The migrations of the Red-billed Quelea Quelea quelea and their relation to crop damage

Recent studies on the migrations of the Red-billed Quelea Quelea quelea have shown that while the species is capable of long-distance movements of hundreds of kilometres, the actual migrations probably more often consist of shorter distances with a flexible timing. This flexibility allows adjustments to be made to the rainfall distribution in a particular year. New information comes from studies on the breeding distribution, on the plumage and moult of local populations, and from attempts to apply new techniques such as mass-marking with fluorescent particles. Breeding has been shown to be both more widespread and more frequent than previously recognized, while local populations can prolong breeding in one place if rainfall continues. Local populations have been identified that are apparently distinct, with limited intermixing with other populations, and some data suggest that intermixing may be reduced by flock or group cohesion. The flexibility of the migrations means that predictions of major influxes of quelea into agricultural areas have proved difficult to make, especially in regions where the rainfall patterns are complex and variable, such as East Africa.     

Evidence of itinerant breeding of the Red-billed Quelea Quelea quelea in the Ethiopian Rift Valley

This paper provides evidence for itinerant breeding by Red-billed Quelea Quelea quelea in the Ethiopian Rift Valley. Queleas were mass-marked with aerially applied fluorescent particles in two separate nesting areas in southwestern Ethiopia during June 1981. Marked adults from both areas were recovered from nesting colonies in the Awash River Valley during August and September, up to 100 days post-spray and between 500 and 700 km to the north of the spray sites. In the Awash colonies, the presence of marked adults in breeding plumage with interrupted primary wing-moult, together with two age classes of juveniles, suggests that this was the second nesting. The progress of both the post-breeding and post-juvenal primary moults was consistent with an earlier breeding in May and June. The timing of the arrival and departure of birds from these nesting areas also supported the occurrence of double breeding by the same birds. Furthermore, the composition of black facial mask types of adult males was more similar between samples from the southern Ethiopian Rift and Awash Valley than between samples from either of these areas and samples from outside the Rift, providing additional evidence that the same population of birds bred in these two areas of the Rift Valley. Nesting colonies in both areas were scattered in time and space. Colonies in the Awash were distributed for more than 300 km and were established over a two-month period, which coincided with local differences in the timing of the seeding in grasses. This wide distribution probably increases nesting success in such areas of locally variable rainfall. This contrasts with a stategy of mass migration, where concentrated breeding occurs where and when suitable conditions are first encountered. Knowledge of the location and timing of previously successful nesting areas may increase the success of itinerant breeding, as Queleas seem to use the same areas in successive years if conditions are favourable. Recoveries of marked birds in the Awash were segregated according to both spray site and sex, suggesting some degree of group cohesion by sex from the first to the second nesting. We speculate that post-nesting group cohesion of adults may provide a means to maintain the integrity of collective group information on seasonal movements. Group cohesion may be facilitated by the high degree of nesting synchrony within colonies.     

Haematocrit values of breeding Red-billed queleas Quelea quelea (Aves: Ploceidae) in relation to body condition and thymus activity

In a Red-billed quelea colony in north-eastern Nigeria that was later abandoned as a result of the poor nutritional condition of the adults, laying females showed low haematocrit values compared with normal pre-breeding haematocrit levels but nestbuilding males did not. In females the low haematocrits were correlated with extremely low levels of reserve lipid and labile protein but males in equally poor condition did not have such low haematocrits. This difference must result in some way from the additional nutritional burden for females of mobilizing sufficient protein to form eggs. Earlier observations of massive red blood cell production in the thymus of queleas during incubation suggest that low haematocrits, indicating anaemia, may be a normal occurrence in queleas during breeding, and were not peculiar to this abnormal abandoned colony.     

Variation in haematozoan parasitism at local and landscape levels in the red-billed quelea Quelea quelea

The red-billed quelea Quelea quelea , one of the most abundant birds in the world, presents two fundamental conundrums that we investigate here with a novel approach using blood parasite assemblages at two spatial scales, landscape and individual. The quelea of southern Africa Q. q. lathamii are split by a hypothesized migratory divide, where birds follow rain fronts in one of two directions (NW or SE). This divide is not detectable in the host population using microsatellite data, and here we show that it is also not apparent from our large-scale phylogeographical analyses of the haematozoan parasite. At a finer scale, the colourful and variable breeding plumage of male red-billed quelea has not previously shown a correlation with predictors of quality, as it does in many other bird species. The male's breeding plumage is partially based on carotenoid colouration, the quality of which has been correlated with haematozoan infection in other bird species. However, we found no correlation between intensity of male carotenoid colouration and haematozoan infection. Our results do not contradict the hypothesis that male breeding plumage in this species serves to identify individuals rather than to indicate quality. Finally, we recovered the greatest number of haematozoan lineages from any phylogenetic survey of a single host species to date. Understanding the reasons for the extreme diversity of parasite lineages in this species may assist in explaining the success of the red-billed quelea in anthropogenic landscapes.     

Apparent range expansion of the Redbilled Quelea Quelea quelea in the Eastern Cape Province of South Africa

Whittington-Jones, C.A. 1997. Apparent range expansion of the Redbilled Quelea Quelea quelea in the Eastern Cape Province of South Africa. Ostrich 68 (2–4): 97–103.

Distribution records obtained from the South African Bird Atlas Project (SABAP) and from published literature show that the known distribution of Redbilled Quelea in the Eastern Cape has changed dramatically over the last century. Increased search effort following the initiation of SABAP may explain the range expansion, but changes in agricultural practice have probably been a contributing factor.     

Aggression and dominance in the weaver bird, Quelea quelea.

Previous work on agonistic behaviour in Quelea has been concerned primarily with hormonal variables. In the present series of experiments, a number of behavioural correlates of aggression and dominance are examined in male and bisexual groups. These include the effects of group arousal level on rates of agonistic encounters, the relationship between an individual's habitual level of activity and its relative dominance, aggressiveness and position on the perch in a resting "flock". The temporal patterning of encounters is analysed and the reasons why encounters tend to clump in time determined. The relationship between dominance in encounters over individual-distance infringements and dominance in encounters over access to a restricted food source is investigated and the effects of this on loss of weight in males and females determined. The results are discussed in relation to Ward's (1965) finging that in the wild females suffer higher mortality than males during the dry season and in relation to the general determinants of aggression in Quelea.     

The timing of breeding and moult of the Lesser Striped Swallow Hirundo abyssinica

The Lesser Striped Swallow seems to have two different breeding populations. The birds south of 10°S breed largely during the spring and summer (July to April) and moult from about April to August. Birds further north breed throughout the year, but mainly during the first seven months of the year. Moult in the birds north of 10°S is from July to February when few birds are breeding. There seem to be two clearly defined moulting populations, with the southern breeding population moulting largely south of 10°S and the east African breeding population moulting largely north of the equator. In both populations moult and breeding seem to be separated in time, at least at the individual level.     

The timing of breeding and moult of the Lesser Striped Swallow Hirundo abyssinica

The Lesser Striped Swallow seems to have two different breeding populations. The birds south of 10°s breed largely during the spring and summer (July to April) and moult from about April to August. Birds further north breed throughout the year, but mainly during the first seven months of the year. Moult in the birds north of 10°s is from July to February when few birds are breeding. There seem to be two clearly defined moulting populations, with the southern breeding population moulting largely south of 10°s and the east African breeding population moulting largely north of the equator. In both populationsmoult and breeding seem to be separated in time, at least at the individual level.     

Sizes and numbers of nuclei in the cortex of thymus glands of red-billed weavers Quelea quelea

The cortex of the thymus glands of embryos, chicks, juveniles, fledglings and adults from several colonies of Quelea quelea were studied using an image analyser (Quantimet 720) to determine cell populations and nuclear sizes. Just prior to hatching the lobes showed a high level of mitosis and consisted of predominantly small lymphocytes. The larger glands of chicks and juveniles had higher cell populations; pyknotic cells and erythrocytes occurred free in the cortex. The lobes of adults were more variable but in general mitosis occurred in enlarging glands of adults from colonies with eggs; most lobes contained pyknotic cells but not in such high numbers as in lobes from chicks and fledglings. Erythrocytes were common, occurring in large numbers in the cortex in some birds. The factors affecting the interpretation of these data are discussed in detail.     

Geographical variation in the timing of breeding and moult in dunlin Calidris alpina on the Palearctic tundra

Studies of how organisms are adapted to regional climatic conditions are valuable when predicting the effects of global climatic changes on biota. Here we report on the geographical variation in timing of breeding and moult of an Arctic breeding wader, the dunlin (Calidris alpina). The Palearctic study sites range latitudinally between 68 and 76°N and longitudinally between 46 and 179°E, and encompass a variety of local climates. The sites were visited in sequence from west to east within 1 year, and therefore the data are not affected by confounding interannual variations. The estimated breeding start ranged from 5 to 25 June across populations. Birds at more southern sites were found to breed earlier than those at more northern breeding sites. Within populations, the breeding start for first clutches spanned a period of 8 days and, when including replacement clutches, 3-4 weeks. No dunlin west of the Taimyr Peninsula were found moulting while incubating at the nest, whereas all dunlin on Taimyr Peninsula and eastwards were in active wing moult while incubating or rearing chicks. The onset of moult in these populations ranged from 23 to 27 June. The consequences of geographical variation of breeding conditions for variation in the annual cycle of this species are discussed.     

Morphological changes in the thymus of young and adult red-billed queleas Quelea quelea (aves).

In a wild population of red-billed queleas Quelea quelea L. (Ploceidae: weaver-birds) sampled throughout the year in East Africa, the thymus was found to enlarge in young birds shortly after hatching, remain enlarged during the juvenile stage, and regress towards the end of the postjuvenile moult. In adults, recrudescence occurred in many individuals during the prenuptial and postnuptial moults, and also in most if not all individuals, of both sexes, for a brief period during a breeding session. Thymus enlargement in both young and adults has been found to be accompanied by marked erythropoietic activity within the gland, and it is suggested that this activity is related to an increased demand for erythrocytes which may occur during moult and breeding.     

Sex-ratio of Skylark Alauda arvensis broods in relation to timing of breeding

Capsule Earlier broods tend to be more male biased than later broods     

Relationships among timing of moult,moult duration and feather mass in long‐distance migratory passerines

Moult is a costly but necessary process in avian life, which displays two main temporal patterns within the annual cycle of birds (summer and winter moult). Timing of moult can affect its duration and consequently the amount of material invested in feathers, which could have a considerable influence on feather structure and functionality. In this study, we used two complementary approaches to test whether moult duration and feather mass vary in relation to the timing of moult. Firstly, we conducted a comparative study between a sample of long‐distance migratory passerine species which differ in moult pattern. Secondly, we took advantage of the willow warbler's Phylloscopus trochilus biannual moult, for which it is well‐known that winter moult takes longer than summer moult, to assess between‐moult variation in feather mass. Our comparative analysis showed that summer moulting species performed significantly shorter moults than winter moulters. We also detected that feathers produced in winter were comparatively heavier than those produced in summer, both in between‐species comparison and between moults of the willow warbler. These results suggest the existence of a trade‐off between moult speed and feather mass mediated by timing of moult, which could contribute to explain the diversity of moult patterns in passerines.     

Histological changes associated with enlargement and regression of the thymus glands of the red-billed quelea Quelea quelea L. (Ploceidae: weaver-birds).

Thymic lobes form over 200 red-billed queleas, Quelea quelea L., were examined histologically. Samples were taken from embryos about to hatch, juveniles and adults. The lobes varied in size from very small to very enlarged (1- greater than 5 mm long). The constituent cell types are described in detail and the occurrence of these cells in different sized lobes is discussed. A cycle of events is proposed which accounts for the observations presented here. It is suggested that the large numbers of erythroid cells found in the cortex of some individuals were developing in situ. The significance of erythropoiesis within the thymus is discussed.     

EMMA-4 analysis of iron in cells of the thymic cortex of a weaver-bird (Quelea quelea).

Combined morphological and analytical studies with the EMMA-4 analytical electron microscope have enabled very early erythroid cells to be identified within the cortex of enlarging thymic lobes of Quelea quelea. These early erythroid cells have pale cytoplasm (sometimes with ferritin-like crystals present), slightly pachychromatic nuclei and have fewer cell organelles (mitochondria) than lymphocytes. Counts for iron were approximately 70% lower than counts from mature erythrocytes found free in the cortex. Iron was also recorded from some epithelial reticular cells and pyknotic nuclei; no iron was recorded from small lymphocytes (thymocytes) in the cortex. The presence of very early erythroid cells is a further indication that erythropoiesis occurs in situ in the avian thymus.