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Does the Aquatic Warbler Acrocephalus paludicola show differential migration by age during the autumn in the Iberian Peninsula?
Abstract
The Aquatic Warbler Acrocephalus paludicola is a globally threatened European migratory songbird that passes through the Iberian Penninsula during its migration from Western Europe to Africa. The aim of our study was to determine the spatial migratory pattern of the species according to age classes during the post-nuptial passage in the Iberian Peninsula by analysing ringing data. The results confirm the existence of differential migration by age according to a longitudinal geographical gradient and suggest that the more westerly the wetlands, the smaller the proportion of juveniles that use them. Our findings also highlight the existence of a very broad migratory front. These results have implications for the conservation of different areas of migratory passage.
Zusammenfassung
Zeigen Seggenrohrsänger Acrocephalus paludicola im Herbst auf der Iberischen Halbinsel eine altersspezifische Differenzierung des Zugverhaltens? Der Seggenrohrsänger Acrocephalus paludicola ist eine weltweit bedrohte europäische Singvogelart, die durch Westeuropa und Afrika zieht. Unser Ziel war es, durch die Auswertung von Beringungsdaten das räumliche Zugmuster der Art während des nachbrutzeitlichen Durchzugs auf der Iberischen Halbinsel nach Altersklassen zu beschreiben. Die Ergebnisse bestätigten das Auftreten altersspezifischer Unterschiede im Zugverhalten entlang eines longitudinalen geografischen Gradienten und deuten darauf hin, dass weiter westlich gelegene Feuchtgebiete in geringerem Maße durch Jungvögel genutzt werden. Dies unterstreicht außerdem das Vorhandensein einer sehr breiten Zugfront. Diese Ergebnisse haben Konsequenzen für den Schutz verschiedener Bereiche des Zugweges.
... Los porcentajes de clases de edad en el paso postnupcial del Brazo de La Torre indican porcentajes de juveniles muy bajos (bajos en el caso del conjunto de Andalucía), que son aún más bajos a los registrados en otras estaciones de anillamiento de la zona occidental ibérica (Miguélez et al. 2014). La escasez de juveniles respecto a otras estaciones del norte de España puede sugerir desde que experimenten tasas de supervivencia más bajas, hasta que estos usen preferentemente otra ruta para alcanzar el norte de África, o bien la posibilidad de que jóvenes y adultos tengan diferentes estrategias migratorias en cuanto a número de paradas, lugares de engorde y distancias de vuelo. ...
... La escasez de juveniles respecto a otras estaciones del norte de España puede sugerir desde que experimenten tasas de supervivencia más bajas, hasta que estos usen preferentemente otra ruta para alcanzar el norte de África, o bien la posibilidad de que jóvenes y adultos tengan diferentes estrategias migratorias en cuanto a número de paradas, lugares de engorde y distancias de vuelo. No obstante, las causas para explicar este patrón aún no están claras, a pesar de plantearse varias hipótesis al respecto en Portugal, Francia y España (Neto et al. 2010, Arizaga et al. 2014, Miguélez 2014. ...
El carricerín cejudo es una especie migrante transahariana, está globalmente amenazada y utiliza hábitats especialmente vulnerables como son los humedales. Por tanto, el conocimiento de la distribución y el hábitat que ocupa es clave para el desarrollo de medidas de conservación adecuadas, que incluyan los lugares de reposo y sedimentación durante sus desplazamientos migratorios por el sur de la Península Ibérica. Entre estos lugares se encuentran los humedales andaluces del litoral atlántico y mediterráneo, que tienen un número de citas elevado respecto al resto del interior de la mitad sur peninsular, incluido el propio valle del Guadalquivir. Se ha realizado una intensa recopilación bibliográfica que ha permitido contabilizar un total de 80 individuos de carricerín cejudo, repartidos en 16 humedales. Destacan por el número de aves registradas las marismas de Doñana, con campañas de seguimiento específico durante 10 años en el Brazo de la Torre (Espacio Natural de Doñana), y en menor medida, el entorno de la desembocadura del río Guadalhorce. Aunque se trata de un migrante regular en este territorio, es escaso y un mayor esfuerzo de seguimiento específico podría determinar mejor el papel que desempeñan los humedales andaluces como escalas durante las migraciones de esta especie, especialmente durante el menos conocido paso prenupcial
Abstract:
The Aquatic Warbler is a Trans-Saharan migrant species, it is globally
threatened and uses especially vulnerable habitats such as wetlands.
Therefore, knowledge about the distribution and habitat it occupies
are key for the development of adequate conservation measures,
including resting and stopover places during its migratory movements
through the south of the Iberian Peninsula. Among these places are
the Andalusian wetlands of the Atlantic and Mediterranean coasts,
which have a high number of records compared to the interior of
southern Iberia, including the Guadalquivir valley. An intense
bibliographic compilation has been carried out that has allowed us
to count a total of 80 individuals of Aquatic Warbler, distributed in
16 wetlands. The Doñana marshes stand out for their number of
registered birds, with specific monitoring campaigns for 10 years in
the Brazo de la Torre (Natural Space of Doñana), and to a lesser
extent, the mouth of the Guadalhorce River. Although it is a regular
migrant in this territory, it is scarce and a greater specific monitoring
effort could better determine the role that Andalusian wetlands play
as stopovers during the migrations of this species, especially during
the less well-known prenuptial passage.
... In this study, we aim to determine levels of mercury contamination in the aquatic warbler (Acrocephalus paludicola), based on feathers sampled from individuals captured along their migration flyway in late summer (autumn migration). The aquatic warbler is a small bird of particular conservation status, being the only globally threatened passerine species to breed in continental Europe (Salewski et al. 2013;Miguélez et al. 2014). Its population size and range have declined bỹ 90% over the last century, mainly due to habitat loss (Julliard et al. 2006;Flade and Lachmann 2008). ...
... Since the aquatic warbler is a long-distance migrant, breeding in continental Europe and wintering in sub-Saharan west Africa (Julliard et al. 2006;Newton 2008;Jiguet et al. 2011;Salewski et al. 2013;Miguélez et al. 2014), it may be exposed to pollution across a large geographical area. Molt occurs once annually on the wintering grounds in Africa. ...
Mercury (Hg) contamination is considered a global concern for humans and wildlife, and although the number of studies dealing with that issue continues to increase, some taxonomic groups such as small passerine birds are largely understudied. In this paper, concentration of mercury in the aquatic warbler (Acrocephalus paludicola) feathers, a globally threatened passerine species, was examined. The concentration differences between two ages and sexes were investigated. The comparison of feathers taken on autumn migrants of two age categories act as a comparison of the species’ exposure within the two different areas (European breeding or African wintering grounds). The average Hg concentration for all sampled individuals [2.32 μg/g dw (range 0.38–12.76)] is relatively high, compared with values found in other passerine species. An age difference was found, with first-year individuals displaying higher mercury concentrations than adults. This indicates that birds are exposed to mercury pollution during the breeding season, i.e., in the continental floodplains of eastern Europe. The average Hg concentration in feathers grown on the breeding grounds was 3.88 ± 2.59 μg/g dw, closer to the critical value of 5 μg/g dw, which is considered to impair the health of individuals. The findings suggest that mercury pollution may constitute a threat so far neglected for the endangered aquatic warbler.
... During the breeding seasons 2020 and 2021, following rather dry winters in the Sahel region, the return rates of Aquatic Warblers were lower. Timing and routes of migration differ between adult and first-year Aquatic Warblers (Miguélez et al. 2014;Wojczulanis-Jakubas et al. 2017). Therefore, varying habitat suitability at different stopover sites may influence age-dependent survival. ...
Translocations are a conservation measure that is increasingly applied to assist the recovery of animal populations threatened with extinction. Long‐distance migrating passerines, however, have been rarely addressed in translocation projects so far. One such species is the globally threatened Aquatic Warbler Acrocephalus paludicola, a habitat specialist breeding in fen mires in Central Europe and wintering in sub‐Saharan Africa. The global breeding population has severely declined during the last decades due to habitat loss. Although the implementation of conservation measures has stopped the decline in the core breeding area, peripheral populations continue to decline. The aim of this pilot study was to reveal whether translocated Aquatic Warblers will return to a distant release site after wintering in Africa. Our translocation method is based on natal habitat imprinting of juvenile passerines before their first migration. In 2018 and 2019, 50 chicks (10–12 entire broods) each year were translocated 526 km from Belarus to Lithuania at an age of about 7 days and hand‐reared with predominantly wild insects captured in the surroundings of the release site. The survival rate of chicks until soft release from outdoor aviaries was 98% (49 fledglings released) in 2018 and 100% (50 fledglings released) in 2019. In 2019, 11 Aquatic Warblers (9 males, 2 females) were resighted at the release site after returning from wintering grounds. In 2020, nine birds (6 males, 3 females) were observed, including three males from the 2018 release cohort. An average apparent first‐year survival of 0.30 was estimated. The very successful outcome gives new impetus for the restoration prospects of declined populations of the Aquatic Warbler to halt extinction at the margins of the breeding range.
... Desde los pioneros trabajos de Bernis [4][5][6][7] han aparecido numerosas publicaciones que, basadas en el anillamiento, han ayudado a esclarecer las rutas, fenología y velocidades de paso de diversas especies, entre otras algunas anátidas [8] , limícolas [9] y varios grupos de paseriformes como túrdidos [10][11][12] , sílvidos [13][14][15][16] , fringílidos [17,18] , emberícidos [19] o motacílidos [20] . En otras ocasiones, los datos de anillamientos y recupera-ciones se han utilizado para validar patrones de distribución geográfica y la relación de tales patrones con las principales rutas migratorias [21][22][23][24][25] o esclarecer la segregación geográfica por edades, sexos o poblaciones [26][27][28][29][30] . ...
... We calculated two types of flight ranges (Appendix 1): 1) mean ranges -based on mean body mass of adults and immatures per stop over site available in literature; for stop-over sites in France, Spain and Portugal, we used published data on body mass for individuals captured at stop-over sites (Miguélez et al. 2009, Neto et al. 2010, Arizaga et al. 2011a, Unanue et al. 2012, 2013; we calculated potential ranges of non-refuelling flights separately for all studied stop-over sites in France and for four sites in Spain based on mean body mass values reported for those sites (Miguélez et al. 2009, Arizaga et al. 2011a; as data from France were provided for two years (Le ), we calculated weighted mean body mass using the number of captured birds in the year as the weight; for all seven sites in Portugal we calculated potential non-refuelling flight ranges based on relative fuel loading values combined for all those sites provided by Neto et al. (2010); for 13 stopover sites in Spain without data on body mass of captured birds (Atienza et al. 2001, Miguélez et al. 2014, we calculated the weighted mean using data from the aforementioned four sites in Spain with reported body mass, with the number of captured birds as the weight; 2) maximal ranges -based on maximal body mass values representing departure fuel reserves; maximal fuel load values were available only for immatures and adults captured at stop-over sites in Portugal and France based on Neto et al. (2010) and Le Nevé et al. (2011); we were not able to calculate maximal range of flights for Spanish stop-over sites as authors of source papers (Miguélez et al. 2009, Arizaga et al. 2011a, Unanue et al. 2012, 2013 provided neither minimal nor maximal body mass. ...
Knowledge about migration strategy and availability of stop-over sites of globally threatened migratory birds is crucial for the implementation of efficient conservation plan. In this study, we investigated the refuelling strategy of the globally threatened Aquatic Warbler Acrocephalus paludicola at stop-over sites during the autumn migration in West Europe and Africa (40 and 72 sites, respectively, documented in published works about stop-over ecology and sites). Based on fuel reserves of captured birds we calculated potential maximal range of non-refuelling flight from stop-over sites located on the Atlantic flyway migration route. We tried to verify the hypothesis that Aquatic Warblers are able to cross the Sahara during one non-stop flight. We found that mean range of flights was affected significantly by the stopover geographic location but not by age of the birds and stop-over habitat. Individuals staging in France are able to cover smaller distances (mean 612.7 km) compared to individuals staging in Portugal and Spain (mean 857.5 km), i.e. closer to two important geographical barriers (the Gibraltar Strait and the Sahara desert). However, maximal ranges of the heaviest individuals were longer (2370 km in France and 1998 km in Portugal). Our study suggests that Aquatic Warblers are generally not able to cross the Sahara during one non-stop flight. Only some individuals with high fat loads starting from stop-overs in Portugal may be able to cross the Sahara without refuelling. However, due to diel air temperature pattern in the desert they need to stop at least once to rest and wait for nighttime drop in temperature to continue migration. Within the Sahara there are many small patches of suitable habitats which can facilitate resting and maybe even refuelling. Observed and predicted reduction of available area of stop-over habitats may have serious negative consequences for population dynamics of many land-bird species, including the globally threatened Aquatic Warbler.
... El paso central en abril está adelantado aproximadamente una semana respecto a los registrados en la costa mediterránea de Francia (Communier et al., 2013; y a los registrados en la República Checa (Flousek & Cepák, 2013). El 77 % de las capturas en paso postnupcial fueron juveniles, dato similar a los porcentajes de edades registrados en otras áreas de la mitad E peninsular donde los adultos son más escasos (Miguélez et al., 2014). ...
The Aquatic Warbler is a trans-Saharan migrant species, it is globally threatened, and uses particularly vulnerable habitats such as wetlands. Therefore, understanding about the distribution and habitat preference are key for the development of adequate conservation measures, including resting and stopover sites during its migratory movements along the Iberian-Mediterranean coast. The marshes of the Comunitat Valenciana are among these places, a region where there are no studies that treat all these aspects.
All the records of Aquatic Warblers were compiled, with a total of 139 individuals detected in 16 wetlands. The marshes of marjal dels Moros and Albufera de Valencia stand out for their number of observations.
Historical records, as well as specific ringing campaigns, confirm a regular passage through the Comunitat Valenciana, and the major significance of the Mediterranean coastal wetlands for the migration of the Aquatic Warbler, especially during the prebreeding passage.
Provided data also improves our knowledge of the distribution, biometrics, stopover parameters, habitat preference and migratory strategies of the Aquatic Warbler, all of which are very little known aspects of the spring migration at a world scale.
En este informe se ofrece información sobre 162 especies que se reparten por toda la geografía nacional. Entre ellas, se incluyen 20 especies que aparecen de forma escasa para las que se muestra su distribución espacio-temporal mediante mapas y gráficas (De Juana y Garcia, 2015; Gil-Velasco et al., 2018; Rouco et al., 2018). Para dar un tratamiento más acorde con su patrón natural de presencia preferentemente invernal se expone la información de estas 20 especies para el periodo julio 2018-junio 2019. Debe tenerse en cuenta que en el Noticiario de Ardeola 66 (2) ya se consideraron los seis últimos meses de 2018, de modo que podría haber alguna información repetida en el presente informe (véanse Molina et al., 2017, 2018 y 2019a y 2019b). Se sigue la secuencia taxonómica de acuerdo con la nueva Lista patrón de las aves de España (Rouco et al., 2019).
Stopover sites are of vital importance for migrating birds, especially long-distance migrant species. This study describes a wetland in NW Spain, as a particular habitat used by the Aquatic Warbler, one of the most threatened passeriformes in Europe, during postnuptial migration. It is a recently abandoned gravel-pit with an artificial water regime, a large area of standing water and a mosaic of vegetation predominated by a rush-meadow of Juncus effusus and a cattail community of Typha domingensis, a priori very favourable conditions for the Aquatic Warbler. The Acrola index value for this locality is very high, and together with some of the results including mean stopover period, fattening rate, interannual site fidelity and calculated potential flight distances, indicates that the mosaic of plant communities offers good conditions as a refuelling site for the Aquatic Warbler. Nevertheless, in only 3 years a process of homogenization has been observed in the vegetation, where rushmeadow cover has decreased noticeably and cattail and willow cover have increased. This process caused a decrease in the Acrola index throughout 2008–2010, as well as a significant decrease in the importance of this wetland with regard to others in Spain. Significant differences were found in body condition between the two age groups: adults are heavier and obtain more body fat, which provides them with greater potential flight autonomy. Although gravel pits can act as alternative wetlands, rapid changes in plant communities succession requires more active management than in the case of natural wetlands.
Analyses a large number of records for Western Europe of Acrocephalus paludicola in an attempt to clarify its migrational habits. Data suggest a ∞-shaped spring migration and a "single-hop' long distance autumn migration from the breeding to the wintering areas. -M.Dean
The Aquatic Warbler Acrocephalus paludicola in Txingudi (N Spain): notes on certain features of the autumn migration period The aim of this paper is to analyze the migratory behaviour of the Aquatic Warbler in Txingudi (N Spain). We considered data obtained over a period of three years (2007–2009) from daily ringing during post-nuptial passage. We captured a total of 29 birds in the months of August (24) and September (5), thus obtaining an Acrola index of 0.924% (percentage of Aquatic Warblers out of the total number of Acrocephalus sps. trapped). This rate is lower than in NW France (> 1 to 3.5%), one of the main areas for fat replenishment and rest on this species' migratory route, similar to that found in SW France (0.8%), but higher than the average for Portugal (0.14%). Altogether, 76% of the captured birds were juveniles. Body mass and fat loads were lower than the values recorded in NW Spain (mouth of the river Miño), but similar to other nearby areas in N Spain (Salburua). In one year four birds were recaptured, giving an estimated average stopover time of 5 days and body mass gain rate of 0.1 g / day (excluding a bird that lost 1 g in a single day). Thus, despite its suboptimal habitats, the length of stay and the body mass gain of Aquatic Warblers in Txingudi did not differ greatly from other wetlands such as La Nava in Palencia, where optimal habitats exist. Txingudi, therefore, would seem to be relevant as a stopover and fat replenishment site for the Aquatic Warbler in the Iberian Peninsula.
The globally-threatened Aquatic Warbler (Acrocephalus paludicola) breeds in Europe and spends the northern winter in sub-Saharan West Africa. We attached 30 geolocators to breeding birds in the central Ukraine in 2010. Three geolocators which collected data from the autumn migration were recovered in 2011. They revealed a previously-unknown migration route via southern Europe to stopover sites in south-western France and Spain. In West Africa, one bird spent some time well south of known non-breeding areas. For the conservation of some Aquatic Warbler populations, protection of hitherto unknown stopover sites in southern Europe and Africa may be crucial.
We show that the low number of aquatic warblers Acrocephalus paludicola ringed in Portugal is explained by the low ringing effort, and that Portugal is an important country for its migration. Most of the seven sites where the species was detected are recognized for their biological importance and protected. There seemed to be a decline in the number of birds caught, particularly of juveniles, which might be associated with a decline in breeding success. All aquatic warblers were captured in August and September, showing a peak at the end of August, and adults migrated significantly earlier than juveniles. Both age classes significantly increased in body condition during the season. The potential non-stop flight range varied substantially between individuals: some birds would be able to migrate to the wintering quarters without refueling, but the low flight range of many individuals suggests that some fueling takes place in Portugal.
The autumn world population of the endangered Aquatic Warbler Acrocephalus paludicola probably numbers between 23 000 and 69 000 individuals, including 5 000 to 44 000 first-year individuals, depending on variation in breed-ing success and post-fledging survival. After breeding, the species migrates as early as August along a westerly route along French coast to reach its African wintering grounds. In 2009, French ringers have carried out targeted mist-net-ting to enhance the capture of the species, using tape luring in suitable habitats. Overall, 874 different individuals were captured in France in that year. In 2010 similar ringing effort allowed the capture of 646 different individuals. From this ringing information, we propose a simple method to estimate the number of individuals which stopped in the country during the autumn migration, considering all birds or first-years only. Splitting the country in two parts (northern and southern), the method uses the total number of captures and the number of southern recaptures of birds first ringed in the north. Overall, we estimated that between 24 000 and 30 000 individuals — most of them in their first calendar year — stop in France each year during the fall migration. These estimates suggest that probably all first-year Aquatic Warblers migrate by this western flyway and stop in France to refuel, while adults may partly use a different flyway or may stop in France, but for shorter times or at fewer sites. The proposed figures highlight the importance of maintain-ing suitable refuelling habitats for the species all along coastal France.
We have studied the migration routes and phenology of the Aquatic Warbler Acrocephalus paludicola throughout Spain by means of ringing and published observation data. The species' migration routes between breeding and winter quarters, both in spring and autumn, regularly take place through Spain. In the present study, two main coastal routes are described: the Atlantic and the Mediterranean. A third one, along the Ebro valley, seems to link the other two. Prenuptial passage, more easterly on average, takes place from early March to late April, though 87% of the records are from April. Postnuptial passage takes place from early August to late October, though 85% of the records are concentrated between 11 August and 29 September. In Spain, the species seems to use a low number of localities as stopover migration sites. We propose the adoption of effective protection measures for those areas that currently lack them. We also suggest the change of the species' conservation status in the National Endangered Species Catalogue.
The Aquatic Warbler Acrocephalus paludicola (AW) is the only globally threatened passerine species of continental Europe. The global population decreased by>90% during
the 20th century. AWs breed in Palaearctic fen mires and sedge meadows and spend the non-breeding season in sub-Saharan Africa,
but until 2007 no regular wintering site had been identified. To date, the only wintering grounds that have been discovered
are in river floodplain marshes along the Senegal River in the Djoudj area, Senegal. Searches for additional wintering sites
in south-western Mauritania, northern Senegal and Gambia have been unsuccessful. In Djoudj, AWs are found in extensive marshes
dominated by Scirpus spp. or Sporobolus robustus, and favour shallow water and the occurrence of Eleocharis mutata and Sporobolus robustus on the microhabitat scale. Within these marshes, however, AW appear to avoid dense homogenous stands dominated by Scirpus maritimus. Estimates of the density of wintering AWs in suitable habitats range between 0.5 and 1.6 birds/ha. According to the estimated
area of suitable habitat (4,000–10,000ha with strong seasonal and inter-annual fluctuations), the Djoudj area may hold between
10 and>50% of the global population during the non-breeding season. Ringing, molecular studies and feather isotope ratios
have failed to provide conclusive evidence for connectivity between the Djoudj area and particular Palaearctic breeding populations.
Based on winter records, habitat data and satellite images, we speculate that the Inner Niger Delta in Mali could be another
important wintering area. A pilot project that equipped 30 AWs in the Ukraine with geolocators in 2010 may reveal more details
about migration routes and lead to the discovery of currently unknown wintering sites.
KeywordsLong-distance migrants–Wintering grounds–Moulting sites–Senegal–Connectivity–Globally threatened species
During migration, birds must fly over suboptimal habitats differing from those selected during breeding and wintering. Nocturnally
migrating passerines need to assess the suitability of potential stopover habitats during landfall. Before actual landfall,
distant cues may play a significant role in habitat selection. In this paper, we studied the possibility that migrant songbirds
use acoustic information as distant cues for habitat selection when ceasing flight. We also investigated differences between
habitat generalists and specialists in their use of acoustic cues by comparing the proportion of species killed at lighthouses
with those captured in mist nets using song playback in both suitable habitats and suboptimal stopover habitats during spring
and fall migratory seasons. Our observations showed that during twilight landfall, birds may respond to acoustic cues, especially
when visual cues are reduced or absent. This was true for habitat specialists (Eurasian reed warblers and sedge warblers)
whose songs are also more attractive to conspecifics and other birds of wetland habitats than to habitat generalists (pied
flycatchers and redwings). Adult Eurasian reed warblers had a tendency to be more attracted by acoustic cues than juveniles.
This finding suggests that previous experience may play a role in habitat recognition using acoustic stimuli.
Understanding the links between breeding and wintering areas of migratory species has important ecological and conservation implications. Recently, stable isotope technology has been used to further our understanding. Stable isotope ratios vary geographically with a range of biogeochemical factors and isotope profiles in organisms reflect those in their food and environment. For inert tissues like feathers, isotope profiles reflect the environment in which they were formed. Following large-scale habitat destruction, the globally threatened aquatic warbler Acrocephalus paludicola has a fragmented breeding population across central Europe, largely in Belarus, Poland and Ukraine. The species' sub-Saharan African wintering grounds have not yet been discovered, and this significantly hampers conservation efforts. Aquatic warblers grow their flight feathers on their wintering grounds, and we analysed stable isotope ratios (delta(15)N, delta(13)C, delta D) in rectrices of adults from six main breeding sites (subpopulations) across Europe to determine whether different breeding subpopulations formed a single mixed population on the wintering grounds. delta(15)N varies considerably with dietary trophic level and environmental factors, and delta D with the delta D in rainfall; neither varied between aquatic warbler subpopulations. Uniform feather delta(15)N signatures suggest no major variation in dietary trophic level during feather formation. High variance and inter-annual differences in mean delta D values hinder interpretation of these data. Significant differences in mean delta(13)C ratios existed between subpopulations. We discuss possible interpretations of this result, and consider differences in moulting latitude of different subpopulations to be the most parsimonious. delta(13)C in plants and animals decreases with latitude, along a steep gradient in sub-Saharan Africa. Birds from the most northwesterly breeding subpopulation (Karsibor, Poland) had significantly lower variance in delta(13)C and delta(15)N than birds from all other sites, suggesting either that birds from Karsibor are less geographically dispersed during moult, or moult in an area with less isotopic heterogeneity. Mean delta(13)C signatures from winter-grown feathers of different subpopulations were positively correlated with the latitude and longitude of breeding sites, suggesting a strong relationship between European breeding and African winter moulting latitudes. The use of stable isotopes provides novel insights into migratory connectivity and migration patterns in this little-known threatened species.
The aim of this paper is to analyze the migratory behaviour of the Aquatic Warbler in Txingudi (N Spain). We considered data obtained over a period of three years (2007-2009) from daily ringing during post-nuptial passage. We captured a total of 29 birds in the months of August (24) and September (5), thus obtaining an Acrola index of 0.924% (percentage of Aquatic Warblers out of the total number of Acrocephalus sps. trapped). This rate is lower than in NW France (> 1 to 3.5%), one of the main areas for fat replenishment and rest on this species' migratory route, similar to that found in SW France (0.8%), but higher than the average for Portugal (0.14%). Altogether, 76% of the captured birds were juveniles. Body mass and fat loads were lower than the values recorded in NW Spain (mouth of the river Miño), but similar to other nearby areas in N Spain (Salburua). In one year four birds were recaptured, giving an estimated average stopover time of 5 days and body mass gain rate of 0.1 g/day (excluding a bird that lost 1 g in a single day). Thus, despite its suboptimal habitats, the length of stay and the body mass gain of Aquatic Warblers in Txingudi did not differ greatly from other wetlands such as La Nava in Palencia, where optimal habitats exist. Txingudi, therefore, would seem to be relevant as a stopover and fat replenishment site for the Aquatic Warbler in the Iberian Peninsula.
This book presents an up-to-date, detailed and thorough review of the most fascinating ecological findings of bird migration. It deals with all aspects of this absorbing subject, including the problems of navigation and vagrancy, the timing and physiological control of migration, the factors that limit their populations, and more. Author, Ian Newton, reveals the extraordinary adaptability of birds to the variable and changing conditions across the globe, including current climate change. This adventurous book places emphasis on ecological aspects, which have received only scant attention in previous publications. Overall, the book provides the most thorough and in-depth appraisal of current information available, with abundant tables, maps and diagrams, and many new insights. Written in a clear and readable style, this book appeals not only to migration researchers in the field and Ornithologists, but to anyone with an interest in this fascinating subject. * Hot ecological aspects include: various types of bird movements, including dispersal and nomadism, and how they relate to food supplies and other external conditions * Contains numerous tables, maps and diagrams, a glossary, and a bibliography of more than 2,700 references * Written by an active researcher with a distinguished career in avian ecology, including migration research.
The migration strategy of the globally threatened Aquatic Warbler Acrocephalus paludicola needs to be known to ensure that effective action is taken to conserve its principal stopover sites. Using data from ringing stations during the autumn migration of reedbed warblers, we developed an index that allowed countries and sites to be compared in terms of their numerical importance to migrating Aquatic Warblers. According to this index, there was no significant decline in the number of Aquatic Warblers migrating through Europe during the 1990s. France appears to receive the largest numbers of this species in autumn compared with other European countries. Within France, only coastal regions are visited by the species (but not in the Mediterranean), with the largest numbers occurring in Normandy and Loire, while Brittany receives large numbers in some years but not in others. We also identified some French sites that are of major importance to migrating Aquatic Warblers depositing reserves on migration. France therefore plays a very important part in providing stopover sites for Aquatic Warblers, which means that France should play a major role in undertaking conservation measures for this threatened species.
The Aquatic Warbler: manual for managing helophytic vegetation and monitoring populations Identifying autumn migration routes for the globally threatened Aquatic Warbler Acrocephalus paludicola
- Torres M S Gó
- S Cirujano
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