Sooty shearwater (

Rakiura Maori annually harvest sooty shearwater (Puffinus griseus) chicks from islands in Foveaux Strait and adjacent to Stewart Island, New Zealand. Chick availability and the number of chicks harvested were estimated during the 1994 and 1995 seasons on Poutama (Evening Island). Burrow entrance densities estimated using circular plots were significantly higher in 1994 (0.45 ± 0.03 per m) than in 1995 (0.41 ± 0.03 per m). A similar burrow entrance density (0.45 ± 0.04 per m) was obtained in 1995 using a transect sampling technique. The number of usable burrows estimated using circular plots in 1994 and 1995 was 387 508 and 337 732 respectively. Of these, chicks occupied 24% ± 6% in 1994 and 29% ± 4% in 1995. It was estimated the muttonbirders harvested 13-24% (15 722) of the chicks present on Poutama in 1994 and 17-28% (22 092) in 1995. Muttonbirders targeted areas of the island with higher chick density and less fallen stems. Excluding chicks rejected by the muttonbirder (less than or equal to 750g), harvested chicks were significantly heavier and had less down than randomly encountered chicks. If larger heavier chicks are more likely to return and breed, then the preference for these chicks by muttonbirders would affect predictions of harvest impacts.     

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.     

Predation on ground-nesting seabirds by island populations of red deer Cervus elaphus and sheep Ovis

On Foula, Shetland, sheep were observed biting off the legs, wings or head of unfledged young Arctic terns. Large numbers of tern chicks and a few Arctic skua chicks were found with amputations characteristic of these attacks by sheep. On Rhum, Inner Hebrides, red deer were watched biting the heads off manx shearwater chicks and occasionally also chewing the shearwaters' legs and wings to excise bone. Killing of birds and the selective ingestion of bone-rich parts by ruminants has not previously been widely documented. It is presumably a response to mineral deficiencies in the vegetation, and it may only occur in rare situations where ruminants feed on mineral-deficient vegetation on which there are dense colonies of ground-nesting birds.     

Estimating regional population size and annual harvest intensity of the sooty shearwater in New Zealand

Abstract

Recent comprehensive survey data from multiple New Zealand offshore islands were combined with demographic population models to produce the first formal estimate of the total population of sooty shearwaters within New Zealand territory. We estimated the total population over 1994–2005 to be 21.3 (19.0–23.6) million individual birds in the New Zealand region. This population consisted of 12.8 (12.0–13.6) million adults, 2.8 (2.5–3.1) million chicks, and 4.4 (4.2–4.7) million breeding pairs. Breeding sooty shearwaters were concentrated primarily around the southern islands of New Zealand, with 53% breeding in the Titi Islands surrounding Rakiura (Stewart Island). Rakiura Maori muttonbirders were estimated to harvest 360 000 (320 000–400 000) sooty shearwaters per year, equivalent to 18% of the chicks produced in the harvested areas and 13% of chicks in the New Zealand region. Overall, 11% of the chicks within the Titi Islands live on unharvested ground. Systematic and widespread surveys of breeding colonies in South America are needed before a reliable global sooty shearwater population estimate can be calculated.     

Prevalence of avian pox virus and effect on the fledging success of Laysan Albatross

ABSTRACT.   Avian pox virus ( Poxvirus avium ) is a mosquito-borne disease that occurs worldwide in a variety of bird species, but little is known about its prevalence or effect on seabirds. We monitored prevalence of pox virus and its effect on fledging success of Laysan Albatross ( Phoebastria immutabilis ) on Oahu, Hawaii, from 2003 to 2007. Pox prevalence in albatross chicks averaged 88% in years with high rainfall and 3% in years with low rainfall. Diagnosis of pox virus was clinically confirmed in two birds by Muscovy Duck ( Cairina moschata ) fibrolast cultures. Severity of infection ranged from small wart-like nodules and lesions on the bill, face, eyes, tarsus, and feet, to large tumorous growths that completely covered both eyes and caused deformation of the bill and skull. Most chicks recovered from infection, and the fledging rate in pox epizootic years (82%) did not differ from that in years with low pox prevalence (80%) or the average fledging rate on Midway Atoll (86%). Three chicks with severe infections were resighted as healthy adults on Kauai and Oahu in 2007, confirming postfledging survival of at least some birds. The high recovery rate, fledging success, and postfledging survival indicate that Laysan Albatross have strong immunity to avian pox virus.     

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.     

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.     

Effects of satellite transmitters fitted to breeding Cory's shearwaters

We studied the effects of a new technique to fix satellite transmitters on the feeding behavior and chick body growth of the Cory's shearwater (Calonectris diomedea). Transmitters did not significantly affect the breeding bird's body mass or diving performance. However, on average, pairs with ≥1 adult equipped with a transmitter brought a lighter meal (54.8 ± 18.9 g) to nestlings than did control birds or the same pair with the transmitter removed (77.4 ± 8.3 g) leading to a decreased chick body growth. However at fledging, chicks in control and treatment groups had similar body mass whether parents were equipped with a PTT or not. Our method of transmitter attachment could therefore be an appropriate alternative for studying the ecology of procellariiforms weighing <1 kg given that birds are fitted with transmitters for <2 weeks and restricted to 1 parent only. © 2011 The Wildlife Society.     

Modeling Harvest Intensity of Sooty Shearwater Chicks by Rakiura Māori in New Zealand

Abstract: Cultural evidence suggests that sooty shearwater (Puffinus griseus) chicks have been harvested by Rakiura Māori on islands in southern New Zealand since prehistoric times. Concerns exist that modern harvests may be impacting sooty shearwater abundance. We modeled human-related and ecological determinants of harvest (total no. of individuals harvested) of sooty shearwater chicks on 11 islands and examined the relationship between shearwater abundance and harvesting rates (chicks/hr) and harvester behavior throughout the harvesting season. Models best explaining variation in harvest between harvesting areas (manu), for both the early and late parts of the harvesting season, included harvester-days (included in all models with change in deviance information criteria [ΔDIC], ΔDIC < 8.36 and ΔDIC < 11.5, for the early and late periods, respectively). Other harvest determinants included shearwater density, size of the manu, and number of people helping harvesters (all included in the top 5 models within ΔDIC = 2.25 for the late period). Areas harvested by several families under a common-property harvesting system had higher harvest intensity for their size (24% points higher, 95% credible interval 11–36%) than those managed as an exclusive resource for one family. The slowest harvesters spent more time harvesting but on average only harvested 36% (95% credible interval 15–65%) and 34% (95% credible interval 12–63%) of the harvest taken by the fastest harvesters during the early and late periods, respectively. Our results highlight the possibility of elevated harvest intensity as the population of harvesters increases. However, our models suggested that a corresponding reduction in harvesting rate at low prey densities during the most productive period could potentially regulate harvest intensity. Future research will integrate these results into prospective shearwater demographic models to assess the utility of a range of harvesting strategies in ensuring harvest sustainability.     

Studying the effects of multiple invasive mammals on Cory��s shearwater nest survival

The most common invasive mammals??mice, rats, and cats??have been introduced to islands around the world, where they continue to negatively affect native biodiversity. The eradication of those invasive mammals has had positive effects on many species of seabirds. However, the removal of one invasive mammal species may result in abundance changes of other species due to trophic and competitive interactions among species. Understanding the overall impact of several invasive species is a key challenge when evaluating the possible effects of eradication programmes. Here we assess the influence of the three most common invasive mammals on nest survival of Cory??s shearwater (Calonectris diomedea). We monitored six breeding colonies over 3?years and measured the activity of mice, rats and cats to examine the influence of invasive mammals on nest survival. We found that nest survival showed a similar temporal trend in all years, with lowest weekly survival probabilities shortly after chicks hatched. Cats were identified as major predators of chicks, but no measure of colony-specific cat activity was able to adequately explain variation in shearwater nest survival. Nest survival was on average 0.38 (95?% confidence interval 0.20?C0.53) and varied among colonies as well as over time. We found a small positive influence of rats on nest survival, which may indicate that the presence of small rodents as alternative prey may reduce cat predation of chicks. Our findings suggest that the eradication of rodents alone may exacerbate the adverse effects of cats on shearwater nest survival.     

Yellow crazy ants (<Emphasis Type="Italic">Anoplolepis gracilipes</Emphasis>) reduce numbers and impede development of a burrow-nesting seabird

Yellow crazy ants (Anoplolepis gracilipes) are a significant threat to biodiversity due to a rapidly expanding range and the potential to disrupt ecosystem interactions at multiple trophic levels. Extirpation of ground-nesting seabirds subsequent to yellow crazy ant invasion has been reported anecdotally. Yellow crazy ant control is difficult and resulting positive effects on nesting seabirds is undocumented. We report the effects of ant invasion and subsequent control on burrow-nesting seabirds following the invasion of more than half of a 1.25-ha wedge-tailed shearwater (Ardenna pacifica) colony located on eastern O‘ahu. The number of active seabird burrows in invaded areas dropped from 125 in 2006 to 6 in 2010, with no corresponding decline in active burrows in adjacent, uninvaded areas. Ant control efforts in 2011 reduced ant densities by more than 97% and resulted in a substantial increase in active burrows (43 in 2011). In invaded areas, burrows appeared to be abandoned by adults prior to egg-laying. Chicks surviving in invaded areas exhibited mild to severe developmental abnormalities, and overall had shorter culmens, tarsi and wingchords, smaller eye diameters, and lower weights than chicks outside invaded areas. We conclude that yellow crazy ants constitute a significant, and likely underestimated, risk to ground-nesting seabirds. Loss of seabird nesting colonies can have significant effects on nutrient inputs, and can bring about shifts in plant communities and faunal composition. Range expansion of yellow crazy ants is expected and ant/seabird interactions are likely to increase.     

Dietary betaine accumulates in the liver and intestinal tissue and stabilizes the intestinal epithelial structure in healthy and coccidia-infected broiler chicks

The aim of this experiment was to study the patterns of betaine accumulation into intestinal tissue, liver and plasma of broiler chicks with or without coccidial infection. The chicks were raised on a corn-based, low-betaine diet with or without 1000 ppm betaine supplementation and with or without intestinal microparasite (Eimeria maxima) challenge to the age of 21 days. Plasma, liver, intestinal tissue and digesta of non-challenged (NC) birds and plasma and intestinal tissue of coccidiosis challenged (CC) birds were analysed for betaine content. NC birds were also analyzed for homocysteine in plasma and S-adenosylmethionine (S-AM) in liver. The jejunal epithelium was histologically examined for the presence of coccidia and the crypt-villus ratio was measured. Dietary betaine supplementation decreased the plasma homocysteine concentration but had no effect on liver S-AM of NC birds. The data suggest that chicks on a low-betaine diet accumulate betaine into the intestinal tissue. When the diet was supplemented with betaine, betaine accumulated heavily into liver and to a lesser degree into intestinal tissue. The concentration of betaine in jejunal and ileal digesta was low suggesting that dietary betaine was mainly absorbed from the proximal small intestine. The coccidial challenge decreased the concentration of betaine in the liver, but greatly increased that in the intestinal tissue. The crypt-villus ratio was decreased by the dietary betaine supplementation in healthy and challenged chicks, suggesting that dietary betaine both protects the jejunal villi against coccidial infection and also stabilizes the mucosal structure in healthy broiler chicks. These results support our earlier findings suggesting that betaine is likely to act as an important intestinal osmolyte in broiler chicks.     

Short-term and long-term effects of food supply on parasite burdens in Tawny Owls, Strix aluco

1. The relationships among food supply (Field Voles, Microtus agrestis ), reproduction and blood parasites was investigated in Tawny Owls, Strix aluco , in Kielder Forest, Northumberland, in 1994 and 1995. Vole populations were significantly lower in 1995 than in 1994.
2. Birds did not lose parasites after initial infection, and the level at which infections were maintained was characteristic of individual birds.
3. In 1994, the number and intensity of parasites was higher in adult owls that had experienced low food supply when they themselves were reared. This indicated that food supplied to chicks in the nest has a long-term effect on the parasite burden of adults.
4. In addition, there was evidence that parasite burdens of adults were influenced by their current food supply. Birds that suffered a decline in food abundance on their territories between 1994 and 1995 showed an increase in parasite load over the same period. In 1995, there was also a significant negative correlation between the parasite loads of owls and vole abundance on their territories.
5. The best predictor of parasite number of chicks reared in 1995 was the parasite load of their fathers. The parasites chicks developed were not the parasites with which their fathers were heavily infested. This result could be due to inherited immunity.
6. Our results indicated that food resources should be measured when investigating interactions between parasites and their hosts, and that offspring quality as well as quantity might suffer when food abundance is low.     

Embryonic heart rate and oxygen pulse in two procellariiform seabirds,Diomedea immutabilis and Puffinus pacificus

Developmental patterns of embryonic heart rate were measured non-invasively in two procellariiform seabirds, the Laysan albatross (Diomedea immutabilis) and wedge-tailed shearwater (Puffinus pacificus), during prepipping and after pipping. The O₂ pulse, defined as the O₂ consumption per single heart beat, was calculated using the previously reported O₂ consumption for these species. The embryonic heart rate of the albatross was not changed by internal pipping (initial pipping event in this species), remained unchanged during the prolonged internal pipping period and tended to increase, although insignificantly, with the initiation of external pipping (second pipping event). Heart rate in the shearwater remained unchanged during the late prepipping stages, did not change with external pipping (initial pipping event), but increased during the prolonged internal pipping period (second pipping event) and reached a maximum on the last day of incubation. The developmental pattern of heart rate in the shearwater was very similar to that reported previously for the brown noddy, a member of the order Charadriiformes but with the same pipping sequence. Developmental patterns of embryonic O₂ pulse were also different between the two procellariiform seabirds. However, those of the shearwater and the noddy were similar. The sequence of access to atmospheric O₂ during development and hatching may be an important factor determining the developmental patterns of embryonic heart rate and O₂ pulse.Abbreviations A-VO₂ difference, arteriovenous oxygen difference - BCG ballistocardiogram of egg - CV coefficient of variation - EP external pipping - HR heart rate - IP internal pipping - mass mass of freshly laid egg - SD standard deviation     

Poxvirus infection of the Manx shearwater (Puffinus puffinus)

During studies on the etiology of puffinosis, a disease of the Manx shearwater, 1 to 4% of full-grown birds were found to have dry, non-pigmented lesions on the webs of the feet. Poxvirus infection was detected in six of seven full-grown birds with such lesions. The lesions contained large encapsulated inclusions which were packed with mature and immature poxvirus particles. Poxvirus infection was not apparent in shearwater fledglings during puffinosis epizootics, and its spatial distribution was not related to that of puffinosis. The results indicate that poxvirus infection produces a mild, self-limiting disease in shearwaters and is not the cause of puffinosis.     

Changes in sooty shearwater (Puffinus griseus) abundance and harvesting on the Rakiura Titi Islands

Abstract

We estimated the change in abundance of sooty shearwater (titi, Puffinus griseus) at six Rakiura Titi Islands, New Zealand, by comparing historical and recent surveys of the density of entrances to breeding burrows. We found evidence that entrance density between 1994 and 2006 was lower than it was between 1961 and 1976. Our overall estimate of the annual rate of change in burrow entrance density is ‐1.0% (95% CI ‐2.3 to ‐ 0.1%). Declines have been slower on four islands where Rakiura Maori maintain a traditional harvest of sooty shearwater chicks ("muttonbirding") compared with three unharvested islands. Density‐dependent population processes may explain this difference: rates of decline have been faster in areas of relatively high initial entrance density, and historically the harvested islands have had lower initial density. There was a strong, apparently linear, relationship between entrance density and chick density on breeding colonies, so changes in entrance density probably do indicate a real population decline. The western side of Taukihepa, the largestof the Titi Islands, first became accessible for muttonbirding with the advent of helicopters in the 1970s, but it is unknown whether this has caused an increase in the number of sooty shearwaters harvested by Rakiura Maori.     

Causes of morbidity and mortality and their effect on reproductive success in double-crested cormorants from Saskatchewan

The objectives of this study were to describe causes of morbidity and mortality in a breeding colony of double-crested cormorants (Phalacrocorax auritus) on Doré Lake (Saskatchewan, Canada), and to determine cause-specific mortality rates of juvenile birds. Morbidity and mortality were monitored every third day during the breeding season from 1994 to 1996 from inside a tunnel-and-blind system. Affected eggs and birds were collected for examination and diagnosis. The cause of mortality was determined for 105 eggs, 178 nestlings (< or = 4-wk-old), 1393 post-nestling chicks (> 4-wk-old), and 10 adults. The main causes of mortality were infertility or embryonal death, avian predation, displacement of eggs and chicks from the nest, starvation from sibling competition, Newcastle disease, coyote predation, human-induced suffocation, and entrapment. In 49% of the cases, avian predation and displacement from the nest of eggs or nestlings was associated with human disturbance. Thirty-six nestlings, 40 post-nestling chicks, and three adults were examined for the presence of parasites. Contracaecum spiculigerum was found in the proventriculus; Amphimerus elongatus in the liver. Piagetiella incomposita in the gular pouch; Eidmanniella pellucida, Pectinopygus farallonii, and Ceratophyllus lari in the plumage; and Theromyzon sp. in the nasal and oral cavity. Contracaecum spiculigerum was associated with ulcerative gastritis, A. elongatus with multifocal hepatitis and bile duct hyperplasia, and P. incomposita with ulcerative stomatitis, but these lesions were not considered fatal. Other diseases included beak deformity, abnormal rotation of the carpal joint, hypopigmentation, and eye loss. Overall mortality of cormorant chicks between hatching and the end of the breeding season varied from 25 to 48%. The most important causes of mortality were Newcastle disease, which killed 21% of hatched chicks in 1995, sibling competition (maximum 12% in 1994), and coyote predation (2% in 1994).     

How important are seabirds in the diet of black rats on islands with a superpredator?

This study assessed the impact of introduced black rats (Rattus rattus) on Cory's shearwater (Calonectris diomedea borealis) in a multi-invaded insular ecosystem where rats are mesopredators. We hypothesized that black rats should have little impact on Cory's shearwaters in the presence of cats as superpredators. Stomach contents and stable isotope analysis (SIA) in tissues of black rats were analyzed to assess the trophic ecology and the importance of Cory's shearwater in their diet. We also studied the isotopic signature in tissues of house mouse (Mus domesticus) to confirm previous data showing no predation of this species on Cory's shearwaters. For both rodent species, temporal variation in diet composition in response to the availability of seabird prey was evaluated, and short- and long-term consistency in diet was tested using different tissues from the same individual. For black rats a Bayesian isotope mixing model (SIAR) was applied to determine the relative contribution of each prey to the individual diet. SIA of mouse tissues varied between the Cory's shearwater breeding and non-breeding periods. However, no significant differences were found in diet and SIA for black rats. In contrast, individuals of both species showed a strong consistency in diet which apparently benefited their body condition index. Although black rats supplement their diet with Cory's shearwater eggs and chicks (8.3% in stomach contents and 10.6% in the SIAR model), their current impact on the Cory's shearwater population appears to be small, probably due to several factors including the small size of the rat population and a high level of rat predation by cats.     

Growth, morphogenesis, and virulence of Candida albicans after oral inoculation in the germ-free and conventional chick

Balish, Edward (Syracuse University, Syracuse, N.Y.), and A. W. Phillips. Growth, morphogenesis, and virulence of Candida albicans after oral inoculation in the germ-free and conventional chick. J. Bacteriol. 91:1736-1743. 1966.-The effects of intestinal bacteria on the multiplication, morphogenesis, and infectivity of Candida albicans in the alimentary tract were investigated by comparing results obtained in germ-free and conventional chicks after oral inoculation. This challenge resulted in the establishment of large numbers of the pathogen in the alimentary tract of each group of chicks; these numbers were increased in crop contents from challenged bacteria-free chicks wherein hyphae predominated over the yeast form. These animals also had lesions of the crop epithelium containing numerous hyphae and few yeast-like forms. In contrast, challenged conventional chicks receiving an adequate diet displayed no evidence of infection. Their alimentary tract contained the yeast form of C. albicans; no hyphae were seen. Although we found bacterial inhibition of C. albicans multiplication in the alimentary tract, this in itself did not seem to explain the resistance to intestinal candidiasis in our conventional chicks. We argued that this resistance to infection was due chiefly to the prevention of hyphal development in C. albicans by intestinal bacteria. C. albicans in the gut of our conventional chicks resulted in some increase in numbers of enterococci in contents from the crop. Increased pH values in contents from the gut of germ-free chicks were not clearly related to infection after challenge. The E(h) of the above crop contents were only slightly decreased in the germ-free crop. Thus the E(h) did not appear to be involved in susceptibility to infection. Invasion of the blood stream and kidneys of conventional chicks by the yeast form of C. albicans occurred in challenged animals receiving a purified diet which had been radiation-sterilized and stored for 6 months at room temperature (25 C). Their growth rate decreased and they became moribund; no hyphae were observed in tissues or intestine of these animals. Challenged bacteria-free chicks receiving the same diet were resistant to the above invasion, although they had crop lesions containing hyphae as described. The resistance of these chicks to systemic invasion was attributed to absence of intestinal bacteria competing for low levels of vitamins in the stored diet. Germ-free chicks had decreased levels of serum gamma-globulin which increased after challenge, whereas this value was unchanged in conventional birds after challenge.     

Foraging and provisioning strategies of black-browed albatrosses in relation to the requirements of the chick: natural variation and experimental study

We studied regulation of the food supply to black-browed albatrosschicks at Kerguelen by simultaneously recording the provisioningrates achieved by individual parents and satellite trackingforaging birds during two seasons, by studying changes in adultmass, and by experimentally manipulating the food requirementof chicks. In 1994 black-browed albatrosses had a higher breedingsuccess and produced heavier chicks that grew faster than in1995. They spent a similar time foraging but brought heaviermeals to their chick in 1994. Satellite tracking indicated thatin both seasons birds foraged in the same oceanographic area,250 km from the colony. Travel times to and from this area remainedunchanged, and similar times were spent foraging there. In ourstudy area, black-browed albatrosses appear to rely on a foodresource that is predictable in location, but whose availabilityvaries from one year to the next. The principal difference betweenyears of differing food availability was that birds broughtlarger meals when food was more abundant Costs of commutingto nearby feeding areas are probably low and allow the deliveryof energy to the chick at a high rate. A study carried out in1991 indicated that there was no relationship between the changesin adult mass from one trip to the next and the duration offoraging trips or feed mass, suggesting that adult body conditionhad little influence on the provisioning strategy of this species.An experiment whereby some chicks were deprived of food andothers received supplementary food showed that parents of underfedchicks spent the same time foraging and brought slightly largeramounts of food to their chicks as control parents. We suggestthat parents are searching for food to the maximum limits oftheir ability and thus cannot reduce further foraging time,but underfed chicks can swallow more food. Parents of overfedchicks delivered less food and increased the time between feeds.The reduction in provisioning frequency is interpreted as thecapacity of parents to modify their foraging behavior accordingto the nutritional status of the chick, but the reduction offeed mass is probably the result of chicks being close to theirmaximum assimilatory capacity. Comparison between Procellariiformspecies indicates extensive differences in the degree to whichparents can regulate the supply of food to their chicks. Neriticspecies like black-browed albatrosses appear to have a reducedability to regulate, and especially to increase provisioningrates, whereas more pelagic species may have a greater regulationability