeding areas in central and northern Europe.