Lyme disease and migrating birds in the Saint Croix River Valley.

During a study of migrating land birds in 1987, we examined over 9,200 individual birds representing 99 species from the Saint Croix River Valley, a Lyme disease-endemic area of east central Minnesota and northwestern Wisconsin. We found that 250 deer tick (Ixodes dammini) larvae and nymphs infested 58 birds from 15 migrant species; 56 ticks (22.4%) were positive for the Lyme disease spirochete Borrelia burgdorferi. Five ground-foraging migrant bird species favoring mesic habitats, veery (Catharus fuscescens), ovenbird (Seiurus aurocapillus), northern waterthrush (S. novaboracensis), common yellowthroat (Geothlypis trichas), and swamp sparrow (Melospiza georgiana), accounted for nearly three-quarters of parasitized individuals. Nearly half of the spirochete-positive ticks were removed from migrating birds taken in a riparian floodplain forest. Recaptured migrants with infected ticks indicate that they transmit B. burgdorferi to hexapod larvae. We suggest that birds may be both an important local reservoir in the upper Mississippi Valley and long-distance dispersal agents for B. burgdorferi-infected ticks to other regions of the continent.     

Orientation and navigation of migrating birds

The question of how migrating birds find their way to winter quarters and back has fascinated humans since the beginning of scientific research into avian biology. Migrating birds have been shown to possess compass systems that allow them to select and maintain certain compass directions. Three such systems are known, solar, stellar and magnetic. Their details are not quite clear and need further research. Hierarchy and interaction of compass systems of migrating birds are poorly studied; different species may vary in this respect. During migration, birds learn to use maps that make true navigation possible, i.e. to detect their position relatively to the goal of movement. The physical nature of navigational maps is an object of intensive research; currently the most promising concepts are the geomagnetic and possibly olfactory maps. A significant contribution to the study of formation of navigational maps was made by Soviet/Russian researchers, whose work was published in Zoologicheskii Zhurnal (Sokolov et al., 1984). Migrating birds have no innate map, and first-autumn individuals reach their species-specific wintering areas by using compass sense and counting time that should be spent moving in certain genetically fixed directions. However, in recent years more and more data surface that suggest that juveniles (maybe not of all species) do have some mechanism of controlling their position on the migratory route that allows them to compensate for errors of the spatio-temporal programme of migration.     

Magnetic versus celestial orientation in migrating birds

When experimental orientation research began more than 35 years ago, the sun, the stars and later the magnetic field were shown to be involved in the orientation of migrating birds, together with wind, weather and certain landscape features. The interaction of these cues, however, was little understood and became a subject of intensive research. Just recently we have begun to understand how these different mechanisms might work together to enable birds to cope with the navigational tasks of migration over distances of up to 5000 km and more.     

Prevalence of Lyme disease Borrelia spp. in ticks from migratory birds on the Japanese mainland

Borrelia sp. prevalence in ticks on migratory birds was surveyed in central Japan. In autumn, a total of 1,733 birds representing 40 species were examined for ticks. A total of 361 ticks were obtained from 173 birds of 15 species, and these ticks were immature Haemaphysalis flava (94.4%), Haemaphysalis longicornis, Ixodes columnae, Ixodes persulcatus, Ixodes turdus, and an unidentified Ixodes species. Of these, 27 juveniles of H. flava on Turdus pallidus, Turdus cardis, or Emberiza spodocephala, 2 juveniles of I. persulcatus on T. pallidus, and 1 female H. flava molted from a T. pallidus-derived nymph were positive for the presence of Borrelia by Barbour-Stoenner-Kelly culture passages. In spring, a total of 16 ticks obtained from 102 birds of 21 species were negative for the spirochete. Isolates from 15 ticks were characterized by 5S-23S rRNA intergenic spacer restriction fragment length polymorphism analysis; all isolates were identified as Borrelia garinii with pattern B/B' based on the previous patterning. According to the intergenic spacer sequences, 2 of 15 isolates, strains Fi14f and Fi24f, were highly similar to B. garinii strains 935T of Korea and ChY13p of Inner Mongolia, China, respectively. These findings indicate that Lyme disease-causing B. garinii may have been introduced to Japan by migratory birds from northeastern China via Korea. Additionally, a case of transstadial transmission of B. garinii from nymph to adult H. flava suggests that the infected H. flava may transmit Borrelia to large animals.     

Long-distance migrating species of birds travel in larger groups

How individuals migrate over long distances is an enduring mystery of animal migration. Strong selection pressure for travelling in groups has been suggested in long-distance migrating species. Travelling in groups can reduce the energetic demands of long migration, increase navigational accuracy and favour group foraging at migratory halts. Nevertheless, this hypothesis has received scant attention. I examined evolutionary transitions in migration distance in all North American breeding species of birds. I documented 72 evolutionary shifts in migration distance in the pool of 409 species. In contrasting clades, long-distance migration, as opposed to short-distance migration, was associated with a larger travelling group size. No other transitions occurred alongside in other traits such as group size in the non-breeding season or body mass. The results suggest that larger group sizes have been beneficial in the evolution of long-distance migration in a large clade of birds.     

The problem of estimating wind drift in migrating birds

Whether migrating birds compensate for wind drift or not is a fundamental question in bird migration research. The procedures to demonstrate and quantitatively estimate wind drift or compensation are fraught with difficulties and pitfalls. In this paper, we evaluate four methods that have been used in several studies over the past decades. We evaluate the methods by analysing a model migratory movement with a realistic scatter in flight directions, for the ideal cases of full drift and complete compensation. Results obtained with the different methods are then compared with the "true behaviour" of the model movement, illustrating that spurious patterns of drift and compensation arise in some cases. We also illustrate and evaluate the different methods of estimating drift for a real case, based on tracking radar measurements of bird migration in relation to winds. Calculating the linear regression of mean geographic track (resulting flight direction) and heading directions (directions of the birds' body axis) of a migratory movement under different wind conditions in relation to the angle alpha (the angle between mean track and heading) always provides robust and reliable results. Comparing mean flight directions between occasions with winds from the left and right of the mean flight direction of the whole migratory movement also always provides expected and correct measures of drift. In contrast, regressions of individual flight directions in relation to alpha (the angle between track and heading for the specific individuals or flocks) are liable to produce biased and spurious results, overestimating compensation/overcompensation if following winds dominate in the analysis and overestimating drift/overdrift if opposed winds are dominating. Comparing mean directions for cases with winds from the left and right in relation to individual flight directions also gives biased and spurious results unless there is full variation in wind directions or an equal distribution of crosswinds from left and right. The results of the methodological evaluation and the analysis of the real case indicate that some earlier analyses of wind drift may have to be re-evaluated.     

Effect of endurance flight on haematocrit in migrating birds

The effects of an endurance flight on the haematocrit, the percentage of packed red blood cells per blood volume, were examined within the framework of six possible factors explaining possible changes in the haematocrit. Two approaches were adopted: (1) the haematocrit was studied in four species of passerine birds which landed on an Italian island after having crossed the Mediterranean Sea on their spring migration in a non-stop flight; (2) the haematocrit was evaluated in six individual red knots after a flight of 1, 2, 4 and 10 h in a wind tunnel and the data thus obtained compared with data on resting birds with or without food. In the four passerine species, the haematocrit decreased from 51% in fat birds to 48% in lean birds. In lean birds, the haematocrit dropped from 48% in birds with well-developed breast muscles to 36% in birds with emaciated breast muscles. In the red knots, the haematocrit was dependent on body mass in flying and resting birds. The haematocrit decreased from about 51% pre-flight to about 49% within 1 h of flight and remained at this level for up to 10 h of flight. Taking the results from the passerines and the red knots together, it seems that the haematocrit drops by a few percentage points within 1 h after the onset of flight, decreases very slowly with decreasing body mass and decreases more steeply in very lean birds having entered stage III of fasting. This indicates that dehydration is not an underlying factor in decreased haematocrit because if this were the case we would expect an increase with endurance flight. We found no effect of the presence of blood parasites on haematocrit. With the onset of flight, haemodilution may be adaptive, because it reduces blood viscosity and, thereby, energy expenditure by the heart, or it may be a sign of water conservation as an insurance against the risk of dehydration during long non-stop flights. During endurance flight, a reduction in the haematocrit may be adaptive, in that oxygen delivery capacity is adjusted to the decreased oxygen needs as body mass decreases. A decreasing haematocrit would also allow birds to reduce heart beat frequency and/or heart size, because blood viscosity decreases disproportionally with decreasing haematocrit. However, when energy stores are about to come to an end and birds increase protein breakdown, the haematocrit decreases even further, and birds probably become anaemic due to a reduced erythropoiesis.     

新疆阿尔泰山喀纳斯河谷鸟兽物种的红外相机监测

2014年6月至2016年8月, 利用红外相机技术对新疆喀纳斯国家级自然保护区内喀纳斯河谷的兽类和鸟类多样性进行了调查, 共布设36个相机位点, 累计12,006个拍摄日, 收集独立有效照片2,038张, 共鉴定野生动物51种, 其中兽类4目8科15种, 鸟类9目15科36种。记录到国家I级重点保护野生动物3种, 即紫貂(Martes zibellina)、貂熊(Gulo gulo)和黑鹳(Ciconia nigra); 国家II级保护动物11种。9种被中国脊椎动物红色名录列为受威胁物种, 其中极危(CR) 1种, 即驼鹿(Alces alces); 濒危(EN) 3种, 即貂熊、马鹿(Cervus canadensis)和松鸡(Tetrao urogallus); 易危(VU) 5种。白背啄木鸟(Dendrocopos leucotos)等14种鸟类为保护区新记录, 我们首次在野外拍摄到驼鹿指名亚种(A. a. alces)。物种相对多度指数(relative abundance index, RAI)分析结果显示, 马鹿为喀纳斯河谷兽类优势种(RAI = 9.878), 鸟类中星鸦(Nucifraga caryocatactes)相对多度最高(0.258)。我们建议保护区进一步对雪豹(Panthera uncia)、原麝(Moschus moschiferus)等物种开展专项调查和评估。本论文为阿尔泰山喀纳斯河谷鸟兽多样性研究提供了基础数据, 有助于后续物种保护和管理计划的开展。     

Heterothermy, and the energetic consequences of huddling in small migrating passerine birds

The success of migration of small passerine birds depends largely on effective refueling at stopover sites. In our previous studies, we found that hypothermia facilitates accumulation of fuel at the beginning of a stopover. Later we found that blackcaps, Sylvia atricapilla, might further reduce their energy expenditure by huddling while at rest. Here, we report experimental results supporting our hypothesis that huddling is beneficial to small migrating passerines both from energetic and thermoregulatory points of view. To test this hypothesis we measured metabolic rates and body temperatures of seven blackcaps placed in respirometry chambers overnight, either solitarily or in groups of three or four at ambient temperatures of 5, 10, and 15°C. Concurring with our predictions, huddling blackcaps maintained higher body temperatures than did solitary birds, but had mass-specific metabolic rates lower by ～30% than those of solitary individuals. Based on our previous studies, we estimated energy savings through huddling to be comparable to energy savings through hypothermia in solitary blackcaps and suggest that huddling may be an important way of saving energy for small passerine birds resting at migratory stopovers. At the same time it might offer the additional benefit of lower risk of predation. In this light, we predict that huddling occurs frequently in nature, leading to significant savings of energy, faster accumulation of fuel, presumably lower risk of becoming a prey, more successful migration, and eventually increased fitness.     

Mass changes in migrating birds: the evidence for fat and protein storage re-examined

The fact that one cannot kill a bird twice makes it very difficult to determine the relative contributions of fat and non-fat components to increases in body mass before migratory flights in individual birds. Knowing the relative contributions of these components is of obvious energetic interest since fat yields about eight times as much energy as fat-free muscle tissue. Several recent studies have failed to demonstrate convincingly, due to flaws in their analyses, that fat-free mass in addition to fat is accumulated before long-distance flights. We point out that regressions of fat or the non-fat component on total body mass cannot yield reliable estimates of the composition of individual mass changes in view of inter-individual variation in structural size, reserve levels or timing of storage. We suggest that studies over time of synchronous populations or marked individuals will give better answers. A re-analysis of published data indicates the widespread existence of fat-free tissue deposition during migration, whereas in some species fat alone explained the increase in total body mass. Larger species tend to incorporate a relatively higher proportion of non-fat components when increasing in mass. However, the comparative data set is not yet of sufficient quality to allow general statements on why, and to what extent in different individuals and species, non-fat tissue in addition to fat is deposited before take-off on migratory flights.     

四川木里县木里河与水洛河流域鸟类资源变化调查

将2004年4~12月对木里县木里河、水洛河流域的鸟类调查结果与1928年美国博物学家约瑟夫.洛克(Joseph F Rock)在该区域内的鸟类调查记录比较,结果表明:①2004年调查的种类为123种,少于1928年调查记录139种,而且2004年调查的时间更长;②2004年调查鸟类群落的多样性指数和均匀度都小于1928年;③2004年调查鸟类的优势种有5种,常见种12种,主要为农耕-民居生境鸟类,1928年没有优势种,常见种有35种,主要为森林-灌丛生境鸟类;④鸟类区系构成没有产生大的变化。优势类群变化的主要原因是海拔3000m以下森林和灌丛生境受到干扰,蜕变为农耕地-民居生境,该区域的生境与1928年相比,已受到了破坏。     

Optimal use of wind by migrating birds: combined drift and overcompensation

Migrating birds may save flying time by allowing themselves to be partially drifted by strong winds at high altitude and correcting for the displacement at low altitude under relatively weaker winds. This behaviour will be favourable with strong upper winds and with wind direction approx. 30 ° to 90 ° in relation to the goal direction (following side winds). Radar observations of drift in high altitude bird migration and visual records of low altitude overcompensation are compatible with the optimal flight behaviour of migrants at high and low altitude, respectively, as predicted from this hypothesis.