SEXUAL SELECTION IN THE BARN SWALLOW HIRUNDO RUSTICA. III. FEMALE TAIL ORNAMENTS

Male secondary sexual characters are often expressed in females, and the maintenance of the character in females can be due to either direct selection on females favoring the maintenance of the trait, or a correlated response to selection in males. Here I report on determinants of and phenotypic selection on tail length of female barn swallows Hirundo rustica. The homologous trait in males is under strong directional sexual selection. Female tail length was positively associated with several reproductive parameters including total seasonal reproductive success, even when controlling for year and age effects. A change in female tail length from one year to another was often associated with a change in the reproductive parameters correlated with absolute tail length. There was little evidence for an association between female tail length and the duration of the incubation period (only females incubate) and absolute and relative female provisioning rates of offspring, and subsequent size of offspring. Tail length of female barn swallows was positively correlated with that of their mates. Female tail length was a heritable trait as determined from regression of the tail trait of offspring on that of their mother and their father, and there was a positive genetic correlation between the tail trait in males and females. In conclusion, female tail length reliably reflects female reproductive potential, and the trait appears to be under directional selection, which may result in an evolutionary response to selection because of the heritability of the tail trait.     

NOTES ON THE BIRDS OF SOUTH-WESTERN NIGERIA.

Notes are based on a collection of 700 skins. Extensions of range include Trachylaemus p. togoensis, Prodotiscus i. flavodorscdis, Campethera n. nivosa, Bleda canicapilla, Phyllastreplms i. icterinus, Pedilorhynchus c. aximensis, Sylvia bnrin, Apalis c. caniceps, Macrosphenus concolor , and Spermophaga h. togoensis recorded from Nigeria and Apus c. strenbelii from West Africa for the first time.
Taxonomic points include reasons for regarding Centropus epomidis as a colour phase of Centropus senegalensis and Sylvietta flavixentris nigeriae as a synonym of Sylvietta flainventris.
Dates of breeding are given for many species, and nests and eggs arc described. Indicator indicator was found in the nest of Hirundo setnirufa.
The chick of Porphyrio alleni is described.     

THE DISTRIBUTION OF WETLANDS IN THE SOUTH-WESTERN CAPE PROVINCE,SOUTH AFRICA

Summary

The hydrological and habitat value of wetlands is beginning to be recognised in South Africa, but only in parts of Natal Province has an effort been made to map wetlands and to record their status over large areas. While the most accurate method of mapping wetlands is a combination of photogrammetry and field surveys, this is time-consuming and expensive. An alternative “desktop” method was therefore used to draw up a preliminary distribution of wetlands in the south-western Cape Province, and this approach consisted of summarising the information contained on 1:50 000 topographical survey maps. The summary shows that shallow, vegetated wetlands (vleis) occur mainly in the wetter south and south-west of the region, while the non-perennial wetlands (pans) predominate inland, where the land is dryer and flatter. There are many estuarine wetlands along the coast, resulting from the tendency of river mouths to be blocked by sand-bars. Farming requirements and suitable topography account for the many small artificial wetlands (farm dams) in the central southern parts. Farm dams predominate in the region (15067 were counted), followed by pans (1741), riverine wetlands (261), vleis (216) and estuarine wetlands (15).     

NOTES ON THE BIRDS OF THE CAPE L'AGULHAS REGION

Gargett, V. 1982. Synchronous hatching and the Cain and Abel struggle in the Black Eagle. Ostrich 53:147-150.

An experiment was conducted to cause two Black Eagle Aquila verrreauxii chicks to hatch synchronously. There was ample food on the nest and the female offered it to both chicks, but the smaller chick, from the smaller second-laid egg, died. The greater reach of the chick from the first-laid egg enabled it to obtain more of the food offered, so that it gained weight. Its greater mass then enabled it to prevent its sibling from taking food. Both chicks showed aggression, but that of the heavier chick was more effective.     

SYSTEMATIC NOTES ON BIRDS OF THE CAPE PROVINCE

Hofshi, H., Gersani, M. &; Katzir, G. 1987. Urban nesting of Tristram's Grackles Onychognathus tristramii in Israel. Ostrich 58: 156–159.

Urban nesting of Tristram's Grackles Onychognathus tristramii is described. Nesting in the town of Arad, Israel, was first observed in the summer of 1983. Breeding behaviour was recorded during two seasons, in six nests. The behaviour of Tristram's Grackles resembled that of related Onychognathus species. The birds were monogamous. Breeding was from March to the end of June, and nests were built in holes and crevices in unoccupied buildings, 6–20 m above the ground. The nest was deep, cup shaped and built predominantly of green Tamarix branches. Three to four eggs were laid. Only the female incubated, while the male guarded. Both parents fed the young on insects fruit and human food remains. The nestlings remained in the nest for approximately 30 days. Parents continued to feed the fledglings for a week after they had left the nest. The fledglings formed juvenile flocks, two weeks after they had left the nest. The adults might then raise a second brood. The process of urbanization of the grackles is discussed.     

TAXONOMY,DISTRIBUTION, MIGRATION AND MOULT OF THE REDBREASTED SWALLOW HIRUNDO SEMIRUFA

Earlé R. A. & Brooke, R. K. 1989. Taxonomy, distribution, migration and moult of the Redbreasted Swallow Hirundo semirufa. Ostrich: 60:151-158.

There are two well defined races of the Redbreasted Swallow Hirundo semirufa, the nominate and gordoni. H. s. neumanni is a synonym of gordoni. The breeding ranges of the two races do not meet. The Redbreasted Swallow has extended its range south and southeast following the construction of concrete road culverts which provide nest sites, together with bush clearance. The strongly migratory southern populations reach their southern limits by August each ear and depart again mainly in March-April although there are some records for May. Males are significantly larger than females in wing length and the length of the longest rectrix but not in other measurements. Moulting birds were found in each month of the year but the moults of the two races are largely separated in time. Moulting birds were found only between 10S and 10N with the majority close to the equator.     

AN EXPERIMENTAL STUDY OF PATERNITY AND TAIL ORNAMENTATION IN THE BARN SWALLOW (HIRUNDO RUSTICA)

Previous studies of the socially monogamous barn swallow (Hirundo rustica) have shown that males that most frequently engage in extrapair copulations and whose partners are least involved in copulations with extrapair males are those with long tail ornaments. In this study, through the use of three highly polymorphic microsatellite markers, we analyze the relationships between length of tail ornaments of male barn swallows and proportion of nestlings fathered in own broods, number of offspring fathered in broods of other pairs, and total number of offspring fathered, using both a correlational and an experimental approach. Consistent with our predictions, we show that males with either naturally long or experimentally elongated tails have higher paternity (proportion of biological offspring in own broods), and they produce more biological offspring during the whole breeding season than males with naturally short or experimentally shortened tails. Males with naturally long tails also had more offspring in extrapair broods than short-tailed males, but the effect of tail manipulation on the number of offspring fathered in extrapair broods, although being in the predicted direction, was not statistically significant. Cuckolded males that did not fertilize extrapair females had smaller postmanipulation tail length than cuckolders. We conclude that there is a causal, positive relationship between male tail length and paternity. Since female barn swallows have extensive control over copulation partners and heritability of tail length is high, this study shows that female choice is a component of selection for larger male ornaments. Benefits from extrapair fertilizations to females may arise because they acquire “good” genes for sexual attractiveness or high viability for their offspring.     

SOME NOTES ON THE CAPE GANNET,Morus capensis

Tarboton, W. R. 1978. Breeding of the Little Banded Goshawk. Ostrich 49:132-143.

The behaviour and vocalizations of a pair of Little Banded Goshawks Accipiter badius during part of their breeding cycle is described. Both sexes built the nest. Two eggs were laid three days apart. The first egg was incubated for 52% of the day, but this increased to 90% when the clutch was complete, of which the female's share was 86% and the male's 4%. The second egg hatched after 29 days, 18 h. The female did not hunt during the incubation or early nestling period and was fed by the male who brought her, on average, 7,0 food objects per day. Lizards formed 73% of the 91 identified prey objects, and small birds, 24%. The female and chick, when 16 days old, were killed by a predator on the nest at night.     

SEXUAL SELECTION IN THE MONOGAMOUS BARN SWALLOW (HIRUNDO RUSTICA). I. DETERMINANTS OF TAIL ORNAMENT SIZE

The proportion of phenotypic variance in the length of the sexually selected tail of the monogamous barn swallow Hirundo rustica that is attributable to genetic variance was studied in the field in Denmark during a seven-year period. Tail length was on average 20% greater in males than in females. Tail length correlated with wing length, but not with other morphological traits. Tail length increased with the first molt, but remained constant during subsequent years. Changes in tail length between years, owing to molt were significantly affected by sex and by degree of infection with an haematophagous mite (Ornithonyssus bursa). There were significant differences in sexual size dimorphism between years, apparently as a result of environmental conditions in the African winter quarters during molt. Tail length was a highly repeatable morphological trait, and standardization of tail length for age effects only marginally increased repeatability. Heritability of tail length as estimated from regression of values for sons on those of their fathers was 0.59. This suggests that secondary sexual traits affected by strong directional selection still may show a statistically significant heritability.     

EFFECTS OF A HAEMATOPHAGOUS MITE ON THE BARN SWALLOW (HIRUNDO RUSTICA): A TEST OF THE HAMILTON AND ZUK HYPOTHESIS

I tested three assumptions of the Hamilton and Zuk hypothesis (1982), which suggests that the extravagant male plumage of many bird species allows females to choose mates that are resistant to the parasites exploiting the host population at a given time. By choosing such males as mates, females will rear offspring carrying the genes for resistance. I tested three necessary conditions for the Hamilton and Zuk model: (1) whether parasites affect the fitness of their hosts; (2) whether there is heritable variation in parasite resistance, and (3) whether the expression of the sexual ornament varies with parasite burden. The haematophagous mite Ornithonyssus bursa (Macronyssidae, Gamasida) sucks blood from their Barn Swallow (Hirundo rustica) hosts. Experimental manipulation of mite loads and partial cross-fostering experiments on Barn Swallows, where half of the nestlings in the brood were exchanged with nestlings from another nest, shows that parasite burdens and origin, but not rearing conditions, of Bam Swallow nestlings, affected their adult tarsus length and maximum body weight shortly before fledging. Mite loads of adult Barn Swallows at spring arrival were more similar to mite loads of their own offspring, whether reared in their own or in foster nests inoculated with mites, than to loads of foster offspring. Parent Barn Swallows with long tail ornaments had offspring with smaller mite loads in the partial cross-fostering experiments. The amount of increase in male tail ornaments from one year to another was negatively related to experimentally manipulated mite loads of Barn Swallow nests during the preceding breeding season. In conclusion, the three assumptions of the hypothesis were supported by the experimental tests.     

SEXUAL SELECTION IN THE BARN SWALLOW (HIRUNDO RUSTICA). IV. PATTERNS OF FLUCTUATING ASYMMETRY AND SELECTION AGAINST ASYMMETRY

The patterns of variation in fluctuating asymmetry were studied in four morphological characters of the barn swallow Hirundo rustica. The level of absolute and relative asymmetry was larger in the secondary sexual character “outer tail length” than in three nonsexual morphological traits (wing, central tail, and tarsus length). The extent of individual asymmetry in outer tail length was negatively correlated with tail-ornament size, whereas the relationship between asymmetry of all other morphological characters and their size was flat or U-shaped. Asymmetry in outer tail length was unrelated to asymmetry in other morphological characters, whereas asymmetries in the length of wing, central tail, and tarsus were positively correlated. Male bam swallows exhibited larger asymmetry in outer tail length than females. Asymmetry of most morphological traits exhibited intermediate repeatabilities between years, with the exception of male and female outer tail length, which were highly repeatable. Tail asymmetry of offspring weakly, though significantly, resembled that of their parents. Asymmetry in wing and outer tail length was also significantly related to several fitness components. Male barn swallows that acquired a mate were less asymmetric in wing and outer tail length than unmated males. Females with more asymmetrical tails laid eggs significantly later. Annual reproductive success was unrelated to fluctuating asymmetry. Male barn swallows that survived were less asymmetric in wing and outer tail length than nonsurvivors, whereas female survivors were less asymmetric in outer tail length than nonsurvivors. These results suggest that levels of fluctuating asymmetry in barn swallows are associated with differences in fitness.