Average Breeding Success Research Articles

Predation of Atlantic Petrel chicks by house mice on Gough Island

The impacts of predation by invasive mammals on island fauna are a major driver of insular biodiversity loss. Devastating, hitherto unsuspected impacts of predatory house mice on breeding seabirds have been described recently. We studied the fate of 178 Atlantic Petrel Pterodroma incerta nests at Gough Island, over four seasons, from October 2003 to January 2008. Introduced house mice Mus musculus were found in all study burrows checked for mouse visits. From October 2003 to September 2004, we video-recorded attacks by mice on six (of 13) live, healthy Atlantic Petrel chicks and on one (of three) great shearwater Puffinus gravis chicks. In all years, chicks died from mouse attacks. Stage-specific daily nest survival rates were modelled, from which estimates of breeding success were derived that accounted for the variable exposure periods studied among years. Average daily survival rate of eggs was 0.998, and hatching success through the entire incubation period (55.5 days) was 0.924 [95% confidence interval (CI) 0.903–0.940]. Daily chick survival rates were 0.990, which gave a modelled fledging success of 0.247 (CI 0.165–0.338) over the 138-day chick period, and average annual breeding success (chicks fledged per breeding attempt) of 0.228 (CI 0.150–0.318), which is low compared with congeners. Productivity estimates were used as a parameter in a population simulation model, which predicted a population multiplication rate (λ) of 0.993 (CI = 0.966–1.021). However, in the one season studied from laying to fledging (2007), from 58 nests, only one chick fledged (1.7%). This suggests the wide errors on the model results may obscure a more severe reality. More than 60% of model simulations resulted in an International Union for Conservation of Nature classification of Endangered. Our results add support to calls to eradicate mice from Gough Island. More generally, mice cannot be ignored as a potential threat to island fauna, and island restoration and management plans should routinely include eradication of introduced mice.

The effect of investigator disturbance on egg laying, chick survival and fledging mass of short-tailed shearwaters (Puffinus tenuirostris) and little penguins (Eudyptula minor)

AbstractField-based animal researchers need to balance the potential adverse effects of their research activities against the benefits of research outcomes, but the data required to do this are often lacking. Assessing, and subsequently reporting the effects of researcher activities on wild animal populations can be difficult, so that studies to detect these effects sometimes lack rigour or fail to encompass sufficient time to ensure that the effects are tested under a range of environmental stresses. We monitored the effect of investigators working in colonies of two seabirds, the short-tailed shearwater (Puffinus tenuirostris) and the little penguin (Eudyptula minor). Disturbance of breeding birds while checking nests or the weighing of chicks to monitor growth are very common activities for demographic and ecological studies, but how these activities may influence the birds is rarely measured. We investigated differing levels of disturbance during both activities between 2002-03 and 2008-09 to assess their effect on egg laying, chick survival and growth rate and observed no effect for nest checking or handling of short-tailed shearwaters and indeterminate effects for handling in little penguins. Over a period of several years the study has observed a large-scale decline in the number of breeding shearwaters and includes years when control nests had above and below average breeding success.

Brood ranging behaviour and breeding success of the threatened little bustard in an intensified cereal farmland area

Cereal pseudo-steppes hold the largest proportion of declining bird species in Europe. Understanding how this process of decline is driven is essential for designing adequate management practices. The little bustard (Tetrax tetrax) is one of such threatened steppe-land bird species, which has suffered recent dramatic range constrictions and population declines. Although low breeding success has been claimed to be the main threat for the viability of future little bustard populations, the surprising lack of studies dealing with ecological requirements of broods hinders the implementation of efficient conservation practices. We studied the ranging behaviour and the reproductive success of a little bustard population by means of female radio-tracking conducted during 2006–2008 breeding seasons in the Ebro basin (NE Spain). We recorded an average breeding success of 0.27 chicks/hen, which is not enough to sustain a viable population according to the demographic models for the species. Early-laid clutches showed more probabilities to hatch and to fledge. This was associated to two different ranging patterns (i.e. sedentary versus wandering respectively) which depended on the ability of the hen and its chicks to settle in suitable areas harbouring enough arthropods and shelter for chicks. Such resources decrease drastically as the breeding season progresses. Overall, data suggest that agricultural practices associated to agricultural intensification, particularly early harvest, reduce breeding success both directly by nest destruction and indirectly through a decrease on resource availability for broods. Based on our findings on the characteristics and structure of the home range of little bustard broods, we propose the creation of a network of permanent vegetation plots interconnected by high-quality field margins as a management practice to raise the breeding success of little bustards and other ground-nesting birds on cereal farmland.

Chick starvation in yellow‐eyed penguins: Evidence for poor diet quality and selective provisioning of chicks from conventional diet analysis and stable isotopes

AbstractThe link between poor reproductive success and diet was investigated in yellow‐eyed penguins Megadyptes antipodes, by assessing diet at two localities separated by about 30 km: the north coast of Stewart Island where breeding success is low (0.38–0.67 chicks per pair in recent years), and Codfish Island where breeding success is higher (0.96–1.51 chicks per pair), and relating this to published data from South Island localities, where average breeding success was 1.1 chicks per pair. Diet composition, meal sizes and energetic content of meals and prey were determined from stomach contents, and stable isotope analyses of chick down, fledgling feathers and adult blood provided information on diet throughout the fledging period. The high proportion of stomachs that were empty or lacked diagnostic remains reduced sample size considerably, and variability between samples reduced the power to detect significant differences in meal size, proportions of empty stomachs and prey diversity of meals. Energetic content of Stewart Island meals was less than Codfish Island meals, and there was a non‐significant trend for smaller meal sizes and reduced prey diversity among Stewart Island samples. Both localities had lower prey diversity and smaller meals than South Island penguins. Blue cod Parapercis colias accounted for 99% of prey biomass in Stewart Island and 70% in Codfish Island stomach samples, where 27% of prey biomass was opalfish Hemerocoetes monopterygius. Isotopic mixing models carried out on larger sample sizes indicated that opalfish comprised a large proportion of the diet at both locations, with adults selectively provisioning chicks with opalfish while feeding mainly on blue cod themselves. We suggest the large blue cod consumed by Codfish Island and Stewart Island penguins, larger than those consumed by South Island penguins, is difficult to transfer to chicks by regurgitation. Oyster dredging around Stewart Island may have reduced the availability and abundance of alternative prey to Stewart Island penguins.

Advancing breeding phenology in response to environmental change in a wild red deer population

Most evidence for advances in phenology of in response to recent climate warming in wild vertebrate populations has come from long-term studies of birds. Few studies have either documented phenological advances or tested their climatic causes and demographic consequences in wild mammal systems. Using a long-term study of red deer on the Isle of Rum, Scotland, we present evidence of significant temporal trends in six phenological traits: oestrus date and parturition date in females, and antler cast date, antler clean date, rut start date and rut end date in males. These traits advanced by between 5 and 12 days across a 28-year study period. Local climate measures associated with plant growth in spring and summer (growing degree days) increased significantly over time and explained a significant amount of variation in all six phenological traits, largely accounting for temporal advances observed in some of the traits. However, there was no evidence for temporal changes in key female reproductive performance traits (offspring birth weight and offspring survival) in this population, despite significant relationships between these traits and female phenology. In males, average antler weights increased over time presumably as a result of improved resource availability and physiological condition through spring and summer. There was no evidence for any temporal change in average male annual breeding success, as might be expected if the timing of male rutting behaviour was failing to track advances in the timing of oestrus in females. Our results provide rare evidence linking phenological advances to climate warming in a wild mammal and highlight the potential complexity of relationships between climate warming, phenology and demography in wild vertebrates.

Kleptoparasitism in Common Guillemots Uria aalge at two colonies during a period of poor food availability

Kleptoparasitism, the stealing of food items from other animals, is an important foraging strategy for many taxa. In many cases the kleptoparasites and hosts are different species but less commonly, prey items are stolen from conspecifics. Recent studies have highlighted the potential importance of intra-specific kleptoparasitism in food-stressed populations, and here we show facultative kleptoparasitism at two North Sea colonies of Common Guillemots Uria aalge during one year of poor breeding success and one year of near average breeding success. The frequency of kleptoparasitism differed between colonies and years, reflecting variation in the magnitude of the benefits from kleptoparasitism, which was probably associated with variation in prey availability at sea. Specialised foraging strategies such as kleptoparasitism may allow individuals to buffer adverse conditions more effectively than those foraging only at sea.

Investigation of Great Egret (Casmerodius albus) breeding success in Hara Biosphere Reserve of Iran

Study of Great Egret breeding success was carried out for the first time in Hara Biosphere Reserve of Iran. Since Great Egret is considered as wading bird as well as wetland-dependent species which is located on top of the food chain in this ecosystem, its breeding study is an appropriate means for evaluating food supply fluctuations and environmental threatening factors by comparison of different years. On the other hand, Great Egret is considered a suitable indicator to examination of biological changes, impact of pollutions, and other effective human activities on Hara Biosphere Reserve. Therefore, read-ahead is required for area management planning in order to maintain the health of mangrove ecosystem and control threatening factors of the sensitive biodiversity of area. The results indicate that the average breeding success of Great Egret in different stages of hatching success, fledging success, and breeding success were equal to 0.54, 0.61, and 0.50 in 2008 and 0.61, 0.59, and 0.42 in 2009, respectively.

Population dynamics of the White Stork Ciconia ciconia in Slovenia between 1999 and 2010

Population dynamics of the White StorkCiconia ciconiain Slovenia between 1999 and 2010Between 1999 and 2010, an annual census of the White StorkCiconia ciconiabreeding population was carried out in Slovenia using standardised methods. The Stork's population was concentrated in the NE and SE parts of Slovenia. In the 1999-2010 period, the breeding range of its population in Slovenia expanded in NW direction (the Savska ravan region), in SW direction (the Notranjsko podolje and Pivško podolje regions), but the species also colonized a part between Central and SE Slovenia (Dolenjsko podolje). Between 193 and 240 pairs were breeding during the study period, 209 pairs on average (HPa). The largest number of breeding pairs was recorded in 2004, the smallest in 2005. During the study period, breeding pairs (HPa) occupied 350 discrete nests in total. Average number of breeding pairs that raised juveniles (HPm) was 161. The highest fecundity was recorded in 2004, when 534 juveniles (JZG) fledged, the lowest in 2006, with only 219 fledged juveniles. On average, 414 juveniles fledged per year. The breeding pairs' (JZa) average breeding success in these 12 years was 2.02, the highest in 2000 (2.41), the lowest in 2006 (1.09). Average breeding success for the successful breeding pairs (JZm) was 2.57. The highest was in 2007 (2.94), the lowest in 2006 (2.07). The largest number of breeding pairs in 2004 and 2008 can be explained by the favourable fecundity in the population in 2000 and 2004, as juveniles become sexually mature at the age of 3-5 years, and at that age they generally return to the breeding grounds for the first time. The lowest number of breeding pairs and poor breeding success in 2005 and 2006 was caused by late arrival of White Storks to the breeding grounds and by unfavourable weather conditions during the breeding period. The pattern of nests placement did not change generally during the last 12 years. The largest proportion of nests was positioned on various kinds of poles (81%) and on chimneys (18%). In total, 27 area surveyors and 239 assistants helped in census realisation.

Changes in the timing of egg-laying of a colonial seabird in relation to population size and environmental conditions

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 393:225-233 (2009) - DOI: https://doi.org/10.3354/meps08258 Changes in the timing of egg-laying of a colonial seabird in relation to population size and environmental conditions Stephen C. Votier1,*, Ben J. Hatchwell2, Meghann Mears2, Tim R. Birkhead2 1Marine Biology & Ecology Research Centre, University of Plymouth, Plymouth PL4 8AA, UK 2Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK *Email: stephen.votier@plymouth.ac.uk ABSTRACT: An emerging consequence of global climate change is its potential effect on the timing of seasonal biological events. Analysis of long-term datasets reveals a high degree of plasticity in the nature of phenological responses both within and among species, and understanding these differences is central to understanding the mechanisms and implications of climate-related change. We investigated factors influencing timing of breeding (median laying date) in a colonial nesting seabird, the common guillemot Uria aalge, over 23 breeding seasons between 1973 and 2008. There was a trend for earlier laying over this period, and earlier laying was associated with higher average breeding success. Multiple regression models (with de-trended explanatory variables to control for linear trends over time) indicate that the timing of breeding is positively correlated with a wide-scale climatic driver, the winter North Atlantic Oscillation (WNAO), and negatively correlated with population size: guillemots lay later in years with high WNAO indices and earlier in years with larger populations. Responses to environmental conditions are probably related to indirect effects on timing or abundance of food availability, direct effects of weather or both. The mechanism(s) leading to a possible relationship between laying date and population size are less clear. They may be related to Allee-type effects associated with social stimulation, improved foraging efficiency or a density-dependent increase in breeding site quality. Given the correlative nature of these results, we are cautious about the role of non-climatic (intrinsic) factors, but we cannot exclude that they play a role alongside climatic (extrinsic) factors in influencing reproductive phenology. KEY WORDS: Phenology · Climate change · Allee effect · Coloniality · NAO · Density dependence Full text in pdf format PreviousNextCite this article as: Votier SC, Hatchwell BJ, Mears M, Birkhead TR (2009) Changes in the timing of egg-laying of a colonial seabird in relation to population size and environmental conditions. Mar Ecol Prog Ser 393:225-233. https://doi.org/10.3354/meps08258 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 393. Online publication date: October 30, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.

Ineividual variation in Parental Provisioning Behaviour Predicts Survival of Cape Gannet Chicks Under Poor Conditions

Cape Gannets Morus capensis are declining in numbers in all breeding colonies at the southern African west coast, potentially caused by deteriorating food availability. The behavioural responses of Individuals to changing conditions can provide insights into the mechanisms that drive population dynamics. We studied the relationship between parental provisioning behaviour and the breeding success of Cape Gannets breeding at Ichaboe Island (Namibia) in two years with different nesting success, to assess the potential role of variation in food availability in explaining variation in chick survival. in 2006/07 parents delayed the onset of breeding and visited nests at a lower frequency than in 2005/06, indicating that food availability was limited. Within the years Individual differences in provisioning rate but not in parental condition were associated with chick growth and survival. These associations remained present when controlling for seasonal changes. Predation, not starvation, was the main cause of mortality. Under poor conditions, as Indicated by long foraging trips, Cape Gannet parents left small chicks unattended, resulting in many being killed by Kelp Gulls Larus dominicanus. Long foraging trips were associated with reduced average breeding success, but impacted some parents more than others. Knowledge of the origin of this inter-individual variability is needed to predict how changes in food availability affect seabird population dynamics, which is one of the steps towards conservation of these birds.

Breeding ecology and behaviour of the last wild oriental Northern Bald Ibises (Geronticus eremita) in Syria

A relict colony of Northern Bald Ibis (Geronticus eremita), a critically endangered species, was unexpectedly discovered in Syria in 2002. During six subsequent breeding seasons (2002-2007), the 3, and then 2, breeding pairs of Northern Bald Ibises have shown to be still vital and, when intensively protected, showed a higher average breeding success than that recorded in Morocco, the only other country where these birds still breed in the wild. During the six breeding seasons, a total of 24 chicks fledged and left the breeding area successfully. Between 2004 and 2007, a total of 5 immature ibises have made a return to the colony, separately and later than adults. As a consequence, two recruitment events have taken place (2006 and 2007), partly compensating for the gradual decrease in the number of adults. Breeding adults arrive from migration during the second half of February, separately, and leave together around mid-July. They nest in cavities and ledges of two limestone cliffs of the central Syria desert, located 20 km apart, well protected from the predominant wind. Breeding behaviour and the cycle are described, summarised and compared with data from the wild colonies of Morocco and the colony of Turkey before the extinction. Key threats still in place at the Syrian breeding quarters are human disturbance during settling and incubation, chick depredation by ravens, uncontrolled hunting and habitat degradation. Recommendations on how to enhance the breeding performance and ensure the survival of this colony in the future are given.

Common Guillemot Uria aalge chick diet and breeding performance at Sumburgh Head, Shetland in 2007–09, compared to 1990–91

Chick diet of Common Guillemots Uria aalge was studied by direct observation at Sumburgh Head, Shetland during 2007–09. Lesser Sandeels Ammodytes marinus comprised 55% of prey items, the remainder being Gadidae, including Whiting Merlangius merlangus and Saithe Pollachius virens, and a few Snake Pipefish Entelurus aequoreus. This contrasts with 1990–91 when chick were fed 80% sandeels, the remainder mostly being unidentified Gadidae. When this shift from a diet dominated by sandeels took place is unknown, but a similar shift in chick diet at Fair Isle (40 km southwest of Sumburgh Head) seems to have occurred some time during 2000–02. Since 2003, weights of chicks near fledging have been lower than during the 1990s, and average breeding success has been reduced.

Population Trend and Breeding Biology of Gentoo Penguin in Martillo Island, Tierra Del Fuego, Argentina

Abstract Data on population size and some aspects of the breeding biology of Gentoo Penguins (Pygocelis papua) have been studied as part of a long-term monitoring program at Martillo Island in the Beagle Channel, Tierra del Fuego. The colony of Gentoo Penguin on Martillo Island is the only one reported in Argentina and has been monitored regularly since 2000. Timing and hatching success were similar to those reported at other colonies in the South Atlantic Ocean/Antarctic Peninsula region. A maximum of twelve nests were recorded during the 2006/2007 season, with an average breeding success of 1.0 chicks/nest. The Gentoo Penguin colony at Martillo Island increased by 19% in the past 13 y, while other colonies in the south Atlantic region and the Antarctic Peninsula have been decreasing or stable.

Breeding biology and ecology of Whinchat Saxicola rubetra on abandoned farmland of Opole Province (SW Poland)

FRANKIEWICZ J. 2008. Breeding biology and ecology of Whinchat Saxicola rubetra on abandoned farmland of Opole Province (SW Poland). Acta zoologica cracoviensia, 51A(1-2): 35-47. Abstract. In 2003-2007 the breeding biology and ecology of Whinchat Saxicola rubetra were investigated on the 500 ha mosaic agricultural landscape (cropland, abandoned cropland, meadows, pastures and young pine plantations) in SWPoland. In the area of uncultivated fields, meadows and pine plantations 36, 34, 31, 27 and 28 pairs bred consecutively in particular seasons of the study period. Most nests were situated in the abandoned fields in the grass and tansy Tanacetum vulgare. In the studied population the median date of egg-laying commencement fell on the 16th May. The first young fledged at the end of May. The average clutch size was 6.2 eggs (SD=0.8). The hatching success amounted to 76%. The average breeding success was 4.17 (n=117, SD=2.62) per nest, and 5.6 (n=87, SD=1.04) per successful pair. The overall breeding success was 74.1% (Mayfield method). The main reason behind the brood loss was predation (76.7% of all losses).

Improving the breeding success of a colonial seabird: a cost-benefit comparison of the eradication and control of its rat predator

Breeding success of 5 Cory's shearwater Calonectris diomedea sub-colonies of Lavezzu Island (Lavezzi Archipelago, Corsica) was checked annually for 25 consecutive years from 1979 to 2004. Between 1989 and 1994, 4 ship rat Rattus rattus controls were performed in several sub- colonies. In November 2000, rats were eradicated from Lavezzu Island and its 16 peripheral islets (85 ha) using traps then toxic baits. We compare cost (number of person-hours required in the field) and benefit (Cory's shearwater breeding success) of control and eradication. The average breeding success doubled when rats were controlled or eradicated (0.82) compared to the situation without rat management (0.45). Moreover, the average breeding success after eradication (0.86) was signifi- cantly (11%) higher than after rat controls (0.75). Furthermore, the great variation in breeding suc- cess recorded among sub-colonies both with and without rat control declined dramatically after eradication, suggesting that rats had a major impact on breeding success. The estimated effort needed to perform eradication and checking of the permanent bait-station system during the year fol- lowing eradication was 1360 person-hours. In contrast, rat control was estimated to require 240 or 1440 person-hours per year when implemented by trained and untrained staff, respectively. Within 6 yr, eradication cost is lower than control cost performed by untrained staff and confers several eco- logical advantages on more ecosystem components than Cory's shearwater alone. Improved eradi- cation tools such as hand or aerial broadcasting of toxic baits instead of the fairly labour-intensive eradication strategy we used would dramatically increase the economic advantage of eradication vs. control. Therefore, when feasible, we recommend eradication rather than control of non-native rat populations. Nevertheless, control remains a useful management tool when eradication is not practicable.

A long-term large-scale study of the breeding biology of the Spanish imperial eagle (Aquila adalberti)

We present data from a 17-year study of the population biology of a growing population of Spanish imperial eagles Aquila adalberti across most of its breeding range. The objective of this study was to analyse the effects of age, supplemental feeding and rabbit haemorrhagic disease (RHD) on several breeding parameters of this population of eagles. Average clutch size was 2.2 eggs per clutch, and the average incubation time was 41.7 days per clutch. Fledging occurred an average of 76.8 days after hatching, the length of the fledgling period was not correlated to clutch size. The annual average percentage of pairs laying eggs was 88%. A significant reduction in the percentage of pairs laying eggs in the period 1992–1994 (from 91 to 81%) coincided with most of the eagles’ territories being affected by the rabbit epizootic disease, RHD, which reduced their food supply significantly. Average productivity was 1.23 chicks per monitored territory, average breeding success was 1.40 chicks in a clutch per territory and the average fledging rate was 1.69 chicks per territory with hatching success. The main known causes of breeding failure during incubation were nest collapse and human disturbance. During chick-rearing, total or partial chick losses were mainly caused by siblicide, disease, malnutrition or nest collapse. In 26.2% of the 1372 monitored breeding attempts, at least one of the breeding birds was a subadult (the male in 56.1% of the cases, the female in 15.5% and both sexes in 28.4% of cases). In cases of mixed-aged pairs (n = 205), 70.7% were the result of a substitution, and 29.3% were the result of the forming of a new pair. Egg laying took place significantly earlier and breeding success was higher in territories occupied by adults than in those occupied by subadults. Breeding parameters were higher in high-quality (rabbit-rich) territories than in low-quality (rabbit-poor) territories, but only for those territories occupied by adults. The values obtained in the territories occupied by adults were only significantly higher than in those of the subadults in high-quality territories. Age and territory quality thus simultaneously affected reproductive output.

Breeding frequency in Grey‐headed Albatrosses Thalassarche chrysostoma

Although Grey‐headed Albatrosses Thalassarche chrysostoma are usually regarded as biennial breeders, taking a year off following a successful breeding attempt, a small proportion of successful birds attempt to breed annually. This proportion was higher at Marion Island (5.4%) than at Bird Island, South Georgia (1.0%), suggesting that conditions are more favourable at Marion Island. This hypothesis is supported by higher average breeding success and shorter lags following both successful and failed breeding attempts at Marion Island. Factors favouring reproduction at Marion Island may include reduced intraspecific competition (given the much smaller breeding population) and/or more predictable food supply (owing to production of meso‐scale eddies associated with the Indian Ocean Ridge). Although annual breeding appeared to increase the risk of adult mortality, with several birds that attempted to breed annually found dead the following year, at least some birds greatly enhanced their reproductive output, with one male raising five chicks in five successive years. Contrary to life‐history theory, there was no evidence that older birds were more likely to attempt annual breeding because of declining reproductive value.

Storlommens Gavia arctica häckningsframgång innanför och utanför fågelskyddsområden i sjöarna Fegen och Sottern

We compared the breeding success of Black-throated Divers Gavia arctica inside and outside bird sanctuaries with restricted public access during the incubation period in Lake Fegen-Svansjöarna and Lake Sottern, South Sweden. Both lakes held populations of approximately 15–20 pairs. At Fegen-Svansjöarna, average breeding success was 0.51 large chicks per pair and year inside and 0.27 outside the sanctuaries (field surveys in 1983—1984 and 1997—2000). The difference was not statistically significant, however, and in two out of the six study years breeding success was higher outside the bird sanctuaries. At Sottern, breeding success was 0.39 and 0.25 large chicks per pair and year inside and outside the bird sanctuary, but breeding success was higher inside the sanctuary only in four out of nine years, 1997—2005. The results from the two lakes together indicated an overall positive effect (P = 0.08). We recommend keeping a constant water-level during incubation to be the primary measure to enhance breeding success. Sanctuaries with limited access may be an additional benefit at lakes highly frequented for out-door recreation.

The effect of body condition on the timing and success of breeding in Little Penguins Eudyptula minor

We studied the effect of parental body condition on the breeding biology of Little Penguins Eudyptula minor. Daily attendance patterns and body mass were recorded using an Automated Penguin Monitoring System, which collected arrival and departure masses for approximately 200 breeding birds over the 2000 and 2001 breeding seasons. Breeding success varied between the two years; 2000 was a year of average breeding success (fledging 1.07 chicks per pair), and 2001 a year of poor breeding success (fledging 0.53 chicks per pair). In both years, adult body condition (body mass divided by flipper length) increased significantly prior to laying. The laying period began over a month later in 2000 than in 2001, and birds in 2000 exhibited significantly better body condition at laying. However, the mean laying dates in 2000 were less variable than in the 2001 breeding season. Body condition appeared to influence both the time of breeding and breeding synchrony in Little Penguins. Breeding success was correlated with adult body condition at incubation in 2000 but not in 2001, indicating that success was not solely influenced by adult body condition at incubation.

Variations of snow petrel breeding success in relation to sea-ice extent: detecting local response to large-scale processes?

Demographic parameters were estimated for snow petrels Pagodroma nivea nesting at the study colony of Reeve Hill near Casey station, Antarctica between 1984 and 2003. Average breeding success for the colony varied from 18.2% to 76.5%. Breeding effort, hatching and fledging success were subject to a high interannual variability. We examined the influence of regional sea-ice extent on the breeding performance of snow petrels at Reeve Hill. Fewer birds were breeding when sea-ice had been extensive during April–May. Overall breeding success and fledging success were improved during years with extensive sea-ice cover in winter. Successful breeding effort and breeding success were depressed when there was extensive sea-ice cover during January–February. Sea surface temperatures also correlated to snow petrel breeding performance parameters. Previous work showed that large-scale climatic events (ENSO, Antarctic circumpolar wave) and the related sea-ice cover around the Antarctic might affect the lower trophic levels of the marine environment and consequently food availability for snow petrels. A comparison with the long-term study conducted at Ile des Petrels (Terre Adelie) suggests that despite similarities in the underlying biological processes that control snow petrel breeding performance, the nature of the correlation of large-scale environmental factors with breeding performance differs substantially between the two colonies, probably because of the confounding effects of other environmental factors acting at a local scale (local weather, nest quality), which also affect bird body condition.