Large-Scale Changes in Community Composition: Determining Land Use and Climate Change Signals

Human land use and climate change are regarded as the main driving forces of present-day and future species extinction. They may potentially lead to a profound reorganisation of the composition and structure of natural communities throughout the world. However, studies that explicitly investigate both forms of impact—land use and climate change—are uncommon. Here, we quantify community change of Dutch breeding bird communities over the past 25 years using time lag analysis. We evaluate the chronological sequence of the community temperature index (CTI) which reflects community response to temperature increase (increasing CTI indicates an increase in relative abundance of more southerly species), and the temporal trend of the community specialisation index (CSI) which reflects community response to land use change (declining CSI indicates an increase of generalist species). We show that the breeding bird fauna underwent distinct directional change accompanied by significant changes both in CTI and CSI which suggests a causal connection between climate and land use change and bird community change. The assemblages of particular breeding habitats neither changed at the same speed and nor were they equally affected by climate versus land use changes. In the rapidly changing farmland community, CTI and CSI both declined slightly. In contrast, CTI increased in the more slowly changing forest and heath communities, while CSI remained stable. Coastal assemblages experienced both an increase in CTI and a decline in CSI. Wetland birds experienced the fastest community change of all breeding habitat assemblages but neither CTI nor CSI showed a significant trend. Overall, our results suggest that the interaction between climate and land use changes differs between habitats, and that comparing trends in CSI and CTI may be useful in tracking the impact of each determinant

Warming temperatures drive at least half of the magnitude of long-term trait changes in European birds

Many wild populations are experiencing temporal changes in life-history and other phenotypic traits, and these changes are frequently assumed to be driven by climate change rather than nonclimatic drivers. However, this assumption relies on three conditions: that local climate is changing, traits are sensitive to climate variability, and other drivers are not also changing over time. Although many studies acknowledge one or more of these conditions, all three are rarely checked simultaneously. Consequently, the relative contribution of climate change to trait change, and the variation in this contribution across traits and species, remain unclear. We used long-term datasets on 60 bird species in Europe to test the three conditions in laying date, offspring number, and body condition and used a method that quantifies the contribution of warming temperatures to changes in traits relative to other effects. Across species, approximately half of the magnitude of changes in traits could be attributed to rising mean temperature, suggesting that increasing temperatures are likely the single most important contributor to temporal trends and emphasizes the impact that global warming is having on natural populations. There were also substantial nontemperature-related temporal trends (presumably due to other changes such as urbanization), which generally caused trait change in the same direction as warming. Attributing temporal trends solely to warming thus overestimates the impact of warming. Furthermore, contributions from nontemperature drivers explained most of the interspecific variation in trait changes, raising concerns about comparative studies that attribute differences in temporal trends to species differences in climate-change sensitivity

Are Dutch Skylarks partial migrants? Ring recovery data and radio-telemetry suggest local coexistence of contrasting migration strategies

In western Europe, farmland birds have declined in recent decades by almost 50% (BirdLife International 2004, EBCC 2009, PECBMS 2009. While declines are frequently associated with changed or changing conditions during the breeding season and deterioration of the breeding habitat In The Netherlands, the Skylark Alauda arvensis is one of the farmland species with the steepest decline: numbers dropped by almost 95% from around 700,000 Are Dutch Skylarks partial migrants? Ring recovery data and radio-telemetry suggest local coexistence of contrasting migration strategies In recent years, Skylarks Alauda arvensis have undergone dramatic population declines in many European countries. Evidence exists for deteriorating conditions during the breeding season, but little is known about the situation during the rest of the annual cycle. Here we use two approaches to test if the Dutch breeding population of Skylarks consists of resident and/or migratory individuals. First, we present an analysis of ring recoveries from the Dutch Ringing Centre "Vogeltrekstation". Out of 25 recoveries, 12 Skylarks were resident in winter, 10 migrated and three were classified as probable migrants. Resident birds were accompanied during winter by birds from northern and eastern Europe. Very limited natal and breeding dispersal recorded in the same dataset suggests that our results were not influenced by long dispersal distances. Next, we compared these results to a local radio-telemetry study in the northern Netherlands. During two different years we equipped a total of 27 Skylarks from a breeding population with radio-transmitters and followed them during the subsequent winter. Four birds were found to winter locally. Out of 23 individuals that we did not find in winter, 14 returned in the following breeding season to the study area, all with a working transmitter, suggesting that they wintered outside our study area. Two ring recoveries of birds from the same study population indeed showed migration to south-west Europe. Based on these two lines of evidence, we conclude local coexistence of a resident and a migrant strategy in Dutch Skylarks. The findings of our study are important for the planning of conservation efforts, as we can only protect this rapidly declining species when we know their behaviour and whereabouts throughout the entire annual cycle. Skylark populations from northern Europe migrate to south-west Europe, mainly to France and Spain, whereas southern European and British populations are thought to be resident Futhermore, it is unclear whether resident and migratory strategies occur within a single Skylark population. Partial migration is defined as occurring when one part of the population remains in the breeding area year round and another part migrates In this study we investigated migration strategies of Skylarks in The Netherlands using two different approaches. First, we analysed all ring recoveries of Skylarks from the database of the Dutch ringing centre "Vogeltrekstation". Second, we conducted a radio-telemetry study in a local breeding population of Skylarks in the northern Netherlands. We combine the results of both approaches to evaluate whether Skylarks that breed in The Netherlands migrate or winter locally. Additionally, we analyse the ring recoveries of Skylarks that spend the winter in The Netherlands, to trace their origin. Finally, we present data on natal and breeding dispersal of Skylarks ringed in The Netherlands during the breeding season to verify that our results on the migratory strategies of Skylarks are not in fact influenced by long-distance dispersal. METHODS Ring recoveries Since 1911 more than 88,000 Skylarks have been ringed in The Netherlands (Vogeltrekstation data until November 2008), of which 497 were recovered. The database contains an additional 35 recoveries of birds ringed in other countries and found in The Netherlands. We selected all cases where distinction between migration strategies (resident in winter vs. migrant) is possible (n = 25, Appendix 1). These include birds that were (1) ringed during the breeding season in The Netherlands (either as nestling or as breeding adult) and recovered in any winter, or during any autumn or spring migration; (2) ringed during winter and reported during the breeding season in The Netherlands; and (3) ringed during migration and recovered during the breeding season within The Netherlands. We define migration based on distance between ringing and recovery site by visually deriving a divide in travelled distance between residents and migrants (see To evaluate whether, in addition to Dutch birds, Skylarks from northern origins also winter in The Netherlands, we selected all birds that were ringed during winter (20 Nov -29 Jan) in The Netherlands and were later recovered further north. We additionally checked for the origin of late migrants (1 Nov -19 Nov). If long-distance natal or breeding dispersal occurs in Skylarks, this could potentially influence our results given the selection criteria we used to classify migrants. Therefore we performed an analysis of natal and breeding dispersal by selecting all recoveries from birds ringed during the breeding season as either nestlings or adults and that were recovered during any subsequent breeding season (n = 43). Of these 43 recoveries, 23 birds were found by the ringer and 20 by another person, and thus estimated dispersal is not only based on birds recaptured by a ringer within a study population. Study area for radiotelemetry We obtained detailed information on a breeding population in the "Aekingerzand", part of the National Park Drents-Friese Wold in the northern Netherlands (52°55'N; 6°18'E). The area is a mixture of open sand, groups of trees, heath-and grasslands on nutrient-poor soil and surrounded by a thin belt of forests. The wider surroundings are characterised by agricultural fields and small villages. The study population consists of about 100 pairs; the vast majority of individuals are colour-ringed. Radio-tracking We equipped 28 Skylarks with radio-transmitters. Eight birds (3 adult males, 4 adult females, 1 juvenile female) received the transmitter in the period 13 Jul -26 Sep 2007 and another 20 (9 adult males, 4 adult females, 4 juvenile males, 2 juvenile females and 1 male of unknown age) in the period 3 Aug -22 Sep 2008 when all birds showed active moult. Ageing of the birds was based on previous ringing or on plumage characteristics; sex was determined by wing length and in doubtful cases confirmed by molecular sexing. The radio-transmitters (172 MHz-band) were specifically designed for this project by JDJC Corp. d.b.a. Sparrow Systems, United States. The life-time was assumed by the manufacturer to be at least 6-7 months. In fact, in all cases where birds returned to the breeding grounds, transmitters continued to work for longer than this expected life-span and one transmitter was still working one year after attachment. Transmitters were fixed on the back of a bird using figure-eight-harnesses (Rappole & Tipton 1991) made from elasticated cotton thread. Transmitters, including harness, ranged in weight from 1.29 to 1.50 g, equalling 3.1-5.2% of a bird's body weight at time of attachment. During the period when transmitters were attached, Skylarks in this study population are close to their minimum weight in the annual cycle (A. Hegemann, unpubl.). From when transmitters were attached until the end of September we carried out repeated searches for birds in the study area to check if birds were still present and to determine if transmitters produced regular signals on the supposed frequency. One transmitter attached to a bird in 2007 failed to work properly due to an antenna that was broken two weeks after attachment. Therefore we excluded this bird from further analysis. Starting in October when birds left the Aekingerzand, we searched for radio-tagged birds using two portable ICOM IC-R20-receivers with hand-held 5-element yagi-antennas. In a radius of up to 8 km around the Aekingerzand, the agricultural landscape was checked for the presence of radio-tagged birds by one person searching for 4-5 days per week and about five hours per day. In the open landscape (excluding villages and wooded areas) we scanned for all used frequencies, conducting scans at regular distances of not more than 1 km apart. In addition we used a dipole antenna mounted on the roof of a car with a automatically scanning receiver to search for birds while driving around the search area. During winter 2008/09 the hand-held antenna was mounted on a 4-m long plastic pole to increase reception. Furthermore we conducted telemetry from a small aircraft (Cessna skyhawk), flying for 2-4 hours at a height of 250-300 m and with a speed of 100-110 km/h in circles over the study area. Flights were completed once in winter 2007/08 (on 8 December) and twice in winter 2008/09 (on 16 January and 6 February). With these flights we covered an area with a radius of about 12 km around the Aekingerzand. During the flight on 8 December 2007 we received signals from one bird we did not find previously by ground telemetry. During the two flights in winter 2008/09 we did not find any additional birds. During all flights radio-tagged birds with known location, or one additional transmitter that was not attached to a 137 bird, were used as references values. From the air we were able to detect these references signals from a distance of at least 2 km. Another search flight was flown in spring 2009 (on 3 March) to search for potentially dispersed birds, but none were found. RESULTS Migration strategies from ringing data Based on 25 ring recoveries, we classified 12 birds as residents, 10 as migrants and three as probable migrants Origin of birds wintering in The Netherlands Eleven birds ringed in winter in The Netherlands were recovered in or on their way towards breeding areas outside The Netherlands, in Denmark (n = 8), Russia (n = 1), Sweden (n = 1) and Norway (n = 1) (Appendix 2). Additionally two birds ringed during the breeding season in Denmark and Norway, respectively, were found in winter in The Netherlands. Furthermore, birds that were ringed during the last part of the southward migration period in The Netherlands (1 Nov -19 Nov) were later reported in Denmark (n = 8) and Russia (n = 1) (Appendix 2). Natal and breeding philopatry Thirty Skylarks ringed as nestlings were reported during a later year as breeding birds. Twenty-six of these birds (1 male, 18 female, 7 unknown) were found within 4 km of the ringing site, and four (all unknown sex) had dispersed further than 10 km from the place of hatching. The furthest recovery was found in a fresh pellet of a Montagu's Harrier Circus pygargus one year after being ringed as a nestling, at a distance of 41 km from its place of hatching (H.J. Ottens, pers. comm.). Because Montagu's Harriers of this specific population hunt over distances of more than 18 km from their nest site (C. Trierweiler, pers. comm.), the actual dispersal distance of this bird remains uncertain. Of the 13 birds ringed as adults (5 males, 7 females, 1 unknown) during the breeding season all were reported in subsequent years within 2 km of the site of ringing. Radio-telemetry of Aekingerzand population In the winter of 2007/08 all radio-tagged birds had left the Aekingerzand by 2 October. In the course of the winter we detected signals from three of the seven radio-tagged birds (43%) at distances of 0-9 km from the Aekingerzand. These included two adult males and one adult female ( In the winter of 2008/09 we located only one of the 20 radio-tagged birds in the search area around the Aekingerzand (5%, Both winters combined, we found three of 17 males and one of 10 females to winter locally (Fisher's Exact Test, P = 1). Four adults were found to winter locally, while we did not detect any of the seven juveniles in winter (Fisher's Exact Test, P = 0.55). The proportion of birds we found in our study area during winter, differed between the two years (Fisher's Exact Test, P = 0.04). DISCUSSION Ring recoveries from the entire Netherlands for the past 100 years clearly demonstrate that Dutch Skylarks are partial migrants; some birds migrate to the southwest and others winter close to their breeding grounds. Our radio-telemetry study on a local breeding population in the northern part of The Netherlands confirmed that some birds winter very close to the breeding location while others were not found in winter in the immediat

Integrated population modeling identifies low duckling survival as a key driver of decline in a European population of the Mallard

Europe’s highest densities of breeding Mallards (Anas platyrhynchos) are found in the Netherlands, but the breeding population there has declined by ~30% since the 1990s. The exact cause of this decline has remained unclear. Here, we used an integrated population model to jointly analyze Mallard population survey, nest survey, duckling survival, and band-recovery data. We used this approach to holistically estimate all relevant vital rates, including duckling survival rates for years for which no explicit data were available. Mean vital rate estimates were high for nest success (0.38 ± 0.01) and egg hatch rate (0.96 ± 0.001), but relatively low for clutch size (8.2 ± 0.05) compared to populations in other regions. Estimates for duckling survival rate for the three years for which explicit data were available were low (0.16–0.27) compared to historical observations, but were comparable to rates reported for other regions with declining populations. Finally, the mean survival rate was low for ducklings (0.18 ± 0.02), but high and stable for adults (0.71 ± 0.03). Population growth rate was only affected by variation in duckling survival, but since this is a predominantly latent state variable, this result should be interpreted with caution. However, it does strongly indicate that none of the other vital rates, all of which were supported by data, was able to sufficiently explain the population decline. Together with a comparison with historic vital rates, these findings point to a reduced duckling survival rate as the likely cause of the decline. Candidate drivers of reduced duckling survival are increased predation pressure and reduced food availability, but this requires future study. Integrated population modeling can provide valuable insights into population dynamics even when empirical data for a key parameter are partly missing

Ontogenetic niche shifts as a driver of seasonal migration

Ontogenetic niche shifts have helped to understand population dynamics. Here we show that ontogenetic niche shifts also offer an explanation, complementary to traditional concepts, as to why certain species show seasonal migration. We describe how demographic processes (survival, reproduction and migration) and associated ecological requirements of species may change with ontogenetic stage (juvenile, adult) and across the migratory range (breeding, non-breeding). We apply this concept to widely different species (dark-bellied brent geese (Branta b. bernicla), humpback whales (Megaptera novaeangliae) and migratory Pacific salmon (Oncorhynchus gorbuscha) to check the generality of this hypothesis. Consistent with the idea that ontogenetic niche shifts are an important driver of seasonal migration, we find that growth and survival of juvenile life stages profit most from ecological conditions that are specific to breeding areas. We suggest that matrix population modelling techniques are promising to detect the importance of the ontogenetic niche shifts in maintaining migratory strategies. As a proof of concept, we applied a first analysis to resident, partial migratory and fully migratory populations of barnacle geese (Branta leucopsis). We argue that recognition of the costs and benefits of migration, and how these vary with life stages, is important to understand and conserve migration under global environmental change

Climate warming may affect the optimal timing of reproduction for migratory geese differently in the low and high Arctic

Rapid climate warming is driving organisms to advance timing of reproduction with earlier springs, but the rate of advancement shows large variation, even among populations of the same species. In this study, we investigated how the rate of advancement in timing of reproduction with a warming climate varies for barnacle goose (Branta leucopsis) populations breeding at different latitudes in the Arctic. We hypothesized that populations breeding further North are generally more time constrained and, therefore, produce clutches earlier relative to the onset of spring than southern populations. Therefore, with increasing temperatures and a progressive relief of time constraint, we expected latitudinal differences to decrease. For the years 2000-2016, we determined the onset of spring from snow cover data derived from satellite images, and compiled data on egg laying date and reproductive performance in one low-Arctic and two high-Arctic sites. As expected, high-Arctic geese laid their eggs earlier relative to snowmelt than low-Arctic geese. Contrary to expectations, advancement in laying dates was similar in high- and low-Arctic colonies, at a rate of 27% of the advance in date of snowmelt. Although advancement of egg laying did not fully compensate for the advancement of snowmelt, geese laying eggs at intermediate dates in the low Arctic were the most successful breeders. In the high Arctic, however, early nesting geese were the most successful breeders, suggesting that high-Arctic geese have not advanced their laying dates sufficiently to earlier springs. This indicates that high-Arctic geese especially are vulnerable to negative effects of climate warming

Climate change leads to differential shifts in the timing of annual cycle stages in a migratory bird

Shifts in reproductive phenology due to climate change have been well documented in many species but how, within the same species, other annual cycle stages (e.g. moult, migration) shift relative to the timing of breeding has rarely been studied. When stages shift at different rates, the interval between stages may change resulting in overlaps, and as each stage is energetically demanding, these overlaps may have negative fitness consequences. We used long-term data of a population of European pied flycatchers (Ficedula hypoleuca) to investigate phenological shifts in three annual cycle stages: spring migration (arrival dates), breeding (egg-laying and hatching dates) and the onset of postbreeding moult. We found different advancements in the timing of breeding compared with moult (moult advances faster) and no advancement in arrival dates. To understand these differential shifts, we explored which temperatures best explain the year-to-year variation in the timing of these stages, and show that they respond differently to temperature increases in the Netherlands, causing the intervals between arrival and breeding and between breeding and moult to decrease. Next, we tested the fitness consequences of these shortened intervals. We found no effect on clutch size, but the probability of a fledged chick to recruit increased with a shorter arrival-breeding interval (earlier breeding). Finally, mark-recapture analyses did not detect an effect of shortened intervals on adult survival. Our results suggest that the advancement of breeding allows more time for fledgling development, increasing their probability to recruit. This may incur costs to other parts of the annual cycle, but, despite the shorter intervals, there was no effect on adult survival. Our results show that to fully understand the consequences of climate change, it is necessary to look carefully at different annual cycle stages, especially for organisms with complex cycles, such as migratory 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

Evaluation of the use of alternative sample types for mosquito-borne flavivirus surveillance: Using Usutu virus as a model

Wild birds are reservoirs of several zoonotic arboviruses including West Nile virus (WNV) and Usutu virus (USUV), and are often monitored as indicators for virus introduction and spread. To optimize the bird surveillance for arboviruses in the Netherlands and to explore the possibilities for citizen science in surveillance, we investigated the suitability of using alternative sample types from live and dead birds. The sensitivity of molecular detection via RT-PCR of viral RNA in feather, heart, lung, throat and cloaca swabs from dead birds, and serum, dried blood spots (DBS) and throat and cloaca swabs from live birds were compared. IgY antibody detection was also assessed from DBS relative to serum on protein-microarray and virus neutralization test. Feathers showed a high detection sensitivity for USUV RNA in both live and dead birds, and no significant decrease was observed in the RNA loads in the feathers after being stored dry at room temperature for 43 days. Additionally, viral RNAs extracted from feathers of day 0 and 43 were successfully sequenced. The results indicated no statistical significant difference in sensitivity and viral loads detection in heart, spleen, and lung relative to corresponding brain samples in dead birds. In live birds, viral RNA loads did not differ between throat and cloaca swabs. This study identified less-invasive sample types that allows involvement of citizens in collecting samples from wild birds for arbovirus surveillance. Sensitivity and specificity of DBS-based antibody detections were significantly lower and therefore need optimization