Increasing winter temperatures explain body size decrease in wintering bird populations of Northern Europe—But response patterns vary along the spatioclimatic gradient

Aim Recent evidence has shown changes in body size and shape of individuals, which are suggested to be a result of global warming caused by climate change. Here, we explored the spatiotemporal changes in wing length and body mass of 24 wintering bird species in Northern Europe and how these relate to temperature anomaly. Location Finland and Sweden, Europe. Time Period 50 years, 1970 to 2020. Major Taxa Studied Birds, 24 species. Methods We used site-specific, long-term winter ringing data containing wing length and body mass measurements from across Sweden and Finland for 24 bird species. We modelled wing length and body mass change over time, in relation to the spatioclimatic gradient and as response to temperature anomalies (of [i] the same winter as the ringing took place, [ii] the previous winter and [iii] the previous spring) by accounting for phylogenetic relatedness between species and their species-specific responses to each predictor of interest. Results We show that across all species, body size has decreased since the 1970s, with a negative relationship between wing length and temperature anomalies of previous winters, suggesting carry-over effects likely linked to body size-related survival or dispersal. Body mass was negatively related to the temperature anomaly of the same winter, indicating more immediate effects related to reduced fat reserves during mild winters. Main Conclusions Our results highlight a climate-driven decrease in body size across several species and its association with positive anomalies in winter temperature in the high latitudes. However, the responses are not spatially uniform and there is considerable species-specific variation, emphasizing the importance of conducting multispecies studies when investigating responses to climate change. The mechanisms of decreasing wing length and body mass seem to differ and underline the immediate and carry-over effects of temperature warming during the nonbreeding season

Migrating Birds and Tickborne Encephalitis Virus

During spring and autumn 2001, we screened 13,260 migrating birds at Ottenby Bird Observatory, Sweden, and found 3.4% were infested with ticks. Four birds, each a different passerine species, carried tickborne encephalitis virus (TBEV)–infected ticks (Ixodes ricinus). Migrating birds may play a role in the geographic dispersal of TBEV-infected ticks

Spatial, temporal, and species variation in prevalence of influenza A viruses in wild migratory birds

Although extensive data exist on avian influenza in wild birds in North America, limited information is available from elsewhere, including Europe. Here, molecular diagnostic tools were employed for high-throughput surveillance of migratory birds, as an alternative to classical labor-intensive methods of virus isolation in eggs. This study included 36,809 samples from 323 bird species belonging to 18 orders, of which only 25 species of three orders were positive for influenza A virus. Information on species, locations, and timing is provided for all samples tested. Seven previously unknown host species for avian influenza virus were identified: barnacle goose, bean goose, brent goose, pink-footed goose, bewick's swan, common gull, and guillemot. Dabbling ducks were more frequently infected than other ducks and Anseriformes; this distinction was probably related to bird behavior rather than population sizes. Waders did not appear to play a role in the epidemiology of avian influenza in Europe, in contrast to the Americas. The high virus prevalence in ducks in Europe in spring as compared with North America could explain the differences in virus-host ecology between these continents. Most influenza A virus subtypes were detected in ducks, but H13 and H16 subtypes were detected primarily in gulls. Viruses of subtype H6 were more promiscuous in host range than other subtypes. Temporal and spatial variation in influenza virus prevalence in wild birds was observed, with influenza A virus prevalence varying by sampling location; this is probably related to migration patterns from northeast to southwest and a higher prevalence farther north along the flyways. We discuss the ecology and epidemiology of avian influenza A virus in wild birds in relation to host ecology and compare our results with published studies. These data are useful for designing new surveillance programs and are particularly relevant due to increased interest in avian influenza in wild birds

Oversigt over ringmærknings- og genfundsdata for ederfugl i Østersø/Nordsøområdet

Ederfuglen er i alvorlig tilbagegang i Østersøen og Nordsøen, kønsbalancen er skæv med et stort overtal af hanner, og derfor er en international forvaltningsplan er under udarbejdelse i regi af Vandfugleaftalen (AEWA). Bæredygtig forvaltning kræver opdateret viden om bestandens trækforhold og dødelighed, og den bedste kilde til denne viden er ringmærkning. Denne rapport giver et overblik over det omfattende materiale om ringmærkede og genmeldte ederfugle i Østersø/Nordsøområdet, i alt næsten 18.000 genmeldinger af mere end 125.000 ringmærkede fugle siden 1970. Detaljerede statistiske analyser af dette materiale vil kunne give vigtig ny viden om hvor ynglefugle fra forskellige områder tilbringer vinteren, og om dødeligheden hos begge køn og alle aldersklasser

Surveillance of Influenza Virus A in Migratory Waterfowl in Northern Europe

Ducks may maintain influenza virus from 1 year to the next

The Indo-European flyway: Opportunities and constraints reflected by Common Rosefinches breeding across Europe

Aim The configuration of the earth's landmasses influences global weather systems and spatiotemporal resource availability, thereby shaping biogeographical patterns and migratory routes of animals. Here, we aim to identify potential migratory barriers and corridors, as well as general migration strategies within the understudied Indo-European flyway.Location Europe, Central Asia.Major taxon studied Common rosefinches.Methods We used a combination of theoretical optimization modelling and empirical tracking of Common Rosefinches (Carpodacus erythrinus) breeding across a large latitudinal gradient in Europe. First, we identified optimal migration routes driven by wind and resource availability along the Indo-European flyway. Second, we tracked rosefinches from five breeding populations using light-level geolocators. Finally, we compared to what extent empirical tracks overlapped with the modelled optimal routes.ResultsIn autumn, theoretical wind driven migration routes formed a broad-front corridor connecting Europe and the Indian Subcontinent while the theoretical resource driven routes formed a distinct north-south divide. The latter pattern also reflected the rosefinch tracks with all but the most southerly breeding birds making a northern detour towards non-breeding sites in Pakistan and India. In spring, the resource availability model predicted a similar migratory divide, however, the southern route seemed relatively more favourable and closely matched with the optimal wind driven migration routes. Spring tracking data showed larger overlap with the modelled wind driven migration routes compared to the resource driven routes.Main conclusionsOptimal wind and resource driven migration routes along the Indo-European flyway are seasonally specific and to a large extend do not overlap with one another. Under these conditions, migratory birds adopt seasonally distinct migration strategies following energy minimization strategy in autumn, driven by resource availability, and time minimizing strategy in spring, driven by wind conditions. Our optimal migration models can be applied worldwide and used to validate against empirical data to explain large-scale biogeographic pattern of migratory animals.</p

Improved mallard survival in Northern Europe over the past forty years

Vital rates are the cornerstones affecting population dynamics, and are necessary to estimate in order to judge population viability. Knowledge about vital rates and their changes over time is especially important for hunted species, for example to be able to determine sustainable harvest levels. We estimated annual age and sex specific survival rates of the most common waterfowl game in Europe, i.e. the Mallard (Anas platyrhynchos), and studied possible links between survival and hunting pressure, weather (winter harshness) and migration behaviour. Ringing data, covering more than forty years (1964-1982 [called ‘yearly period’] and 2002-2008 [called ‘late period’]), were collected in one stationary duck trap located at Ottenby, south-east Sweden, and mark-recovery data were analysed with a theoretic-information approach using program MARK. In total 10,490 Mallards were marked, i.e. 6,409 in the early period and 4,081 in the late, of which 13.3% (early period) and 4.7% (late period) were recovered dead (mostly hunting; &gt;92%). Within each time period, the survival of Mallards was not dependent on age, sex and year. However, when the different time periods were compared, annual survival was lower in the early period (0.58–0.63) compared to the late (0.69–0.71). There are several possible explanations why survival has improved. Although winter harshness did not directly correlate to survival in the modelling analyses, relationships may be more intricate than as it first appears. Firstly, data show that Mallards in the late period have better body condition (body mass) than in the early period, which may have several explanations, including climate aspects. Secondly, data suggest that the Mallard has shortened its migratory route when time periods are contrasted, with wintering areas further to the north in the late period. Again milder winters may have contributed to this pattern as migrating distances for female Mallards were correlated with winter harshness data. As a consequence, this could potentially also affect survival since migration is costly. Finally, although it is hard to quantify, hunting pressure may also have played a role since it seems to be lower in the late period compared to the early

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During long-distance flights, birds catabolize not only fat but also protein, which results in structural or functional loss as protein is stored in organs. In this study we investigated breast muscle size in relation to body mass in garden warblers Sylvia borin before and after crossing the Sahara desert and the Mediterranean Sea in autumn and spring migration, respectively. Breast muscle size was measured by moulding the shape of the muscles of live birds. Samples were collected on the Greek island of Antikythira during spring after the barrier crossing and on Crete during autumn, where garden warblers prepare for barrier crossing on their southward migration. Breast muscle size on Antikythira was significantly smaller than the equivalent size measured on Crete. Breast muscle size followed the changes in total body mass when garden warblers had a low body mass while this relationship disappeared when body mass is above 17.5 g. The combination of low body masses and small breast muscle size of birds that have just crossed the Sahara desert and the Mediterranean Sea and landed on Antikythira indicates a severe protein break down. During extended flights, when fat reserves are insufficient, the use of protein can also be a lifeline to reach the destination. The weak association between body mass and breast muscle size during autumn implies that the increase of breast muscle, as a preparation for the barrier crossing, does not take place en route from breeding sites to the Mediterranean area