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.     

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.     

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.     

Flexibility in the timing of post-nuptial moult among Red-billed Queleas Quelea quelea in Botswana in relation to the timing of breeding

The timing of primary moult of adult Red-billed Queleas Quelea quelea, captured as they were completing an unusually late breeding attempt at Francistown, northern Botswana, in June 2004, was compared with the timing of moult of birds breeding earlier in the season in north-west Botswana during two earlier years, 1971 and 1972. Differences between years in the dates when local colonies finished breeding (mid-March to late June) and between two localities in the same year (mid-March and late May) were matched by corresponding differences in the estimated dates of moult onset, ranging from mid-April to mid-June. Flexibility in the timing of moult among Red-billed Queleas in southern Africa evidently enables birds to take advantage of unusually late breeding opportunities by delaying moult onset and overlapping moult and breeding at the end of the nesting cycle. Such flexibility may also include moult interruption to permit late breeding, although its incidence in southern Africa is apparently low.     

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.     

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.     

Haematocrit values in chinstrap penguins (Pygoscelis antarctica): variation with age and reproductive status

We studied haematocrit variation with age and reproductive status in chinstrap penguins (Pygoscelis antarctica) at Deception Island, South Shetlands. There was a significant difference in haematocrit values between different age groups (adults vs nestlings and juveniles). Adults had a higher haematocrit value than juveniles and nestlings and juveniles had higher haematocrit values than nestlings. There was also a significant difference in haematocrit values between adults of different status (breeding vs moulting). Breeding adults had higher haematocrit values than moulting adults. The observed differences between age groups were thought to be the result of different oxygen demands due to exercise. The observed differences between adults of different status could reflect the different demands associated with reproduction and moult fasting.     

Plasma proteins in young and adult Spermestes c. cucculatus (Swainson) (Aves - Ploceidae - Estrildinae)]

The blood plasma of Spermestes c. cucullatus (Swainson) analysed electrophoretically on agar shows seven fractions. Immunoelectrophoresis against an antispermestes rabbit serum reveals 16 fractions. Individual variation of the plasma protein fractions is very low, as is also the case for the mobility of the fractions. With age, the alpha-globulins disappear gradually. In the newly hatched bird, the protein variations are more pronounced than in adults. Most important are the lower relative content of albumin and a corresponding relatively higher content of beta- and gamma-globulins. There seems to exist a slight sexual dimorphism in albumin level, which is higher in males than in females. During the reproduction period, both sexes show a fall of the relative concentration of albumin. Injections of gonadotropine hormone produce an increase of the plasma-proteins level and a marked decrease of the relative concentration of albumin. The overall figure is comparable with that of birds in natural breeding condition.     

Isolation and characterization of dinucleotide microsatellite loci in communally breeding Guira cuckoos (Aves: Cuculidae)

Guira cuckoos (Guira guira) are communal nesting birds endemic to South America that show high levels of conflict between members of the group over the contribution to the clutch. Adults eject eggs and even nestlings from the communal nest, sometimes leading to the loss of the entire brood. We developed seven polymorphic microsatellites for Guira cuckoos using an enrichment protocol. The number of alleles ranged from 5 to 14 (mean 9.86) and the heterozygosity ranged from 0.41 to 0.89 for the eight to 88 individuals screened. These loci will allow parentage assignments and population analysis in this species.     

The evolution of tail-length in widowbirds (Ploceidae): tests of alternatives to sexual selection

The long tails of male widowbirds (Euplectes , Ploceidae) have been used to test sexual selection theory, but alternatives to sexual selection have not been investigated. This study tests three alternative hypotheses for the evolution of tail-length in widowbirds: apose-matism, the unprofitable prey hypothesis and species recognition. Using museum specimens, geographic patterns of tail-length were examined for evidence of character convergence (as predicted by the aposematism and unprofitable prey hypotheses) or character divergence (as predicted by the species recognition hypothesis) in areas where two pairs of species were sympatric. There was no consistent trend: one species showed evidence of character convergence and the other some evidence of divergence. Experimental manipulation of tail-length in the Yellow-shouldered Widowbird Euplectes macrourus also failed to support the species recognition hypothesis: there was no preference for males with species-typical tail-lengths but only a slight and non-significant trend to favour short-tailed males. There was also no evidence that mistaken identity led to territory loss following these experimental manipulations. Tail-length of six Euplectes species did not correlate with unpalatability scores, as predicted by the aposematism hypothesis. These hypotheses do not appear to explain the evolution of long tails in widowbirds, suggesting that sexual selection is the sole factor favouring long tails. Interspecific variation in tail-length remains unexplained.     

Genetic structure in Brazilian breeding colonies of the Roseate Spoonbill (Platalea ajaja, Aves: Threskiornithidae)

Roseate Spoonbills (Platalea ajaja, Linnaeus) are wading birds present in two of the most important Brazilian wetlands: the Pantanal wetlands and Rio Grande do Sul marshes. Natural populations of these species have not been previously studied with variable nuclear molecular markers. In order to support decision making regarding the management and conservation of these populations, we estimated and characterized the distribution of genetic variability among five Brazilian breeding colonies. The average observed heterozygosity in Brazilian Roseate Spoonbill populations (Ho = 0.575) did not differ significantly from the value determined in a U.S. wild-caught sample of 15 individuals, using data generated by the same set of microsatellite loci. Considering that the U.S. population underwent a recent reduction in size, we discuss this result supposing that the U.S. population was not genetically affected or that both populations had suffered a bottleneck. Global F(ST) indicated the lack of genetic differentiation among colonies, indicating the occurrence of past and/or present gene flow among them. Analysis of molecular variance revealed that most of the genetic variation is distributed within the colonies. Results are explained by a recent origin of colonies or by high levels of gene flow. Management decisions should take into consideration the fact that, even in the presence of high genetic exchange, ecological adaptations to different environments are important for species survival.     

The comparative breeding biology of magpies Pica pica in an urban and a rural habitat (Aves: Corvidae)

The breeding biology of magpies in an adjacent urban and rural area in the same year was compared. Breeding commenced earlier in the urban habitat. This was attributed to the earlier availability of invertebrate food in the urban habitat as a result of higher urban ambient temperature. Hatching success and the amount of nest predation were lower in the urban area than in the rural area. Low levels of nest predation in urban areas were due to reduced human predation and probably to the relatively low numbers of many natural predators. Differences in the nest tree species utilized also influenced the probability of human predation. Despite these differences in the causes of egg and chick mortality, the number of young reared to 14 days of age per nest was similar in both habitats.     

Food partitioning between breeding White-tailed Kites (Elanus leucurus; Aves; Accipitridae) and Barn Owls (Tyto alba; Aves; Tytonidae) in southern Brazil.

I examined the diet of breeding White-tailed Kites (Elanus leucurus; Aves; Accipitridae) and Barn Owls (Tyto alba; Aves; Tytonidae) in an agrarian area of southern Brazil by analyzing regurgitated prey remains. The objective was to evaluate how these raptors, which differ markedly in their hunting activity periods (owls are nocturnal and kites diurnal), share their mammalian food component. 2,087 prey consumed by Barn Owls and 1,276 by White-tailed Kites were identified. They presented a high overlap of food-niches (Piankas index was 0.98). Based on the daily activity period of their main small mammal prey, a lower overlap would be expected. The crepuscular/nocturnal Mus musculus was the main prey for the diet of breeding Barn Owls (81%) and White-tailed Kites (63%). This small exotic rodent provided 63% of the small mammal biomass ingested by owls and 44% by kites. Larger native small mammals were also considered important for the diet of kites, mainly because of their biomass contribution. Although these raptors differ markedly in their hunting activity periods, Barn Owls and White-tailed Kites are very similar predators in southern Brazil, overlapping their diets.     

Population size and breeding success of the Cinereous Vulture,Aegypius monachus,in a newly found breeding area in western Anatolia (Aves: Falconiformes)

A total of 123 nests of the Cinereous Vulture, Aegypius monachus, was found in three different nesting areas in Middle Sakarya Region, Western Turkey, during three years. The number of breeding pairs was 32 in 2010, 46 in 2011 and 42 in 2012. This is the largest Cinereous Vulture colony in Turkey and the most important breeding area in the western part of its distribution outside Spain. Breeding success was 0.78 fledgling per occupied nest in 2010, 0.73 in 2011 and 0.54 in 2012. The most unsuccessful breeding occurred mostly between May and July, when recreational activities and various economic human activities increased in the area.     

Haemosporidian parasitism in the blackcap Sylvia atricapilla in relation to spring arrival and body condition

Parasites can exert strong selection on hosts. Throughout the year migrants are exposed to different sets of parasites, which may affect life history traits such as migratory schedules. Here, we studied the relationship between parasite infection and arrival date of blackcaps Sylvia atricapilla to their breeding grounds in Germany throughout a period of six years (2007–2012). We used two data sets, one that included all blackcaps and one that included only recaptured birds. We assesed whether parasites influence spring arrival to breeding grounds, and for the recaptured data set, we analysed temporal variation in parasitism (i.e. infection status and parasitaemia) throughout the breeding season. We used both microscopy and PCR (a fragment of ? 479 bp of the mtDNA cyt b) to determine haemosporidian infection. Blackcaps were mostly infected with Haemoproteus parabelopolskyi (lineages SYAT01 and SYAT02). Infection status, but not parasitaemia, was constant through time for individual birds; meaning that once a bird is infected, it most likely will retain the infection for life. We found that infection by haemosporidian parasites has no relationship to arrival date in this blackcap population; however, infection by H. parabelopolskyi has a marginally significant effect on arrival date of recaptured blackcaps, somewhat delaying their arrival to breeding grounds. Birds captured later in the season were more likely to be infected than those from early spring, and parasitaemia was frequently lower in birds captured earlier in the season compared to those captured later (summer).