Manipulation of laying effort reveals habitat-specific variation in egg production constraints in Great Tits (Parus major)

It has been suggested that a bird's clutch size is not limited by the amount of resources available at the time of laying but that differences in the availability of food for nestlings is the ultimate underlying factor determining spatio-temporal variations in clutch size. However, habitat-related variations in egg production ability has yet to be investigated explicitly. We studied the breeding of Great Tits Parus major in deciduous and coniferous forests in the same area. The sizes of both the clutches and the eggs were, on average, larger in the former habitat than in the latter. A number of females were induced to lay more eggs than usual by removing four eggs from designated experimental clutches early in the laying period. These manipulated females laid approximately one egg more than control females, with the number of additional eggs laid not differing between the habitats. However, in both study years the relative size of the extra eggs – relative to the mean size of earlier laid eggs of the same clutch – was smaller in the coniferous habitat than in the deciduous habitat, while there was no habitat-related difference in the relative size of the last-laid eggs of control clutches. This result indicates that some form of proximate limitation during egg-laying period can contribute to the relatively small clutches and eggs in the coniferous habitat. Our results emphasize the need to take egg production costs into account when attempting to account for spatial variation in the reproductive behaviour of birds.     

Body mass of female great tits (Parus major) at egg laying

Based on automated weighing of nest-boxes, we found that female great tits (Parus major) usually maintained their body mass during the egg-laying period. A drop in temperature (3°C or more) during laying was followed by a drop in body mass, and female body mass also depended slightly but significantly on mean temperature on the other days. Day to day change in body mass depended negatively on the actual body mass. Moreover, the repeatability of the morning body mass was high (r _I =0.90, n=24). Thus, female body mass seems to be regulated around a female specific, but temperature-dependent, level during laying. The lack of strong correlation between female average body mass and clutch size makes it improbable that body mass at laying plays a leading, proximate role in the control of clutch-size of great tits.     

Breeding patterns of great tits ( Parus major ) in pine forests along the Portuguese west coast

The breeding biology of great tits (Parus major) was studied in two forests of maritime pine (Pinus pinaster) on the west coast of Portugal, 200 km apart: Leiria (north) and Aposti?a (south). These two forests are located in a transition zone between Atlantic climate in the north, and Mediterranean climate in the south. Breeding onset was, on average, in the second and third week of March, which are the earliest records of breeding for this species. The southern population started to breed earlier than the northern one and produced a larger first clutch, 8.3 and 7.4 eggs, respectively. Corresponding to larger clutch sizes, we also found a higher first brood fledgling production in Aposti?a compared to Leiria, 6.1 and 5.4 fledglings, respectively. However, the total number of fledglings produced per pair was higher in Leiria (8.3) than in Aposti?a (7.7), due to higher productivity of second clutches (4.7 and 2.7 fledglings, respectively). Accordingly, the allocation of eggs between successive breeding attempts was more equal in Leiria. Results are discussed in accordance to the different climatic patterns in the two areas. It is suggested that the timing of breeding and different allocation of reproductive investment between successive breeding attempts play an important role in optimizing breeding tactics in this facultative multiple-brooded passerine in different climatic areas.     

Blood sampling does not affect fledging success and fledgling local recruitment in coal tits ( Parus ater)

In order to assess the potentially harmful consequences of blood sampling in nestling coal tits (Parus ater), we analysed fledging success, fledgling local recruitment and recruit natal dispersal for nestlings originating from 27 blood-sampled broods and nestlings from 39 control broods. No adverse effects of blood sampling were detectable.     

大车前胚乳发育的超微结构研究

采用透射电镜技术对大车前(Plantago major L.)胚乳发育的超微结构进行了研究。结果表明:(1)大车前为细胞型胚乳;初生胚乳核经一次横分裂产生1个珠孔室细胞和1个合点室细胞;珠孔室两次纵向分裂一次横向分裂形成2层8个细胞,位于上层的4个细胞发育为4个珠孔吸器,位于下层的4个细胞发育为胚乳本体;合点室细胞进行一次核分裂,发育为两核的合点吸器。(2)珠孔吸器呈管状插入珠被组织,珠孔端细胞壁加厚呈现少量分支并具有壁内突,壁内突周围细胞质里分布着大量线粒体、粗面内质网、高尔基体、质体等,细胞核与核仁明显,细胞质浓厚,代谢活动旺盛;球胚期,珠孔吸器的体积呈现最大值,珠孔吸器周围的珠被组织均被水解,形成明显的空腔。珠孔吸器从珠被组织吸收并转运营养物质至胚乳本体,参与胚乳的构建与营养物质的贮藏。球胚后期,珠孔吸器逐渐退化。(3)4个胚乳本体原始细胞具旺盛的分生能力,经不断的平周与垂周分裂增加胚乳细胞数目,使胚乳本体呈现圆球体状,并将胚包围其中;珠孔吸器、合点吸器以及珠被绒毡层吸收转运的营养物质贮存在胚乳本体;球胚后期,随着胚柄的退化,胚体周围的胚乳细胞被水解,为发育的胚所利用。(4)合点吸器的2个细胞核与核仁巨大,线粒体、质体、高尔基体、内质网主要绕核分布,液泡化明显;胚体与胚乳本体的体积增大,逐渐将合点吸器向胚珠合点部位挤压,合点吸器周围的合点组织逐渐被水解,形成巨大空腔。合点吸器自珠心组织吸收并转运营养物质至胚乳本体,参与胚乳的结构构建与营养物质的贮藏。球胚后期,合点吸器逐渐失去功能,呈现退化状态。     

Peritrophic matrix of Phlebotomus duboscqi and its kinetics during Leishmania major development

Light microscopy of native preparations, histology, and electron microscopy have revealed that Phlebotomus duboscqi belongs to a class of sand fly species with prompt development of the peritrophic matrix (PM). Secretion of electron-lucent fibrils, presumably chitin, starts immediately after the ingestion of a blood meal and, about 6 h later, is followed by secretion of amorphous electron-dense components, presumably proteins and glycoproteins. The PM matures in less than 12 h and consists of a thin laminar outer layer and a thick amorphous inner layer. No differences have been found in the timing of the disintegration of the PM in females infected with Leishmania major. In both groups of females (infected and uninfected), the disintegration of the PM is initiated at the posterior end. Although parasites are present at high densities in the anterior part of the blood meal bolus, they escape from the PM at the posterior end only. These results suggest that L. major chitinase does not have an important role in parasite escape from the PM. Promastigotes remain in the intraperitrophic space until the PM is broken down by sand-fly-derived chitinases and only then migrate anteriorly. Disintegration of the PM occurs simultaneously with the morphological transformation of parasites from procyclic forms to long nectomonads. A novel role is ascribed to the anterior plug, a component of the PM secreted by the thoracic midgut; this plug functions as a temporary barrier to stop the forward migration of nectomonads to the thoracic midgut. This work was supported by the Ministry of Education of the Czech Republic (projects MSM0021620828 and LC06009).     

Cuckoldry and recapture probability of adult males are not related in the socially monogamous coal tit ( Parus ater)

Despite substantial research effort, the benefits of female extra-pair matings in socially monogamous bird species remain elusive. The good genes hypothesis assumes that females engage in extra-pair copulations with males of superior genetic quality compared to their respective social mate. Therefore, a negative association between the degree of cuckoldry and male survival is predicted, if genetic quality is phenotypically reflected by high viability. Furthermore, genetic sires of extra-pair offspring (EPO) should survive better than the social fathers they cuckolded. We tested these predictions in a nestbox population of the coal tit (Parus ater), a socially monogamous passerine with low breeding dispersal and high rates of extra-pair paternity (EPP). Based on 257 genotyped first broods of two consecutive years, we found no relationship between the incidence of EPP or the proportion of EPO within a given brood and male or female recapture probabilities. Furthermore, recapture rates did not differ between social and genetic fathers of EPO or males that did or did not appear as extra-pair sires in other broods. Our results were not affected by differential (short-range) breeding dispersal with respect to EPP or by other potentially confounding variables. Hence, they are not in accordance with the good genes as viability genes hypothesis.Communicated by F. Bairlein     

Variation in diapause and sex ratio in the parasitoidAsobara tabida

Asobara tabida Nees (Hymenoptera: Braconidae) is a widespread parasitoid, attacking larvae ofDrosophila (Diptera: Drosophilidae) species in fermenting substrates. In this species, geographic variation is found in the percentage of parasitoids entering diapause and in the sex ratio of emerging parasitoids. Percentage diapause appears to be influenced by host species (more parasitoids enter diapause inD. melanogaster Meigen than inD. subobscura Collin) and temperature. It is not correlated with any of the abiotic factors investigated, but is correlated with survival probability inD. melanogaster larvae and with the time of year in which the experiment was conducted (even though none of the parasitoids experienced natural day light). Sex ratio was only found to correlate with percentage diapause, suggesting that males enter diapause more frequently than females. It is concluded thatA. tabida uses diapause to survive both unfavourable abiotic and biotic circumstances.     

Blood values of Bald Ibis ( Geronticus eremita) in captivity: comparative ranges and variability with age, sex and physical condition

The Bald Ibis (Geronticus eremita) is one of the worlds most threatened species of birds. The number of individuals in captivity is several times greater than the number of individuals in the wild, so that the re-introduction of individuals from captive breeding into their natural habitat may be vital for the recovery of the species. A knowledge of the health problems associated with the handling of captive individuals and the improvement of their veterinary care could have great importance in determining the success of these captive breeding programs. Haematology and blood chemistry are very useful complementary tools in the diagnosis and treatment of diseases in birds, and provide valuable information about the individuals nutritional status and physical condition. The present work reports haematocrit and blood chemistry values for individuals belonging to a captive population of this species, and analyses their variability with respect to age, sex, and physical condition of the animals. Adults presented greater values of haematocrit, uric acid, total proteins, cholesterol, and aspartate amine transferase than the young. With respect to sex differences, adult female birds had higher concentrations of alkaline phosphatase than males, contrary to previous results for captive individuals of this species. The condition index of adults was positively correlated with triglycerides, glucose, and alkaline phosphatase levels, and negatively with urea and lactate dehydrogenase levels. These results may be very useful as a complementary diagnosis tool during the veterinary care of individuals of this species included in re-introduction programs.     

Morphological variation in a European population of Great Crested GrebesPodiceps cristatus in relation to age, sex and season

Summary A sample of 1450 Great Crested Grebes from the non-breeding season (August–March) which had accidentally drowned in fishing nets in Lake IJsselmeer, The Netherlands, was examined for age and sex differences in linear measurements, body mass, plumage, leg colour and gonad condition. During skinning and drying, wings of non-moulting birds decreased 2.41 mm in length, and wings of wing-moulting birds significantly more: 4.72 mm. The shrinkage is due to changes in the feather follicles and wing elements and not to changes in the actual feather length. Measurements of body, wing, bill, tarsus and keel lengths showed that males are larger than females. The sexual dimorphism is most pronounced in bill length (11 % difference). Differences between juvenile (first winter) and adult birds are small or non-existent. A discriminant function incorporating wing and bill length (age groups lumped), correctly classified the sex of 89 % of the original sample, and 85 % of an independent sample of starved beached birds. The presence (in juveniles) or absence (in adults) of brown lesser upper wing-coverts is a reliable ageing criterion during the whole non-breeding season: only 2 % juvenile females are misidentified. The striped head plumage of juveniles disappears during winter, but there is a large variation between individuals. Adults tend to have one or more greater upper wing-coverts with white inner vanes. Adults often have a wider white stripe between eye and crest than juveniles. Adult males in summer plumage have longer crests and tippets than females. The colour and barring patterns of the inner tarsi vary greatly. Adults generally have a higher density of black bars than juveniles. Adult males appear to have two peaks in testis size: one in spring and a second one in autumn. The grebes weigh least during the wing moult period in August–September. Average body masses of all age and sex groups increase from September to November and then remain essentially stable until April. This pattern is very different from the peaked body mass pattern, described for dabbling ducks and waders wintering at the same latitudes, but resembles the body mass patterns of two sawbill species which also feed on fish in Lake IJsselmeer.

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Morphologische Variation einer europäischen Population des HaubentauchersPodiceps cristatus in Beziehung zu Alter, Geschlecht und Jahreszeit

Zusammenfassung 1450 in Fischernetzen im IJsselmeer/Niederlande außerhalb der Brutzeit (August bis März) ertrunkenen Haubentaucher wurden auf Alters- und Geschlechtsunterschiede in linearen Körpermaßen, Gewicht, Gefieder, Beinfarbe und Gonadenzustand untersucht. Während des Abhäutens und Trocknens schrumpfte die Flügellänge nicht mausernder Vögel um 2,41 mm, die von Vögeln mit Flügelmauser signifikant mehr um 4,72 mm. Die Verkürzungen konnten auf Veränderungen der Federfollikel und des Flügelkörpers zurückgeführt werden; die Federlängen blieben gleich. Die Werte für Körper-, Flügel-, Schnabel-, Tarsus- und Brustbeinlänge sind bei größer als bei . Der Sexualdimorphismus wird am deutlichsten bei der Schnabellänge (11 % Differenz). Unterschiede zwischen Jungvögeln (1. Winter) und Altvögeln sind klein oder existieren nicht. Eine Diskriminanzfunktion basierend auf Flügel-und Schnabellänge (alle Altersklassen) klassifizierte nach Geschlechtern 89 % der Original-Stichprobe und 85 % einer unabhängigen Stichprobe am Strand gefundener Vögel richtig. Das Vorhandensein (Jungvögel) oder das Fehlen (Altvögel) von braunen kleinen Armdecken ist ein verläßliches Alterskriterium während der gesamten Nicht-Brutzeit (nur 2 % der jungen fehlbestimmt). Das gestreifte Kopfgefieder der Jungvögel verschwindet während des Winters; die individuelle Streuung ist aber groß. Altvögel haben oft eine oder mehrere große Armdecken mit weißen Innenfahnen. Altvögel weisen oft einen breiteren Streifen zwischen Auge und Haube als Jungvögel auf. Ad. im Sommerkleid haben längere Hauben und Krausen als . Die Farbe und das Muster der Streifung der inneren Tarsi variiert erheblich. Ad. weisen im allgemeinen eine höhere Dichte schwarzer Streifen auf als Jungvögel. Ad. scheinen zwei Maxima der Hodengröße aufzuweisen: eines im Frühjahr und eines im Herbst. Die Taucher wiegen am wenigsten während der Flügelmauser im August–September. Die mittleren Massen aller Alters- und Geschlechtsklassen steigen von September bis November an und bleiben dann im wesentlichen konstant bis zum April. Dieses Muster unterscheidet sich von dem mit einem Gipfel bei Schwimmenten und Limikolen, die in den gleichen Breiten überwintern, ähnelt aber dem Massenmuster zweier Sägerarten, die sich ebenfalls von Fischen im IJsselmeer ernähren.

     

华北平原地区景观格局对麦田害螨种群数量的影响

农业生产的集约化经营导致农田景观格局日趋单一,而农田景观格局的变化势必对害虫种群产生深刻的影响,阐明景观因子对害虫种群的作用是通过生境管理进行害虫控制的基础。以华北平原地区的山东省为研究区域,24个县级单元为样点,通过对卫星遥感影像和土地覆盖分类数据的分析,获取了样点单元的景观格局指数,同时定点调查了样点单元的麦田害螨种群数量。利用相关性分析明确了影响麦田中两种害螨—麦岩螨(Petrobia latens(Müller))和麦圆叶爪螨(Penthaleus major(Duges))种群发生的主要景观因子。研究结果表明景观因子对麦田中两种害螨种群均有显著影响,而两种害螨对景观因子的响应并不一致。麦岩螨的发生量与森林的最大斑块面积指数和平均斑块面积均呈显著正相关,而与森林类的形状和水体的景观形状指数均存在显著负相关;麦圆叶爪螨的发生量同水体的总面积、斑块面积比例、最大斑块面积指数以及县域范围的平均斑块面积均呈显著负相关,而与水体类的形状呈显著正相关。因此在麦田害螨发生较重的地区,在区域性景观规划时,可以通过优化农田周围的森林和水体管理,不利于其种群发生,从而达到对麦田害螨种群生态调控的目的。     

Phylogeography of the blue tit ( Parus teneriffae -group) on the Canary Islands based on mitochondrial DNA sequence data and morphometrics

An analysis of the sequences of the mitochondrial cytochrome b gene (1005 bp) of the Parus teneriffae-group from the Canary Islands and North Africa revealed new insights into the phylogeography of this taxon. The origin of the radiation on the Canarian Archipelago was apparently one of the central islands—Tenerife or Gran Canaria. The populations on El Hierro (P. t. ombriosus) and La Palma (P. t. palmensis) represent distinct monophyletic lineages. Blue tits from Gran Canaria are genetically distinct from those of La Gomera and Tenerife (P. t. teneriffae), which supports the results of other studies and suggests the existence of an—until now—undescribed taxon there. In contrast, the populations on the eastern islands of Fuerteventura and Lanzarote (P. t. degener) could not be distinguished from North African blue tits (P. t. ultramarinus), and these populations should be subsumed under the subspecies ultramarinus. Taxonomic recommendations based on these results include the distinction of the northern European P. caeruleus from P. teneriffae, including blue tits from North Africa and the Canary Islands, the treatment of degener and ultramarinus as synonymous (P. teneriffae ultramarinus) and a new blue tit taxon on the island of Gran Canaria (P. t. hedwigii nov. ssp.), which is formally described. The genetic results are in parts supported by bioacoustic and morphological data.     

Host age, sex, and pathogen exposure level as factors in the susceptibility of Musca domestica to Entomophthora muscae

Adult Musca domestica were exposed to conidial showers from cadavers that were killed by Entomophthora muscae. Of the 4 host ages (14 days, 7 days, 3 days and <1 day), older flies were more likely to die without postmortem signs of infection, while younger flies were more likely to die with signs and produce primary conidia. The youngest fly group also succumbed to infection significantly sooner than older flies. Total mortality did not differ for the 2 sexes, but females died significantly more often with signs in one trial. Males died significantly earlier than did females, but differences were not significant when the sexes were paired by weight. Increased levels of pathogen exposure significantly increased both total mortality and the number of flies dying with signs; it also decreased incubation period. The potential significance of these findings in the epidemiology of the disease is discussed.

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Zusammenfassung Die Mortalitätsrate von Musca domestica nach Behandlung mit Entomophthora muscae Sporen wurde in Laborversuchen in Abhängigkeit von Wirtsalter,-geschlecht und Expositionsdauer festgestellt. Fliegen verschiedenen Alters (14 Tage, 7 Tage, 3 Tage und jünger als 1 Tag) wurden gemeinsam in 237 ml Kartonbehältern gehalten. Die Behälter besassen Netzdeckel, auf denen frisch an einer Entomophthora Infektion gestorbene Fliegen ausgelegt wurden. Auf diese Weise wurden die Versuchstiere 8 Stunden (low exposure) bzw. 48 Stunden (high exposure) lang mit Entomophthora Sporen kontaminiert. Mit Hilfe von am Boden der Versuchsgefässe ausgelegten Objektträgern wurde die relative Menge Entomophthora Sporen festgestellt, der die Versuchstiere ausgesetzt waren. Der Totenfall wurde täglich für die Dauer von 10 Tagen registriert; dabei wurde zwischen Konidienträgern (external signs) und Leichen ohne Konidien (no external signs) unterschieden.Die Versuchsgruppen, die 48 Stunden lang mit Entomophthora Sporen behandelt worden waren, wiesen im Vergleich zu den kürzer behandelten Versuchsgruppen höhere Mortalität und einen höheren Anteil an Konidienträgern auf. Darüber hinaus wurde das Auftreten von Konidienträgern bei den länger behandelten Gruppen früher beobachtet. Im Vergleich zu unbehandelten Kontrollgruppen erhöhte die Behandlung mit Entomophthora Sporen auch die Rate nicht konidientragender Leichen.Bei gleicher Expositionsdauer zeigten Weibchen und Männchen ähnliche Mortalitätsraten. Ein höherer Anteil Konidienträger bei den Weibchen wurde bei einem von zwei entsprechenden Versuchen beobachtet. Konidienträger traten bei Weibchen später als bei Männchen auf. In Bezug auf die Inkubationszeit konnte kein geschlechsspezifischer Unterschied festgestellt werden, wenn Versuchsgruppen mit gleichem Gewicht verglichen wurden. Bei beiden Geschlechtern erfolgte die Bildung von Konidien bei grösseren Individuen später als bei kleineren Individuen.Das Alter der Versuchstiere beeinflusste sowohl die Mortalitätsrate als auch die Häufigkeit und das zeitliche Auftreten von Konidienträgern. Jüngere Fliegen wiesen einen höheren Anteil Konidienträger auf; bei Fliegen mit einem Alter von weniger als einem Tag wurde das Auftreten von Konidienträgern früher beobachtet als bei älteren Individuen.Die untersuchten Faktoren können auch für die Epidemiologie von Entomophthora freilebender Musca domestica Populationen eine wichtige Rolle spielen. In Populationen mit niedrigerem Durchschnittsalter wird sich eine Infektion rascher ausbreiten, da jüngere Fliegen eine kürzere Inkubationszeit aufweisen und auch nach kürzerer Kontaminationsdauer Konidien an den getöteten Individuen ausgebildet werden. Darüber hinaus wird sich eine Infektion dann rascher ausbreiten, wenn die Population mit einer grösseren Sporenmenge infiziert wird, da dann eine kürzere Inkubationzeit und ein höherer Anteil Konidienträger zu erwarten ist.

     

Plasma Glutathione and Carotenoid Coloration as Potential Biomarkers of Environmental Stress in Great Tits

Measures of oxidative stress in animals may be useful biomarkers of environmental stressors, such as anthropogenic pollution. In birds, studies of oxidative stress have focused on dietary antioxidants, primarily carotenoids, which are interesting due to their multiple physiological and pigmentary functions but therefore also unspecifically related to oxidative stress. A useful complementary biomarker may be the glutathione system, commonly used in human medicine, but rarely applied to wild, terrestrial vertebrates. In this study of urban versus rural adult and nestling great tits Parus major, we investigated both the carotenoid-based yellow plumage (by reflectance spectrometry) and the plasma levels of glutathione, the latter measured as total glutathione (tGSH) and as the ratio between oxidized and reduced glutathione (GSSG:GSH), respectively. We found that urban adults had higher current oxidative stress (GSSG:GSH) and paler yellow plumage compared to rural adults, suggesting elevated stress in the urban environment. Total glutathione levels (tGSH), however, which may indicate long-term up-regulation of the GSH reservoir, did not differ between the environments. Nestlings did not show any consistent pattern between environments in either tGSH or GSSG:GSH and, among individuals, glutathione levels were uncorrelated with carotenoid coloration. The results thus suggest some population-level correspondence between the two stress biomarkers in adult birds, but more work is obviously needed to understand how the two antioxidant systems interact in different individuals and in response to different environmental disturbances.     

Cost of reproduction: parental survival and production of recruits in the Willow Tit Parus montanus

Summary Brood sizes of the Willow Tit were altered experimentally by subtracting or adding two nestlings in 1986 and 1987 in the vicinity of Oulu, northern Finland. The manipulated broods were within the normal range observed in natural conditions. Unaltered broods were used as controls. Data from natural broods from 1978–1985 were available for comparison. When the nestlings were 13 days old they were ringed and weighed and their tarsus, wing, and tail lengths were measured. On the same day the parents were caught, weighed, and measured. In 1986 there were no differences in nestling mortality between the reduced, control, or enlarged broods; i.e. parents were able to fledge the two extra young. In 1987 starvation was most pronounced in the enlarged broods. This resulted in the number of fledglings being practically the same in each manipulation category. Especially the body weight, but also the other indices of body size, decreased as a function of the brood size category, suggesting that there may be quality differences between the young reared in different experimental groups. In 1986 there was a non-significant trend towards lower body weight of the parents attending reduced, control, or enlarged broods, in that order. In 1987 the differences were much smaller. These results were not due to size differences between the groups, so possibly the increased reproductive effort of raising extra young was responsible for the trend observed in 1986. There were no significant differences in parental survival associated with the manipulation category, although the trend in the females was consistent with the hypothesis of reproductive cost. It is possible that environmental conditions in 1986 were so favourable that the tits were not unduly stressed even when attending two extra young. Correlative data from 1978–1985 did not support the cost hypothesis either. A non-significant trend towards reduced post-fledging survival and recruitment of the young was observed with increased brood size. The average fitness value of parents, incorporating parental survival and number of recruits, showed that the success of the adults raising enlarged broods may be lower than that of others. It seems that the reproductive cost, if it exists, decreases individual fitness value by reducing the chances of recruiting descendants into the next generation. The reproductive stress may be insufficient to reduce the subsequent survival of parents. More data are however needed to confirm these results.