Incubation and brooding performance of the Antarctic Petrel Thalassoica antarctica at Svarthamaren, Dronning Maud Land

Antarctic Petrel Thalassoica antarctica incubation and brooding effort was studied at Svarthamaren, Dronning Maud Land, during the austral summer of 1991–1992. The females probably left the nest site shortly after egg laying. The duration of incubation and brooding shifts as well as the daily weight loss (absolute and proportionate) were comparable with those of other similar-sized procellariform species. Males spent more time incubating and brooding than did females, suggesting higher female energy stress due to egg laying. Incubating birds which were below average weight were likely to desert the nests before their mates returned from feeding trips. Both males and females lost approximately one-fifth of their body-weight during their first incubation shifts. Nevertheless, they increased their initial weights from egg laying to hatching and had their highest initial weights when they returned to start the shift during which the egg hatched. No factors related to adult body-weight explained the duration of the incubation shifts. Both males and females gained weight at a higher rate when at sea than they lost it during incubation, and it is suggested that factors unrelated to food availability or individual feeding skills may be important in regulating the duration of the incubation shifts and the stay at sea.     

Breeding ecology of the Fulmar Fulmarus glacialis and the Kittiwake Rissa tridactyla in high-arctic northeastern Greenland, 1993

The breeding ecology of the Fulmar Fulmarus glacialis and the Kittiwake Rissa tridactyla in the high Arctic was studied in relation to the occurrence of the northeast water polynya in northeasternmost Greenland (80̀N). Mean laying dates were 31 May in the Fulmar and 18 June in the Kittiwake; the total nesting season for the Fulmar just matched the time window of the polynya opening period. Fulmar colony attendance fluctuated within a period of 11.6 days because of variation in nonbreeding prospectors but showed no clear diurnal variation. Fulmar incubation shifts, on average, lasted 6.1 days (range 1–13 days), which is significantly longer than elsewhere, and the average chick-guard period of 10.9 days (range 1–17 days) was significantly shorter than in other studies. Egg neglect occurred in 18% of Fulmar nests or 0.7% of nests per day. Overall breeding success (chicks fledged per egg laid) was 0.56 in the Fulmar and 0.67 in the Kittiwake; the latter produced 1.4 young per active nest or 1.2 per completed nest. Mean Kittiwake clutch size was 2.03; larger clutches were laid early. Nest site characteristics (presumably reflecting nest predation risk) and breeding behaviour affected breeding success. in the Fulmar, hatching success was negatively correlated with laying date and the proportion of egg neglect, while overall breeding success was correlated negatively with distance to nearest neighbouring site and positively with the length of the chick-guard period. Kittiwake breeding success was negatively correlated with laying date. Using seabirds as indicators of marine food supply, breeding success in both species suggested moderate to good food supply in the northeast water polynya in 1993, although at least in the Fulmar the high reproductive output appeared partly maintained by behavioural buffering; long incubation shifts, egg neglect and short chick-guard periods were symptoms of foraging constraints.     

FULMAR DISTRIBUTION: A CANADIAN PERSPECTIVE

The pelagic distribution of the Fulmar Fulmarus glacialis off eastern Canada has been used to test Fisher's (1952, 1966) hypothesis that Fulmar numbers are controlled by the availability of offal from the fishing industry. Fulmars are abundant on the fishing Banks off Newfoundland but not on those off Nova Scotia; by contrast, they are fairly common in the unfished waters south of Greenland. The Newfoundland and Greenland waters are colder than those off Nova Scotia, and it seems likely that temperature and other oceanographic factors, not fish offal, control Fulmar distribution in the western Atlantic. Since the ringing returns show that many of these Canadian birds are from British colonies, it is possible that fish offal may not be the key factor in the eastern Atlantic either.
Since there are no reliable quantitative data on the Fulmar's diet, it is difficult to suggest a specific alternative. However, the Fulmar is, over much of its range, a cold-water species; it may eventually be possible to interpret Fulmar distribution in oceanographic terms, the key factor being its macroplanktonic food. However, the Fulmar population in the warmer waters of the eastern Atlantic remains an anomaly; it is not yet possible to explain the differences in ecology between the eastern and western Atlantic birds, either in oceanographic terms, or by the availability of fish offal.     

Incubation rhythm in the Fulmar Fulmarus glacialis: annual variation and sex roles

I monitored the incubation schedules of Fulmars Fulmarus glacialis in an Alaskan colony by observing nests where the male and female were of different colour phases. Complete shifts of up to 16 days were recorded; the average shift in mid-incubation was 4–6 days. Mean shift length was inversely correlated with hatching success in 5 years, suggesting that Fulmars adjusted their foraging patterns to annual differences in food availability. Males assumed the larger share (55%) of incubation on average, and a larger share in years with lower hatching success. Serial correlation in the length of incubation shifts had two components—the influence of prior shift lengths on time spent foraging and individual variation. Failure of the male to relieve the female soon after laying resulted in a few breeding failures and egg losses were associated with exceptionally long shifts throughout incubation.     

Endocrine correlates of parental care in an Antarctic winter breeding seabird, the emperor penguin, Aptenodytes forsteri

Plasma levels of luteinizing hormone (LH) and prolactin associated with parental behavior were measured in the Antarctic winter breeding emperor penguin, Aptenodytes forsteri. Males exclusively incubate the egg while females exclusively brood the nonhomeothermic young; both sexes alternate in rearing the homeothermic young. Birds were sampled on arrival from the sea through egg laying, incubation, and brooding. All parent birds lost their chicks at the end of the brooding period due to harsh weather but sampling continued. In females, LH titers dropped after egg laying but levels were restored when the birds returned from the sea to brood the chicks and were not depressed by high prolactin levels. Plasma prolactin remained low in males captured on arrival and kept until the free-living males finished incubation. In breeders, prolactin secretion increased during the prelaying period when day length decreased. Prolactin levels stayed elevated in males during incubation and in brooding females returning after a 2-month absence at sea. Prolactin values were higher in brooding females than in males ending incubation or returning in late brooding. These levels did not drop after chick loss, and the sexual difference in prolactin values was maintained after breeding failure. In emperor penguins, increased prolactin secretion appears to be triggered around the time of egg laying and continues, driven by an endogenous mechanism, through incubation and brooding until rearing is completed. Prolactin secretion independent of external stimuli may have evolved in pelagic seabirds to maintain parental care despite long absences at sea from the breeding colony.     

Parental behaviour of Spanish Imperial Eagles Aquila adalberti: sexual differences in a moderately dimorphic raptor

Capsule The sexes make significantly different contributions in the tasks of nest-building, incubation and food provisioning to chicks.

Aims To determine the division of parental activities during breeding (nest-building, incubation, brooding, food provisioning and feeding).

Methods Between 1991 and 1998 focal observations were made at nests using 20–60× telescopes. During the incubation period, 11 pairs were studied involving a total of 2812 observation hours over 269 days. During the chick-rearing period, seven pairs were studied involving a total of 5499 observation hours spread over 503 days. The birds were sexed and identified individually on the basis of size, position during copulation, vocalization and plumage differences.

Results Significant differences were found between the sexes in parental behaviour. Males scarcely participated in incubation and contributed significantly more than the females only in food provisioning, both during incubation (food transfers to feed the female) and during chick-rearing (to feed the chicks). Females were responsible for most of the incubation, nest-building (during incubation and chick-rearing), brooding, shading and feeding of chicks. Nest attendance by females decreased over time. In both sexes, food provisioning increased with brood size.

Conclusion Intersexual differences are discussed in the context of the reversed sexual size dimorphism and parental investment strategies. We suggest that in Spanish Imperial Eagles reversed sexual size dimorphism is best explained by the prey capture difficulty hypothesis, than by parental role division during reproduction.     

Hypothalamic monoamine turnover in ring doves (streptopelia risoria), courting,incubating and brooding young

1. The turnovers of hypothalamic 5-hydroxytryptamine (5HT), dopamine (DA) and noradrenaline (NE) were measured in male and female ring doves (Streptopelia risoria) at three stages of the breeding cycle: courtship, 3 days after pairing; early incubation, 1–2 days after egg laying; and brooding, 1–3 days after the squabs had hatched.2. In both sexes plasma LH decreased progressively from courtship through incubation to brooding young. Crop sacs were fully developed in doves brooding young but not at other stages of the reproductive cycle, indicating increased concentrations of plasma prolactin.3. The turnovers of 5HT and DA in both sexes were significantly higher (P<0.001) in doves brooding young than in birds incubating eggs or nest building. The turnover of DA was higher in females than in males at the onset of incubation. The turnover of NE was lower (P > 0.01) in females at the onset of incubation than during courtship or brooding.4. Increased turnover of hypothalamic DA may be more closely related to brooding behaviour than to changes in prolactin or LH secretion.5. Increased hypothalamic 5HT turnover in brooding doves appears to be more directly related to crop sac development, and by inference increased prolactin secretion, than to depressed plasma LH concentrations.     

THE ANNUAL RE-OCCUPATION OF BREEDING SITES BY THE FULMAR

The Fulmar has a long period at the breeding colony prior to egg-laying. The pattern of annual occupation and build-up in numbers has been examined in detail at Marsden, Co. Durham, at a colony in which over 100 eggs are laid annually (Order 3 of Fisher's classification). The re-occupation of the cliff starts in early November with an occasional visit by one or two birds. The main period of activity at the cliff is during the morning and, as the numbers build up, the diurnal period of occupation increases. By mid-December the first birds to arrive in the colony do so before dawn and the last to leave remain well after dark until near midnight. Almost throughout the pre-egg stage, the colony is deserted each night and re-occupied the next day and birds only stay regularly overnight just before egg-laying. A similar pattern of occupation occurs after breeding but in the reverse order. The numbers of birds at the colony in January and February exceed the breeding population and include many non-breeders. The non-breeders progressively decline in numbers until May when only the breeding birds remain with a few non-breeding birds. The daily variation in the numbers of birds at the cliff is influenced by the wind speed. In general, the birds leave the colony under freshening conditions and the number present at the colony can be interpreted in terms of the wind conditions over the last three days. It is suggested that the synchronised departures are primarily feeding trips, the birds using the strong winds to reach feeding areas, except that the departure just before egg-laying is linked to egg development and synchronised laying in the colony. Competition between Fulmars and Kittiwakes for nesting sites usually results in the Kittiwakes gaining the site. This is achieved by the Kittiwakes taking over the Fulmar sites during one of the latter's departures.     

A comparison of Antarctic petrel (Thalassoica antarctica) diets with net samples of Antarctic krill (Euphausia superba) taken from the Prydz Bay region

Samples of the stomach contents of Antarctic petrels (Thalassoica antarctica) were obtained on board ship in the Prydz Bay region of Antarctica from birds which had spontaneously regurgitated. The weight of food and the species composition of the stomach contents were measured. Antarctic krill,Euphausia superba, the sole prey item taken, were compared to krill obtained by nets in the same region as part of a large-scale krill survey. Krill from petrel stomach samples were larger in mean size than those sampled by nets. This may be attributed to selection of the larger sized krill by the petrels, it may be caused by the nets sampling different populations of krill or it may be due to net avoidance by the larger krill.     

Flight speeds of two seabirds: a test of Norberg's hypothesis

Norberg suggested that birds should increase their flight speed when rearing chicks in order to maximize chick energy intake by reducing commuting time. We measured the incubation and chick-rearing flight speeds of a medium-range (Brünnich's Guillemot Uria lomvia ) and long-range (Northern Fulmar Fulmarus glacialis ) forager near the Prince Leopold Island colony, Nunavut, Canada. The mean flight speed for the long-range forager was significantly higher during chick-rearing than during incubation. The medium-range forager showed no difference in mean flight speed during the two periods. We suggest that because petrels fly close to their minimum power velocity and have a low wing-loading, whereas alcids fly close to their maximum range velocity and have a high wing-loading, petrels have a greater ability than alcids to alter their flight speed according to changes in the demands of different breeding stages. Consequently, whereas Northern Fulmars adapt to the additional cost of chick-rearing partially by altering flight speed, Brünnich's Guillemots can only do so by reducing mass.     

Breeding strategies of Antarctic Petrels Thalassoica antarctica and Southern Fulmars Fulmarus glacialoides in the high Antarctic and implications for reproductive success

Breeding strategies of two closely related fulmarine petrels were studied on Ardery Island, on the continental coast of East Antarctica, where short summers are expected to narrow the time-window for reproduction. Both species had a similar breeding period (97 days from laying to fledging) but Antarctic Petrels Thalassoica antarctica bred up to 16 days earlier than Southern Fulmars. During the pre-laying exodus, all Antarctic Petrels deserted the colony, whereas some Southern Fulmars Fulmarus glacialoides remained. Antarctic Petrels exhibited stronger synchronization in breeding, made longer foraging trips and spent less time guarding their chicks than Southern Fulmars. Overall breeding success of both species was similar but failures of Antarctic Petrels were concentrated in the early egg-phase and after hatching, when parents ceased guarding. Southern Fulmars lost eggs and chicks later in the breeding cycle and so wasted more parental investment in failed breeding attempts. Different breeding strategies may be imposed by flight characteristics; Southern Fulmars are less capable of crossing large expanses of pack ice and need to delay breeding until the sea ice retreats and breaks up. However, due to the short summer they risk chick failure when weather conditions deteriorate late in the season.     

The breeding biology and population dynamics of King Penguins Aptenodytes patagonica on the Crozet Islands

Among King Penguins Aptenodytes patagonica at Possession Island, one of the Crozet Islands, the length of the moult period, pre-laying period, incubating and brooding shifts were highly variable according to the year and to the stage of the breeding season. The moulting period was shorter in late breeders than in early breeders. Only half of the birds which successfully reared a chick bred the following cycle, but late in the season. Almost all these late breeders were unsuccessful. The reasons for the high variability in the breeding pattern observed in this species between years, as well as between colonies and between individuals are discussed. Breeding success was on average 30.6% and survival during the first year at sea could reach 50%. The survival of adult birds has increased during the past 10 years from 90.7% to 95.2% per annum. Despite an almost biennial breeding frequency and a very high rate of chick loss during the winter fast, the King Penguin population of Possession Island has doubled between 1966 and 1985 due to a high survival rate of adult and immature birds. The increase during the last decade in adult survival and in adult and chick condition suggests that the population increase could be the result of an improvement in food availability.     

Effect of experimental conditions on the stomach evacuation of Coregonus lavaretus L.

The gastric evacuation of juveniles of Coregonus lavaretus L. fed on living Daphnia pulicaria was investigated. Three successive stages of stomach evacuation were observed when one meal per day was given: (i) a lag phase between the end of food intake and the beginning of stomach evacuation, (ii) a linear reduction of stomach content, (iii) a long residence time for food relics in the stomach. The initial stomach content and the stomach evacuation time are correlated positively. The stomach content increased during feeding when three meals day ⁻¹ were provided and it decreased when no food was available. During the course of an experiment the highest stomach content found increased with increasing daly ration. Excess feeding resulted in a low stomach content similar to that found with rations about 30–50% of the maximum daily food intake. Therefore the daily food intake cannot be determined by the single parameter of stomach content alone. Identical initial stomach contents showed significantly higher stomach evacuation rates under three meals day⁻¹ conditions than under one meal day⁻¹ conditions.     

Growth and provisioning strategies of Northern Fulmars Fulmarus glacialis

Growth and foraging strategies in procellariiforms show a great deal of variation, but the fulmarine petrels are notable in that chicks are fed frequently and develop unusually rapidly. This study examined age-related and daily variation in provisioning of the Northern Fulmar Fulmarus glacialis throughout the chick-rearing period at Fair Isle in 1997. In common with many other petrels, meal mass showed an initial rise with age, probably because of a gradual increase in chick gut capacity, but then levelled off. By comparison, feeding frequency showed little age-specific variation until chicks reached the oldest age-class, when the number of meals declined to less than a third of the previous level as chicks underwent mass recession prior to fledging. Compared with the limited day-to-day variation in mean provisioning rates for the whole sample, food delivery to particular chicks was much more variable, suggesting that differences in feeding rates were determined by stochastic factors influencing the feeding success of individual parents. The caloric density of feeds and their size in relation to adult mass were lower in Northern Fulmars than in most other Procellariiformes. This implies that adults are not heavily dependent on stomach oil formation to raise the energy content of the payload, but rely on a high feeding frequency to maintain adequate rates of energy transfer to chicks.     

Decrease in stomach contents in the Antarctic minke whale (Balaenoptera bonaerensis) in the Southern Ocean

The Antarctic minke whale (Balaenoptera bonaerensis) is one of the major krill predators in Antarctic waters. A reported decline in energy storage over almost two decades indicates that food availability for the whales may also have declined recently. To test this hypothesis, catch data from 20 survey years in the Japanese Whale Research Program in the Antarctic (JARPA) and its second phase (JARPA II) (1990/91–2009/10), which covered the longitudinal sector between 35°E and 145°W south of 58°S, were used to investigate whether there was any annual trend in the stomach contents weight of Antarctic minke whales. A linear mixed-effects analysis showed a 31 % (95 % CI 12.6–45.3 %) decrease in the weight of stomach contents over the 20 years since 1990/1991. A similar pattern of decrease was found in both males and females, except in the case of females sampled at higher latitude in the Ross Sea. These results suggest a decrease in the availability of krill for Antarctic minke whales in the lower latitudinal range of the research area. The results are consistent with the decline in energy storage reported previously. The decrease in krill availability could be due to environmental changes or to an increase in the abundance of other krill-feeding predators. The latter appears somewhat more likely, given the recent rapid recovery of humpback whale. Furthermore, humpback whales are not found in the Ross Sea, where both Antarctic krill and ice krill (Euphausia crystallorophias) are available, and where no change in prey availability for Antarctic minke whales is indicated.     

Incubation scheduling by Northern Fulmars ( Fulmarus glacialis ) in the Canadian High Arctic

Northern Fulmars (Fulmarus glacialis) are a ubiquitous seabird of the North Atlantic and North Pacific oceans that breed in colonies surrounded by markedly different marine environmental conditions. I have studied the incubation behavior of fulmars at a remote colony in the Canadian High Arctic, where the birds had to cross 200 km of sea-ice during the early incubation period to reach feeding areas. These fulmars completed incubation in fewer shifts and had a longer mean incubation shift duration (5.3 days) than their counterparts breeding in the Boreal oceanographic zone. In particular, the mean duration of the first incubation shift by males in successful pairs (10.3 days) was 2 days longer than that for males in unsuccessful pairs and was longer than that reported at any other colony. This exceptionally long shift by the male may be required at this site to give females enough time to recoup energetic reserves after egg-laying, at a time when marine productivity in the Arctic is still seasonably low.     

Species‐specific foraging strategies and segregation mechanisms of sympatric Antarctic fulmarine petrels throughout the annual cycle

Determining the year‐round distribution and behaviour of birds is necessary for a better understanding of their ecology and foraging strategies. Petrels form an important component of the high‐latitude seabird assemblages in terms of species and individuals. The distribution and foraging ecology of three sympatric fulmarine petrels (Southern Fulmar Fulmarus glacialoides, Cape Petrel Daption capense and Snow Petrel Pagodroma nivea) were studied at Adélie Land, East Antarctica, by combining information from miniaturized saltwater immersion geolocators and stable isotopes from feathers. During the breeding season at a large spatial scale (c. 200 km), the three species overlapped in their foraging areas located in the vicinity of the colonies but were segregated by their diet and trophic level, as indicated by the different chick δ¹⁵N values that increased in the order Cape Petrel < Southern Fulmar < Snow Petrel. During the non‐breeding season, the three fulmarines showed species‐specific migration strategies along a wide latitudinal gradient. Snow Petrels largely remained in ice‐associated Antarctic waters, Southern Fulmars targeted primarily the sub‐Antarctic zone and Cape Petrels migrated further north. Overall, birds spent less time in flight during the non‐breeding period than during the breeding season, with the highest percentage of time spent sitting on the water occurring during the breeding season and at the beginning of the non‐breeding period before migration. This activity pattern, together with the δ¹³C values of most feathers, strongly suggests that moult of the three fulmarine petrels occurred at that time in the very productive high Antarctic waters, where birds fed on a combination of crustaceans and fish. The study highlights different segregating mechanisms that allow the coexistence of closely related species, specifically, prey partitioning during the breeding season and spatial segregation at sea during the non‐breeding season.     

The effects of food abundance on breeding performance and adult time budgets of Guillemots Uria aalge

The breeding performance, food fed to chicks and adult time budgets of Guillemots Uria aalge were examined in a year of high and a year of low food availabiIity. There was no difference between the 2 years in reproductive success, although the rate of chick feeding, chick weight and fledging success were greater in the year of high food availability. On average, chick prey items were larger in the poor food year, but this was insufficient to compensate for the lower feeding frequency. Chick feeding frequency did not differ between days in the good year but did increase later in the season in the poor food year. Compared with the high food availability year, adult Guillemots in the year of low food availability spent much less time resting at the breeding colony. and their foraging trips were twice as long. Foraging birds tended to make several successive trips before resuming brooding duties from their mates when food supplies were good, but in the low food availability year single trips were the norm. These results demonstrate that predators experiencing reduced food supply may mitigate the effects on their reproductive output by shifting their time allocation such that more time is available for foraging.     

Behavioural time budget of breeding king penguins (Aptenodytes patagonica)

As do so many other seabirds, penguins fast when ashore for breeding. For penguins in dense colonies, territory defence seems to imply conflicting energetic requirements because of its assumed high energy cost, when the birds need to limit energy expenditure to cope with their fast. In this context, behavioural time budget over 24 h was investigated during breeding in the king penguin, Aptenodytes putugonicu , by using a remote-controlled videocamera. The comparison of day-night activity was performed in relation to breeding status (incubation vs. brooding) and duration of fasting (beginning vs. end of incubation shift). Five categories of behaviours were quantified: territoly defence, comfort, resting, sleeping and chick-feeding. Breeding king penguins remain active by day as well as by night. Between incubation and brooding we found a three-fold increase in the energy consuming temtory defence, together with a drastic decrease in that posture which corresponds to deep sleep, is. when most energy is saved. These increases in aggressiveness and vigilance may be related to protection of the newly hatched chick. Between the onset and the end of an incubation shift, the time spent in sleep increases three-fold, whereas territory defence remains unchanged. These data for penguins under natural conditions accord with previous studies on captive birds which have shown that an increasing proportion of sleep during the course of fasting may contribute to energy saving. On the other hand, both resting (which is the main component of penguins'time budget; about 65%) and comfort (about 16% of time) show no change either between incubation and brooding or during the course of fasting.     

Body mass changes in Brünnich's guillemots Uria lomvia with age and breeding stage

Body mass of Brünnich's guillemots Uria lomvia breeding at Coats Island, Canada, was measured during incubation and chick-rearing in 1988–2001. In most years, mass increased during incubation and fell after hatching, leveling off by the time chicks were 18 d old, close to the age at which chicks departed. Mass during incubation increased with age up to about 12 yr, but the mass of birds brooding chicks was not related to age. The trend towards increasing mass during incubation was mainly a consequence of mass increases of young breeders as older birds maintained a constant mass. The variation in adult mass with age during incubation seems likely to reflect age-related variation in foraging ability, but the loss of mass after hatching, being greater for older birds, appears best explained as a response to the demands of provisioning chicks, with older birds transferring their accumulated reserves to their chicks via higher provisioning rates.