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.     

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.     

Traditional capture of Red-billed Quelea Quelea quelea in the Lake Chad Basin and its possible role in reducing damage levels in cereals

Mullié, W.C. 2000. Traditional capture of Red-billed Quelea Quelea quelea in the Lake Chad Basin and its possible role in reducing damage levels in cereals. Ostrich 71 (1 & 2): 15–20.

Three traditional methods of capturing Red-billed Quelea Quelea quelea practised by different ethnic groups, were studied in the Lake Chad Basin in Chad and Cameroon: capture of birds by triangular hand-held nets by Hadjeraï piégeurs (trappers); with standing fishing nets of the “mist net” type by Gambai; and by cast nets (épervier) by Massa and Mousgoum fishermen.

The Hadjeraï net was found to be both selective for queleas and highly efficient. As many as 1.2 million birds were captured from 13 June to 21 August 1994 around N'Djamena, Chad, alone, until activities ceased due to heavy rains. Birds were trapped in tree roosts during moonless periods of the night. They were plucked and fried the following morning, subsequently dried in the sun, and eventually transported to the market in N'Djamena to be sold. The piégeurs operated in teams of about 6 men and each team could process about 20 000 birds per day. Once this number had been captured, they withdrew from further trapping. The catches were almost entirely composed of queleas, with sometimes a small percentage (<1%) of Golden Sparrow Passer luteus. It was estimated that annually at least 5–10 million queleas were trapped, with a market value of about 19–38 million FCFA (USA37 500–75 000).

The impact of trapping on the population of queleas in the Lake Chad Basin, estimated at about 200 million individuals in 1976/77, was insignificant. Since activities of piégeurs are aimed at maximising revenues, and not at minimising damage levels, there is no causal relationship between crop damage and number of birds trapped. However, compared to crop losses in pearl millet due to quelea damage, revenues from selling quelea are up to 40% of capitalized crop losses due to quelea in the same area.     

Migration orientation behaviour of the red-billed quelea Quelea quelea

Migration patterns in the red-billed quelea Quelea quelea have been the focus of intense research as the species is a major crop pest in Africa. The direction and timing of migration are believed to be controlled by the seasonal passage of rainfronts across Africa. In order to assess the validity of hypothesised migration directions in southern Africa, we tested the migration orientation behaviour of wild-caught red-billed queleas using Emlen orientation funnels. Queleas tested in Zimbabwe showed mean orientation directions to the west-north-west and east-south-east. Both directions are in agreement with current hypotheses explaining quelea migration.     

Genetic evidence for male biased dispersal in the red-billed quelea Quelea quelea

In order to detect sex-biased dispersal in the red-billed quelea Quelea quelea in southern Africa, we used the assignment index technique to determine the probability that individuals originated from the population in which they were sampled. This is the first time that this multilocus genetic test has been used in a bird species and is informative despite evidence that the population under study exhibits little genetic structure. There was a pattern of male-biased dispersal, the first example in a passerine, and the first time that evidence of a sex-biased pattern of dispersal has been shown for queleas.     

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.     

First Red-billed Quelea breeding record in the winter rainfall region of South Africa

The Red-billed Quelea Quelea quelea is a serious pest of agricultural crops throughout most of sub-Saharan Africa. Since the 1980s, it has expanded its range into the Eastern Cape and Western Cape, South Africa, facilitated by changes in agricultural practices. This note documents the first breeding of Red-billed Quelea in the winter rainfall region of South Africa. A colony of 350–600 nests was found, with evidence of recent breeding. Red-billed Quelea numbers were low in this region, but if numbers increase in the future in the Western Cape, winter crops could be under threat.     

A physiological basis for colony desertion by Red-billed queleas (Quelea quelea)

A breeding colony of Red-billed queleas, established in N.E. Nigeria under poor feeding conditions occasioned by drought, was abandoned after the eggs had been laid. Inadequate energy intake caused males to leave before completing the nests. This resulted in thousands of eggs being laid through bottomless nests onto the ground. The females left progressively as they completed their clutches; below normal protein- and fat-reserves probably combined to induce abandonment. Some individuals, predominantly females, died on the last night of occupation. Death apparently resulted from an adverse nutritional balance at a crucial stage in the laying sequence. The main value of the fat reserves in females beginning to lay appears to be in allowing maximal foraging "for protein".     

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.     

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.     

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.     

The effects of luteinizing hormone, oestrogen and ovariectomy on the agonistic behaviour of female Quelea quelea

Previous work with male Quelea showed that agonistic behaviour in relation to individual distance is controlled by luteinizing hormone (LH), rather than by testosterone, and that males are more aggressive than females. Experiments with female groups are reported which show that: (a) LH injections increase aggressive encounter frequency; (b) ovariectomy in the breeding season (but not outside it) also increases encounter frequency; and (c) oestrogen injections decrease encounter frequency. The effects of LH were shown to be specific to agonistic responses rather than mediated through changes in activity. Correlations between changes in natural hormone levels and encounter frequency support the injection findings. These results are consistent with the hypothesis that LH controls aggressive encounters over individual distance in the female as in the male and that oestrogenic inhibition of this LH-mediated aggressiveness is a cause of female subordination and the lower encounter frequency found in female groups. The annual cycle of encounter frequency is described and the significance of different systems of hormonal control 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.     

Lack of genetic and plumage differentiation in the red-billed quelea Quelea quelea across a migratory divide in southern Africa

A migratory divide usually signals the presence of a geographical region over which other traits, such as morphology and genotypes, also undergo rapid change. A migratory divide has been hypothesized in central southern Africa for the abundant migratory weaver, the red-billed quelea Quelea quelea. The positioning of the divide in the region is based on the patterns of rainfall in the region that stimulate the annual migrations of queleas. Evidence indicates that premigratory queleas near the divide show two distinct preferred directions for migration. We used eight polymorphic microsatellite loci and a range of plumage characters to determine whether there was population structure among red-billed queleas in southern Africa, and specifically whether this structure coincided with the location of the migratory divide. There was no evidence of population genetic structure. An amova revealed no significant differences between samples taken either side of the migratory divide. Similarly, there was no geographical variation in plumage patterns across southern Africa. For both microsatellites and plumage characteristics, the variation that does exist occurs within each sampled site, with little differentiation between sites. We were therefore unable to find any evidence that either plumage or microsatellite genotypes varied in a similar way to migratory direction preference in red-billed queleas in southern Africa. This is perhaps because the migratory divide does not act to separate individuals into populations within which genetic and plumage differentiation can be maintained.     

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.