BREEDING BIOLOGY OF THE BEARDED VULTURE IN SOUTHERN AFRICA,PART II: THE NESTLING PERIOD

Brown, C. J. 1990. Breeding biology of the Bearded Vulture in southern Africa, Part I: The nestling period. Ostrich 61: 24–32.

The nestling period of the Bearded Vulture Gypaetus barbatus in southern Africa was 124–128 days. The hatching interval between the normal two-egg. clutch was usually 3–6 days (range 2–9 days Only one nestling per clutch survived to the third day. Tittle sibling aggression and no infanticide took place, but the older nestling dominated the younger which obtained no food. For the first 40 days the nestling was closely brooded. The nest duties were evenly shared by both parents, but females brooded at night. Food was brought to the nest usually once or twice per day by both parents, and was stored behind the nest. During days 41–90 parental attendance steadily decreased. Dunng this stage the female spent more time in the nesting area (57%) and on the nest (91%) than the male. Towards the end of this stage the nestlin started to feed itself but preferred to be fed by a parent. From da 91 to first flight the nestling was left unattended and was visited by its parents only to provide food, which it fed from itself. All pars monitored (40 pair-years) attempted to breed every year. The breeding success (n = 18 pair-years) was 0,89 young fledged per pair per year.     

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.     

NESTING OF THE PURPLE-THROATED CARIB HUMMINGBIRD

We present data on certain parts of the nesting biology of the Purple-throated Carib Humming- bird Eulampis jugularis on the island of Dominica, British West Indies. We watched two nests with eggs and young and a single nest under construction. Incubation was in short periods averaging about six minutes. Females at both nests with eggs continued adding material to the nest until the end of incubation. We suggest that this common practice among hummingbirds may insure that a limited amount of energy at the time of initial nest-building and egg-production is optimally apportioned between the two activities. Brooding ceased in one nest when the young were about 13 days old. Feeding rates stayed relatively constant at one to two per hour throughout the nearly complete nestling period in one nest. Average time per feeding declined, apparently as the female-young interaction became more efficient with maturation of the young. Nesting females foraged on both insects and nectar. We could not be sure what they were feeding the young. Defence of the nest varied with the position of the female and the type of intruder. The aggressive behaviour associated with defence varied according to the size and type of intruder. We concluded that for the one nest of Eulampis for which we had the most complete data, had there been three young, the female would have been unable to provide sufficient food to nourish them. However, the universal clutch size of two and nearly universal promiscuity in humming- birds is strong evidence that factors other than the ability of adults to feed more than two young are important in determining clutch size.     

6. GENERAL NOTES

Stutterheim, C. J. 1982. Breeding biology of the Redbilled Oxpecker in the Kruger National Park. Ostrich 53:99-90.

The nest of the Redbilled Oxpecker Buphagus erythrorhynchus in the Kruger National Park is a natural hole in a tree where no excavation is required. No evidence of a territorial system WBS observed and only the nesting tree is defended. Mammal hair, dung, grass and rootlets are used for nesting material. The average clutch size was 2.8 eggs with a mean incubation period of 12,6 days. The average nestling period was 30 days. The Redbilled Oxpecker can raise three broods in a season of 176 days such as in the 1973/74 breeding season. The activity area of one breeding group was 7,0 km². The breeding unit consists of two to five birds with helpers of both sexes. All the birds in a group help to select a nest site, build the nest and feed the young. Only one male and one female participate in incubation. Post-hatching development was studied in 13 chicks.     

人工巢箱条件下白眉姬鹟的繁殖参数

2005～2006年,在吉林省左家自然保护区的次生林中,对人工巢箱条件下白眉姬鹟(Ficedulazanthopygia)的繁殖参数开展了初步研究.结果表明,人工巢箱中自眉姬鹟的窝卵数为5～7枚,平均6.0枚;卵重平均为1.6 g.卵大小平均为17.0 mm×13.1 mm.孵化期平均为13.1 d,每巢平均出雏5.4只,育雏期平均为12.8 d,每巢平均出飞雏鸟5.3只.白眉姬鹟的营巢成功率为70.0%,繁殖成功率为81.3%.     

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.     

BREEDING BEHAVIOUR OF OSPREYS PANDION HALIAETUS IN SCOTLAND

Ospreys Pandion haliaetus nested at a site near Loch Garten, Inverness-shire continuously from 1959 to 1973. Each year the Royal Society for the Protection of Birds has organized a continuous watch on the eyrie in the breeding season. The detailed records kept of the activities of Ospreys at the nest by those participating in the watch were analysed and the results presented here. Ospreys are migratory and arrived in the breeding area in early April. Nesting material was usually added to an existing eyrie platform. The male collected more material than the female. The female lined the nest cup. The extent of nest building activity and the frequencies of mating and other activities prior to laying varied markedly from year to year. These differences may have been related to changes in the identity of the nesting female, but the birds were not individually marked. Both sexes incubated but the female took the greater share and normally incubated at night. When the young hatched they were brooded by the female. The female stayed in the vicinity of the nest for most of the time until the young fledged at about 53 days old. The male Osprey caught almost all the fish eaten by his mate and young during the breeding season. The number of fish caught per day increased markedly after the young hatched. Pike Esox lucius and Trout Salmo trutta were the main species taken, and some Rainbow Trout Salmo gairdnerii were identified. There were seasonal and diurnal changes in the size and the species composition of the catch. The effects of weather conditions on hunting are examined. The occurrence of Ospreys other than the resident birds at the nest site is described. The behaviour of another pair of Ospreys which repeatedly failed to hatch eggs is described. There was an instance of egg eating in this pair, and some differences in behaviour were found between these birds and those at Loch Garten whose breeding success was good. The breeding biology of Ospreys is compared with that of other British diurnal birds of prey. In other species the female leaves the young unguarded at some stage in the nestling period and hunts food for them, whereas female Ospreys do not usually hunt in the nesting period.     

Breeding biology of the White-rumped Swallow Tachycineta leucorrhoa in Buenos Aires Province, Argentina

We conducted a study of the breeding biology of the White-rumped Swallow Tachycineta leucorrhoa nesting in nestboxes in a flat, farming landscape in Buenos Aires Province, Argentina. White-rumped Swallow nesting attempts were detected from the end of September to mid December, with most clutches laid during October. Birds laid clutches of 4–6 eggs with a mode of five eggs; most broods hatched synchronously (58%), but hatching spread could last up to 4 days. Nestling growth curves adjust well to logistic functions, and at day 15 nestlings attain the asymptotic weight of 21.6 g. Clutch size in White-rumped Swallows declined significantly as the season progressed. In addition, late-season eggs were smaller and late-season nestlings had a shorter nestling period and lower weight at day 15, probably leaving the nest lighter than early-season nestlings. These data suggest that the Swallows would benefit greatly from laying early in the season, which would provide nestlings with better survival prospects. However, both major sources of nest mortality, interspecific competition for nest-sites and nestling mortality during bad weather, decreased through the season. White-rumped Swallows follow the pattern found for other southern species, as it has smaller clutch size, lower growth rate and remains longer at the nest than its Northern Hemisphere congener the Tree Swallow Tachycineta bicolor .     

Reproductive biology of the endangered Ouvea Parakeet Eunymphicus cornutus uvaeensis

The reproductive biology of the endangered Ouvea Parakeet Eunymphicus cornutus uvaeensis , an endemic subspecies of Ouvea island (Territory of New Caledonia, Southwest Pacific) was studied from June 1994 to February 1996. Breeding was recorded from early August until late January. All nests were sited in cavities of native forest trees, 90% of them in Syzygium sp. and Mimusops sp. Mean clutch size was 2.9 eggs (range 2–3), and double clutches were recorded. Incubation lasted 21 days and the nestling period averaging 43 days. An average of 1.65 chicks fledged per nest but only 0.75 per breeding pair were still alive 30 days after fledging. The main causes of chick loss were starvation of the third sibling during the first week due to hatching asynchrony, raptor (presumably Brown Goshawk) predation of fledglings and human harvest for the pet trade. Growth curves and multiple regressions of weight, culmen-width and -length, tarsus- and wing-length, showed that wing-length was a good predictor of age, and that there were significant differences between the sexes for weight and culmen-width. The pattern of the breeding season, brood reduction, nest-site characteristics and presumed size of breeding territories suggest that both food and availability of suitable nest-sites may be factors limiting breeding productivity. Proposals for conservation of this endangered bird are presented.     

Annual and seasonal reproductive trends in the Lesser Spotted Woodpecker Dendrocopos minor

Annual and seasonal variation in reproductive timing and performance were studied in a population of the Lesser Spotted Woodpecker Dendrocopos minor over 10 years in southern Sweden. The median laying date of the first egg varied by up to 17 days between years, being generally larger than the variation of laying dates within years. Neither clutch size, brood size in successful nests, fledging success in successful nests nor mean nestling weight differed significantly between years. There was no trend for mean clutch size to vary between early and late years. In spite of a more than threefold variation in population size, no reproductive variable demonstrated an apparent density-dependence. Within the season, clutch size declined steeply with increasing clutch initiation date, whereas fledging success and nesting success did not, leading to a trend in brood size almost identical to the trend in clutch size. The survival prospects of fledged young declined with increasing clutch initiation date, and it is argued that the clutch size laid is a strategic adjustment to laying date. Out of 124 breeding attempts, 34% did not produce fledged young. In 9% of the breeding attempts, pairs laid no eggs. At least 20% of the breeding attempts failed after egg-laying. The most common cause of breeding failure was loss of the breeding partner followed by nest abandonment (40% of the failures). Only 16–28% of the failures were due to predation on the nest. Most complete failures, and also partial losses from nests, occurred at the early breeding stages. It is argued that the early nestling phase may be a critical stage, which the woodpeckers adjust to coincide with the seasonal food peak, explaining the strikingly late breeding season compared with other non-migrant species.     

Breeding biology of rooks (Corvus frugilegus L.) in Hawke's Bay,New Zealand

Abstract

Three rookeries in Hawke's Bay were studied during 1966–68. First or replacement clutches were started between 26 August and 23 October. First clutches averaged 4.3 eggs and replacements 3.7 eggs. The mean size of first clutches varied between years from 4.1 to 4.6 eggs. Incubation took 17–18 days. Most losses occurred around hatching, when about 40% of the eggs or young were lost. Incubated eggs and small nestlings incurred losses of 20% and 10% respectively, and all nestlings older than 10 days survived to at least 20 days. On average, 1.4 young were reared per nest in which eggs were laid; successful nests averaged 2.2 young. First clutches averaged 1.3 young (2.4 per successful first clutch). During the season, mean clutch size declined from 4.2 to 3.5, the mean number of young hatched declined from 2.0 to 0.6 per clutch, and the mean number of young fledged from all clutches declined from 1.3 to 0.4 per clutch. Mean nestling weight increased with age from 14 g on the first day after hatching to 360 g on the 19th day. The causes of egg and nestling mortality and the adaptiveness of clutch size are discussed.     

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.     

OBSERVATIONS ON THE BEHAVIOUR OF BIRDS IN SOUTHERN RHODESIA

Maclean, G. L. 1974. The breeding biology of the Rufouseared Warbler and its bearing on the genus Prinia. Ostrich 45: 9–14.

The Rufouseared Warbler Prinia pectoralis, a common species of the Kalahari scrub, nests after rain at any time of the year. Nest construction and nest sites are described. The clutch is normally three or four eggs. Incubation takes 12 to 13 days and the nestling period is 11 to 13 days. Data suggest that the Rufouseared Warbler is not a member of the genus Priniu, the generic position it currently occupies.     

1. ADDITIONAL NOTES ON THE BIRDS OF BLOEMHOF DISTRICT

Olver, M.D. 1984. Breeding biology of the Reed Cormorant. Ostrich 55:133-140.

The breeding biology of the Reed Cormorant Phalacrocorax africanus was studied at Cedara Dam, Natal, South Africa, from 1973 to 1975. Breeding occurred from November to February and was preceded by a period of courtship. Mean clutch size was 3,6 eggs and mean egg measurements were 44,2 x 29,5 mm. The average incubation period was 23,3 days. Young leave the nest at 28 days when alarmed but cannot fly until 35 days old. Hatching success was 84,1%, and fledging success 60,6%.     

Breeding biology of Orange‐breasted (Harpactes oreskios) and Red‐headed (H. erythrocephalus) trogons in Khao Yai National Park,Thailand

ABSTRACT As tropical habitats continue to be cleared or degraded, obtaining basic information about the ecology of birds in intact habitats is essential for understanding their life histories. We studied the breeding biology of Orange‐breasted Trogons (Harpactes oreskios) and Red‐headed Trogons (H. erythrocephalus) in Khao Yai National Park in Thailand from 2003 to 2009. Nests were in excavated cavities in well‐rotted stumps or other tree parts. Mean cavity heights were 2.1 m (N= 19) for Orange‐breasted Trogons and 2.0 m (N= 49) for Red‐headed Trogons. Eggs were laid every other day. For Orange‐breasted Trogons, the mean clutch size was 2.4 ± 0.1 (SE) eggs (N= 17); incubation periods for two nests were 17 and 18 d, respectively, and the nestling period ranged from 12 to at least 14 d (N= 4). For Red‐headed Trogons, the mean clutch size was 2.6 ± 0.1 eggs (N= 48), the mean incubation period was 18 d (N= 9), and the mean nestling period was 13.4 d (N= 5). In both species, both males and females excavated nest sites, incubated eggs, and brooded and provisioned nestlings. Only females incubated and brooded at night, and males provisioned nestlings more than females. Breeding seasons lasted from January to March for Orange‐breasted Trogons, and from late February to July for Red‐headed Trogons. Mayfield estimates of nest success were 8% and 9% for Orange‐breasted and Red‐headed trogons, respectively. Unusual for cavity nesters, nest failure due to predation was high and nestling periods short. The low nesting success is typical of many other tropical species, but considerably lower than reported for some Neotropical trogons, possibly due to the unenclosed structure of the nests of these Asian trogons.     

BREEDING OF SACRED IBIS THRESKIORNIS AETHIOPICA AT LAKE SHALA, ETHIOPIA

Data are based on more than 200 h of observation at Ethiopia's Lake Shala from 1966 to 1972. Except for differences in size of bill, there are no useful field characters separating male and female Sacred Ibis. The breeding plumage is described; vivid blood-red colour underneath the wings and the ornamental plumes are especially obvious when nesting commences. Physical and biological features of Lake Shala, Ethiopia, and its nesting islands are described; the species of birds nesting on the Shala islands are given. Ibises nest at Shah from March to August; no nesting has been recorded from September to February during the last months of the ‘big’ rains through the main dry season. Nesting normally begins in the ‘small’ rains (between 14 March-24 April), although instances were recorded as early as 1 March and as late as 20 August. The ibises normally nest once per year, although it is possible that occasionally a second nesting may occur after an unsuccessful first attempt. The ibises at Shala nest in discrete groups; several nesting groups may form on any or all of the islands; the number of groups attempting to nest varied from year to year. Nesting activity begins when males arrive and establish pairing territories, usually in a small tree but sometimes on the ground. When females and other males arrive at the pairing territories, pair formation ensues. At this time males perform forward threat, modified forward threat, pursuit flight, supplanting attack and modified snap displays, while both sexes perform stretch and bow displays. Once established, the pair abandons the pairing territory and moves to the nesting area, usually near but always distinct from the pairing territory, and establishes a nest-site territory. Most members of the nesting group move to the nesting area on the same day. Copulation then takes place, and is followed by collection of nest material, usually by the male. Nests are built close together. The average area of 10 nests measured was 0.09 m². Nests are usually less than 20 cm thick and are made of many small branches and sticks. The average clutch in 34 nests was 2.24 eggs; the average size of 34 eggs was 63.4×43.5 mm. Incubation probably begins when the clutch is complete. Both sexes incubate, and the incubation period probably lasts 28–29 days. The development of the young is described. The young leave the nest-site territory when 14–21 days old. Although they are capable of some flight when 35–40 days old, the young do not leave the colony until they are 44–48 days old. In the colony, both parents care for the young. Usually only one parent at a time is with the young. The parents recognize their own young and are usually recognized by them. The behavioural interactions between young and parents are described. Fledging success in 1968 was 1.06 young per pair. The number of pairs successfully rearing young varied annually from none to 81%, on average over six years (1966–70, 1972) 35%. Predation at the breeding colonies is minimal. The food of one one-month old chick consisted of beetle larvae, lepidopteran larvae and beetles. Feeding areas, although undetermined, must be widespread. Inter-specific competition between Sacred Ibis and other nesting birds at Shala is discussed. Among possible factors stimulating nesting at Shala one, fairly heavy rainfall, seems to be especially important. It is also suggested that especially heavy rain-storms cause ibises to abandon the colonies, and result in poor breeding success.     

ASPECTS OF THE BREEDING BIOLOGY OF THE FIERYNECKED NIGHTJAR

Jackson H. D. 1985. Aspects of the breeding biology of the Fierynecked Nightjar. Ostrich 56: 263–276.

A marked population of nightjars in Zimbabwe was studied intensively for four breeding seasons. This paper covers certain aspects of the breeding biology of the Fierynecked Nightjar Caprimulgus pectoralis. The male shows strong site fidelity during the breeding season (September to December), singing, feeding and breeding within an area of about 5,8 ha. There is some evidence of site defence by the male. The female shows strong mate fidelity, resulting in a pair bond for life. Egg laying starts with full moon in September and is further stimulated by the next two full moon periods. The eggs are laid directly on dense leaf litter at a site overhung by foliage. The normal clutch is two eggs (12S % are one egg) laid on successive days during the afternoon. Incubation starts with the first egg and is by the male at night and the female by day. The incubation period is 18 days. The birds respond to undue disturbance by deserting the eggs and laying a replacement clutch. The chicks usually hatch on successive afternoons; they are mobile on the first day and will move to a parent if called. Both parents feed and brood the young during twilight and moonlight; the male broods them on dark nights and the female does so by day. The species is double-brooded when time permits, the female laying again once the first brood has reached independence; she may even lay a third clutch if the second one comes to grief. There is no evidence of adults transporting eggs or young.     

BREEDING BIOLOGY AND BEHAVIOUR OF THE QUAIL FINCH ORTYGOSPIZA ATRICOLUS

Summary

Nuttall, R.J. 1992. Breeding biology and behaviour of the Quail Finch Ortygospiza atricollis. Ostrich 63:110-117.

During a study of the breeding biology of the Quail Finch Ortygospiza atricollis, observations of nest-building, egg-laying, incubation and nestling periods, and nestling development in a grassland near Pietermaritzburg, South Africa were supplemented with observations of breeding behaviour in captivity. Mean clutch size was 4,5 and eggs were laid at intervals of approximately one day. Incubation began after the third or fourth egg was laid. An incubation period of 15–16 days and an estimated nestling period of 18–19 days was recorded. Incubation and brooding are shared by both sexes. Breeding success was low (26,7% ?28,6%), with most losses resulting from predation during either the egg-laying or incubation stages.     

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.     

Nesting ecology of a naturalized population of Mallards Anas platyrhynchos in New Zealand

Investigating the reproductive ecology of naturalized species provides insights into the role of the source population's characteristics vs. post‐release adaptation that influence the success of introduction programmes. Introduced and naturalized Mallards Anas platyrhynchos are widely established in New Zealand (NZ), but little is known regarding their reproductive ecology. We evaluated the nesting ecology of female Mallards at two study sites in NZ (Southland and Waikato) in 2014–15. We radiotagged 241 pre‐breeding females with abdominal‐implant transmitters and measured breeding incidence, nesting chronology and re‐nesting propensity. We monitored 271 nests to evaluate nest survival, clutch and egg size, egg hatchability and partial clutch depredation. Breeding incidence averaged (mean ± se) 0.91 ± 0.03, clutch size averaged 9.9 ± 0.1 eggs, 94 ± 2% of eggs hatched in successful nests, partial depredation affected 6 ± 1% of eggs in clutches that were not fully destroyed by predators, and re‐nesting propensity following failure of nests or broods was 0.50 ± 0.003. Nesting season (first nest initiated to last nest hatched) lasted 4.5 months and mean initiation date of first detected nest attempts was 28 August ± 3.3 days. Smaller females were less likely to nest, but older, larger or better condition females nested earlier, re‐nested more often and laid larger clutches than did younger, smaller or poorer condition females. Younger females in Southland had higher nest survival; cumulative nest survival ranged from 0.25 ± 0.007 for adult females in Waikato to 0.50 ± 0.007 for yearling females in Southland. Compared with Mallards in their native range, the nesting season in NZ was longer, clutches and eggs were larger, and nest survival was generally greater. Different predators and climate, introgression with native heterospecifics and/or the sedentary nature of Mallards in NZ may have contributed to these differences.