Restricted dispersal in a long-distance migrant bird with patchy distribution,the great reed warbler

In patchily distributed species dispersal connects local populations into metapopulations. Reliable quantifications of dispersal are therefore crucial to understanding the population dynamics and genetic structure of such metapopulation systems. The great reed warbler (Acrocephalus arundinaceus) inhabits eutrophic lakes and has a patchy breeding distribution. In this study we investigated the dispersal pattern of the great reed warbler based on an extensive capture-recapture effort covering a large census area (22,500 km²). At two adjacent breeding sites (10 km apart) in southern Central Sweden, the "main study area", we ringed the majority of adult and nestling great reed warblers between 1992 and 1999. In 1998 and 1999, we opportunistically searched for territorial males at the majority of the Swedish breeding sites, and were able to examine about 56% of all males in the region. Analyses of recaptured males demonstrated that philopatry predominated. Sixty-nine percent of the recruiting nestlings returned to breed in the main study area (their natal area), and 92% of the resighted adults were found at the same breeding locality in both study years. Breeding dispersal was significantly more restricted than natal dispersal. Additional data on natal and breeding dispersal within the main study area in 1992-1999 suggested that females were as philopatric as males. The overall high level of philopatry, with only occasional longer dispersal distances documented, yielded a root-mean-square dispersal distance of 33 km per generation. High philopatry, short dispersal distances and similar dispersal patterns of male and female great reed warblers contrast the findings among birds in general, but conform to data of species having patchy breeding habitat and isolated populations. Restricted dispersal suggests limited gene flow even among several Swedish populations, which is in line with some previous findings of the population ecology of the great reed warbler: (1) structured mtDNA lineages among European populations; (2) small-scale population differences in song patterns; and (3) low genetic variation and occurrence of inbreeding depression in our main study population.     

Phenological advancement in arctic bird species: relative importance of snow melt and ecological factors

Previous studies have documented advancement in clutch initiation dates (CIDs) in response to climate change, most notably for temperate-breeding passerines. Despite accelerated climate change in the Arctic, few studies have examined nest phenology shifts in arctic breeding species. We investigated whether CIDs have advanced for the most abundant breeding shorebird and passerine species at a long-term monitoring site in arctic Alaska. We pooled data from three additional nearby sites to determine the explanatory power of snow melt and ecological variables (predator abundance, green-up) on changes in breeding phenology. As predicted, all species (semipalmated sandpiper, Calidris pusilla, pectoral sandpiper, Calidris melanotos, red-necked phalarope, Phalaropus lobatus, red phalarope, Phalaropus fulicarius, Lapland longspur, Calcarius lapponicus) exhibited advanced CIDs ranging from 0.40 to 0.80 days/year over 9 years. Timing of snow melt was the most important variable in explaining clutch initiation advancement (“climate/snow hypothesis”) for four of the five species, while green-up was a much less important explanatory factor. We found no evidence that high predator abundances led to earlier laying dates (“predator/re-nest hypothesis”). Our results support previous arctic studies in that climate change in the cryosphere will have a strong impact on nesting phenology although factors explaining changes in nest phenology are not necessarily uniform across the entire Arctic. Our results suggest some arctic-breeding shorebird and passerine species are altering their breeding phenology to initiate nesting earlier enabling them to, at least temporarily, avoid the negative consequences of a trophic mismatch.     

Migration speeds among eleven species of long-distance migrating passerines across Europe, the desert and eastern Africa

Based on phenology, passage and median dates gathered from large number of study sites, we measured autumn and spring migration speeds of eleven long distance migratory passerines in four different ecogeographic sectors: Europe, desert, north-eastern and eastern Africa. Results demonstrate that, during the southward autumn migration, late-departing species, such as lesser whitethroat Sylvia curruca , garden warbler S. borin , spotted flycatcher Muscicapa striata , whitethroat S. borin , and willow warbler Phylloscopus trochilus cover their migration route with a slower average migration speed across Europe than do early migrating species. During spring migration, late-departing species (marsh warbler Acrocephalus palustris , garden warbler, spotted flycatcher, red-backed shrike Lanius collurio ) across north-eastern Africa showed a higher speed than early migrating species. Our results show overall shorter migration duration estimates in spring than autumn. Sector-wise seasonal comparisons of duration indicate that migration journey in the African and desert sectors are covered in a relatively shorter time in spring than in autumn. Periods required to cover the distance between northern latitude breeding grounds and desert during both seasons were equivalent.     

Genetic differences among language families in Europe

We investigated whether 59 allele frequencies and 10 cranial variables differed among speakers of the 12 modern language families in Europe. Although this is a classical analysis of variance design, special techniques had to be developed for the analysis because of spatial autocorrelation of both biological and language data. The method examines pooled sums of squares within language families. These are compared with the same quantities obtained by randomly partitioning the available data points in Europe into internally cohesive subsets representing the same sample sizes for each language family as in the originally observed data. Our results suggest that for numerous genetic systems, population samples differ more among language families than they do within families. These findings are considered in relation to two contrasting models: a model of random spatial differentiation of gene frequencies unrelated to language and a model of aboriginal genetic differences among speakers of different language groups. Our observed findings suggest partial validity of both models.     

Body mass of six long-distance migrant passerine species along the autumn migration route

Summary We analysed body mass and moult data of six passerine species along their autumn migration route from northern Europe to North Africa and derived hypothetical models of the organisation of their migration in terms of fuel store accumulation. We analysed data of 46,541 first-year birds from 34 trapping sites, sampled in a network of collaborating European and African ringing stations. After accounting for effects of time of day and size, there were marked differences between the six species examined in the change of body mass along the migration route and in the timing of moult. Garden Warblers (Sylvia borin) and Pied Flycatchers (Ficedula hypoleuca) underwent their postjuvenile moult prior to migration and increased their average body mass along the migration route. Sedge Warblers (Acrocephalus schoenobaenus) also increased body mass towards the south, but started the migration bout without further refuelling well before the Sahara and moulted mainly in the wintering grounds. Reed Warblers (Acrocephalus scirpaceus) and Whitethroats (Sylvia communis) migrated while still moulting and did not increase average body mass towards south. They accumulated the energy needed to fly over the Sahara just before it. Spotted Flycatchers (Muscicapa striata) behaved in the same way, but contrary to Reed Warblers and Whitethroats they did not accumulate much fat stores in North Africa, which might urge them to stop and fuel up regularly in the Sahara. In the course of the season average body mass of all species increased slightly, which enabled them to migrate faster. In general, average body mass of first-year birds in northern and central Europe during the migration period was comparable to that of adults during breeding.

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Körpermassen von sechs Arten von Langstreckenziehern entlang des Herbstzugweges

Zusammenfassung Wir analysierten Körpermassen- und Mauserdaten von sechs Singvogelarten auf dem Herbstzug entlang ihres Zugweges von Nordeuropa bis Nordafrika. Die Körpermassen von 46 541 diesjährigen Vögeln, die auf 34 Beringungsstationen im Rahmen eines internationalen Projektes gesammelt wurden, sind die Grundlage dieser Untersuchung. Neben der Entwicklung der Körpermassen entlang des Zugweges untersuchten wir den Einfluss der Mauser, des Fangdatums, der Tageszeit und der Körpergröße auf die Körpermasse. Mausernde Vögel waren schwerer als nichtmausernde mit der gleichen Fettmenge. Die Körpermasse nahm im Laufe der Saison und im Verlauf des Tages zu. Große Vögel (mit einer längeren 8. Handschwinge) waren schwerer als kleine. Gartengrasmücken (Sylvia borin) und Trauerschnäpper (Ficedula hypoleuca) wurden entlang des Zugweges kontinuierlich schwerer. Beide Arten machten die Jugendteilmauser hauptsächlich noch im Brutgebiet durch. Schilfrohrsänger (Acrocephalus schoenobaenus) wurden nach Süden ebenfalls etwas schwerer, aber sie begannen mit einem Reiseabschnitt ohne weiteren Fettaufbau schon in Mitteleuropa und mauserten ihr Kleingefieder hauptsächlich erst in Afrika. Die Körpermassen von Teichrohrsängern (Acrocephalus scirpaceus) und Dorngrasmücken (Sylvia communis) blieben nach Süden weitgehend konstant. Beide Arten lagerten die nötigen Energiereserven zum Überfliegen der Sahara erst kurz davor an. Sie trennten Jugendteilmauser und Zug nicht vollständig. Ähnlich verhielten sich Grauschnäpper (Muscicapa striata), doch im Gegensatz zu den zwei vorherigen Arten, wurden sie auch im Mittelmeergebiet nicht wesentlich fetter. Sie scheinen daher regelmässig in der Wüste zu rasten und zu fressen.

     

Learning and signal copying facilitate communication among bird species

Signals relevant to different sets of receivers in different contexts create a conflict for signal design. A classic example is vocal alarm signals, often used both during intraspecific and interspecific interactions. How can signals alert individuals from a variety of other species in some contexts, while also maintaining efficient communication among conspecifics? We studied heterospecific responses to avian alarm signals that drive the formation of anti-predator groups but are also used during intraspecific interactions. In three species-rich communities in the western Himalayas, alarm signals vary drastically across species. We show that, independently of differences in their calls, birds respond strongly to the alarm signals of other species with which they co-occur and much more weakly to those of species with which they do not co-occur. These results suggest that previous exposure and learning maintain heterospecific responses in the face of widespread signal divergence. At an area where only two species regularly interact, one species'' calls incorporate the call of the other. We demonstrate experimentally that signal copying allows strong responses even without previous exposure and suggest that such hybrid calls may be especially favoured when pairwise interactions between species are strong.     

Patterns of endemic extinctions among island bird species

The relationship between island biogeography and the vulnerability of island biota to extinction as a result of human activities was examined. In particular, this study analyzed whether island area, maximum elevation of an island, isolation from the nearest continental landmass, or date of human colonization had statistically significant relationships with the proportion of endemic island bird species that have become endangered or extinct. The study examined islands or island groups with endemic bird species, and which have never been connected to a continental landmass. Both modern and fossil bird species were incorporated into the analysis. Islands that were colonized by humans earliest had the lowest proportion of modern species alone, and modern and fossil species combined, that have gone extinct. However, date of human arrival was not correlated with the proportion of modern species that are endangered. Maximum elevation of an island was negatively correlated with the proportion of modern species that are extinct, and was positively correlated with the proportion of modern species that are endangered. Area was negatively correlated with the proportion of modern species that are endangered. Isolation of islands was not significantly correlated with the proportion of modern species extinct or endangered, but was positively correlated with the proportion of modern and fossil species combined that have gone extinct. These results indicate that the initial spasm of island bird extinctions due to human contact may have, in part, passed. They also indicate that bird species on islands colonized earliest by humans may have had more time to adapt to the presence of man and his commensal species, resulting in reduced extinction rates.     

Arrival fat and reproductive performance in a long-distance passerine migrant

Long-distance passerine migrants deposit substantial fat stores to fuel their migratory journey. Many of those migratory birds arrive at their northerly breeding grounds with larger fat stores than were necessary to reach their breeding area. Both male and female American Redstarts ( Setophaga ruticilla) arrived to breed in Michigan's Upper Peninsula with fat, and females arrived with more fat than males in 2 out of 3 years. We test the hypothesis that migrants arriving at the breeding grounds with more body fat have higher reproductive success than birds arriving with little or no fat. Females, and to a lesser extent males, that arrive with fat experience gains in reproductive performance as evidenced by increased clutch size, egg volume, and nestling mass. The results have implications for understanding how events occurring during one phase of the annual cycle influence survival and/or reproductive performance in subsequent phases.     

Corticosterone,food intake and refueling in a long-distance migrant

Elevated baseline corticosterone levels function to mobilize energy in predictable life-history stages, such as bird migration. At the same time, baseline corticosterone has a permissive effect on the accumulation of fat stores (fueling) needed for migratory flight. Most migrants alternate flight bouts with stopovers, during which they replenish the fuel used during the preceding flight (refueling). The role of corticosterone in refueling is currently unclear. In a fasting–re-feeding experiment on northern wheatears (Oenanthe oenanthe) in autumn we found that baseline total and free corticosterone levels were negatively related with both food intake and the rate of fuel deposition after fasting. This confirms our earlier findings in wild conspecifics in spring and indicates that corticosterone does not stimulate stopover refueling. Whether the negative relationship between baseline corticosterone level and fuel deposition rate is causal is questionable, because within-individual comparison of corticosterone metabolite levels in droppings did not reveal differences between refueling and control periods. In other words, corticosterone does not appear to be down-regulated during refueling, which would be expected if it directly hampers refueling. We discuss possible correlates of corticosterone level that may explain the negative association between corticosterone and stopover refueling. Additionally, we found that fasting decreases total corticosterone level, which contrasts with previous studies. We propose that the difference is due to the other studies being conducted outside of the migration life-history stage, and provide a possible explanation for the decrease in corticosterone during fasting in migrating birds.     

Migratory connectivity and population-specific migration routes in a long-distance migratory bird

Knowledge about migratory connectivity, the degree to which individuals from the same breeding site migrate to the same wintering site, is essential to understand processes affecting populations of migrants throughout the annual cycle. Here, we study the migration system of a long-distance migratory bird, the Montagu''s harrier Circus pygargus, by tracking individuals from different breeding populations throughout northern Europe. We identified three main migration routes towards wintering areas in sub-Saharan Africa. Wintering areas and migration routes of different breeding populations overlapped, a pattern best described by ‘weak (diffuse) connectivity’. Migratory performance, i.e. timing, duration, distance and speed of migration, was surprisingly similar for the three routes despite differences in habitat characteristics. This study provides, to our knowledge, a first comprehensive overview of the migration system of a Palaearctic-African long-distance migrant. We emphasize the importance of spatial scale (e.g. distances between breeding populations) in defining patterns of connectivity and suggest that knowledge about fundamental aspects determining distribution patterns, such as the among-individual variation in mean migration directions, is required to ultimately understand migratory connectivity. Furthermore, we stress that for conservation purposes it is pivotal to consider wintering areas as well as migration routes and in particular stopover sites.     

Long-term trends in first arrival and first egg laying dates of some migrant and resident bird species in northern Italy

Climate change is affecting the phenology of seasonal events in Europe and the Northern Hemisphere, as shown by several studies of birds’ timing of migration and reproduction. Here, we analyse the long-term (1982–2006) trends of first arrival dates of four long-distance migratory birds [swift (Apus apus), nightingale (Luscinia megarhynchos), barn swallow (Hirundo rustica), and house martin (Delichon urbicum)] and first egg laying dates of two migrant (swift, barn swallow) and two resident species [starling (Sturnus vulgaris), Italian sparrow (Passer italiae)] at a study site in northern Italy. We also addressed the effects of local weather (temperature and precipitation) and a climate index (the North Atlantic Oscillation, NAO) on the interannual variability of phenological events. We found that the swift and the barn swallow significantly advanced both arrival and laying dates, whereas all other species did not show any significant temporal trend in either arrival or laying date. The earlier arrival of swifts was explained by increasing local temperatures in April, whereas this was not the case for arrival dates of swallows and first egg laying dates of both species. In addition, arrival dates of house martins were earlier following high NAO winters, while nightingale arrival was earlier when local spring rainfall was greater. Finally, Italian sparrow onset of reproduction was anticipated by greater spring rainfall, but delayed by high spring NAO anomalies, and swift’s onset of reproduction was anticipated by abundant rainfall prior to reproduction. There were no significant temporal trends in the interval between onset of laying and arrival in either the swift or the barn swallow. Our findings therefore indicate that birds may show idiosyncratic responses to climate variability at different spatial scales, though some species may be adjusting their calendar to rapidly changing climatic conditions.     

Phenological observations of major plant growth forms and species in montane and Eriophorum vaginatum tussock tundra in central Alaska

The development stages of several tundra plant species were observed during the summers of 1977 and 1978 in different vegetation zones in a snow accumulation area and in tussock tundra. Leaf maturation and senescence tend towards synchrony regardless of the time of emergence from under the snow. Flowering stages are less synchronous and general than are the vegetation stages within a growth form.     

Similarities and differences in rubber biochemistry among plant species.

This report reviews aspects of the biochemical regulation of rubber yield and rubber quality in three contrasting rubber-producing species, Hevea brasiliensis, Parthenium argentatum and Ficus elastica. Although many similarities are revealed, considerable differences also exist in enzymatic mechanisms regulating biosynthetic rate and the molecular weight of the rubber biopolymers produced. In all three species, rubber molecule initiation, biosynthetic rate and molecular weight, in vitro, are dependent upon substrate concentration and the ratio of isopentenyl pyrophosphate (IPP, the elongation substrate, or monomer) and farnesyl pyrophosphate (FPP, an initiator), but these parameters are affected by intrinsic properties of the rubber transferases as well. All three rubber transferases are capable of producing a wide range of rubber molecular weight, depending upon substrate concentration, clearly demonstrating that the transferases are not the prime determinants of product size in vivo. However, despite these commonalities, considerable differences exist between the species with respect to cosubstrate effects, binding constants, effective concentration ranges, and the role of negative cooperativity in vitro. The P. argentatum rubber transferase appears to exert more control over the molecular weight it produces than the other two species and may, therefore, provide the best prospect for the source of genes for transformation of annual crop species.The kinetic data, from the three contrasting rubber-producing species, also were used to develop a model of the rubber transferase active site in which, in addition to separate IPP and allylic-PP binding sites, there exists a hydrophobic region that interacts with the linear portion of allylic-PP initiator proximal to the pyrophosphate. Substrate affinity increases until the active site is traversed and the rubber interior of the rubber particle is reached. The kinetic data suggest that the hydrophobic region in H. brasiliensis and F. elastica is about 1.8 nm long but only 1.3 nm in P. argentatum. The estimates are supported by measurements of the rubber particle monolayer membrane using electron paramagnetic resonance spectroscopy.     

Migratory stopover in the long-distance migrant silver-haired bat, Lasionycteris noctivagans

1. Some bat species make long-distance latitudinal migrations between summer and winter grounds, but because of their elusive nature, few aspects of their biology are well understood. The need for migratory stopover sites to rest and refuel, such as used by birds, has been repeatedly suggested, but not previously tested empirically in bats. 2. We studied migrating silver-haired bats (Lasionycteris noctivagans) at Long Point, ON, Canada. We used digital radio-transmitters to track 30 bats using an array of five towers that effectively covered the entire region (c. 20 × 40 km). We measured stopover duration and departure direction, and documented movement patterns, foraging activity and roost sites. We measured body composition on arrival using quantitative magnetic resonance and simulated long-distance migration using observed body composition to predict migration range and rate. 3. Migration occurred in two waves (late August and mid-September). Most bats stayed 1-2 days, although two remained >2 weeks. One third of the bats foraged while at the site, many foraging opportunistically on nights when rain precluded continued migration. Bats roosted in a variety of tree species and manmade structures in natural and developed areas. Half of the bats departed across Lake Erie (minimum crossing distance c. 38 km) while half departed along the shoreline. 4. Simulations predicted a migration rate of c. 250-275 km per day and suggest that all but one of the bats in our study carried sufficient fuel stores to reach the putative wintering area (estimated distance 1500 km) without further refuelling. 5. Our results suggest that migrating bats stopover for sanctuary or short-term rest as opposed to extended rest and refuelling as in many songbirds. Daily torpor could reduce energy costs when not in flight, minimizing the need for extended stopovers and allowing bats to potentially complete their migration at a fraction of the time and energy cost of similar sized birds.     

Assessing the risk of potentially invasive plant species in central Europe

A risk assessment system was developed to assess the invasion potential of new environmental weeds in central Europe. A pre-evaluation step excludes species that are officially controlled, widespread, or intended for use in protected cultures only. Species eligible for risk assessment are classified into three categories (high risk, further observation required, low risk) by rating them according to various biogeographical and ecological aspects. The rating system was validated by testing 47 well-known invasive plant species of temperate Europe and 193 exotic plants which have failed to establish themselves in Switzerland. The overall accuracy was 65%. Accuracy of correctly predicting invasive species was 77%, while accuracy of correctly predicting non-invasive species was 62%. The proposed risk assessment protocol should be understood as a first attempt for a European country and needs modifications. These can only be achieved by applying the system in practice.     

The pattern of influenza virus attachment varies among wild bird species

The ability to attach to host cells is one of the main determinants of the host range of influenza A viruses. By using virus histochemistry, we investigate the pattern of virus attachment of both a human and an avian influenza virus in colon and trachea sections from 12 wild bird species. We show that significant variations exist, even between closely related avian species, which suggests that the ability of wild birds to serve as hosts for influenza viruses strongly varies among species. These results will prove valuable to assess the possibilities of interspecies transmission of influenza viruses in natural environments and better understand the ecology of influenza.     

Ecological similarities and differences among littoral species of Ceriodaphnia

In Artemia franciscana, enriched for 24 h with emulsified lipids, thefatty acid DHA (22:63) is unstable. In rotifers the level of DHA canbe stabilised by adding algae rich in DHA to the fish tanks. To test thismethod for A. franciscana, enriched A. franciscana was incubated with thealga Isochrysis galbana, which is rich in lipids and DHA, at sixconcentrations ranging from 1 to 20 mg C l^–1 at 13–14°C. After lipid enrichment, A. franciscana contained15% lipids of which 79% (116 mg g DW^–1) werefatty acids. Of the fatty acids, 17% was DHA (19.8 mg gDW^–1). After 72 hours incubation with I. galbana, the level ofDHA decreased to 1.6–3.2 mg g DW^–1, which was areduction by 84–92%. This was independent of the algalconcentration. The amount of total fatty acids decreased to 53–73 mg gDW^–1, a reduction by 37–54%, independent of thealgal concentration. The rates of loss of the fatty acids, and especiallyDHA, was greater during the first 24 h at the highest algal concentrations(8, 10 and 20 mg C l^–1). Enriched A. franciscana shouldtherefore not be incubated with high algal concentrations (>6 mg Cl^–1) during first feeding of marine fish larvae.     

Assessment of genetic variability among selected species of Apocynaceae

Family Apocynaceae is an economically important family grown as ornamental plants and many wild species have medicinal uses as well. The aim of the present study was to understand the level and pattern of genetic variability among the selected individuals of Apocynaceae. For this purpose, three species of different genera of Apocynaceae, Thevetia peruviana, Alstonia scholaris and Catharanthus roseus, were collected from Rawalpindi and Quaid-i-Azam University forest, Islamabad. To evaluate the level of polymorphism within the species and members of different species, randomly amplified polymorphic DNA (RAPD) markers were used. A series of OPC RAPD primers were used; only six primers of OPC series gave amplification. Highest genetic variation at interspecific and intraspecific levels was shown by OPC 9 and the lowest polymorphism was observed in OPC 4. The data was analyzed by using software Statistica 5.5. In total 105 monomorphic and 272 polymorphic bands were produced from all primers. Therefore, out of 322 amplified products, 26% were monomorphic and 68% were polymorphic. Low genetic diversification was observed both at intraspecific and interspecific level. At the molecular level Alstonia scholaris and Catharanthus roseus (subfamily Plumerioideae) appeared in a group and Thevetia peruviana (subfamily Rauvolfoideae) formed another group, confirming the classification based on morphological characters.