EDITORIAL

Olver, M. D. &; Kuyper, M. A. 1978. Breeding biology of the Whitebreasted Cormorant in Natal. Ostrich 49:25-30.

From 1972–1975 Whitebreasted Cormorants Phalacrocorax carbo bred at the Cedara Dam, Natal, South Africa (29 32S, 30 17E), and from 1973 they fished for food at Midmar Dam, 5 km away and carried the food back to the nestlings. Breeding occurred from April to October and was preceded by a period of courtship. Nesting material was collected by the males and the nests built by the females. The mean clutch size for 1972–1973 was 3,1. Both parents incubated the eggs and guarded the nest and chicks. Growth of the chicks was studied in 1972–1973. The mean number of chicks reared was 1,6 per nest although seven nests contained three nestlings. At 28 days they left the nest when alarmed, but could not fly until 49 days old. The average flying age appeared to be about 53 days. The height of the nests above the ground seemed to determine the nest leaving age. Of the 186 eggs laid in the 60 nests observed over two years, 74% hatched. Fledging success was 52% of eggs laid and 69% of eggs hatched. Chick mortality seemed to be caused mainly by falling from the nests and dying of starvation.     

Breeding biology of the Redwing Francolin in the highland grasslands of Mpumalanga Province,South Africa

We studied the breeding biology of the Redwing Francolin, Francolinus levaillantii, in the highland grasslands of Mpumalanga Province, South Africa, from 1995–1996. The breeding season is from August to March. Clutches were incubated by hens only and all nests were located in rank grass close to surface water. Mean clutch size was 4.3 eggs (S.D. = 0.78, n = 10) and mean egg dimensions were 40.1 × 32.3 mm (S.D. = 1.07 and 0.81, n = 44). Hatching success was 83.7% and clutch survival rate to 22 days of incubation was 82.8%. A mean of 3 chicks was produced per clutch; observed mean production (counts of hens with chicks) was 2.6 chicks per brood (n = 24 clutches; 62 chicks). The hunting season for Redwing Francolin in Mpumalanga should be from 15 April to 15 July.     

Sooty Falcon Falco concolor reproduction and population dynamics on the islands in the Sea of Oman

Knowledge of demographic parameters affecting population dynamics is critical to the formulation of effective conservation strategies. Sooty Falcon Falco concolor is a little‐studied, Near‐threatened species; estimates of global population size and trend for this species are uncertain. They lay eggs during mid‐summer and sometimes nest in colonies. This unusual breeding ecology suggests that demographic parameters driving their population growth rate may differ from those of most other falcons. We studied Sooty Falcon reproduction at breeding aggregations on Fahal Island and the Daymaniyat islands in the Sea of Oman during 2007–2014, modelled population growth and identified important life history parameters using elasticity analysis. The mean (± se) clutch and brood size was 2.83 ± 0.06 and 2.11 ± 0.07, respectively. Overall, 11.7% of nests failed between the egg and nestling stages, and the failure rate differed significantly between Fahal and the Daymaniyats, and across years. The mean proportion of eggs that hatched annually was 0.66 ± 0.02, and broods were significantly smaller on the Daymaniyats than on Fahal. Falcons on Fahal Island had a higher rate of hatching, a higher rate of nests that produced at least one chick, and produced more chicks per nest than on the Daymaniyats. We suggest that Fahal's proximity to the mainland gives breeding Sooty Falcons access to a more plentiful and stable source of food, especially during the period between arrival from the wintering grounds and the onset of the autumn migration of prey birds, resulting in the better reproductive rates for falcons on Fahal Island, relative to those on the Daymaniyat Islands. The annual asymptotic population growth rate (λ) was 0.87 (95% confidence interval (CI) 0.75–0.99), suggesting a declining population, although Sooty Falcons enjoyed a slightly higher population growth rate on Fahal than on the Daymaniyats. Because our study population is on the edge of the breeding range and is isolated from other breeding areas, measures to improve reproductive success of Sooty Falcons breeding on the islands in the Sea of Oman could be important for conservation of Sooty Falcons in Oman.     

Breeding ecology of Red‐faced Cormorants in the Pribilof Islands,Alaska

ABSTRACT Red‐faced Cormorants (Phalacrocorax urile) are North Pacific endemics recognized as a vulnerable species, but little is known about their breeding ecology. We studied Red‐faced Cormorants on St. Paul Island, Alaska, from 1975 to 2009, with more detailed data collected in 2004 and 2005. Mean clutch sizes in 2004 (3.2 ± 0.8 [SD] eggs) and 2005 (3.1 ± 0.8 eggs) were similar to the long‐term average (2.9 ± 0.3 eggs from 1976 to 2009). The mean laying interval in 2004 and 2005 was 2.15 ± 0.80 d (N= 407), and the mean egg period (number of days between laying of an egg and hatching) was 31.1 ± 1.4 d (N= 158). Approximately 64 ± 17% of eggs hatched during the period from 1975 to 2009. The mean number of chicks per nest in 2004 and 2005 was 2.8 ± 0.8 (N= 232), and the mean number of fledglings per initiated nest in all years was 1.22 ± 0.52. Chicks fledged 46 to 66 d posthatching. In 2004 and 2005, the primary causes of egg loss were predation by Arctic foxes (Vulpes lagopus) and destruction of eggs and abandonment of nests due to storms. Starvation was the primary cause of nestling mortality in both years. Because chicks are dependent on parents to provide food for over 45 d, consistent near‐shore foraging opportunities must be available. From 1975 to 2009, Red‐faced Cormorants experienced only 1 yr of complete reproductive failure (1984). The consistent reproductive success of Red‐faced Cormorants suggests that conditions may be relatively stable for this species on St. Paul Island, or that the variability in their breeding ecology (e.g., phenology, clutch sizes, and incubation strategies) provides the flexibility needed to successfully fledge some chicks nearly every year.     

Effect of brood size and hatching sequence on prefledging mortality of Sandwich terns: why lay two eggs?

The mortality of Sandwich tern Sterna sandvicensis chicks held in enclosures was studied in colonies on Griend, in the Dutch Wadden Sea, from 1992 to 1999, and on Hirsholm, in the Danish Kattegat, in 1997. Survival of chicks until fledging was 73% for chicks hatching from first-laid eggs or single-egg clutches and 59–64% for partially hatched two-egg clutches, whereas 6% of second hatchlings survived until fledging. Less than 2% of all two-chick broods actually fledged two chicks. Because 18% of the two-egg clutches only hatched one egg, 7% of fledglings of two-egg clutches originated from a second-laid egg. In nests where both eggs hatched, the number of chicks was usually reduced soon after hatching. Within five days of hatching more than 50% of the second hatchlings died of starvation or were preyed upon. It seems that overproduction commonly occurs in Sandwich terns and that investment in a surplus egg mainly serves as an insurance mechanism. On Griend and Hirsholm, chick productivity of two-egg clutches was somewhat higher than for one-egg clutches. Undernourishment was an important cause of death, either directly by starvation or by selective predation of chicks in poor condition. This, in combination with earlier, studies suggests that Sandwich tern parents on Griend are exposed to severe food stress.     

People in Antarctica — how much do Adélie Penguins Pygoscelis adeliae care?

Summary In the course of physiological field studies, we opportunistically examined the effects of humans and aircraft on breeding Adélie Penguins Pygoscelis adeliae. Proximity to both aircraft and humans caused substantial increases in penguin heart rate even when no external stress was manifest. A solitary human at 20 m distance from commuting penguins on a well-used pathway caused the birds to deviate by 70 m. Birds at nests exposed to a single human fled much more readily when the brood consisted of large chicks (critical distance 6.1 m) rather than small chicks (critical distance 1.3 m) or eggs (critical distance 0.3 m). Aircraft caused birds to panic at distances greater than 1,000 m and 3 days exposure to a helicopter inhibited birds that had been foraging from returning to their nests, caused bird numbers in the colonies to decrease by 15% and produced an active nest mortality of 8%. Based on this data, we make recommendations to minimize stress on Adélie Penguin colonies exposed to man.     

Load Lightening in Southern Lapwings: Group‐Living Mothers Lay Smaller Eggs than Pair‐Living Mothers

Females of some cooperative‐breeding species can decrease their egg investment without costs for their offspring because helpers‐at‐the‐nest compensate for this reduction either by feeding more or by better protecting offspring from predation. We used the southern lapwing (Vanellus chilensis) to evaluate the effects of the presence of helpers on maternal investment. Southern lapwings are cooperative (some breeding pairs are aided by helpers), chick development is precocial, thus adults do not feed the chicks, and adults offer protection from predators through mobbing behaviors. We tested whether southern lapwing females reduced their reproductive investment (i.e. load‐lightening [LL] hypothesis) or increased their investment (i.e. differential allocation hypothesis) when breeding in groups when compared with females that bred in pairs. We found that increased group size was associated with lower egg volume. A significant negative association between the combined egg nutritional investment (yolk, protein, and lipid mass) and group size was observed. Chicks that hatched from eggs laid in nests of groups were also smaller than chicks hatched in nests of pairs. However, there was no relationship between the body mass index of chicks, or clutch size and group size, which suggests that such eggs are, simply, proportionally smaller. Our results support the LL hypothesis even in a situation where adults do not feed the chicks, allowing females to reduce investment in eggs without incurring a cost to their offspring.     

Intraspecific nest parasitism in the Spotless Starling Sturnus unicolor

Intraspecific nest parasitism in two colonies of Spotless Starling Sturnus unicolor breeding in nestboxes was studied in central Spain from 1991 to 1994. Nests were monitored regularly and three criteria were used to detect nest parasitism: the appearance of more than one egg per day during the laying period of the host; the appearance of an egg after the start of incubation; eggs with unusual shape or pigmentation. The proportion of parasitized nests in first clutches (37%) was twice that of intermediate (19%) or second (20%) clutches in colony B, whereas parasitism occurred in first (35%) and intermediate (12%) but not in second clutches in colony A. Most clutches (52–70%) were parasitized during the host's laying period and received one parasitic egg. In 10% of the parasitized clutches in colony B, one of the host's eggs disappeared on the day the parasitic egg was added, suggesting that the parasitic female removed this egg. Although parasitism increased clutch size significantly, it led to a decrease in host breeding success, mainly through the removal of eggs and the loss of host nestlings and the survival of parasitic chicks. Observations suggested that parasitic females were young individuals without their own nests and/or those whose breeding attempt had been disrupted while laying in their own nest.     

Rates and consequences of relaying in little auks Alle alle breeding in the High Arctic an experimental study with egg removal

Most seabirds have a small clutch size. Thus, replacement of a clutch after loss can make important contributions to an individual’s lifetime reproductive success. However, in the condition of short polar summer, relaying propensity may be time‐constrained. In this study, we investigated rates and consequences of relaying in a small High Arctic seabird, the little auk Alle alle. We performed an experiment in which we removed the single egg from 20 nests of early‐laying breeders. We measured relaying rates, and compared chick body mass and breeding success between the experimental and control nests. Despite the narrow window of the Arctic summer and the closely synchronized breeding, 75% of females produced a replacement egg just 2.7% smaller in volume than the first egg. This indicates that in little auks, the demographic effects of disruptions to breeding attempts (by predators, adverse weather or human activity) may be mitigated to some extent by replacement clutches. However, peak body mass and fledging body mass were lower in the experimental than the control chicks. This effect was rather a consequence of late hatching – chicks from replacement clutches followed seasonal decline in peak body mass and fledging mass. Finally, breeding success and chick survival up to 20 d in the experimental nests were respectively 34 and 37% lower than in the control nests. Thus, the quality and post‐fledging survival of chicks from the replacement clutches were probably lower compared to the chicks hatched from the first‐laid eggs.     

Reproductive biology and ecology of white‐winged trumpeters (Psophia leucoptera) and recommendations for the breeding of captive trumpeters

The reproductive biology and ecology of a wild population of white‐winged trumpeters (Psophia leucoptera) were studied in southeastern Peru from 1983 to 1987. Because little information is available about any of the trumpeter species and because trumpeters have proven difficult to breed in captivity, information relevant to breeding and management of captive trumpeters is reported in this paper. White‐winged trumpeters lived in territorial social groups that ranged in size from four to 13 individuals. A typical territorial group contained three adult males, two adult females, and several sexually immature offspring, but smaller temporary groups sometimes formed for the duration of the breeding season. Only the dominant female contributed eggs to the clutch, and all adult males in the group competed to obtain copulations with her. Eggs were laid in elevated nesting cavities and no nest was constructed. The average clutch size was three eggs and incubation was not begun until the final egg was laid. The dominant male and female shared most of the incubation duties, but subordinate males covered approximately 15% of the incubation shifts. Eggs hatched approximately 27 days after incubation was begun and chicks left the nesting cavity the day after they hatched. Chicks were completely dependent on older birds to feed them for their first 3 weeks and then gradually began to feed themselves more and more food. The subordinate adult males fed chicks the most food, the dominant male and female and older offspring fed chicks an intermediate amount, and the subordinate adult female fed chicks the least. Young chicks behaved aggressively toward each other but were separated by adults before they injured each other. If at least one chick from the clutch survived, trumpeters did not breed again until the beginning of the next breeding season the following year. Zoo Biol 19:65–84, 2000. © 2000 Wiley‐Liss, Inc.     

Artificial incubation of California condor Gymnogyps californianus eggs removed from the wild

The currrent California condor (Gymnogyps californianus) recovery plan entails increasing the reproductive rate via replacement-clutch manipulation of eggs. During the period from 1983 to 1985, 15 eggs were removed from wild nesting pairs for artificial incubation. The eggs were incubated at a dry bulb temperature of 36.4°C in modified forced-air Lyon Electric incubators. The incubation humidity was adjusted for individual eggs based on weight loss data (water = weight), 25.6–30.0°C wet bulb (41.0–63.0% Relative Humidity (RH)). The chicks were hatched initially under forced-air conditions of 36.1°C dry bulb, 31.1–01.7°C wet bulb (70.0–73.0% RH). In 1984, hatching parameters were changed to still-air conditions, 36.1°C dry bulb (top of the egg), 35.0°C dry bulb (bottom of the egg), 31.1–31.7°C wet bulb (70.0-73.0% RH). Tactile and auditory stimulation was utilized during the pip-to-hatch interval. From among 15 eggs collected, 13 hatched, and 12 condor chicks were raised successfully (hatchability: 86.7%; survivability: 92.3%).     

Timing of Spawning and Host-nest Choice for Brood Parasitism by the Japanese Minnow,Pungtungia herzi,on the Japanese Aucha Perch,Siniperca kawamebari

A field study of the breeding ecology of the Japanese aucha perch, Siniperca kawamebari, and brood parasitism by the Japanese minnow, Pungtungia herzi, on nests of the perch was carried out from 1989 to 1991. Observations of perch nests under natural conditions in 1990 showed that brood parasitism by the minnow was concentrated on host nests in which nest owners had just begun their nesting cycle. When spawned in a perch nest with recently spawned perch eggs, parasite eggs always hatched earlier than host eggs. An experiment with imitation perch eggs in 1991 confirmed that changing colour of host eggs was the cue for the parasites to distinguish between different developmental stages of host eggs. Parasite eggs rapidly disappeared without guarding by a host male (Baba et al. 1990). This loss was caused by predation by fishes. Parasite fry left the nest immediately after hatching, so parasite eggs spawned in a host nest in an early stage should be well guarded until they hatch. In the field, minnows deposited their eggs in perch nests which had larger numbers of newly spawned perch eggs. Since the perch males always deserted their nests when their own eggs disappeared, the parasite's choice of host nests with larger numbers of host eggs may ensure survival of the parasite eggs. The timing of egg deposition and choice of host nest by the minnow appear to be adaptive in terms of brood parasitism on nests of the perch.     

Hatching order affects offspring growth,survival and adult dominance in the joint‐laying Pukeko Porphyrio melanotus melanotus

In birds with asynchronous hatching, hatching order is an important factor in determining offspring phenotype. Many previous studies have demonstrated that later‐hatched offspring show reduced growth and survival during development. However, few studies have followed individuals from hatching to adulthood to test whether the effects of hatching order persist into later life. Here, we explore patterns of hatching order and fitness‐related traits in the Pukeko Porphyrio melanotus melanotus, a cooperatively breeding bird that lives in stable social groups that form linear dominance hierarchies. Pukeko groups sometimes contain two breeding females that lay eggs in the same nest (joint‐laying). Thus, competition between nest‐mates can influence the relative fitness of each laying female. We show that in both single‐clutch and joint‐clutch nests, earlier‐hatched Pukeko chicks grow faster and survive better than later‐hatched brood‐mates. Moreover, earlier‐hatched chicks achieve higher dominance ranks as adults, making this study one of the first to find a relationship between hatching order and adult dominance in wild birds. Finally, we show that in groups with two breeding females, the chicks of the primary female hatch earlier than the chicks of the secondary female. As a result, the offspring of the primary female may be at a competitive advantage, which could have important implications for social dynamics in this species.     

Brood reduction in temperate and sub-tropical ospreys

Summary In an effort to understand patterns and causes of nestling loss in Ospreys (Pandion haliaetus), I studied brood reduction in three eastern U.S. Osprey colonies during 1978 and 1979. The colonies, located in Florida Bay (1) and on coastal Long Island, N.Y. (2), differed in the average daily amount of food delivered to nestlings; Florida nests received 43% and 11% less fish per day than nests in the two N.Y. colonies, largely because latitude and season restricted day length and thus foraging time for the winter-breeding Florida Ospreys. Increased distance from stable food sources accounted for the lower rate of feeding at one of the N.Y. colonies. Variation in clutch size in the three colonies reflected differences in latitude more than in food availability; average clutch sizes in Long Island were larger than Florida clutches by 0.5 of an egg, but were similar to each other and to those in other northeastern U.S. Osprey populations.Increased nestling loss coincided with reduced food delivery rates and, in food stressed colonies, this loss was 2–3 times greater than any recorded for Ospreys. Starvation was the primary cause of nestling death, with mortality concentrated on third chicks, which hatched on average 3.9 d later and from eggs 5.6% smaller than chicks hatching first. Sibling aggression accounted for the preferential feeding of older nestmates,but only in colonies or nests where food was limited. Aggressive chicks nearly always stopped fighting after being fed. This behavior provided a reversible mechanism for controling brood reduction that was based on nutrition. Growth rates of young measured during the first half of the growth period were more variable between colonies than within nests. This is interpreted as reflecting both the differences in colony food delivery rates as well as the evolutionary pressures of sibling competition to equalize the growth of nestmates.     

Effects of clutch size and egg-laying order on the breeding success in the Little Tern Sterna albifrons on the Nakdong Estuary, Republic of Korea

Survivorship of Little Tern Sterna albifrons eggs and chicks was followed on an islet in the Nakdong Estuary, Republic of Korea, in 1995 and 1996. Mean egg size and incubation period were significantly different between the 2 years. The maximum clutch size was three eggs, and the second egg in the clutch often hatched earlier than the first, while most of the third eggs hatched last. In 1996, when the fate of 249 eggs from 106 nests was followed for 40 days, hatching success, fledging success and breeding success were 77%, 40% and 31%, respectively. High mortality occurred in the early chick stage, mostly because of rain and predation by Weasels Mustela sibirica. The breeding success per egg was 14% in one-egg clutches, 28% in two-egg clutches and 34% in three-egg clutches. This difference was mainly attributed to the lower hatching success in the smaller clutches. In three-egg clutches, the third egg showed significantly lower breeding success than siblings. The main foods of the Little Tern were Tridentiger obscurus, Engraulis japonicus, Hyporhamphus intermedius, Acanthogobius flavimanus (all fish), Palaemon sp. and Crangon affinis (shrimps). The feeding frequency was, apparently, not affected by time of day and age of chicks but was probably influenced by weather conditions. Newly hatched chicks failed to eat 25% of the prey brought to them, although this decreased with the age of the chicks.     

Breeding success in a Houbara Bustard Chlamydotis [undulata] macqueenii population on the eastern fringe of the Jungar Basin, People's Republic of China

Nesting success and chick survival of a migratory population of Houbara Bustard Chlamydotis [undulata] macqueenii were studied during three consecutive years (1998–2000) in the Xinjiang province of north‐west China. A total of 45 nests was monitored and 85 broods comprising 227 chicks were captured, of which 82 chicks were radio‐tracked. Start of laying varied between 6 and 17 April between years but the laying mode fell consistently between 26 and 30 April. Mean clutch size was 4.0 (sd = 0.8) (range 2–6) for early clutches and 3.3 (sd = 1.1) for late clutches (range 2–5). The average nesting success was 0.588 (sd = 0.270) but great variations were observed between years –0.882 in 1998, 0.530 in 1999 and 0.351 in 2000. This was related to increased predation in 1999 and 2000, which is reflected by increased predator density (chiefly Corsac Fox Vulpes corsac and Long‐legged Buzzards Buteo rufinus). The overall hatchability, defined as the proportion of eggs hatched in successful nests was 0.839 sd = 0.238). The average brood size at hatching varied from 2.9 (sd = 0.8) to 3.3 (sd = 0.9) according to years, and no significant decrease in brood size was observed in the first 5 days post‐hatching. In 1999 and 2000 the brood size diminished sharply (14% and 27%, respectively) in prefledging chicks. A further severe decrease (37%) was observed in fledglings in 2000, probably due to predation by raptors. For the 3 years of the study, a successful female Houbara would bring on average 2.3 (sd = 0.9) chicks to fledging and would have lost 30.2% (sd = 14.9%) of its brood to adversity during the rearing process. The proportion of females that lost their entire brood was 0.181 in 1998, 0.708 in 1999 and 0.453 in 2000. For the 3 years of the study, only 55.3% (sd = 26.3%) of the females hatching eggs brought chicks to fledging. The overall chick production was 0.827 per breeding female per year and the probability of an egg laid producing a fledgling of 8 weeks old was 0.190.     

THE BREEDING ECOLOGY OF ROYAL TERNS STERNA (THALASSEUS) MAXIMA MAXIMA

The breeding ecology of the New World race of the Royal Tern Sterna maxima maxima was studied at colonies in Virginia and North Carolina, U.S.A., from 1967 to 1970. Colony sites are quite varied, but isolation, good distance visibility and (especially) freedom from quadruped predators seem important if not essential prerequisites. In Virginia, most adults arrive at the colony site in the last few days of March. Courtship, displaying and copulation take place at, near, and some distance from the colony site. In this the Royal Tern differs from its near relative S. sandvicensis sandvicensis which carries out these activities away from the colony site, presumably as an anti-predator device. Courtship displays are not described, but in their essentials are similar to those of other terns. Copulations continue throughout incubation and gradually disappear when the eggs hatch. No post-copulatory displays are known. Some synchrony of egg-laying is evident, but no “mass laying” occurs, the colony increasing in size steadily over a period of weeks and months. Defaecation on the nest is normal and probably serves to strengthen the nest rim against flooding by high tides. Contrary to published reports, the normal clutch is one; the largest is two, probably often from two different females. All incubating adults examined had two brood patches. Average egg measurements are 63 × 44-5 mm, and average egg weight is 64.3 g. Egg colour varies greatly, and evaluation is difficult. Eggs are probably not cryptically coloured and individual variation, as well as nest-site, are used by returning adults to identify their own eggs. Average maximum nest density is c. 7/m². Sterna sandvicensis acuflavida nests regularly, if not obligatorily, with m. maxima; interactions between the two, and possible benefits accruing to each, are discussed. Unhatched eggs were significantly nearer other nests than were successfully hatched eggs, and possible explanations are given. Incubation lasts about 30–31 days, a week longer than in most terns; both sexes incubate. Broken eggshells are never removed by the adults. Instead, after 2–3 days, the chicks leave the nest permanently to join a creche that roams freely about the immediate vicinity of the colony. Chicks remain in the creche for about 25–30 days, leaving it at fledging, approximately 30 days after hatching. While in the creche, chicks are normally fed only by their parents, who probably recognise them both vocally and visually, using the extensive variation in voice and colour of chicks characteristic of the species. Sandvicensis acuflavida chicks also are highly variable, and join Royal creches, adults of both species attending. Variation also occurs in Royals' juvenal plumage, and seems associated with extended parental care. Feeding adults normally wander up to 40 km from their colony, and this probably facilitates the intercolonial exchange of breeding birds we recorded. They feed inshore, in shallow waters, taking small fish by dives which do not go below the surface. They regularly take small soft-shell crabs in this way, and frequently water-skim like skimmers Rynchops spp., sometimes capturing food while doing so. A relationship between crab capture and water-skimming is established for the first time, and water-skimming in non-feeding contexts is mentioned. Besides the quadruped predators which they normally avoid by fleeing the colony site, Royals have no known predators beyond the egg stage. Eggs, although not chicks, are readily taken by Laughing Gulls. Relationships between the two species are discussed, emphasising their constant association the year round.     

3. NOTES OF THE BIRDS OF THE KRUGER NATIONAL PARK

Mundy. P. J. &; Cook. A. W. 1975. Hatching and rearing of two chicks by the Hooded Vulture. Ostrich 46:45-50

The single-egg clutches of 10 pairs of Hooded Vultures Necrosyrtes monachus were doubled by the addition of one egg to each in the breeding season of 1971/72 at Sokoto, Nigeria. Three pairs hatched both eggs and a further two pairs hatched one egg each. Only one pair raised both chicks to fledging and, apart from a depressed weight gain and tail growth of the younger “sibling”, the chicks grew at approximately the average rate for the species. The average rate was determined by following 27 normal nests in the study area. There was no evidence of aggression between the “siblings”. It was suggested that the success of one adult pair in raising two chicks was partly occasioned by the chicks' ages being only four days apart, and by the unusually rich food supply available from nearby human activities.     

Cave breeding by African Penguins near the northern extreme of their range: Sylvia Hill,Namibia

Only three mainland sites are known among the total 27 breeding colonies of the African Penguin, Spheniscus demersus: two in South Africa and one in Namibia. The latter is a unique cave site near the northern extreme of the species' range on the edge of the Namib Desert. To determine the colony size, long-term viability and any difference in breeding ecology relative to more southern sites we combined data from previous visits to the site with four visits in 2001. We found that about 240 to 300 birds use the Sylvia Hill cave, and about 90 nests are active with a laying peak in January. Eggs are laid on top of guano mounds not in burrows as is usual for this species. Smaller clutches (1.68 eggs/nest) but larger broods (x = 1.31 chicks/nest) were apparent in this colony than those farther south. Larger mean clutches farther south suggest a latitudinal trend in clutch size for Namibia's penguins. We found no evidence for a population decline over 17 years, and thus no evidence that birds at the periphery of their range moved southwards into core areas. We conclude that the colony is healthy and thriving despite a general decline in penguin numbers in southern Africa.     

4. UNUSUAL EXPERIENCES WITH BIRDS

Earlé, R. A. 1989. Breeding biology of the Redbreasted Swallow Hirundo semirufa. Ostrich 60: 13–21.

The two races of the Redbreasted Swallow Hirundo semirufa seem to have separate breeding seasons with the northern race H. s. gordoni breeding April-July, while most records for the nominate race fall in October-February. All nests studied were in concrete culverts less than 1 m high. Eggs laid in second clutches by individual females weighed significantly less than eggs laid in first clutches. Eggs hatched on average 16,2 days after incubation started or 18–21 days after the eggs were laid. Only females incubated. Chicks fledged 23–25 days after hatching and reached a maximum body mass of about 31,5 g on day 18 before a steady decline in mass until fledging. Most nesting failures resulted from infertile eggs or starvation of young in the nest (16,2% of all young starved). Overall breeding success was 60,6%. In all, 81,8% of first clutches produced fledglings but only 44,4% of second clutches. Over a three year period 4,9 young were produced per pair breeding in the area (1,6 young/pair/breeding season).