Incubation routine, body mass regulation and egg neglect in the Blue Petrel Halobaena caerulea

The incubation routine and mass changes of male and female Blue Petrel Halobaena caerulea were studied at the Kerguelen Islands to investigate factors influencing the durations of incubation stints and foraging trips at sea and the factors determining nest desertion and return to the nest.
The body mass at the start of an incubation shift and also when the bird was relieved varied throughout the incubation period, whereas the mass when birds deserted the nest was stable. Birds deserted the nest when their mass decreased to threshold, independent of the duration of the fast. Temporary egg neglect was observed in successful as well as in unsuccessful breeding attempts, but it increased the risk of breeding failure. The net and daily massgained at sea during the second part of the incubation period were higher than during the first part, suggesting an increase in food availability. During the first part, the mass gained at sea and time spent foraging were inversely related to the mass of the bird before it left the burrow, whereas a similar relationship did not occur thereafter.
The results suggest the occurrence of a fixed mass threshold when birds decide to leave the nest if not relieved by their partner. The mass when a bird left its nest inffuenced the time spent foraging or mass gained when food was scarce. Although decision rules to leave the nest or return from the sea are related to body condition. the possibility of neglecting the eggs temporarily enables Blue Petrels to regulate the trade-off between risks of breeding failure and risks of an increase in adult mortality. A model for behavioural decision to stop incubating or stop feeding, based on a variable set point, is proposed.     

Energy expenditure, body-weight and foraging performance of Storm Petrels Hydrobates pelagicus breeding in artificial nesting chambers

Many avian species, such as Storm Petrels Hydrobates pelagicus, are intolerant of disturbance at the nest, which complicates the collection of data relating to metabolic rate and the use of body reserves during incubation. I describe the design of an artificial nest chamber, which is simple and inexpensive to construct and facilitates the collection of such data. Eighty-one nest chambers situated in a large colony of breeding Storm Petrels had high occupancy rates (29/81 in each of 2 years), and the breeding success of birds nesting in boxes was similar to that of pairs nesting in natural crevices. Direct measurement of carbon dioxide production using standard respirometry techniques and estimations of metabolic rate based on the rates of mass loss during incubation indicated close agreement between the two methods of estimating energy consumption. Assuming the metabolic requirements during incubation are furnished entirely from stomach oil, 76% of the daily mass lost represented stomach oil catabolism. The duration of incubation shifts was unrelated to the body mass, and presumably to body reserves, of Storm Petrels on arrival at the nest. Shifts were usually terminated by the return of the foraging partner. The body mass of birds returning from foraging was relatively constant and was unrelated to the amount of time spent foraging at sea, indicating that the decision rule to return from foraging was the acquisition of a threshold level of body mass (about 31 g). There was a negative relationship between the duration of foraging trips and the body mass of Storm Petrels at departure from the nest and a positive relationship between trip duration and the net mass gain at sea. The use of nestboxes based on the design described here would have a wide variety of applications in facilitating data collection for many cavity-or burrow-nesting species which are sensitive to disturbance.     

Regulation of foraging trips and costs of incubation shifts in the Antarctic petrel (Thalassoica antarctica)

In species where incubation is shared by both parents, the mate'sability to fast on the nest may constrain the time availablefor foraging. The decision to return to the nest should thereforebe a compromise between an animal's own foraging success andits mate's ability to fast on the nest. To examine how the bodyconditions of incubating Antarctic petrels, Thalassoica antarctica,influence both the length of foraging trips and incubation shifts,we experimentally handicapped females by increasing their flightcosts during a foraging trip by adding lead weights to theirlegs. Handicapped females spent more time at sea and had lowerbody conditions at arrival to the colony than controls, and,moreover, females in poor body condition at arrival to the colonyspent generally more time at sea than those with higher bodycondition. The prolonged time period spent at sea by handicappedfemales was associated with higher desertion rates than amongcontrols. The time the incubating mates fasted increased withtheir body condition at arrival to the colony, suggesting thata high body condition of the incubating bird may reduce theprobability of nest desertion. Accordingly, our results suggestthat the time spent foraging is adjusted to the body conditionsof both the foraging and incubating mate.     

Moulting fast and time constraint for reproduction in the king penguin

King penguins (Aptenodytes patagonicus) replace their complete plumage during a 3- to 4-week moulting fast on shore. After moulting, birds forage at sea for 2-3 weeks to store energy reserves for reproduction. Using an automatic identification and weighing system coupled with visual observations, we investigated the trade-off between the moulting fast and the following breeding attempt, in terms of body condition and in relation to time constraints, in free-living king penguins. King penguins reached their lowest body mass of the yearly cycle at the end of the moulting fast; this was lower than that at the end of the incubation fasts and not different from the body mass at egg desertion. Later in the season, the duration of the moulting fast became shorter and old feather loss occurred earlier after arrival ashore. Postmoulting foraging trips were shorter, but at the expense of body condition at the beginning of courtship. These results are discussed in relation to the synchronisation of the breeding cycle with food availability and mate choice.     

Sexual dimorphism and sexual segregation in foraging strategies of northern giant petrels, Macronectes halli, during incubation

Giant petrels ( Macronectes spp.) are the most sexually dimorphic of all seabirds. We used satellite-tracking and mass change during incubation to investigate the influence of sexual size dimorphism, in terms of the intersexual food competition hypothesis, on foraging and fasting strategies of northern giant petrels at South Georgia. Females foraged at sea whereas males foraged mainly on the South Georgia coast, scavenging on seal and penguin carcasses. Foraging effort (flight speed, distance covered, duration of foraging trips) was greater for females than for males. In contrast, foraging efficiency (proportionate daily mass gain while foraging) was significantly greater for males than for females. Females were significantly closer to the desertion mass threshold than males and could not compensate for the mass loss during the incubation fast while foraging, suggesting greater incubation costs for females than for males. Both sexes regulated the duration and food intake of foraging trips depending on the depletion of the body reserves. In males the total mass gain was best explained by mass at departure and body size. We suggest that sexual segregation of foraging strategies arose from size-related dominance at carcasses, promoting sexual size dimorphism. Our results indicate that sex-specific differences in fasting endurance, contest competition over food and flight metabolic rates are key elements in maintenance of sexual size dimorphism, segregating foraging strategies and presumably reducing competition between sexes.     

Foraging trip decisions by the streaked shearwater Calonectris leucomelas depend on both parental and chick state

Parents of albatross and shearwater species employ a dual foraging strategy, feeding their chicks quickly in repeated short trips and then restoring their own fuel reserves during longer trips. A decline in parental body condition is believed to trigger longer trips, but chick body condition and age may also play a role. To investigate these factors in the little-studied streaked shearwater Calonectris leucomelas, we monitored the nest attendance of 17 pairs on Mikura Island in 2005 using an automated identification system. We also monitored body mass changes and meal masses of 5 of the 17 pairs using an automated weighing system. Although the birds did not show a clear dual foraging pattern, trip duration varied widely from 1 to 15 days. On average, the birds fed chicks 67.6 g during nighttime meals at 2.74-day intervals. Since meal mass did not depend on trip duration, feeding efficiency (meal mass delivered per unit trip duration) decreased as trip duration increased. Parents accumulated more energy reserves when they took longer trips. Parents appeared likely to initiate longer trips when their body condition declined or chick body condition recovered.     

Corticosterone alone does not trigger a short term behavioural shift in incubating female common eiders Somateria mollissima, but does modify long term reproductive success

The trade-off between reproductive effort and adult survival in birds is modulated by several factors. Corticosterone and prolactin have additive effects on reproductive behaviour by stimulating foraging and parental behaviours, respectively. When incubation is associated with fasting, nest desertion is supposed to be activated by an unknown refeeding signal when body condition becomes critically deteriorated. The concomitant rise in corticosterone levels has been suggested to be the triggering factor. We tested the role of corticosterone on reproductive success by observing the effect of corticosterone implants on reproductive success and on plasma prolactin concentration in female common eiders Somateria mollissima . Implanted females showed a significant increase in corticosterone and a decrease in prolactin levels. Despite their enhanced daily body mass loss, females did not abandon incubation nor did they start to refeed in the four days following implantation. These data show that the experimentally induced rise in plasma corticosterone concentration alone does not trigger nest desertion. However, after 25 days of incubation, implanted females displayed a higher rate of egg loss, suggesting lower nest attentiveness towards the end of incubation. We suggest that the short-term effects of corticosterone may be dependent on the energy state of the bird. However, the late-induced change in reproductive success is indirectly linked to corticosterone, and we suggest that either a prolactin decrease, or a depletion in protein body reserves, may participate in the long-term adjustment of incubation behaviour in female eiders.     

Breeding limits foraging time: evidence of interrupted foraging response from body mass variation in a tropical environment

Birds should store body reserves if starvation risk is anticipated; this is known as an ‘interrupted foraging response’. If foraging remains unrestricted, however, body mass should remain low to limit the predation risk that gaining and carrying body reserves entails. In temperate environments mass gain in female birds during breeding is often attributed to egg formation and mass loss after incubation to flight adaptation or the effect of reproductive workload, rather than as a result of an adaptive interrupted foraging response to the limited foraging time or unpredictable foraging conditions that breeding demands. In tropical environments, foraging conditions vary more within the breeding season than in temperate environments, and so studies in tropical environments are more suited to decouple the potentially confounded effects of increase in body reserves versus egg formation on the body mass of breeding birds. In this study, we test whether breeding results in an interrupted foraging response in a tropical savannah system using body mass data collected over a 15‐year period from female common bulbuls Pycnonotus barbatus. This species breeds both in the wet and dry season, despite fewer resources being available in the dry season. Breeding stage predicted female body mass: body mass peaked abruptly during incubation, but was not closely associated with the egg‐laying stage, and declined during brood rearing. Breeding females were heavier in the dry season than in the wet season. In the dry season, heavier birds were more likely to incubate eggs or brood chicks. These observations suggest that increased body reserves are required to buffer the consequence of limited foraging time or impoverished foraging conditions, which may be most pronounced during incubation and in the dry season, respectively. Such mass increases are consistent with an interrupted foraging response, which may apply to temperate zone birds experiencing foraging restrictions during breeding.     

Orientation in the wandering albatross: interfering with magnetic perception does not affect orientation performance

After making foraging flights of several thousands of kilometers, wandering albatrosses (Diomedea exulans) are able to pinpoint a specific remote island where their nests are located. This impressive navigation ability is highly precise but its nature is mysterious. Here we examined whether albatrosses rely on the perception of the Earth's magnetic field to accomplish this task. We disturbed the perception of the magnetic field using mobile magnets glued to the head of nine albatrosses and compared their performances with those of 11 control birds. We then used satellite telemetry to monitor their behavior. We found that the ability of birds to home specific nest sites was unimpaired by this manipulation. In particular, experimental and control birds did not show significant differences with respect to either foraging trip duration, or length, or with respect to homing straightness index. Our data suggest that wandering albatrosses do not require magnetic cues to navigate back to their nesting birds.     

Incubation routines and foraging-trip regulation in the Grey-faced Petrel Pterodroma macroptera gouldi

In Grey-faced Petrels Pterodroma macroptera gouldi parental care during the 55-day incubation period is mainly achieved by three long shifts (two by the male) when one partner is ashore while the other forages at sea. This situation would seem to carry high risks of parental desertion and failure of the hatching chick to receive a meal before its yolk sac is exhausted. We examined incubation routines of 51 pairs of Grey-faced Petrels to investigate factors implicated in parental desertion and in the duration of the final foraging trip before hatching. The duration of the final long foraging trip (by the female) during incubation is not predicted by the time spent fasting on the nest but by the time elapsed since laying. Desertions accounted for 6.5% of egg losses. Eggs were deserted not after the delay of the foraging bird to return to the nest, but when the incubating bird departed early in the incubation spell. Desertions were not a response to critically depleted energy reserves.     

Reversed sexual size dimorphism and parental care in the Red-footed Booby Sula sula

The 'division-of-labour' hypothesis predicts that males and females perform different roles in parental care and that natural selection acts differently on each sex so as to produce different body size optima suited to their particular roles. Reversed sexual size dimorphism in avian species (females larger than males) may therefore be an adaptive consequence of different roles of males and females in parental care. We investigated patterns of nest attendance, brooding, foraging and provisioning rate in a tropical seabird, the Red-footed Booby Sula sula , a species showing a reversed sexual size dimorphism. During incubation, females attended the nest more often than males, and spent more time brooding the small chick than did males during daytime. Males and females did not differ in the average duration of their foraging trips. During incubation, there was a positive relationship between nest attendance and the duration of foraging trips in males, but not in females. During the small-chick stage, for the same time spent at the nest, males spent significantly more time than females at sea. On average, females fed the chick more often than did males. In males, there was a significant and positive relationship between the probability of feeding the chick and the duration of the foraging trip, whereas in females, this probability was much less dependent on the duration of the foraging trip. Overall, female Red-footed Boobies achieved slightly, but significantly, more parental commitment than did males. However, these sexual differences in parental participation were small, suggesting a minimal division of labour in the Red-footed Booby. Our results suggest that the division of labour hypothesis is unlikely to explain fully the adult size dimorphism in Red-footed Boobies.     

Evolution of passerine incubation behavior: influence of food, temperature, and nest predation

Abstract.— Incubation behavior is one component of reproductive effort and thus influences the evolution of life-history strategies. We examined the relative importance of body mass, frequency of mate feeding, food, nest predation, and ambient temperature to explain interspecific variation in incubation behavior (nest attentiveness, on- and off-bout durations, and nest trips per hour) using comparative analyses for North American passerines in which only females incubate. Body mass and frequency of mate feeding explained little variation in incubation behavior. We were also unable to detect any influence of food; diet and foraging strategy explained little interspecific variation in incubation behavior. However, the typical temperature encountered during reproduction explained significant variation in incubation behavior: Species breeding in colder environments take shorter bouts off the nest, which prevents eggs from cooling to temperatures below the physiological zero temperature. These species must compensate for shorter off-bouts by taking more of them (thus shorter on-bouts) to obtain needed energy for incubation. Nest predation also explains significant variation in incubation behavior among passerines: Species that endure high nest predation have evolved an incubation strategy (long on- and off-bouts) that minimizes activity that could attract predators. Nest substrate explained additional variation in incubation behavior (cavity-nesting birds have shorter on-bouts and make more frequent nest trips), presumably because nest predation and/or temperature varies among nest substrates. Thus, nest predation can influence reproductive effort in a way previously not demonstrated–by placing a constraint on parental activity at the nest. Incubating birds face an ecological cost associated with reproductive effort (predation of entire brood) that should be considered in future attempts to explain avian life-history evolution.     

Relationship between reversed sexual dimorphism,breeding investment and foraging ecology in a pelagic seabird,the masked booby

Reversed sexual dimorphism (RSD) may be related to different roles in breeding investment and/or foraging, but little information is available on foraging ecology. We studied the foraging behaviour and parental investment by male and female masked boobies, a species with RSD, by combining studies of foraging ecology using miniaturised activity and GPS data loggers of nest attendance, with an experimental study where flight costs were increased. Males attended the chick more often than females, but females provided more food to the chick than males. Males and females foraged during similar periods of the day, had similar prey types and sizes, diving depths, durations of foraging trips, foraging zones and ranges. Females spent a smaller proportion of the foraging trip sitting on the water and had higher diving rate than males, suggesting higher foraging effort by females. In females, trip duration correlated with mass at departure, suggesting a flexible investment through control by body mass. The experimental study showed that handicapped females and female partners of handicapped males lost mass compared to control birds, whereas there was no difference for males. These results indicate that the larger female is the main provisioner of the chick in the pair, and regulates breeding effort in relation to its own body mass, whereas males have a fixed investment. The different breeding investment between the sexes is associated with contrasting foraging strategies, but no clear niche differentiation was observed. The larger size of the females may be advantageous for provisioning the chick with large quantities of energy and for flexible breeding effort, while the smaller male invests in territory defence and nest guarding, a crucial task when breeding at high densities. In masked boobies, division of labour appears to be maximal during chick rearing—the most energy-demanding period—and may be related to evolution of RSD.     

Ultimate and proximate factors affecting the breeding performance of a marine top-predator

Variability in ecosystems affects the life history of organisms. In marine ecosystems where interannual variability is high, relationships between fluctuations in oceanographic parameters and top-predator breeding performance are increasingly documented but it is less clear why such relationships exist. In this study, we examined the connections between marine environment fluctuations and breeding performance of a long-lived top-predator, the black-browed albatross Diomedea melanophris at Kerguelen, through study of resource acquisition and allocation processes. Our results show that this population used the same foraging zones and spent similar time foraging year after year, but adult body condition varied between years. Foraging trips are regulated mainly by changes in body condition. During years of low resource availability, birds return to their nest with lower body condition and adults in low body condition were more frequent and therefore were more likely to stop breeding. Poor breeding success was related to the presence of colder waters in the foraging zones of breeding albatrosses as measured by the positive correlation between sea surface temperatures and breeding success measured over 18 years. Lower breeding success was mainly due to failure by inexperienced birds. The results of this study demonstrate how oceanographic conditions affect breeding performance through allocation processes. We compared these results to those at South Georgia where the breeding success is lower and more variable. This population relies mainly on krill, a resource that shows a very variable year-to-year availability compared to fish prey consumed by Kerguelen birds. This study shows that, in the same species, differences in resource variability and availability affect the demographic strategies probably through differences in allocation strategies.     

Luxury in freshwater and stress at sea? The foraging of the Common Tern Sterna hirundo

We compared the foraging strategies of Common Terns Sterna hirundo in freshwater (Lake Jeziorsko, Brzeg, Poland) and marine environments (Minsener Oldeoog, German Wadden Sea). Body mass changes, nest relief and duration and number of feeding trips per day were studied by automatically weighing the adults, using electronic balances under the nests. At the freshwater site, adults were lighter both before and after feeding and gained less mass during a trip. in the Wadden Sea, single feeding trips lasted longer than at the freshwater site and the terns made fewer trips per day. To achieve the same mass gain per day as in birds in freshwater, trips at sea had to be longer and food intake per trip was higher. The daily duration of absence for feeding and the daily mass gain were about the same in both areas. The limnetic feeders finished foraging earlier in the evening than the terns foraging at sea. These differences are consistent with the hypothesis that limnetic prey availability was consistent, whereas the tides limited the availability of marine prey. In consequence, foraging over freshwater presents several advantages, such as higher colony attendance, better mate coordination and better parental care.     

Body condition and retaliation in the parental effort decisions of incubating great frigatebirds (Fregata minor)

Decisions about parental effort have the potential to be affectedby an individual's body condition and, among species with biparentalcare, by the level of effort made by one's mate. Previous studies,primarily of short-lived species, have found that a reductionin the parental effort of one pair member typically leads toa compensatory increase by the mate. However, long-lived specieswith short-term pair bonds might be expected to retaliate, ratherthan compensate, for a reduction in a mate's effort. I studiedthe factors affecting parental effort decisions during incubationby the great frigatebird, a long-lived seabird that forms newpair bonds for each breeding attempt. During incubation, malesand females took turns incubating and foraging. Individualslost mass during an incubation shift and regained this massduring the subsequent foraging bout. If an individual was lefton the nest for a long period of time while its mate was foraging,it subsequently went on a long foraging trip after being relievedby its mate, despite the fact that longer shifts were likelyto lead to nest failure. This relationship between incubationshift length and duration of subsequent foraging excursion could be due to a need to regain body condition after a longfast, or it could reflect a retaliatory response to the mate'sprolonged absence. To test these alternatives, I conducteda food supplementation experiment. Individuals engaged in along incubation shift were assigned to a control group or toa treatment group that was fed until the end of that particularincubation shift. Overall, fed birds returned from the subsequentforaging trip sooner than control birds, demonstrating thatthe relationship between incubation shift duration and foragingtrip duration is due primarily to a need to increase body mass,rather than being a retaliatory response to a mate's low levelof parental effort. However, males and females differed in theextent of their responses to the experimental treatment, indicatingthat males may also exhibit some degree of retaliation.     

Female and male Leach's Storm Petrels (Hydrobates leucorhous) pursue different foraging strategies during the incubation period

Reproduction in procellariiform birds is characterized by a single egg clutch, slow development, a long breeding season and obligate biparental care. Female Leach's Storm Petrels Hydrobates leucorhous, nearly monomorphic members of this order, produce eggs that are between 20 and 25% of adult bodyweight. We tested whether female foraging behaviour differs from male foraging behaviour during the ~ 44-day incubation period across seven breeding colonies in the Northwest Atlantic. Over six breeding seasons, we used a combination of Global Positioning System and Global Location Sensor devices to measure characteristics of individual foraging trips during the incubation period. Females travelled significantly greater distances and went farther from the breeding colony than did males on individual foraging trips. For both sexes, the longer the foraging trip, the greater the distance. Independent of trip duration, females travelled farther, and spent a greater proportion of their foraging trips prospecting widely, as defined by behavioural categories derived from a hidden Markov Model. For both sexes, trip duration decreased with date. Sex differences in these foraging metrics were apparently not a consequence of morphological differences or spatial segregation. Our data are consistent with the idea that female foraging strategies differed from male foraging strategies during incubation in ways that would be expected if females were still compensating for egg formation.     

Origin, age, sex and breeding status of wandering albatrosses (Diomedea exulans), northern (Macronectes halli) and southern giant petrels (Macronectes giganteus) attending demersal longliners in Falkland Islands and Scotia Ridge waters, 2001–2005

A total of 547 sightings of 291 banded wandering albatrosses Diomedea exulans and 21 sightings of 14 banded giant petrels Macronectes spp. were made from toothfish longliners operating on the southern Patagonian Shelf during 2001–2005. This included 25% of the wandering albatrosses with Darvic bands that bred at Bird Island (South Georgia) during this period. Thirteen of the northern Macronectes halli and southern giant petrels Macronectes giganteus had been banded at South Georgia, and there was one sighting of a southern giant petrel from Argentina. Male and female wandering albatrosses of all age classes except young birds (<15 years old) were equally likely to attend longline vessels. Most sightings of all age classes were made during the incubation period and fewest during the brood period. Eighty-six percent of birds sighted had bred at least once before, with half currently breeding and half on sabbatical (i.e. between breeding attempts). Almost half of the wandering albatrosses were sighted on more than one occasion. The data confirms that the southern Patagonian shelf is an important foraging area for wandering albatrosses and northern and southern giant petrels, and that some individuals show consistent associations in multiple years with longline vessels fishing in the region.     

Partitioning of foraging effort in Adélie penguins provisioning chicks at Béchervaise Island, Antarctica

Analyses of the body masses of Adélie penguins (Pygoscelis adeliae) departing on foraging trips of long and short duration (> and<40 h, respectively) during chick rearing showed that the departure weights of birds prior to long trips were significantly lighter than were those prior to short trips. Penguins, particularly males, were significantly heavier at the start of the guard stage than at the end and both sexes gained similar amounts of body mass during the crèche period. Results support the hypothesis that the foraging effort of Adélie penguins at Béchervaise Island is partitioned between the sexes, with males accepting a net rate of negative energy gain to provide regular meals for their offspring during the guard stage. Adélie penguin foraging behaviour may be driven by a trade-off between the allocation of food to chicks and the storage of parental body reserves, similar to that previously postulated for some species of flying seabirds. The relevance of such a foraging strategy to the breeding success of penguins in the Mawson region of eastern Antarctica is discussed in relation to micronekton distribution in the area. Accepted: 3 June 2000     

Human-induced behaviour in Adélie penguins Pygoscelis adeliae

Summary Adélie penguins Pygoscelis adeliae appear to be little perturbed by man. We examined the incidence of nest desertion and duration of foraging trip in Adélie penguins when manipulated and fitted with devices of differing sizes. Birds with ca. 1 cm clipped from their tail feathers stayed at sea 50% longer than unmarked controls. The length of foraging trip and incidence of nest desertion increased with increasing device volume. Penguins fitted with devices did not reduce foraging trip length to that of unpackaged birds for at least 19 days. The susceptibility of Adélie penguins to disturbance should be carefully considered when activity patterns are being studied.