The breeding biology of the white-chinned petrel Procellaria aequinoctialis at South Georgia

Aspects of the breeding biology of the whitc-chinned petrel Procellaria aequinoctialis were studied at South Georgia. Laying, hatching and fledging dates, together with egg and adult measurements, rate of weight loss of eggs and incubating adults and data on the duration of incubation shifts were recorded. Chick growth in weight, tarsus length, culmen length and wing length from hatching to fledging was followed in detail and breeding success and causes of mortality documented. Comparisons are made with other populations of the species, other members of the genus Procellaria and other Procellariiformes. Despite being the largest burrow-nesting petrel in the world, P. aequinoctialis conforms well to the overall relationships between body weight and breeding parameters for Procellariiformes in general.     

Influence of adult breeding experience on growth and provisioning of Wandering Albatross Diomedea exulans chicks at South Georgia

For most seabirds, reproductive performance improves with age; in albatrosses this is thought not to be so (experience being acquired before starting breeding) but only one study (of chick growth in a single season at one site) has specifically addressed this. We compared the provisioning performance and growth rates of chicks of Wandering Albatrosses Diomedea exulans breeding for the first (IN), second and third (LE) and fourth or more times (EE) on Bird Island, South Georgia in the austral winters of 1996 and 1997. Eggs from EE adults were significantly heavier than the other two categories and these chicks had a greater mass and longer wings up to 160 days of age and longer culmen and tarsus up to 115 days old. However chicks from all categories fledged at the same average mass, size and age. No significant differences between categories in feeding frequency or meal size were detected but experienced adults made shorter long foraging trips and spent more time at the nest than less experienced birds. Adults that remained at the nest gave chicks smaller meals than those that left immediately after feeding the chick. Although provision of smaller but more frequent meals by experienced adults promotes more rapid chick growth, the resulting differences do not persist into the late chick-rearing period. Our results were very similar to those from Iles Crozet in the Indian Ocean, supporting the hypothesis that when Wandering Albatrosses start to breed they are fully competent foragers but that it takes a while, during early chick-rearing, for birds breeding for the first time to adapt to the additional demands of provisioning a chick.     

Interannual variation in the breeding biology of the Antarctic prion Pachyptila desolata at Bird Island, South Georgia

Interannual variation in aspects of the breeding biology of Antarctic prions was studied for three summers (1989–1992) at Bird island, South Georgia. Egg size, mass and incubation period remained constant. Laying, hatching and fledging were significantly delayed and less synchronous in 1991/92 (range of laying dates 51 days compared to 10–15 days in the two other seasons). This was due to an unusually cold and protracted winter, with ice blocking burrows into the spring, restricting availability of nest sites. Brooding lasted longer in 1991/92 but the overall fledging period was unchanged. Skeletal growth rates did not vary amongst years; growth in mass was slower in 1989/90 but fledging mass was similar in all three years. In 1989/90 and 1991/ 92 later hatched chicks grew (in mass) faster. The survival of chicks from hatching to fledging did not vary amongst years or with hatching date. Feeding frequency was similar between years, once allowance had been made for starlit nights. Thus late and asynchronous breeding in 1991/92 did not result in reduced breeding success either through predation or starvation.
Crustaceans formed 98–99% of the mass of the identifiable portion of regurgitated food samples. Significant annual variation was found within these crustaceans with the presence of krill (least in 1990/91) being inversely related to that of amphipods and copepods. There was no relationship between diet composition and chick growth or survival. Other seabird species, lacking the morphological specialization for feeding on copepods and amphipods, had very low breeding success in 1990/91, when krill was scarce.     

Provisioning and growth in chicks of Wilson's storm-petrels (Oceanites oceanicus) on King George Island, South Shetland Islands

We present data on chick growth and chick feeding in Wilson's storm-petrel (Oceanites oceanicus) in a colony on King George Island, South Shetland Islands. Chicks were repeatedly weighed and the weight differences over 24 h were corrected for metabolic loss in order to obtain an estimation of meal sizes. Chicks were fed on 93% of the nights (n=688 nights). The average meal size for a single feeding was 8.5 g. Chicks received on average 1.2 feedings per night. These results are compared with data for this species from other locations. There was a trend for increased meal sizes from northern to southern populations, parallel to an increase in the adult mass, indicating that Wilson's storm-petrels carry optimal meal sizes according to their body size and may take advantage of increased food abundance by increasing feeding frequencies. We describe chick growth and discuss the influence of egg size, hatching date and feeding frequency on chick growth. The egg size had a positive influence on tarsus growth and body mass of chicks. Later-hatched chicks started wing growth and finished mass growth at a younger age and reached lower peak masses, indicating that late chicks may adapt to the restricted breeding season in their Antarctic breeding grounds by a more rapid development, but will fledge with a lower degree of development and less resources. Accepted: 22 May 2000     

Factors affecting chick growth in the South Polar Skua (Catharacta maccormicki): food supply, weather and hatching date

This study investigated chick growth in a pelagic Antarctic seabird, the South Polar Skua (Catharacta maccormicki). The factors food supply, weather and hatching date were analysed in a population of 54 breeding pairs at King George Island/South Shetland Islands. Food supply was manipulated by offering fish corresponding to 20% of daily energy demand of chicks to half of the breeding pairs every second day. Growth of mass, head, wing and tarsus was followed and related to the treatment, weather conditions, hatching date and interactive effects. Food supply did not limit chick growth in the studied season. Parents seemed to try to feed their chicks at a maximum rate and succeeded in the studied season because the general food supply was very good. Low temperatures and strong winds depressed chick growth. A growth advantage of food-supplemented chicks could be observed when the natural conditions for chick growth were sub-optimal. Chick growth rate was strongly negatively associated with hatching date and worsening weather during the reproductive season could be excluded as explanatory variable for this finding.     

Foraging location and range of White-chinned Petrels Procellaria aequinoctialis breeding in the South Atlantic

The foraging range and principal feeding areas of White‐chinned Petrels breeding at South Georgia were determined using satellite telemetry. Foraging trips during incubation lasted 12–15 days and covered 3000–8000 km and 2–11 days and 1100–5900 km during chick‐rearing. Adults covered less distance per day during chick‐rearing (71 km) than during incubation (91 km) but the proportion covered at night (47%) was the same. Mean (31–34 km/h) and maximum (80 km/h) flight velocities were similar during both periods of the breeding season and during day and night. Between incubation shifts, White‐chinned Petrels travelled to the Patagonian shelf; during chick‐rearing they foraged more extensively. Most locations were between 30° to 55°W and 52° to 60°W around South Georgia/Shag Rocks and south to the South Orkney Islands. Diet samples from known foraging locations suggested birds fed mainly on krill and squid. They caught the squid Brachioteuthis? picta and Galiteuthis glacialis around Shag Rocks/South Georgia and also at sites close to the South Orkney Islands; Illex argentinus on the Patagonian shelf. Dispersal of adults after breeding failure was south to the South Orkney Islands then west to the Falkland Islands. This study confirms that breeding White‐chinned Petrels are amongst the widest‐ranging of seabirds; they may minimise competition with other Procellariiformes in the South Atlantic by their more extensive foraging range. The nature and extent of their range also brings substantial risk of high mortality rate in South Atlantic long‐line fisheries.     

Aspects of the biology of Antarctomysis maxima (Crustacea: Mysidacea)

Summary Population structure and aspects of the reproductive biology of Antarctomysis maxima from South Georgia and the South Orkney Islands were examined. Size frequency analysis indicated that the generation time is two years at South Georgia, but may approach four years at the South Orkneys. Egg production is greater for a given size of female at South Georgia but by virtue of a larger egg, brood production in terms of ash-free dry weight is slightly greater at the South Orkneys. Young are brooded over winter at both sites and are released in spring. Females are clearly capable of breeding twice at South Georgia and it is suggested that this is also the case at the South Orkneys. These results are discussed in relation to other studies on cold water mysids and to environmental adaptations exhibited by other Antarctic marine invertebrates.     

The food and feeding ecology of Blue petrel (Halobaena caerulea) and Dove prion (Pachyptila desolata)

The diet of two small burrow dwelling petrels, Dove prion, Pachyptila desolata and Blue petrel Halobaena caerulea , was studied at the subantarctic island of South Georgia by quantitative analysis of 246 food samples regurgitated by adults about to feed chicks. Crustaceans, and particularly krill Euphausia superba , predominate in both species' diet but fish is considerably more important to the Blue petrel. Other dietary differences between the species chiefly involve the relative proportions of krill, copepods (nearly exclusive to Dove prion) and seven amphipod species taken.
There is no overlap in the species' chick feeding periods but food differences are likely to reflect prey selection rather than resource availability; differences in prey size are ascribed to use of different feeding techniques particularly relating to bill structure and function. Data on frequency of chick feeding, proportion of oil and presence of pumice in food samples are used to indicate that the Blue petrel feeds further away from the breeding colony than the Dove prion. The significance of the various adaptive differences is discussed.     

Egg formation and the pre-laying period of Black-browed and Grey-headed Albatrosses Diomedea melanophris and D. chrysostoma at Bird Island, South Georgia

Egg composition and factors influencing egg formation were studied in Black-browed and Grey-headed Albatrosses Diomedea melanophris and D. chrysostoma at Bird Island, South Georgia. At nests where eggs were laid, females arrived 6–7 days after males, stayed one day during which 96% of observed copulations occurred, then departed to sea for c. 16 days in D. chrysostoma, c. 10 days in D. melanophris , returning c. two days before laying. Yolk deposition, however, lasted 21 and 20 days, and started 32 and 29 days before laying, in D. chrysostoma and D. melanophris respectively. Therefore, it is probably initiated by environmental factors not by copulation. Egg, albumen and yolk mass are significantly greater in D. chrysostoma but the proportionate composition of the species' eggs is nearly identical. Reduced differences in chick mass at hatching may reflect the longer incubation period in D. chrysostoma or relate to subsequent differences in chick growth rate.     

Breeding biology of the thin-billed prion<Emphasis Type="Italic"> Pachyptila belcheri</Emphasis> at New Island,Falkland Islands: egg desertion,breeding success and chick provisioning in the poor season 2002/2003

We present data on breeding success, chick growth and chick feeding in thin-billed prions, Pachyptila belcheri, at New Island, Falkland Islands, in the breeding season 2002/2003. As in many populations of seabirds in the region, the overall breeding success was very low. This was mainly caused by low rate of observed burrow occupancy (60%) and hatching (57%) of thin-billed prions, while chick survival was closer to normal. Sixty-eight percent of the chicks survived to fledging. In total, a chick was successfully reared in 23% of the nests or from 38% of recorded eggs. The failed eggs were found to be incubated for 30 days, on average. The time of egg desertion coincided with the time of desertion of other seabirds at New Island, with a period of high sea-surface temperatures and low catch rates by the commercial fisheries. We describe chick growth and use repeated weighings, corrected for metabolic loss, to estimate meal sizes. Chicks were fed a mean 39.2 g in 77% of the nights. We discuss possible reasons for the observed extremely low hatching success, and compare with the breeding success of other seabirds at the Falkland Islands.     

Variations in growth of Cape petrel Daption capense chicks

This study reports on the growth of Cape petrel chicks at Nelson Island, South Shetland Islands, Antarctica, during the breeding seasons 1990/91 and 1991/92. Parameters of logistic growth model fitted to mass, wing, culmen and tarsus measurements were compared between available composite data sets. Differential growth rate of morphometric characters and their proportional development at hatching and fledging conform to the pattern observed in other fulmarine petrels, overall growth rate being among the fastest found in Procellariiformes. Composite growth curves varied significantly between populations, but few annual, seasonal, and intercolony differences were found within the Nelson Island population. As the differences between chicks from equally disturbed colonies were less marked than in comparison with the control colony, regular handling most probably reduced the growth in this study. Larger eggs produced heavier rather than structurally larger hatchlings, which attained higher peak and fledging mass and size. Strength of the relationship between egg-size and chick measurements initially declined with chick age but, in contrast with results of earlier studies, increased again after around the middle of the chick-rearing period. This suggests that pre-hatching maternal factors probably influenced initial and fledging (peak) size and mass of chicks via egg-size, while intermediate stages of growth were less affected. A difference in mass between chicks from small and large eggs was maintained until fledging and increased gradually until peak mass was reached.     

Reproductive measures and chick provisioning of Cory's Shearwater Calonectris diomedea borealis in the Azores

Capsule Timing of breeding influenced wing-length at fledging, and egg size may be an indicator of fledging weight and the amount of food received by chicks.

Aims To investigate chick growth, temporal patterns of chick food provisioning and the importance of indices of parental condition or quality, egg size and hatching date, to predict nestling body mass and wing-length at fledging, and compare breeding and chick feeding characteristics between colonies in the northeast Atlantic.

Methods A survey of Cory's Shearwater nests was carried out at Vila islet. A sample of 52 chicks, ringed and weighed at hatching, was selected to study chick growth and food provisioning.

Results Hatching success (51%) was much lower than fledging success (87%). Both hatching date and egg size contributed to explain wing-length at fledging, but hatching date, which was negatively correlated with wing-length at fledging, had the most important contribution (22%). There was some indication that egg size may explain variation in fledging weight and the amount of food received by chicks. Food delivery and feeding frequency of chicks varied throughout the chick development stage and three phases were distinguished: (1) 0–29 days, the highest feeding frequency values and a linear increase in food delivery; (2) 30–69 days, an oscillation in food delivery and medium feeding frequencies; (3) 70–90+ days, a sharp decrease in both food delivery and feeding frequency.

Conclusion Variation in food availability did not seem sufficient to override the overall importance of indices of parental quality in determining reproductive measures and chick provisioning. Breeding and feeding characteristics were similar between colonies in the northeast Atlantic, with variability in chick provisioning higher further south.     

Subcolony variation in phenology and breeding parameters in little auk Alle alle

In seabirds, variation in breeding phenology and success is often induced by macro- and mesoscale fluctuations in oceanographic conditions, which is recordable at the regional or colony scale. Variation in breeding parameters may also exist at the microscale—among discrete breeding aggregations and subcolonies. The aim of this study was to compare breeding phenology and parameters (hatching success, chick survival, chick body mass indices) among little auks (Alle alle) nesting in three subcolonies differing in their microtopographic and microclimatic features, situated in Magdalenefjorden (north-western Spitsbergen). The hatching phenology varied significantly among the subcolonies. This was probably due to the different duration of snow persistence in spring, as nests are occupied as soon as the snow cover melts sufficiently to allow access to them. The earliest hatching was recorded in the subcolony located on steep slopes at low altitude in the vicinity of the fjord, which favours early ice and snow melting in spring. Hatching success differed significantly among subcolonies, which could also have been due to the microclimatic features of the subcolonies. Hatching success was the lowest in the subcolony where birds started to breed while patchy snow was still persisting. Water from the melting snow could have flooded some of the nests. Alternatively, the low hatchability could have been caused by a higher frequency of less experienced breeders (e.g., first-time breeders) among the individuals nesting in this subcolony. Other breeding parameters (chick survival and growth) were generally similar in all the subcolonies.     

Use of cloacal sexing techniques in mark-recapture estimates of breeding population size in Wilson's stormpetrel Oceanites oceanicus at South Georgia

Summary Many stormpetrel species breed in habitats where their populations cannot be estimated by direct counts of burrows or birds; mark-recapture experiments have been confounded by the presence of many wandering non-breeders. With a population of Wilson's Stormpetrel Oceanites oceanicus at Bird Island, South Georgia, we tried to estimate the proportion of breeding females in samples obtained during a mark-recapture experiment. These were identified by measurements of the cloaca, which greatly enlarges at egg-laying. A concurrent experiment with individually marked birds determined that breeding females could be discriminated from males and non-breeders for c 30 days after laying. The technique is probably applicable to other petrels, though it will work best with those that lay most synchronously. The overall population estimate was 4841–5515 birds (SE 856–1417); estimates of breeding females gave a population of 2300 paris early in the incubation period and 1400 pairs near hatching.     

VARIATION IN THE CAPPED WHEATEAR

Williams, A. J. 1980. Aspects of the breeding biology of the Subantarctic Skua at Marion Island. Ostrich 51:160-167.

The breeding biology of the Subantarctic Skua Catharacta antarctica lonnbergi was studied in two austral summers at Marion Island. Eggs were laid between 23 October and 19 December. The clutch size was one (6%) or two (94%) eggs. The laying interval was two (20%) or three (80%) days and the incubation period was 29 days. Chicks could fly at 50–65 days after hatching. Chicks from first and second hatched eggs in the same brood had similar growth rates. Chicks in one- and two-chick broods had similar growth rates until 50 days after hatching when chicks reared singly were heavier. Egg mortality was 15,8%, chick mortality was 34,8% and the overall breeding success was 50,9%. The results are discussed in comparison with previous studies of Subantarctic and South Polar C. maccormicki Skuas.     

Comparative ecology of the six albatross species breeding on the Crozet Islands

Six species of albatrosses breed sympatrically at the Crozet Islands. The population size, masses and measurements of adults, nesting habitats and coloniality, laying, hatching and fledging dates, duration of incubation and brooding shifts are compared. The growth of chicks, diets and feeding methods of the six species are reviewed. Their distribution in the south Indian Ocean is described in relation to the feeding frequency of chicks. Various aspects of ecological isolation among the species are analysed. Overlaps exist in the timing of breeding in the small albatrosses and to a lesser extent in their diet. Differences in the foraging zones at sea appear to be the most important factor in reducing interspecific competition. It is shown that the effective division of resources results from a relative scarcity of resources around the Crozet Islands. Finally the close interrelationship between foraging strategy, breeding biology, diet, chick growth and breeding frequency in the small albatrosses is demonstrated.     

Moult of the giant petrels Macronectes halli and M. giganteus at South Georgia

Moult scores were collected from colour-ringed individuals of known reproductive status of the two species of giant petrel, Macronectes halli and M. giganteus , at Bird Island, South Georgia between 1978–81.
Both species showed a substantial overlap between breeding and wing-moult, unlike most other Southern Ocean seabirds. Males started moult before females and both sexes of M. giganteus moulted at an earlier stage of the breeding cycle than M. halli , which breeds six weeks earlier than its congener.
Changes in moult rate during the breeding season are documented for both species, with Id. halli showing a rapid increase as the chick nears fledging. Male M. giganteus show a notably different pattern to the other three species-sex groups, starting moult much earlier (at egg-laying), with greater individual synchrony and usually suspending primary moult throughout the main chick growth period, whereas only two male M. halli and no females of either species suspended moult. Differences in pattern, timing and rate of moult are interpreted in terms of availability of food resources and the competing energy demands of other activities, especially chick-rearing.
Completion of primary moult could not be observed in the field but was estimated using data frcsm non-breeding birds and failed breeders; the latter started a rapid moult almost immediately they failed. In both sexes of both species moult is probably concluded at least by early winter.
The general pattern of moult in giant petrels at Bird Island is contrasted with that of other populations and species of Southern Ocean seabirds. It is suggested that the unusually extensive overlap between breeding and moult in giant petrels is a consequence of the very abundant and easily available summer food supplies (especially carrion) and the much diminished winter resources, favouring a completion of moult by the beginning of the winter.     

Chick‐provisioning behaviour of two shearwaters breeding in south‐eastern Australia

The chick‐provisioning behaviour of the short‐tailed shearwater Puffinus tenuirostris and the wedge‐tailed shearwater Puffinus pacificus was investigated in a mixed colony on Montague Island, New South Wales, Australia, over two breeding seasons. This colony is located at opposite edges of the breeding distribution of the two species. Frequent weighing techniques were used to determine chick feeding frequency, feed timing, meal size, chick weight loss and indices of food conversion efficiency of the chicks. Short‐tailed shearwater parents fed their chicks larger more infrequent meals than wedge‐tailed shearwater parents. Short‐tailed shearwater chicks demonstrated higher food conversion efficiencies and lower weight loss than wedge‐tailed shearwater chicks, indicating either differences in diet or metabolic rates. The feeding frequency in wedge‐tailed shearwaters also fluctuated more widely than for short‐tailed shearwaters over the two breeding seasons. Despite the fact that the timing of the breeding cycle on Montague Island is almost identical for the two species, these differences in chick provisioning are probably a result of differences in prey type and location, so they may help explain variations in annual breeding success and limits to the distribution of the two species.     

THE BREEDING BIOLOGY OF THE BLACK-BELLIED STORM-PETREL FREGETTA TROPICA

The breeding cycie and habits of the Black-bellied Storm-petrel are described from observations made over three seasons at Signy Island, South Orkney Islands. The species is strictly nocturnal on land and nests in stable scree slopes. With an estimated population of 100–200 pairs, Fregetta tropica is the rarest petrel breeding on the island. In general, the breeding cycle of F. tropica resembles that of Oceanites oceanicus. Birds usually arrive from mid-November onward and return to the same nest and mate in successive seasons. The female is absent from the nest for a week or more before the egg is laid, during which time the male continues to visit the site. From ten laying dates, egg laying appears normally to begin during the last week in December, but evidence is given that, in 1966-67, laying was delayed by heavy winter snow build-up coupled with a late melt. The egg comprises 26 % of the body weight of the female. Incubation is by both sexes in alternate spells of three days, the whole period lasting 38–44 days. The chick is left alone in the nest by the parents almost immediately after hatching. Chick growth is described briefly and the effects of drift snow on development are discussed. The fledging periods of two chicks were 65 and 71 days, departure from the nest taking place in mid-April. Measurements of 36 Signy Island birds show considerable variability but are similar to those from other breeding localities.     

Individual quality and reproductive performance in the Grey-headed Albatross Diomedea chrysostoma

The reproductive performances of Grey-headed Albatrosses Diomedea chrysostoma with a previous record (≤5 years) of consistent success (≤70% chicks fledged from eggs laid—"top" birds) or failure (≤ 70% of attempts failed—"bottom" birds) were compared during 1993 -1995. In 1995, top birds arrived back at the colony significantly earlier, had significantly shorter first and second incubation shifts and hatched larger chicks which grew significantly faster than bottom birds. In 1994, top birds also had larger hatchlings with higher rates of growth than bottom birds. In 1994, top birds had significantly higher hatching, fledging and therefore overall breeding success than bottom birds; very similar trends were evident in 1993 and 1995. Chick-rearing success and all indices of chick growth suggested that food availability was high in 1995 (and 1993) and low in 1994. Therefore the superior performance of top birds was maintained in years of very different conditions, with the chick-rearing period particularly critical. A simple model (using published demographic parameters for Grey-headed Albatrosses on South Georgia) suggests that top birds would produce 2.5 more chicks over their lifetime than bottom birds. With the currently declining population numbers, the relative contribution of top birds to the next generation may be even greater than this.