Why do few Afro-Siberian Knots Calidris canutus canutus now visit Britain?

The nominate (Afro-Siberian) subspecies of the Knot Calidris canutus canutus breeds on the Taimyr Peninsula in Siberia and occurs commonly in the westernmost Wadden Sea during migration to West and South Africa. The recoveries and controls of 2045 Knots ringed in Britain and Ireland provide no evidence for canutus wintering there nor for their regular passage during autumn and spring migration. Five juveniles ringed in the first week of September 1963 were recovered in Africa between eight and 37 days later, and another two birds ringed at the same time (one as an adult) showed up in subsequent years in Spain and Germany at times typical for Afro-Siberian Knots. There haz,e been no comparable bursts of southern recoveries since. The period in 1963 driving which the Afro-Siberian juveniles were captured on the Wash tons characterized by sustained wind patterns conducive to bringing naive juvenile waders from the Siberian tundra to the southwest. Such conditions have been increasingly rare in later years. The paucity of recent records may Additionally reflect a decline in this population. Juveniles leading Siberia would probably fly a constant compass course to western Europe, a flight of more than 5000 km logically ending in southeastern England. The scarcity of Afro-Siberian type recoveries based on Knots ringed a mere 350 km (five to sis hours of flight) west of the Wadden Sea is therefore remarkable

Changing balance between survival and recruitment explains population trends in Red Knots Calidris canutus islandica wintering in Britain, 1969-1995

The demography of Red Knots Calidris canutus islandica wintering in Britain from 1969 to 1995 was examined using published data on winter numbers, unpublished ringing data, and information on the percentages first year birds in late autumn and winter (defined here as 'recruitment'). The maximum time between ringing and reporting was 24 years for a Red Knot ringed as an adult. The mortality rate of juveniles during their first winter was four times that of adults, but did not differ later. For three periods, recruitment minus mortality corresponded qualitatively with changes in population size. In 1969-77, when the numbers wintering in Britain were declining by 8.7% annually, the mean percentage juveniles in the wintering population was estimated at 12.1% and the mean adult mortality rate was estimated at 23.6% per year (balance -11.5%). In 1977-85, when numbers were increasing by 4.6% per annum, the average juvenile percentage was high (28.8%), but the adult mortality rate was lower than in the previous period (19.6%; balance +9.2%). In 1985-95, when wintering numbers showed no clear trend (average +0.9% per annum) but were still below those in 1969-72, juvenile percentages were again quite low (mean of 13.8%), but the adult mortality rate was also low (14.2%; balance -0.4%). Cold summers reduced both recruitment and adult survival. British Knot populations appear to fluctuate as a consequence of factors affecting survival as well as reproduction. There is evidence for density-dependent processes that affect overall reproductive success. Although probably acting some time from late winter to early autumn, the mechanisms causing such density-dependence remain mysterious

High daily energy expenditure of incubating shorebirds on High Arctic tundra: a circumpolar study

1. Given the allometric scaling of thermoregulatory capacity in birds, and the cold and exposed Arctic environment, it was predicted that Arctic-breeding shorebirds should incur high costs during incubation. Using doubly labelled water (DLW), daily energy expenditure (DEE) during incubation was measured in eight shorebird species weighing between 29 and 142 g at various sites in the Eurasian and Canadian High Arctic. The results are compared with a compilation of similar data for birds at lower latitudes. 2. There was a significant positive correlation between species average DEE and body mass (DEE (kJ day−1) = 28·12 BM (g)^0·524, r^2 = 0·90). The slopes of the allometric regression lines for DEE on body mass of tundra-breeding birds and lower latitude species (a sample mostly of passerines but including several shorebirds) are similar (0·548 vs 0·545). DEE is about 50% higher in birds on the tundra than in temperate breeding areas. 3. Data for radiomarked Red Knots for which the time budgets during DLW measurements were known, indicated that foraging away from the nest on open tundra is almost twice as costly as incubating a four-egg clutch. 4. During the incubation phase in the High Arctic, tundra-breeding shorebirds appear to incur among the highest DEE levels of any time of the year. The rates of energy expenditure measured here are among the highest reported in the literature so far, reaching inferred ceilings of sustainable energy turnover rates.

Stochastic atmospheric assistance and the use of emergency staging sites by migrants

Numerous animals move vast distances through media with stochastic dynamic properties. Avian migrants must cope with variable wind speeds and directions en route, which potentially jeopardize fine-tuned migration routes and itineraries. We show how unpredictable winds affect flight times and the use of an intermediate staging site by red knots (Calidris canutus canutus) migrating from west Africa to the central north Siberian breeding areas via the German Wadden Sea. A dynamic migration model incorporating wind conditions during flight shows that flight durations between Mauritania and the Wadden Sea vary between 2 and 8 days. The number of birds counted at the only known intermediate staging site on the French Atlantic coast was strongly positively correlated with simulated flight times. In addition, particularly light-weight birds occurred at this location. These independent results support the idea that stochastic wind conditions are the main driver of the use of this intermediate stopover site as an emergency staging area. Because of the ubiquity of stochastically varying media, we expect such emergency habitats to exist in many other migratory systems, both airborne and oceanic. Our model provides a tool to quantify the effect of winds and currents en route

Genomic Organization and Control of the Grb7 Gene Family

Grb7 and their related family members Grb10 and Grb14 are adaptor proteins, which participate in the functionality of multiple signal transduction pathways under the control of a variety of activated tyrosine kinase receptors and other tyrosine-phosphorylated proteins. They are involved in the modulation of important cellular and organismal functions such as cell migration, cell proliferation, apoptosis, gene expression, protein degradation, protein phosphorylation, angiogenesis, embryonic development and metabolic control. In this short review we shall describe the organization of the genes encoding the Grb7 protein family, their transcriptional products and the regulatory mechanisms implicated in the control of their expression. Finally, the alterations found in these genes and the mechanisms affecting their expression under pathological conditions such as cancer, diabetes and some congenital disorders will be highlighted

Feasibility of a dose-intensive CMF regimen with granulocyte colony-stimulating factor as adjuvant therapy in premenopausal patients with node-positive breast cancer

Our aim was to study the feasibility of an intensified intravenous CMF (cyclophosphamide, methotrexate and 5-fluorouracil) schedule with the aim to escalate dose intensity (DI). Twenty-three premenopausal breast cancer patients received 6 cycles of adjuvant CMF intravenously on days 1 and 8 every 3 weeks and granulocyte colony-stimulating factor days 9–18. Endpoints were DI and toxicity. Twenty-one out of 23 patients (91%) received the projected total dose and reached ≥ 85% of the projected DI. Compared to ‘classical’ CMF, all patients reached ≥ 111% DI. Nine patients received the planned schedule without delay. Thirteen patients (57%) were treated for infection and four patients (17%) were hospitalized for febrile neutropenia. Twelve patients received red blood cell transfusions (52%). Radiation therapy (n= 6) had no adverse impact on dose intensity or haematological toxicity. This dose-intensified CMF schedule was accompanied by enhanced haematological toxicity with clinical sequelae, namely fever, intravenous antibiotics and red blood cell transfusions, but allows a high dose intensity in a majority of patients. © 2000 Cancer Research Campaig

Adverse wind conditions during northward Sahara crossings increase the in-flight mortality of Black-tailed Godwits

Long-distance migratory flights are predicted to be associated with higher mortality rates when individuals encounter adverse weather conditions. However, directly connecting environmental conditions experienced in-flight with the survival of migrants has proven difficult. We studied how the in-flight mortality of 53 satellite-tagged Black-tailed Godwits (Limosa limosa limosa) during 132 crossings of the Sahara Desert, a major geographical barrier along their migration route between The Netherlands and sub-Saharan Africa, is correlated with the experienced wind conditions and departure date during both southward and northward migration. We show that godwits experienced higher wind assistance during southward crossings, which seems to reflect local prevailing trade winds. Critically, we found that fatal northward crossings (15 deaths during 61 crossings) were associated with adverse wind conditions. Wind conditions during migration can thus directly influence vital rates. Changing wind conditions associated with global change may thus profoundly influence the costs of long-distance migration in the future