摘要:

The extent to which genetic factors are directly involved in the control of bird migration and the mode of inheritance involved has been studied systematically over the past 15 years in the BlackcapSylvia atricapillaby cross‐breeding and selective breeding. Results have also been obtained from a few experimental and field studies on RobinsEritfiacus rubecula,BlackbirdsTurdus merulaand Song SparrowsMelospiza melodia.Cross‐breeding of migrants with nonmigrants has resulted in the partial transmission of migratory activity into the F, generation indicating that the urge to migrate is inherited and is based on a multilocus system with a threshold for expression. Migratoriness and sedentariness in obligate partial migrants is probably inherited in a similar way, suggesting that the decision to migrate also has a strong genetic basis. Both traits can be selected to phenotypic uniformity within 3–6 generations indicating an extremely high evolutionary potential. Orientation behaviour can also be transmitted to the offspring of a nonmigratory population by cross‐breeding. Cross‐breeding individuals with different migratory directions produced offspring with phenotypically intermediate directional preferences, suggesting that the migratory direction is also a predominantly heritable character. In the current development of novel migratory habits in those Central European Blackcaps that now winter in the British Isles, the inheritance of the novel migratory direction may be crucial. Genetic variation in migratory events seems to be sufficient to allow for many microevolutionary

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1992.tb04749.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Many palaearctic migrants in tropical Africa have to cross the inhospitable land of the Sahara desert. Moreau (1961, 1972) hypothesized that these migrants crossed the Sahara in a single non‐stop flight. Recent field data, however, revealed that some migrants stop‐over in suitable desert habitats. The majority of grounded migrants showed a high body‐mass and fat‐loading, indicating sufficient reserves for onward flights. Further evidence on resting periods, retrapping rates and experiments with caged migrants supports the hypothesis of an intermittent migratory strategy, with regular stopovers during the day and flight at night, for some desert‐crossing p

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1992.tb04750.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Nest‐site choice and reproductive success of Curlews Numenius arquata in different habitats were studied at a mixed farmland site (grasslands and flooded tilled fields relatively common) and at an arable farmland site (dry tilled fields more dominant than at the mixed site) in central Sweden. At both sites Curlews preferred to nest on grassland and fallow fields, where hatching success was higher than on tillage fields. Nests were also situated further away from forest edges than random sites, but hatching success did not vary with distance to the forest edge. Only 35.6% of the pairs were estimated to hatch young. The main cause of nest loss was predation and the second most important factor was destruction by farming practices, which was an important factor in tillage early in season. Surprisingly, nest survival was higher at the arable than at the mixed farmland site, probably being an effect of the increased proportion of fallowing during recent years. Mortality of chicks was 79.7% before fledgling age (both sites combined) and, surprisingly, chick survival was lower on meadows than on arable fields and leys. The mean production of young was only 0.25 fledglings per pair, which is lower than in areas less affected by farming practice. The low production of young is probably an important factor in the decline of Curlew populations on Swedish farmland. On bogs 1.4 fledglings per pair were produced, indicating that reproductive success of Curlews is higher in more natural habitat

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1992.tb07228.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Arguments in support of the non‐stop and the intermittent strategies for crossing the Sahara have been based on data on the fat reserves of birds before the crossing and of birds grounded in the desert. In this paper, flight‐range estimates were calculated and the necessary assumptions about air speed, energy input during flight, and energy equivalent of body reserves were evaluated. As examples, Willow WarblersPhylloscopus trochilusand Garden WarblersSylvia borinwere investigated during autumn migration from two study sites north of the Sahara and two study sites in the desert. In still air, the flight‐range for both species at all study sites was too short to reach the Sahel zone without refuelling. It is concluded that birds depend on tailwinds for a successful crossing, independent of a non‐stop or an intermittent migratory strategy, and that weather conditions in autumn allow them to rely on ta

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1992.tb04751.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The hypothesis that polygynous species start breeding later in the season than monogamous ones was examined using two data sets, each with both monogamous and polygynous species—the eight species of wrens which breed in the USA, and five genera (15 species) of British passerines. Comparisons were made within each of 16 states in the USA from which data were available and for each genus in Britain. The hypothesis is supported for most subsets of data, but in some cases polygynous and monogamous species start breeding at the same time (but in no case do polygynous breed earlier than monogamous species). The late breeding of the polygynous species is probably an outcome of the fact that polygynous males tend to participate less in nest activities than monogamous one

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1992.tb07229.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The hunting of 20 species of migratory birds in Europe and countries bordering the Mediterranean Sea was investigated using ringing recovery data. The intensity of the hunting of birds in each country was measured by the calculation of an index which controls for ringing effort and reporting rates. The hunting of birds was shown to be consistently high in western Mediterranean countries, particularly in southern France, northern and southwestern Iberia, northern Italy and in northwest Africa. Geographical patterns in the relative magnitude of hunting indices for different breeding populations were species‐specific. In Europe most birds are taken during autumn and winter but in North Africa hunting is almost equally prevalent in spring. All species investigated, other than those that remain legitimate quarry species, showed a general reduction in index values after 1980. Analysis of long‐term trends in index values since 1950 indicated a statistically significant overall decrease in the hunting of the majority of species. These changes are thought to be at least partly attributable to a real decline in the taking of birds but they may also reflect changed attitudes to reporting the hunting of species which are now protected. This analysis provides the first quantitative Europe‐wide assessment of geographical and temporal trends in the hunting of migratory

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1992.tb04752.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Helpers at the nest of cooperatively breeding birds often ‘lighten‐the‐load’ of the breeders, by allowing them to decrease their effort. When the shape of the relationship between survival cost and provisioning effort is concave‐up then a helper incurs only a small increment in mortality, for a given amount of help, but the breeder benefits from a larger fall in mortality. A convex‐up relationship for pre‐breeders may explain why some groups (such as larids) do not breed cooperatively. Load‐lightening could provide significant extra gains to the helper's future indirect fitness by increasing the lifespan and life‐time reproductive success of

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1992.tb07230.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The Pied and Collared Flycatchers Ficedula hypoleuca and F. albicollis hybridize on the Baltic islands of Öland and Gotland. Field studies of hatching success in clutches from 36 breeding hybrid males indicate that male hybrids reproduce successfully. In comparison, 25 hybrid females had normal clutch sizes but failed to hatch nestlings, suggesting female hybrid sterility. The paternity of seven hybrid males was investigated by DNA fingerprinting using two hypervariable minisatellite probes. Of these hybrid males, six were assessed as fertile. Three of the hybrid male families (43%) contained nestlings with extra‐pair paternity and the frequency of extra‐pair fertilization among 37 nestlings was 22%. One nestling originated from intraspeciflc female nest parasitism. The sterility pattern in hybrids between these two flycatchers with sterile female and fertile male hybrids is in agreement with Haldane's

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1992.tb07231.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The biology of one passerine migrant, the Yellow WagtailMotacilla flava,is examined in order to identify factors which need to be considered when attempting to conserve migrants on passage. The distribution of Yellow Wagtails in West Africa, prior to northward (spring) migration, is affected by food supplies and by different racial and sexual responses to environmental factors. Consequently, each breeding population relies on a wide range of sites, but those occupied towards the end of the dry season and ones used as stepping‐off points for migration may be particularly vital.Energetic considerations point towards a non‐stop trans‐Saharan flight being used rather than a series of short flights with resting stops in the desert. However, adverse conditions during migration could make stop‐overs unavoidable. The most direct routes between wintering and breeding areas are preferred, and the initial desert crossing is accomplished at a faster pace than later stages of the journey.Yellow Wagtails emigrate from West Africa in a sequence related to the onset of spring on their breeding sites, rather than in response to rainfall in Africa: moult, fattening and emigration are probably endogenously controlled. However, competition from African resident birds may also be an important factor affecting the timing of migration.Races breeding in southern Europe are most likely to be adversely affected by degradation of the Sahel. Empirical evidence suggests that conditions on the wintering grounds are more likely to regulate population size than conditions experienced on migration, but more detailed studies are needed in Africa before sound conservation strategies can be d

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1992.tb04753.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The ontogeny of food storage in Crested Tits Parus cristatus and Willow Tits P. montanus starts during the period of parental care after the young have left the nest and develops gradually. In southern Norway, the storing behaviour becomes fully developed during August‐September, i.e. at a time when most juveniles have completed their dispersal period and settled in permanent winter flocks. The food storing behaviour is largely innate, but is improved by practice and experienc

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1992.tb07232.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY