THE BREEDING BIOLOGY OF THE BLACK-FACED DIOCH QUELEA QUELEA IN NIGERIA

A study of the breeding biology of Quelea quelea in Nigeria, and particularly at a large breeding colony near Lake Chad, showed that losses of eggs and young were extremely small. 95% of eggs laid hatched successfully, and 87% give rise to fledglings. Nestling deaths were density-dependent and apparently due to starvation.
The incubation period was 10 days or less. By day, eggs were heated to 34°- 37° C. by the sun; at night the females incubated. The nestlings were initially fed mainly on insects, their diet gradually changing to one of seeds—mostly of the grass Echinochloa pyramidalis . The deep body temperatures of young birds were determined. It is suggested that the nestlings left the nest after, on average, 11¹/₂ days to escape intolerable temperature conditions in the nest.
Fat reserves were accumulated by nestlings and fledglings, and were utilized when the young became independent. The adults put on fat during the incubation period and lost it during the time spent feeding nestlings.
It is concluded that the most common clutch-size of Q. quelea , which is everywhere three, corresponds to the largest number of young the parents can normally nourish. This conforms to Lack's theory on the significance of clutch-size, and gives no support to Skutch's opinion that the theory does not apply to tropical birds.     

FEEDING ECOLOGY OF THE BLACK-FACED DIOCH QUELEA QUELEA IN NIGERIA

The results of a three-year study of the diet of Quelea quelea in the Lake Chad region of Nigeria indicate why this bird periodically does extensive damage to crops of dry-season guinea-corn.
The normal food of the birds in the early dry-season consists of small grass seeds collected off the ground. As the supply of these diminishes there is a gradual change-over to larger seeds.
In years when this change begins early, it is liable to coincide with the ripening of the cereal crop and severe damage may be caused.
At the beginning of the rains the dry-season food supply is lost owing to the simultaneous germination of the seeds over large areas.
The birds lay down fat reserves in preparation for this lean period.
After a short time the birds migrate south to regions where rain has been falling for some weeks.
In the short period spent in these parts, Queleas feed on ripening grass seeds—including those of cultivated millet.
There is evidence for considerable mortality during this time of food scarcity and it is suggested that the numbers of Queleas are limited by the food supply.
The significance of communal roosting is discussed. It is proposed that the phenomenon is related to food finding, the roost being considered as an "information centre" for the large area prospected by the birds constituting the roosting community. A method is outlined by which information on food availability within the feeding area may feasibly be transmitted within the community.     

THE MIGRATION PATTERNS OF QUELEA QUELEA IN AFRICA

Red-billed Queleas migrate, at the beginning of the wet season, away from their dry-season concentration areas and towards areas where rain started several weeks earlier. Considerable fat deposits are accumulated for this “early-rains migration”. The direction taken by the migrants, the distance they must fly, and the timing of the movement are dependent upon the timing of the rains and the way the rain-front moves. On the return “breeding migration” individuals in breeding condition stop to breed (in large aggregations) wherever they find conditions suitable for the founding of colonies. The location of the colonies can vary greatly from year to year. The migrations performed by several populations, in different parts of Africa, are predicted on the basis of general rainfall patterns, and the predictions tested against the facts available. There is evidence that individual females are able to produce a succession of broods in the same breeding season, at colonies which may be very far apart, and probably with different mates. The adaptive value of this “itinerant breeding” is discussed. Many other bird species, which breed at a particular phase of the wet-season/dry-season cycle, are expected to perform similar “itinerant breeding”.     

THE LEVEL OF RESERVE PROTEIN AS THE PROXIMATE FACTOR CONTROLLING THE TIMING OF BREEDING AND CLUTCH-SIZE IN THE RED-BILLED QUELEA QUELEA QUELEA

Changes in the fat and flight muscle protein reserves of adult Red-billed Queleas Quelea quelea were followed in two colonies in Tanzania and Botswana. At the start of a breeding attempt the protein reserves were higher that at any other time of the year, particularly in females which had heavier flight muscles (non-fat dry weight) than did the (larger) males at that time. The pre-breeding increase in the labile component of the muscle protein (the actual protein reserve) is calculated at 80% for females, but only 14% for males. The fat reserve was only increased slightly at the beginning of the breeding attempt.
In both sexes, though for different reasons, the protein and fat reserves fell rapidly during the first few days of the attempt, in some individuals to dangerously low levels. During the incubation period there was rapid recovery while the situation during the rearing period appeared to vary between colonies.
It is proposed that the proximate control of breeding is provided by the individual's own body condition, and particularly the state of its protein reserves. No environmental releasers are required for the birds to breed at the appropriate time of the year.
Individual females producing two, three and four egg clutches differed in the rate at which their reserves fell during egg formation. The results are used to support the view that in this quelea the actual clutch-size produced on any occasion is the largest the female can produce before becoming too enfeebled. Thus, clutch-size appears to be determined phenotypically downward from a maximum which is indirectly under genetic control.     

DISTRIBUTION, SYSTEMATICS, AND POLYMORPHISM OF THE AFRICAN WEAVER-BIRD QUELEA QUELEA

Quelea quelea is distributed throughout Africa south of the Sahara in the Grass Steppe, Dry Savanna, and Montane Grassland biomes. It is most numerous where its staple food–the seeds of annual grasses–is most plentiful. In all parts of the range, the males in nuptial plumage are dimorphic. Everywhere the “black—faced” morph is commoner, but with up to 25% of “white-faced”. Proportions of the morphs are given for samples from various parts of Africa. Only three races are accepted: quelea of western West Africa, aethiopica of the Sudan area, and lathami of southern Africa. In the Lake Chad basin there are hybrid swarms breeding (queleaj aethiopica), as there are in East Africa where aethiopica/lathami swarms occur.     

DETRIMENTAL EFFECTS OF FENTHION (QUELETOX® UL), USED TO CONTROL RED-BILLED QUELEA (QUELEA QUELEA), ON RHEOPHILIC BENTHIC MACROINVERTEBRATES IN THE ORANGE RIVER

Summary

The relative abundance of rheophilic macroinvertebrates in the Orange River was assessed before and 15 hrs after two aerial applications of fenthion (QUELETOX® UL) above roosting sites of the red-billed quelea (Quelea quelea). The first treatment had no detectable effect on benthic macroinvertebrate abundance, whereas the second treatment caused mortality among at least 17 taxa (over half the taxa present). The most sensitive species were nymphs of the mayflies Baetis glaucus and Tricorythus discolor, followed by larvae of the midge Rheotanytarsus fuscus. Fenthion had no detrimental effect on the population densities of the mayfly Afroptilum excisum.

The results of this study warn of the dangers of fenthion in water supplies. It is suggested that alternative methods of quelea control along the Orange River should be sought.     

THE ORIGIN OF THE ACETYLCHOLINE RELEASED FROM THE SURFACE OF THE CORTEX

—The specific radioactivity of acetylcholine liberated from the surface of the rabbit occipital cortex has been compared with that of the underlying cortical synaptosomal and vesicular acetylcholine at varying times after the administration of [N-Me-³H]choline. Choline was administered by diffusion from solutions placed in cups formed by Perspex cylinders applied to the surface of the cortex. Acetylcholine was collected by diffusion into these cups. The specific radioactivity of the acetylcholine declined progressively. The effect of stimulation of afferent cholinergic pathways was to cause a fall in the specific radioactivity of the released acetylcholine. However this was always higher than that of the synaptosomal or vesicular acetylcholine as represented by fractions P₂ and D of the authors’fractionation scheme. It is concluded that acetylcholine released from the cortex must come from a store or stores more recently synthesized than the endogenous acetylcholine of these subcellular fractions.