Migration and orientation of passerine night migrants in northeast England

Evening departures of passerine migrants were watched by radar in northeast England on 193 nights in the months of August to November 1961 to 1963. It was found that migrants were not departing each night on the same heading, from which they were drifted passively by the wind, but rather were departing on similar tracks night after night. On ten nights they maintained their tracks even when the upper-air wind changed during the night. This indicates that migrants can, at least sometimes, compensate completely for the effect of the wind and fly on a fixed track, but calculations show that there are certain wind conditions when this becomes impossible.
Movements were grouped according to the months in which they took place and the tracks which they followed, and then related to variousweather factors. Migration was seen most frequently with light winds favourable to the birds'track, after a marked drop in temperature (in October/November, but not August/September), and withabsence of cloud. However, it was also recorded on 17 nights when the cloud cover was complete.
The departures of small passerines from Britain in August and September follow tracks east of south, yet the same birds reach western Iberia later in their journey. It is suggested that the direction of departure from Britain has been evolved to take advantage of the prevailing (westerly) upper-air winds. Certain warblers leave their breeding areas in Northumberland without laying down much migratory fat, yet the same species make long flights non-stop (across the Mediterranean and Sahara) later in their migrations. These migrants change froman insect to a fruit diet in autumn, and can presumably IaKdown fat more quickly the further south they travel in Europe, as the soft fruit ripens earlier in southern areas.     

Niche partitioning of two Palearctic passerine migrants with Afrotropical residents in their West African winter quarters

In bird migration systems, the question of coexistence and competitionof migrants with residents in the nonbreeding season and theirrole in shaping the evolution of present avian communities ismuch debated. However, conclusions are often drawn in a speculativeway. In the Palearctic-African bird migration system, many studieshave addressed the question of coexistence of Palearctic breedingbirds with Afrotropical species in the former's wintering grounds.These studies have led to some generalizations concerning habitatselection and foraging ecology about the traits that might enablemigrants to coexist with residents. Migrants were thereforeassumed to forage in more open habitats, in more peripheralparts of the vegetation and with a higher foraging speed thanresidents. Furthermore, they were also assumed to be more flexiblein foraging behavior by using a wider range of foraging tactics,but some studies revealed contradicting results. We studiedthe ecology of Palearctic migrants in Comoé NationalPark, Ivory Coast, West Africa, during three successive wintersto explore the factors of niche partitioning between migrantsand residents and to test the hypothesis of whether there arecommon behavioral traits in migrants. Therefore, we comparedthe ecology of two Palearctic breeding species: pied flycatcher,Ficedula hypoleuca, and willow warbler, Phylloscopus trochilus,with resident members of the respective guilds. With respectto use of microhabitat, foraging speed, and intake rates, wecould not confirm the above-mentioned generalizations, showingthat care has to be taken into account when drawing conclusionsfrom few studies for a whole migration system on a huge continent.However, both migrating species were more flexible in foragingbehavior than were their Afrotropical counterparts. As thereare hints that this is also the case when migrants are comparedwith residents on their breeding grounds, we suggest that thisflexibility enables migrants to partition resources with residentsand, therefore, coexist with Afrotropical species. We discuss,however, whether this flexibility is an adaptation to migratorybehavior or a prerequisite for the evolution of migration. Therole that competition plays in present communities cannot besolved with a few observational studies because of the followingproblems. First, it is difficult to detect competition in thefield. Second, there are constraints of performing field experimentsthat have not previously been performed in Africa, and third,there are several possible hypothetical scenarios about therole of competition in shaping present communities, includingfactors that might have been important in the past and are thereforeimpossible to detect at present.     

Rationale for stopping cervical screening in women over 50.

OBJECTIVE--To investigate whether the currently recommended age at which to stop cervical screening (64) can be lowered and what criteria should be used for safely doing so. DESIGN--Retrospective case analysis study. SETTING--Dundee and Angus districts of Scotland. SUBJECTS--Women diagnosed as having cervical intraepithelial neoplasia and microinvasive or invasive cancer of the cervix in 1989 and 1990 (798 cases). MAIN OUTCOME MEASURE--History of cervical cytology results according to age (age groups of five years) and screening interval (three years and five years). RESULTS--Cervical intraepithelial neoplasia was most common in women under 45 (711 cases in women of 45 and under v 38 cases in those of 46 and over). Cervical intraepithelial neoplasia occurring de novo was not seen in women over 50 who had been screened every three years. Microinvasive or invasive cancer of the cervix was diagnosed in 26 women over 50. None of these women had participated adequately in the cervical screening programme. CONCLUSION--Cervical intraepithelial neoplasia typically occurs in younger women. All women over 50 with an adequate history of negative results on smear testing every three years may be safely discharged from further screening if these findings are confirmed in other populations.     

Food availability but not melatonin affects nocturnal restlessness in a wild migrating passerine

A large number of passerine species migrate at night, although most of them are diurnal outside the migratory seasons. This diurnal-to-nocturnal transition is a major life-history event, yet little is known about its physiological control. Previous work showed that during the migratory periods captive birds showing nocturnal migratory restlessness (Zugunruhe) have reduced concentrations of circulating melatonin at night compared to non-migratory periods. This suggested that the hormone melatonin, a main component of the avian circadian system, is involved in the expression of Zugunruhe. Other studies demonstrated that the relationship between low melatonin levels and Zugunruhe is not a seasonal correlation. When Zugunruhe was interrupted by exposing birds to a fasting-and-refeeding protocol, melatonin levels increased. Here we studied whether melatonin and food availability influence the intensity of Zugunruhe in wild migrating garden warblers (Sylvia borin) at a stopover site. Birds were held in recording cages overnight, with or without food available, and either bled to determine melatonin concentrations or treated transdermally with melatonin. We found that melatonin levels at night were correlated with the intensity of diurnal locomotor activity and with condition, but were not correlated with Zugunruhe. Similarly, the melatonin treatment did not have effects on Zugunruhe, whereas food availability increased it. Our study shows that the nocturnal melatonin levels in migrating warblers depend on food availability and are correlated with condition. In addition, it suggests that melatonin does not control Zugunruhe and might rather be involved in energy conservation and/or clock synchronization during migration.     

Holocene environments in the central Sahara

Palynological investigations of corings in the sebkhas of Taoudenni (N-Mali) and Segedim (N-Niger), archaeological excavations in the Acacus Mts. (SW-Libya) and charcoal records in the central Ténéré (Niger) give evidence for a northward shift of the desert-savanna boundary to 22°–20° N during the middle Holocene. Between Niger and S-Libya there was a ecological gradient from the sudanian, sahelian and saharan savannas to a denser saharan desert vegetation. After a transition phase between 6000 and 4000 BP the saharan desert vegetation was finally established in the Taoudenni and Segedim region and this degraded from ca. 2000 BP to its present condition.During the middle Holocene the central Sahara had a monsoonal summer rain climate with an effective rainfall of 250–300 mm per year near the desert-savanna boundary (ca. 22° N). Interaction between the monsoon and the atlantic cyclones also allowed rainfall in other periods of the year.     

Long-term changes in numbers of geese stopping over and wintering in south-western Poland

South-western Poland belongs to the key staging areas for geese in Europe, supporting some 100000 birds in recent years. We compared goose counts conducted in the 1970s, 1990s and during 2009–2011 in this region, and linked the findings to the recent assessments of trends in the flyway-populations. Numbers increased several dozen times between the first two counts and have stabilized to the present. More than 14% of the flyway Tundra Bean Goose (Anser fabalis rossicus) stopped over in SW Poland on passage. Smaller numbers of White-fronted Goose (A. albifrons), Greylag Goose (A. anser), and four other rarer species, have all increased since the 1970s. The likely factors responsible for these changes are mild weather conditions, increased availability of large water bodies and shifts in winter ranges of particular species. Temporal mismatch between SW Poland and the total flyways in Bean and White-fronted Geese was recorded when we compared the long-term and the short-term population trends. Increasing reports of other species in SW Poland match the general tendencies in Europe. These data document that regional trends are not a simple reflection of those in flyways as a whole. To understand changes in goose populations a re-established international count network is desired.     

Environmental and not maternal effects determine variation in offspring phenotypes in a passerine bird

Maternal and environmental effects can profoundly influence offspring phenotypes, independent of genetic effects. Within avian broods, both the asymmetric post‐hatching environment created by hatching asynchrony and the differential maternal investment through the laying sequence have important consequences for individual nestlings in terms of the allocation of resources to body structures with different contributions to fitness. The purpose of this study was to evaluate the relative importance of post‐hatching environmental and maternal effects in generating variation in offspring phenotypes. First, an observational study showed that within blue tit, Cyanistes caeruleus, broods, late‐hatched nestlings allocated resources to tarsus development, maintained mass gain and head‐bill growth and directed resources away from the development of fourth primary feathers. Second, a hatching order manipulation experiment resulted in nestlings from first‐laid eggs hatching last, thereby allowing comparison with both late and early‐hatched nestlings. Experimental nestlings had growth patterns which were closer to late‐hatched nestlings, suggesting that within‐brood growth patterns are determined by post‐hatching environmental effects. Therefore, we conclude that post‐hatching environmental effects play an important role in generating variation in offspring phenotypes.     

Pancreatic and intestinal carbohydrases are matched to dietary starch level in wild passerine birds

Evolutionary shifts in diet composition are presumably accompanied by simultaneous changes in digestive physiology. The adaptive modulation hypothesis predicts that activities of digestive enzymes should match the relative levels of their substrates in an animal's diet so that available membrane space and synthetic energy are not wasted on enzymes in excess of need. However, previous studies on captive passerine birds showed high intraspecific phenotypic flexibility only in proteases but not in carbohydrases in response to varying diet composition. In this study, we measured the activities of pancreatic, intestinal, and hepatic enzymes in six wild-caught passerine species. We predicted that if the adaptive modulation hypothesis holds during evolutionary shifts in diet composition in birds, then mass-specific activities of digestive enzymes should be correlated positively with the content of their relevant substrates in species' diets. Whereas mass-specific activities of proteases (aminopeptidase-N, trypsin, chymotrypsin, alanine aminotransferase) were not correlated with estimated dietary protein content, mass-specific activities of all studied carbohydrases (amylase, maltase, sucrase) were positively correlated with estimated dietary starch content. We conclude that activities of carbohydrases but not proteases are evolutionarily matched to diet composition in passerine birds. We hypothesize that the need for nitrogen and essential amino acids can prevent the evolution of a low activity of proteases, even in species feeding on a low-protein diet.     

Cognitive control reflects context monitoring, not motoric stopping, in response inhibition

The inhibition of unwanted behaviors is considered an effortful and controlled ability. However, inhibition also requires the detection of contexts indicating that old behaviors may be inappropriate--in other words, inhibition requires the ability to monitor context in the service of goals, which we refer to as context-monitoring. Using behavioral, neuroimaging, electrophysiological and computational approaches, we tested whether motoric stopping per se is the cognitively-controlled process supporting response inhibition, or whether context-monitoring may fill this role. Our results demonstrate that inhibition does not require control mechanisms beyond those involved in context-monitoring, and that such control mechanisms are the same regardless of stopping demands. These results challenge dominant accounts of inhibitory control, which posit that motoric stopping is the cognitively-controlled process of response inhibition, and clarify emerging debates on the frontal substrates of response inhibition by replacing the centrality of controlled mechanisms for motoric stopping with context-monitoring.