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Abstract: Throughout North America, many species of aerial insectivorous birds have exhibited steep declines. The timing of these declines coincides with changes in agriculture, perhaps signaling a causal link. Increased [...]

Abstract: Timing of breeding varies among waterfowl species and individuals, with strong effects on reproductive success, and may be related to habitat quality. Here, we analyse the start, span, and [...]

Temporal variation in exposure and (or) susceptibility to disease-causing agents may result in changing disease risks for offspring of seasonally reproducing organisms. Although increases in disease risk and disease-related mortality have been observed during the course of the breeding cycle in some systems, the extent to which this is a generalized ecological pattern remains uncertain. We obtained data during an outbreak of West Nile virus (WNV) associated mortality in 50 semicaptive Lesser Scaup (Aythya affinis (Eyton, 1838)) ducklings and used known-fate survival models to assess whether daily survival rate (DSR) was related to age, hatch date, immunogenic challenge, vector abundance, and risk of WNV infection. Ducklings produced late in the breeding cycle had lower survival probabilities, relative to earlier conspecifics, but the best predictor of DSR was relative risk, suggesting that reduced survival of late-hatched individuals may have been related to increasing exposure to WNV- infected vectors. Key words: Lesser Scaup, Aythya affinis, Culex tarsalis, disease risk, duckling mortality, hatch date, vector abundance. Les variations temporelles de l'exposition et de la susceptibilite a des agents pathogenes peuvent se traduire par des variations des risques de maladie pour la progeniture d'organismes a reproduction saisonniere. Si des augmentations des risques de maladie et de la mortalite associee aux maladies ont ete observees au fil du cycle de reproduction dans certains systemes, la question a savoir s'il s'agit d'un phenomene ecologique generalise ou non n'est pas resolue. Nous avons obtenu des donnees durant une flambee de mortalite associee au virus du Nil occidental (VNO) chez 50 canetons de petit fuligule (Aythya affinis (Eyton, 1838)) semi-captifs et utilise des modeles de survie reposant sur le sort connu pour evaluer si le taux de survie quotidien (TSQ) etait relie a l'age, la date de l'eclosion, des problemes immunogenes, l'abondance des vecteurs et le risque d'infection au VNO. Si les canetons produits tard durant le cycle de reproduction presentaient des probabilites de survie plus faibles que celles de leurs congeneres plus precoces, le risque relatif etait le meilleur predicteur du TSQ, ce qui donne a penser que les taux de survie plus faibles des individus eclos tardivement pourraient etre associes a une exposition accrue a des vecteurs infectes par le VNO. [Traduit par la Redaction] Mots-cles: petit fuligule, Aythya affinis, Culex tarsalis, risque de maladie, mortalite des canetons, date d'eclosion, abondance des vecteurs., Introduction Disease--any impairment of health resulting from microbes, parasites, or other pathogens--can affect the abundance of wildlife both directly and indirectly, either by causing mortality or by reducing the health [...]

Reproductive success often declines with breeding date in diverse taxa, including temperate-nesting bird species. The date hypothesis predicts that seasonally deteriorating environmental quality drives this pattern. While mechanisms are not fully understood, a seasonal increase in parasitism may contribute to the declining quality of nestlings hatched later in the season. We examined the effect of ectoparasites on seasonal variation in indices of nestling quality and survival in Tree Swallows (Tachycineta bicolor (Vieillot, 1808)) at breeding sites in British Columbia (PG) and Saskatchewan (SDNRA). In a parasite removal experiment, we detected no seasonal trend in flea abundance and, contrary to expectation, there were fewer blow flies in nests of late breeders. Negative effects of parasites on nestlings were documented at PG, where lengths of primary feather and head- bill were affected. Parental, rather than environmental, quality had the greatest effect on reproductive success at PG, as nestling survival declined seasonally regardless of treatment and despite seasonally increasing food biomass. Nestlings in control (i.e., parasitized) nests at SDNRA had elevated feather corticosterone levels, but no other effects of parasites were detected possibly because parent birds were of higher quality or parents and offspring had greater access to food such that nestlings were capable of coping with parasite-related challenges. Key words: date hypothesis, feather corticosterone, insecticide, nest parasites, nestling growth, nestling size, PHA test, quality hypothesis, Tachycineta bicolor, Tree Swallow. Resume : Le succes de reproduction diminue souvent plus la date de reproduction est tardive pour divers taxons, dont des especes d'oiseaux nidicoles de region temperee. L'hypothese de la date predit que ce phenomene est cause par la deterioration de la qualite du milieu au fil de la saison. Si la comprehension des mecanismes sous-jacents demeure incomplete, une augmentation saisonniere du parasitisme pourrait participer a la diminution de la qualite des oisillons d'eclosion tardive. Nous avons examine l'effet des ectoparasites sur les variations saisonnieres des indices de qualite et de survie des oisillons d'hirondelle bicolore (Tachycineta bicolor (Vieillot, 1808)) dans des aires de reproduction en Colombie-Britannique (PG) et en Saskatchewan (SDNRA). Dans une experience de retrait des parasites, nous n'avons decele aucune tendance saisonniere de l'abondance des puces et, contre toute attente, les nids d'oisillons plus tardifs comptaient moins de calliphores. Des effets negatifs de parasites sur les oisillons ont ete documentes au site PG, notamment sur la longueur tete-bec et des plumes primaires. La qualite parentale, plutot que du milieu ambiant, avait le plus important effet sur le succes de reproduction au site PG, la survie des oisillons diminuant au cours de la saison peu importe le traitement et malgre l'augmentation de la biomasse alimentaire durant cette periode. Les oisillons dans les nids temoins (c.-a-d., parasites) au site SDNRA presentaient de concentrations elevees de corticosterone dans les plumes, mais aucun autre effet de parasites n'a ete detecte, possiblement parce que la qualite des parents etait plus grande ou que les parents et leur progeniture beneficiaient d'un meilleur acces a la nourriture, de sorte que les oisillons etaient capables de s'adapter aux defis associes aux parasites. [Traduit par la Redaction] Mots-cles: hypothese de la date, corticosterone dans les plumes, insecticide, parasites du nid, croissance des oisillons, taille des oisillons, test a la PHA, hypothese de la qualite, Tachycineta bicolor, hirondelle bicolore., Introduction In many avian species, quality and survival of offspring declines with later breeding dates (Perrins 1970; Shutler et al. 2006; Verhulst and Nilsson 2008). Two general hypotheses have been [...]

Declining reproductive success among individuals that breed later in the season occurs in numerous taxa and is particularly well-documented in birds. Principal ideas advanced to explain this pattern, the date and parental quality hypotheses, consider the ultimate causes of this phenomenon and have received much attention; however, proximate mechanisms have not been clearly elucidated. Parental provisioning could mediate a seasonal decline in nestling fitness. We delayed hatch dates and manipulated brood sizes of Tree Swallows (Tachycineta bicolor (Vieillot, 1808)) to assess the ability of parents to compensate for deteriorating environmental conditions and increased demands of more chicks. We measured provisioning rates using audio recordings of nestlings begging. Brood size was the best predictor of provisioning frequency, with parents feeding larger broods more frequently than smaller ones. Delayed hatching did not reduce provisioning rate despite declining food abundance. Date and food abundance were unrelated to provisioning rate, suggesting no seasonal change in the quantity of food nestlings receive. However, provisioning frequency was informative about life-history strategies of Tree Swallows, showing that late breeders incurred the costs of deteriorating environmental conditions rather than passing these costs on to their offspring. Il se produit un succes reproductif reduit chez les individus qui se reproduisent plus tard en saison chez de nombreux taxons et le phenomene a ete particulierement bien etudie chez les oiseaux. Les theories principales avancees pour expliquer le phenomene, les hypotheses de la date et de la qualite des parents, considerent les causes ultimes et ont ete bien etudiees; les mecanismes proximaux n'ont cependant pas ete clairement elucides. L'approvisionnement parental pourrait expliquer un declin saisonnier de la fitness des petits au nid. Nous avons retarde les dates d'eclosion et manipule les tailles des couvees chez des hirondelles bicolores (Tachycineta bicolor (Vieillot, 1808)) afin d'evaluer la capacite des parents a compenser la degradation des conditions du milieu et les besoins accrus d' un nombre plus grand de petits. Nous avons mesure les taux d' approvisionnement a l' aide d' enregistrements audio des cris de sollicitation des petits au nid. La taille de la couvee est la meilleure variable predictive de la frequence des approvisionnements et les parents alimentent plus frequemment les couvees plus grandes que les plus petites. L'eclosion retardee ne reduit pas le taux d'approvisionnement malgre le declin de l'abondance de nourriture. Il n'y a pas de relation entre la date et l'abondance de nourriture, d'une part, et le taux d'approvisionnement, d'autre part, ce qui laisse croire qu'il n'y a pas de changement saisonnier dans la quantite de nourriture recue par les petits au nid. Cependant, la frequence des approvisionnements renseigne sur les strategies du cycle biologique des hirondelles bicolores, en montrant que les oiseaux qui se reproduisent tardivement subissent eux-memes les couts de la degradation des conditions du milieu plutot que de les transmettre a leurs rejetons. [Traduit par la Redaction], Introduction Declining reproductive success among individuals that breed later in the season has been observed in diverse taxa, including plants (Kelly and Levin 2000), arthropods (Cushman et al. 1994; Varpe [...]

A study was conducted to determine the central-cell correction for two donor impurities, sulfur and silicon, in gallium arsenide in a strong magnetic field. The far-infared source was a molecular-gas cavity pumped by a carbon dioxide laser. Radiation was carried out using light pipes and a top-loading probe. Results indicated that chemical shifts resulting from transition for two donors in gallium arsenide was over the range 0

We monitored wetland habitat use and inter-wetland moves of 52 Mallard (Anas platyrhynchos) broods near Yorkton, Saskatchewan. Brood-attending females were equipped with radio transmitters and their locations monitored daily. Duckling survival in the first two weeks after hatching was not related to distance traveled to the first wetland nor the total distance traveled overland in the 14-day period. Brood-rearing females were found on one to five wetlands in the first week after hatch (mode = 2), and most (17 of 32) remained on one wetland in the second week (range = 1-5). Broods were found most frequently (69-95% of days) on semi-permanent wetlands. Conductivity on most (>95%) of these wetlands was, Mallard broods typically use several wetlands during the brood-rearing period, but causes and consequences of these moves remain unresolved. Early studies of wetland use by Mallards (Anas platyrhynchos) relied on [...]

Several pulsed high field magnets for the pulsed field facilities in Australia and Belgium were developed and tested. Based on the requirements of a long life and a regular use at 60 T, the conductor was chosen to be CuAg with Kapton insulation. This conductor was developed by the NRIM, Japan and is presently produced by Showa, Japan. It offers a good combination of conductivity and strength and is available with large cross sections. As a first step, a prototype with 17 mm bore and [Alpha] = 4.8 with conventional internal glass fibre reinforcement was made and tested up to 62 T. The user magnets have a bore of 22 mm and [Alpha] = 4.6. Based on the inductance changes during the training, the field limit for normal operation is set at 58 T. In a next step, a 12 mm bore [Alpha] = 7 magnet was fabricated using carbon fibre as internal reinforcement and a field of 69 T was obtained. The combination with carbon fibre thus opens the possibility of further increasing the peak field of the larger bore magnets. Details of the design criteria and construction of the magnet will be presented.

The measurement of the turnover of naturally occurring stable isotopes such as carbon-13 in the blood of birds may be a used as a sampling method in avian dietary research. Blood plasma and cell fractions may both be used for such purposes. The technique is ideal when non-destructive diet sampling is desired. Other tissues may be sampled if short-term and long-term dietary information is needed. The use of stable-isotope determinations in the blood of crows to obtain information on the crows' diet is described.

Telegraph noise, which originates from the switching of charge between metastable trapping sites, becomes increasingly important as device sizes approach the nanoscale. For charge-based quantum computing, this noise may lead to decoherence and loss of readout fidelity. Here we use a radio frequency single electron transistor (rf-SET) to probe the telegraph noise present in a typical semiconductor-based quantum computer architecture. We frequently observe microsecond telegraph noise, which is a strong function of the local electrostatic potential defined by surface gate biases. We present a method for studying telegraph noise using the rf-SET and show results for a charge trap in which the capture and emission of a single electron is controlled by the bias applied to a surface gate. [ABSTRACT FROM AUTHOR]

The milli-Kevin charge sensing measurements of a silicon double-dot system, which is fabricated by phosphorous ion implantation, is described. The implantation of a Si:P double dot system with gate tunable interdot coupling has enabled relatively straightforward incorporation into more complex circuits.

A twin radio frequency single electron transistor (rf-SET) detector that uses two super conducting rf-SETS to perform fast, real-time cross-correlated measurements to distinguish subelectron signals from charge noise on microsecond time scales is described. The proposed technique suppresses charge noise and enables true signals associated with readent.

Scanning tunneling microscopy (STM) is used to image charged defects on the clean Si(100)-(2*1) surface. It is observed that the charge is associated with typical defects but not all of a particular type is charged.