POPULATION,DIET AND THE ANNUAL CYCLE OF THE LAUGHING DOVE AT BARBERSPAN,PART 3: THE ANNUAL CYCLE

Dean, W. R. J. 1979. Population, diet and the annual cycle of the Laughing Dove at Barbers-pan, Part 3: The annual cycle. Ostrich 50:234-239.

Laughing Doves Streptopelia senegalensis were collected each month from July 1976 to June 1977. In each sample some males and females were breeding. Breeding and primary moult overlapped, and some birds began to moult after starting to breed, and began to breed after starting moult. Adult Laughing Doves require about 120 days to complete primary moult, and juveniles require about 90 days. Weights of moulting birds were not significantly different from those of non-moulting birds, and there were no seasonal trends in the weights of either group. The mean weight of 79 males was 101,6 g and of 39 females was 100,2 g.     

THE INFLUENCE OF THE ENVIRONMENT ON BREEDING SUCCESS OF A SUBURBAN POPULATION OF CRESTED BARBETS TRACHYPHONUS VAILLANTII

Van Zyl, A.J. 1994. The influence of the environment on the breeding success of a suburban population of Crested Barbets Trachyphonus vaillantii. Ostrich 65: 291–296.

I studied the breeding biology of the Crested Barbet Trachyphonus vaillantii in Colbyn, a suburb east of Pretoria, South Africa, for nine breeding seasons from 1981 to 1989 to examine patterns in annual breeding success, breeding attempt success in multiple broods, and rainfall. The modal incubation period was 14 days and the nestling period ranged from 28 to 31 days. Average clutch size for all the years was 3,3 eggs/clutch and there was no significant difference in clutch size or number of young fledged/nest between years. On average, Crested Barbet pairs made 2,4 breeding attempts/season. There was no difference in clutch size or breeding success between the breeding attempts. Crested Barbets nesting in natural nests laid on average larger clutches than those in artificial nestboxes, but had non-signficantly lower breeding success. Failure to raise Crested Barbet chicks was attributed to parasitism by Lesser Honeyguides Indicator minor, bee swarms occupying nestboxes, and flooding of natural nests. Breeding performance was not correlated with rainfall or adult body size. The suburban environment may be less variable than a natural environment, resulting in a stable breeding Crested Barbet population.     

THE POPULATION,ECOLOGY AND CONSERVATION OF THE BLACK OYSTERCATCHER HAEMATOPUS MOQUINI

Summers, R. W. & Cooper, J. 1977. The population, ecology and conservation of the Black Oystercatcher Haematopus moquini. Ostrich 48:28-40.

The population of Black Oystercatchers Haematopus moquini in the southwestern Cape, South Africa, was estimated to be 2 942 birds. Birds occurred most abundantly on coastal islands and were also abundant on mixed (sandy and rocky) shores of the mainland. Sandy shores and coastal wetlands supported few birds. Black Oystercatchers bred mainly from December to February with the number of clutches present reaching a peak in the first half of January. The most frequent clutch size was two eggs, the mean clutch size was 1,81. No significant differences were found in either linear dimensions or mass between the first and second eggs. The mean proportion of juveniles in groups of birds in July was 3,6 % suggesting a low recruitment to the adult population. The breeding population at Marcus Island is apparently sedentary throughout the year. The primary moult season for adults extends from March to October (eight months). Introduced mammalian predators should be controlled on islands and important mainland breeding sites should be protected by the creation of nature reserves and restricting human access during the breeding season.     

POPULATION,DIET AND THE ANNUAL CYCLE OF THE LAUGHING DOVE AT BAR-BERSPAN,PART 2: DIET

Dean, W. R. J. 1979. Population, diet and the annual cycle of the Laughing Dove at Barberspan, Part 2: Diet. Ostrich 50:215-219.

Laughing Doves Streptopelia senegalensis were collected each month from July 1976 to to June 1977. The diet was found to be mainly seeds of commercial crops (sunflower and make) during most of the year. One species of grass, Eleusine indica, occurred in 100% of stomachs, but often was present only in small amounts. Ovulating females took significantly more animal matter than non-ovulating females.     

BREEDING BIOLOGY OF THE BATELEUR

Watson, R. T. 1990. Breeding biology of the Bateleur. Ostrich 61: 13–23.

Observations were made on the breeding biology of the Bateleur Terathpoius ecaudataus between 1981 and 1984, in the central region of the Kruger Nabonal Park. Nests were uniformly distributed with a mean inter-nest distance of 5,1 km and density of 3,1 nests/100km². Single-egg clutches were laid from January to June, and laying appeared to be suressed by unusually high rainfall events. The mean productivity was 0,47 young per pair per year, an a breeding failures were mainly due to failure to lay or predation. Breeding adults chaned nest sites within their territory on average once every 2,8 years, but territories and pairs were stable from year to year. Both members of a pair put equal time into care of the young.     

THE PRESENT AND PAST DISTRIBUTION OF THE BALD IBIS IN THE PROVINCE OF THE CAPE OF GOOD HOPE

Tarboton, W. R. 1981. Cooperative breeding and group territoriality in the Black Tit. Ostrich 52:216-225.

In a small, colour-ringed population of Black Tits Parus niger in central Transvaal, 11 of 19 observed breeding units comprised pairs with one to three helper-males. These pairs and groups defended permanent territories, the size of which correlated with the size of the group. There were significantly more territorial disputes during winter when less food was available than in summer. Breeding occurred in summer and the female alone built the nest, incubated the eggs and brooded the young while they were small. During this time she was fed by the alpha male and helper males, although before egg-laying the alpha male prevented helpers from courtship-feeding her. On average, unassisted pairs reared 0,88 young/season whereas pairs with helpers reared 1,55 young/season. However the feeding rate of nestlings of pairs with helpers was not higher than that of unassisted pairs and the number of young reared per group did not correlate with the number of helpers within the group.

The helper system in Black Tits was associated with a skewed sex-ratio (1,7:1 males: females) in the adult population and the data are consistent with the “hopeful reproductive” hypothesis for cooperative breeding.     

Blue penguin (Eudyptula minor) nest distribution and breeding success on Otago Peninsula, 1992 to 1998

Abstract

Annual counts of nests with eggs or chicks (known nests) were made at blue penguin (Eudyptula minor) breeding sites on the Otago Peninsula in each November from 1994 to 1997. Although the population has doubled to an estimated 600 known nests over this period, the number of breeding sites on the Otago Peninsula has reduced since the 1970s. Breeding success at three areas at Taiaroa Head were monitored by regular nest checks in the breeding season from 1992 to 1998. At Taiaroa Head reproductive success ranged from 41 to 78% at the three sites during the seven‐year study and was generally higher for pairs nesting in nest boxes than for those in burrows. The percentage of breeding pairs that laid a second clutch after fledging at least one chick from their first clutch (double brooded) varied between seasons (0–48%) and was correlated with the date of the onset of breeding. Egg loss, possibly through predation by Norway rats (Rattus norvegicus), influenced the significantly lower reproductive success at one area (Area A) at Taiaroa Head during the 1996 season.     

Determining productivity of Maui Parrotbills,an endangered Hawaiian honeycreeper

ABSTRACT Maui Parrotbills (Pseudonestor xanthophrys), critically endangered Hawaiian honeycreepers endemic to the island of Maui, are restricted to a single population of ～500 individuals located in remote, mountainous terrain. From January to June 2006–2011, we located nests and fledglings in the Hanawi Natural Area Reserve (NAR) in east Maui, Hawaii, to document nest success and annual reproductive success. Nest success is a commonly used measure of productivity and is a central component of many demographic studies. Annual reproductive success is less frequently documented because greater effort is required to monitor the reproductive success of breeding pairs through time. However, for species whose nests are difficult to locate or access, such as Maui Parrotbills, the presence or absence of fledged young may provide a more accurate measure of breeding success than monitoring nests. During our study, we located and determined the outcome of 30 nests to document nest success, and monitored 106 territories for the presence or absence of fledglings to calculate annual reproductive success. Nest success probability was 19% (N= 30) and seasonal nest success was 46%. During our monitoring efforts, 49 of 106 breeding pairs produced a single fledged young. Because parrotbills typically have single egg clutches and only re‐nest after nests fail, the presence or absence of a fledgling is an indication of a pair's overall reproductive success for a breeding season. Based on the number of fledglings per pair, our estimate of annual reproductive success was 46%, confirming our initial productivity estimate from nests. Thus, our results indicate that the two methods, determining annual reproductive success by monitoring fledglings and calculating nest success, provide similar estimates of annual productivity for Maui Parrotbills. Based on our estimates, the parrotbill population appears to be demographically stable. However, our productivity estimate was based only on the population at Hanawi, an area representing just 3% of the total range of parrotbills. Thus, our results may not accurately reflect the status of parrotbills over their entire range.     

BREEDING PERFORMANCE OF PUFFINS FRATERCULA ARCTICA IN RELATION TO NEST DENSITY, LAYING DATE AND YEAR

The paper presents data on the breeding and predation of Puffins in two areas of different nest density within a single colony on Dun, St Kilda group, Outer Hebrides in 1973-78.
Within a season birds laying early had a slightly higher nesting success than birds laying late, but laying date had little influence on the peak and fledging weights of young. The main disadvantage in late laying was a reduced chance of relaying if the first egg was lost.
Breeding success and chick weights varied from year to year. The 1974 season was the least successful with the lowest nesting success, lowest frequency of feeds, lowest calorific value of feeds, lightest chicks and slowest growth. Overall breeding performance was not related to the annual mean laying dates.
In all years pairs nesting in the area of high nest density did better than pairs nesting at low density. The effect is attributed to differential predation and disturbance by predatory gulls. At least 4.2% of adult Puffins breeding in the area of low burrow density were killed by gulls each breeding season; this is higher than the total annual mortality found in three other studies. Only 0.9% of adults from the high density area were found killed. The subpopulation in the low density area cannot survive without much immigration, yet there is no evidence that this happens.     

Nesting Biology of Urban Cooper's Hawks in Milwaukee,Wisconsin

ABSTRACT Urban landscapes vary greatly across North America and long-term data on the nesting biology of Cooper's hawks (Accipiter cooperii) from a variety of urban environments will improve our understanding of these poorly studied populations. We studied Cooper's hawks nesting in the metropolitan Milwaukee area, Wisconsin, USA, over a 12-year period, 1993–2004. Nesting success for 254 first nesting attempts averaged 64.6% with means of 2.27 young per laying pair and 3.53 young per successful pair. For 8 second nesting attempts (i.e., re-nests), nesting success averaged 87.5% with means of 2.57 young per laying pair and 3.00 young per successful pair. Productivity for first nesting attempts did not vary over the 12-year period, and productivity for re-nests did not differ from first nesting attempts. We documented evidence of nest predation by raccoons (Procyon lotor) and red-tailed hawks (Buteo jamaicensis). On average, second year (SY [i.e., 1-yr-old]) Cooper's hawks comprised 14.6% (43 of 295 breeding birds; 21.5% [37 of 172] of F and 4.9% [6 of 123] of M) of the known breeding population. The percentage of SY breeders within this population declined over the 12-year period, suggesting a relatively young population. Cooper's hawks consistently reoccupied nest sites annually after initial discovery over an estimated 2 generations of breeding adults, suggesting that population density for our study was at least stable. We trapped 105 breeding adults, including 5 natal dispersal birds. Based on long-term, relatively high reproduction, repeated re-occupancy of nest sites, and confirmed recruitment from within this population, we suggest that these nesting areas were not marginal or inferior habitats and that urban Cooper's hawks in this study area were not a sink population. We recommend no active management of this population at this time; however, additional information for nesting Cooper's hawks from other urban environs will expand our knowledge base for these populations.     

Breeding success and chronology of Wood Storks Mycteria americana in northern and central Florida, U.S.A.

The breeding success and chronology of Wood Storks Mycteria americana were studied at eight colonies in northern and central Florida during 1981–1985. Mean ± s.d. clutch size for all colony-years was 3.07 ± 0.56 (n = 2694 nests), with three-egg clutches (72%) most frequent. Mean clutch size among all colonies and years ranged from 2.73 ± 0.55 to 3.41 ± 0.61. Many colonies exhibited significant negative trends in clutch size with, hatching date because of a proportional decrease in four-egg clutches later in the season. Mean colony clutch size was not correlated with nest numbers, nesting density or mean hatching date within most years. Mean ± s.d. number of fledglings for all colonies and years was 1.29 ± 1.16 fledglings per nest (n = 2812 nests). Mean annual fledging rates in colonies ranged from 0 (colony failed) to 2.66 fledglings per nest. Most breeding failure occurred prior to egg hatching, and the second highest mortality occurred between hatching and 2 weeks of age. Four-egg clutches fledged more storks than three-egg clutches, which in turn were more successful than two-egg clutches. However, all clutch sizes showed similar fledgling per egg rates. The seasonal decline in productivity was associated proportionally with smaller clutch sizes later in the breeding season. An increase in mean hatching date was correlated with an increase in latitude. There was greater within-year breeding synchrony among colonies than interyear breeding synchrony within each colony. Breeding synchrony was not correlated with mean hatching date, latitude, longitude, nest numbers or nesting density.     

ON THE LIFE-EXPECTANCY OF THE MATOPOS BLACK EAGLES

Oatley, T. B. 1982. The Starred Robin in Natal, Part 3: Breeding, populations and plumages. Ostrich 53: 206–221 The female Starred Robin Pogonocichla stellata constructs a domed nest of moss and dead leaves usually on sloping ground and well concealed in the herb layer. The normal clutch is three eggs laid on consecutive days. Incubation usually starts with the laying of the third egg. The mean size of 138 eggs was 22 x 16 mm. The female incubates the eggs for 16 to 18 days and intermittently broods the young for the fist five of the average 14-day nestling period. Both sexes feed the young from the time of hatching and parental care lasts for some 42 days after leaving the nest. Eggs are laid from October to December with 63% of clutches started in November. Data on sex ratios indicate a surplus of adult males in the population and annual survival rates are estimated at 0,84 for males and 0,76 for females. 51% of eggs laid in 60 nests give rise to fledged young. About 21.3% of eggs laid produce adults. The level of brood parasitism by cuckoos is relatively low. Most adult mortality occurs outside of the breeding seasons. Chilling and overnight starvation from January to March when incidence of late afternoon thunderstorms is highMaycause significant mortality. The subadult plumage appears to confer crypsis and enable the immature bird to reside in adult territories without harassment. AdultsMaybenefit through an effective reduction in competitive stress.     

THE BIRDS OF BLYTHSWOOD AND SOME NOTES ON BIRDS OF THE DISTRICT

Wintle, C. C. &; Taylor, P. B. 1993. Sequential polyandry, behaviour and moult in captive Striped Crakes Aenigmatolimnas marginalis. Ostrich 64:115-122.

Captive Striped Crakes showed sequential polyandry, the female laying for a second male when the clutch of her first mate was about to hatch. Where aviary space permitted each male set up a breeding territory and each female defended a larger area encompassing the territories of one or two males. Non-territorial subordinate males and females did not breed. The female initiated breeding by attracting the male and soliciting copulation, and the male incubated the eggs and cared for the young. Incubation took 17–18 days, the chicks left the nest at 4–5 days of age and were fully grown and capable of flight at 46–53 days. Breeding occurred from September to March and males normally reared two broods per season. Territoriality was evident only during the breeding season. Juvenile plumage was a duller version of the sexually dimorphic adult plumage; post-juvenile moult bean at 13–15 weeks and was complete at 21 weeks. Remex moult was simultaneous and a complete moult regular1 occurred twice a year in adults, in December and April (males) and September and March/April (females).     

POPULATION DYNAMICS OF THE FLIGHTLESS CORMORANT NANNOPTERUM HARRISI

A small population of Flightless Cormorants was followed from 1970 to 1975 inclusive. The birds were extremely sedentary, most never moving more than 2 km from where hatched. Many birds bred several times within a year, almost always with different mates. After successful breeding the mean interval to the next attempt among females was significantly shorter than among males, probably because the male continued to attend the juvenile for longer than did the female. There was an annual peak of nesting in April to November, when sea temperatures were lowest; some nesting occurred in other months but these nests were less successful. About 73% of juveniles survived at least three months after going to sea. Adult females had a significantly higher rate of annual survival (91%) than did males (82%). The mean annual survival of both sexes combined over a 13 year period was 87%. The mean age of first breeding was about 30 months for both males and females. In 1972 breeding success (0·14 young fledged per pair) was much lower than in other years (0·60 young per pair), a lower proportion of juveniles survived, no birds bred for the first time and probably many fewer pairs nested. Adult survival was not affected. This reduced breeding output was associated with an influx of anomalously warm sea water to the area (El Niño). The availability of food is probably both the ultimate and the proximate factor controlling the timing of breeding.     

NOTES ON THE PEARL-BREASTED SWALLOW HIRUNDO DIMIDIATA IN THE SOUTH-WESTERN CAPE

Earlé R. A. &; Herholdt, J. J. 1988. Breeding and moult of the Anteating Chat Myrmecocichla formicivora. Ostrich 59: 155–161.

The general breeding biology and moult of the Anteating Chat Myrmecocichla formicivora was studied in open grassveld over a two-year period. During the winter (July), groups were significantly smaller than during summer (December) (1,81 ± 0,50 versus 2,85 ± 1,35 birds per group). There was a large turnover of individuals in the study area but the total population stayed the same. The breeding season in the study area lasted from September to February but analysis of nest record cards from a larger area gave a breeding season of August-April. Two types of nests were used: 90,6% were burrows in sand banks or other excavations, but 9,4%were in the mud pellet nests of Greater Striped Swallows Hirundo cucullata (n = 53). Consecutive breeding attempts were never made in the same burrow. Clutches consisted of three, four or five eggs ([Xbar] = 3,73 ± 0,67). Incubation lasted 14–14,5-15 days. The nestling period lasted 15–18 days. Fledgling/egg breeding success was 41,8% with 48,2% of all eggs not reaching the hatching stage. Juveniles showed an unequal sex ratio of 0,57 ♂ ♂: 1,0 ♀ ♀ but adults had a nearly equal ratio (0,9 ♂ ♂: 1,0 ♀ ♀). There was a significant positive correlation between the primary moult score and the week of the seven months in which moult was recorded. Juveniles underwent a complete body moult and partial primary moult 3–4 months after fledging.     

A 13-YEAR POPULATION STUDY OF THE BLACK EAGLES IN THEMATOPOS,RHODESIA, 1964–1976

Gargett, V. 1977. A 13-year population study of the Black Eagles in the Matopos, Rhodesia, 1964–1976. Ostrich 48:17-27.

The resident black Eagle Aquila verreauxi population in approximately 620 km² of the Matopos, Rhodesia, underwent changes from 1971 and appeared less stable than in the first five years. Six new territories were established in the National Park; two territories in Tribal Trust Land were abandoned; one territory in the National Park vacant for five years and one in Tribal Land vacant for at least 11 years were reoccupied. breeding data covering 13 years confirm the five-year findings. In 652 pair-years 442 breeding attempts were made with 339 young eagles f edging: a reproductive success rate of 0,52 young per pair per year. On average 68 % of the population bred every year, each pair attempted breeding in two years out of three, and one attempt in four was unsuccessful. Annual and individual variations in breeding performance were considerable, from 46% to 89% of the population breeding, and from two successes in six attempts for one pair to 12 successes in 12 attempts for two pairs. Over 13 years the percentage of the population breeding annually followed the form of a sine curve with a ten year period.

Fourteen factors that might affect annual and/or individual performance are considered. Below average rainfall years were followed by above average breeding; and generally fewer clutches were laid early after heavy rainfall in the three months preceding laying. Clutches laid late were less successful than those laid early. Breeding was affected by the proximity and intervisibility of nests, the previous year's performance and intraspecific disturbance. Appropriation of nests by other species prevented breeding and no new pair bred while establishing or re-establishing its territory. Building a new nest was followed by laying in the same season only if the nest was completed by mid-May, the peak laying period, building or partly building two nests in one season did not prevent breeding in the following year. At least 76% of clutches were c/2. The causes of two eaglets' deaths were ascertained and the remains of two adults were found. Pairs with territories in Tribal Trust Land had a significantly lower breeding performance than pairs in the protected National Park. Only traces of pesticide residues were found in four eggs. Observers' visits did not affect reproductive success.     

THE BREEDING BIOLOGY OF AN URBAN POPULATION OF ROCK PIGEONS COLUMBA GUINEA

Elliott, C. C. H. & Cooper, J. 1980. The breeding biology of an urban population of Rock Pigeons Columba guinea. Ostrich 51:198-203.

The breeding biology of the Rock Pigeon Columba guinea was studied for three seasons from 1972 to 1975 at the University of Cape Town, southwestern Cape, South Africa. Nests were visited at approximately weekly intervals. The breeding season (September to February) coincided with the end of the winter rainy season and the presence of cereal crops. Clutch size was two eggs in 99% of cases. Mean incubation period was 14,8 days. Incubation was shared as two continuous shifts per day. Growth rate was similar to that in other studies. The mean nestling period was 23,6 days. Second broods after the successful departure of chicks were frequent, the interval between nest departure and re-laying being as little as five days. Hatching success was 66%, chick rearing success 83% and overall breeding success 49%, similar to other Columba pigeons. It is suggested that the production of pigeon's milk is the limiting factor controlling the invariable clutch size.     

THE SOCIABLE WEAVER,PART 3: BREEDING BIOLOGY AND MOULT

Maclean, G. L. 1973. The Sociable Weaver, Part 3: Breeding biology and moult. Ostrich 44: 219–240.

Rain or some associated phenomenon is the principal Zeitgeber releasing breeding in the Sociable Weaver. The species does not breed in the absence of rain. The same nest chambers are used for breeding as are used for roosting throughout the year. The Sociable Weaver is monogamous. The clutch size varies from two to six eggs, larger clutches being more common after good rains than in relatively poorer breeding periods. Food supply may therefore be the proximate factor regulating clutch size. Replacement clutches are not necessarily smaller than first clutches. The mean clutch size within a breeding period decreases with an apparent decrease in food supply. The parents share parental duties about equally. Up to four successive broods may be raised in a single breeding period; a breeding period may last up to nine months and may occur at any time of the year according to the somewhat erratic rainfall which averages about 226 mm per year in the study area.

First broods help their parents to feed later broods; fourth brood chicks may therefore be fed by as many as 11 birds (nine young and two parents). This has survival value especially toward the end of a breeding period when food is scarce. Of similar value is the habit of starting incubation with the first or second egg of the clutch; in a relatively poor season older chicks will survive while younger ones will starve, thereby effectively and quickly reducing brood size. Young birds moult into adult plumage at four months, but do not normally leave the home colony. The sexes are indistinguishable at all ages, but there is an approximate ratio of eight males to five females in the study area.

Wing moult is slow: each remex takes about a month for replacement. Body moult occurs within the space of a month, usually after rain while the birds are breeding. Primary remiges are moulted proximo-distally from 1 to 9; secondaries are moulted disto-proximally from 1 to 6. Body moult is antero-posterior with the dorsal surface slightly in advance of the ventral surface.     

Breeding performance of the red-throated diver Gavia stellata in Shetland

Breeding red-throated divers Gavia stellata were studied in Shetland during 1981-1983. The overall probabilities of nest success were 0.35 in 1981 and 0.25 in 1982, as calculated by the Mayfield method. Productivity was shown to be at least 0.51 chicks fledged per breeding pair in 1981 (n = 100) and 0.36 in 1982 (n = 91), and a review of all field studies for Shetland gave a mean value of 0.45 per year (n = 1104) with no detectable trends in productivity since 1918; this was considered probably sufficient to maintain a stable population. Nests at lochs smaller than one hectare experienced the greatest hatching success. The majority of known breeding lochs wore used in three consecutive years, with a significantly greater re-use of lochs which had previously supported successful pairs. Breeding success declined with season in 1981 and 1982 largely due to reduced hatching success of late nesters, and a slight seasonal decline in egg volume was found in 1983.     

Nest location, clutch size and nest success in the Scarlet Ibis Eudocimus ruber

Breeding success and nest-site characteristics were studied during the 1996–1997 breeding season in a colony of Scarlet Ibises Eudocimus ruber in south-eastern Brazil to test the hypothesis that nest-site characteristics and clutch size affect nest success. Two nesting pulses produced young, the earlier being more successful. Predation accounted for most failures during the first pulse, wind destruction during the second. A third pulse with few nests produced no young. Adult Ibises abandoned nests when they lost sight of other incubating birds. Logistic regression analysis indicated that nest success during the first pulse was positively related to clutch size, number of nests in the nest tree and in the nearest tree, and negatively to the distance to the nearest neighbour. During the second pulse there were significant negative associations between success, nest height and distance to the fourth nearest nest, and a positive association between success and nest cover. The results agree with the 'selfish herd' hypothesis, indicating that nest aggregation may increase breeding success, but the nest-site characteristics affecting success can differ over the course of one breeding season.