Annual variation in reproductive parameters of Adélie penguins at Edmonson Point,Victoria Land,Antarctica

Annual egg and chick production and breeding success at the Adélie penguin (Pygoscelis adeliae) colony Edmonson Point (74°21′S–165°10′E), Victoria Land, is presented for eight breeding seasons between 1995 and 2005. During this period the colony consisted of 10–13 subcolonies and averaged 2098 ± 278 breeding pairs. A sample of over 100 nests (114–150), belonging to two subcolonies, was monitored each year. Some breeding parameters remained constant while others showed substantial annual variation. Laying date showed little variation, and laying was highly synchronous: 82.5% of clutches were initiated in a 10-day period, 9–18 November. In contrast, clutch size (1.77–1.97) and incubation period (34.4 ± 2.5) varied significantly. Variation among years was also recorded in hatching success (from 58 to 86%) and breeding success. This last parameter, measured as number of chicks reared to crèche per nest with eggs, varied between 0.34 and 0.97.     

Nest maintenance and stone theft in the Chinstrap penguin (Pygoscelis antarctica)

The intensity of stone collection and stone theft by breeding Chinstrap penguins was measured, and estimations made of the number of stones per nest in large (> 400 nests) and small subcolonies (< 50 nests) in the large Vapour Col colony on Deception Island, South Shetland Islands. Stone availability was significantly higher both inside and outside small subcolonies. Penguins carried stones to the nest at the same rate in large and small subcolonies, but stole more intensively in large subcolonies. Stones obtained by theft were significantly larger than those collected elsewhere. When stone availability was increased experimentally, individuals of large subcolonies collected more intensively than control individuals in large and small subcolonies, and stole significantly less than control individuals in large subcolonies, and as much as individuals in small subcolonies. The greater theft pressure in large subcolonies was accompanied by more aggressive defence by nest owners and by reduced succession stealing. However, the reduced availability of stones on the ground near large subcolonies led to a significantly lower number of stones per nest than in small subcolonies. These results are interpreted in the light of the geometric effects of breeding group size (perimeter to surface ratio) on stone accessibility.     

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

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

Effects of habitat fragmentation on provisioning rates, diet and breeding success in two species of tit (great tit and blue tit)

The aim of this study was to examine the effects of forest fragmentation on the ability of parent birds to provide their young with an adequate food supply. To examine whether prey population densities of the great tit (Parus major L.) and the blue tit (P. caeruleus L.) vary between study areas in different forest size classes we compared provisioning rates and chick diet and related these parameters to breeding success. We filmed 217 nests over two breeding seasons and collected data on frass fall as a general estimate of caterpillar availability. Nests which were attended by none or one parent only during filming (n = 46) were excluded from the analyses. In both years and for both species feeding rates were highest in the smallest fragments and lowest in the large forest. There was also a suggestion that differences in feeding rates between areas vary between years. We found no consistent tendency for prey size to change with forest size, although both species brought slightly smaller prey items to the nest in the smallest forest fragments and feeding rates correlated negatively with prey size. Caterpillars were the main item fed to nestlings, in both species. We found no evidence to suggest that either frass fall or the proportion of caterpillars in the diet varied with forest size. There was also no correlation between mean frass fall and the total number of caterpillars brought to the nests, in either species. Breeding success, as measured by clutch size, brood size, fledging weight and fledging success, did not differ between the small fragments and the large forest, in either species. There was also no relationship between provisioning rate (as concerns volume of prey fed to nestlings and the quality of chick diet) and breeding success parameters. In conclusion, this study does not suggest suboptimal foraging or breeding conditions in small fragments compared to a nearby large forest, for either species. Received: 23 June 1997 / Accepted: 29 December 1997     

Heat loss and site-dependent fecundity in chinstrap penguins (Pygoscelis antarctica)

We study the effects of heat loss and nest site quality on fecundity in a chinstrap penguin (Pygoscelis antarctica) colony on Deception Island, Antarctica. During the austral summers of 1990–1991, 1993–1994, and 1995–1996, 441 randomly selected nests were analyzed. Penguins breeding in the center of subcolonies hatched significantly earlier and had larger broods and than those nesting near or at the edge of the subcolonies. These differences, however, were significantly affected by interaction between year and nest location, being highly significant in colder years, when peripheral nests produce fewer young. Analysis of the rate of heat loss showed that penguins breeding at the edge of subcolonies lost heat twice as rapidly as those breeding in the interior of the subcolony. In a re-occupation experiment, evacuated center nests were re-occupied almost ten times as rapidly as edge nests. An analysis of mean fecundity in the period 1991–1996 and mean wind chill suggested that most of the variability in fecundity among years was related to differences in the rate of heat loss. Subcolonies tend to be as circular as possible, thereby decreasing the proportion of edge nests as the size of subcolony increases. Our results support the site-dependent fecundity hypothesis.     

Blue penguin (Eudyptula minor) nest distribution and breeding success on Otago Peninsula, 1992 to 1998

Abstract

Annual counts of nests with eggs or chicks (known nests) were made at blue penguin (Eudyptula minor) breeding sites on the Otago Peninsula in each November from 1994 to 1997. Although the population has doubled to an estimated 600 known nests over this period, the number of breeding sites on the Otago Peninsula has reduced since the 1970s. Breeding success at three areas at Taiaroa Head were monitored by regular nest checks in the breeding season from 1992 to 1998. At Taiaroa Head reproductive success ranged from 41 to 78% at the three sites during the seven‐year study and was generally higher for pairs nesting in nest boxes than for those in burrows. The percentage of breeding pairs that laid a second clutch after fledging at least one chick from their first clutch (double brooded) varied between seasons (0–48%) and was correlated with the date of the onset of breeding. Egg loss, possibly through predation by Norway rats (Rattus norvegicus), influenced the significantly lower reproductive success at one area (Area A) at Taiaroa Head during the 1996 season.     

BREEDING OF THE ADÉLIE PENGUIN PYGOSCELIS ADELIAE AT CAPE BIRD

Observations were made during four seasons (1967–68, 1968–69, 1969–70, 1970–71) on the breeding of Adelie Penguins at Cape Bird, Ross Island, Antarctica. Breeding data from individuals were related to date of return, laying date, clutch-size, nest location, and change of mate. Some females consistently laid near the mean date of laying, while others were consistently early or late layers. Laying date may be under direct genetic control, or may reflect feeding ability. The mean clutch-size was smaller in peripheral compared to central nests, and smallest of all in isolated nests. Clutches laid late in the season were smaller than those laid near the peak date, and small, late clutches were laid in peripheral rather than central nests. These differences may reflect age and/or feeding ability. Penguins that are better able to find food will return earlier, obtain central sites, and have larger clutches than those with a lesser ability. The two main causes of egg and chick losses were predation and parental failure. Losses were highest in single-egg clutches, at isolated and peripheral nests, and among eggs laid late in the season. These results may be partly related to the age and experience of the penguins. However, regardless of age, peripheral nesting and late laying were always disadvantageous. The sex ratio of adults in the colonies was 117♂:100♀. This may be explained by the higher mortality of females. Some males could not find partners, but females that did not breed had probably been unable to obtain sufficient food for gonad development. The return of penguins, incidence of non-breeding, adult mortality, clutch-size, and breeding success at Cape Bird were all markedly different in 1968–69 compared to the other three seasons studied. This season was marked by the persistence of sea-ice along the northwestern shores of Ross Island. The low reproductive output in 1968–69 was thought to result from a shortage of food for egg-laying and incubation.     

Effect of nest-site microclimatic conditions on nesting success in the Lesser Kestrel Falco naumanni

Capsule: Microclimatic conditions in the nests of the Lesser Kestrel Falco naumanni, particularly the percentage of time of extremely low humidity, affect breeding success.

Aim: To study the effect of within-nest temperature and humidity on nest productivity, and the correlation between nest productivity and the order of dates on which nests were occupied by the parents. To compare microclimatic conditions in the nest, breeding success and order of occupation between nests under tile roofs and in artificial nest boxes.

Methods: Three different Lesser Kestrel colonies were monitored in Israel – one rural, one urban and one in an open country habitat. Data loggers were placed in 39 nests for the entire breeding period to measure temperature and humidity. The number of fledglings was recorded for each nest, as well as the date of occupation.

Results: Full microclimatic data from 35 nests suggest that percentage of time of extremely low humidity is the major predictor of nest productivity – low humidity is negatively correlated with nest productivity. Sites of more successful nests were occupied earlier. Considering only successful nests, the urban colony had the lowest breeding success of the three colonies. There was no significant difference in mean productivity between nests in roofs and nest boxes, but nests in roofs were occupied earlier.

Conclusion: Nest microclimate, particularly low humidity, affects nesting success in addition to colony location.     

Drivers of the breeding success of American Oystercatchers (Haematopus palliatus frazari) at a critical site in Sinaloa,Mexico

Understanding breeding phenology and success can elucidate population dynamics, which is especially important for species in need of conservation. We describe the factors affecting the breeding biology of American Oystercatchers (Haematopus palliatus frazari) at El Rancho Island, a critical site that contains ~ 7% of the total estimated population, on the coast of Sinaloa, Mexico. We monitored 192 nests over four years (2016–2019). The breeding season lasted from March to June and mean laying dates differed among years, with the mean laying date in 2019 an average of 20 days earlier than in 2016. Clutch sizes decreased as the breeding season progressed. Both breeding success and productivity differed among years, with the lowest values in 2016 (30% hatching success and 0.6 chicks/nest) and the highest in 2019 (66% hatching success and 1.2 chicks/nest). Hatching success was affected by year, laying date, type of habitat, and distance to the high tide line. American Oystercatchers that laid eggs earlier in the season, used mixed marsh and dune habitat, and with nests relatively close to the waterline (< 50 m) had greater breeding success. Overall, however, the breeding success of American Oystercatchers was low and influenced by a combination of several intrinsic and extrinsic factors. Management measures may be required to increase breeding success and ensure the conservation of this subspecies.     

Effect of predation by skuas on breeding success of the Cape petrel Daption capense at Nelson Island, Antarctica

Breeding success of Cape petrels at Nelson Island (South Shetland Islands) in 1991/1992 averaged 29%. Predation by skuas accounted for 76% of all nesting failures. Direct attacks prevailed over opportunistic predation. Intensity of observer disturbance alone could not account for the inter-colony variation in predation rate, which tended to increase with colony size, presence of nearby breeding skuas and local availability of other prey species (penguins). Predation was significantly lower on nests that could be attacked only, or more easily, from the air and nests with close neighbours. Selective predation on nests in which relatively narrower eggs were laid was independent of nest-site characteristics and laying date, suggesting an effect of parental age/experience on breeding success through antipredator behaviour. Development of oil-spitting behaviour in growing chicks balanced the parental attendance and effort in nest defence, which declined as chick age increased. Increased predation on lighter but not smaller chicks may reflect the lower ability of such chicks to defend themselves by spitting stomach oil. Seasonal variations of predation rate on Cape petrel nests did not result from predator swamping by numbers of simultaneously active nests, but rather reflected temporal availability of alternative prey. Success of all phases of nesting declined with later laying date. Received: 15 December 1997 / Accepted: 11 April 1998     

Breeding biology and breeding success of the Lesser Grey Shrike Lanius minor in a stable and dense population

The Lesser Grey Shrike Lanius minor is highly endangered throughout Europe, having declined markedly in abundance and range. Long-term changes in climate and agricultural practices have been identified as the main reasons for its decline. To determine which factors influence short-term changes in breeding success, we examined several aspects of its breeding biology. Our investigation revealed that our study area bears a large and stable population of this species. In 1996 and 1997, we recorded 84 and 77 breeding pairs in an area of 20 km², with an average of 4.20 and 3.85 pairs/km² respectively. Data on breeding density, clutch size and fledging success from 1989 to 1997 (excluding 1992) indicate a stable breeding population with a constant high breeding success. Reproductive success declined through the season, mainly through seasonal variation in clutch size rather than chick mortality. However, breeding success was generally high (69% and 79% of the nests produced chicks], with low hatching failure and few nest losses. The main cause of breeding failure was nest predation (at least 50% of nest losses), mainly by magpies (at least 66% of depredated nests). Although in this population the Lesser Grey Shrike tends to aggregate in clusters, breeding density had no obvious effect on breeding success and nest predation.     

Feeding frequency influences crèching age in the Dalmatian pelican, Pelecanus crispus

Crèching behaviour is common in colonial seabirds; nevertheless, the factors inducing chicks to aggregate remain relatively poorly understood. It has been proposed that brood size, laying date and nest attendance are important factors in the formation of a crèche. Moreover, in most species of pelicans, chicks join crèches following the development of homoeothermy and coincident with the end of the brooding behaviour. We studied effects of feeding rate, nest attendance, brood size, laying date and homoeothermy on the age at which chicks entered the crèche at a colony of Dalmatian pelicans (Pelecanus crispus), in Srebarna, Bulgaria. Single chicks were fed more frequently than chicks from two-chick broods. Unlike American white pelicans (Pelecanus erythrorhynchos), Dalmatian pelicans maintained brooding behaviour a further 9 days after chicks had developed thermoregulation abilities. In contrast to nests with two chicks, nests with only one chick were never left unattended by the parents before the chick reached the crèching stage. Laying date, nest attendance and brood size did not affect the age that the chick entered the crèche. The age the chick entered the crèche was not correlated with the age of homoeothermy acquisition, but chicks significantly joined the crèche at younger ages when the mean number of feeds per chick per day during the rearing period in the nest was higher. This result suggests an implication of growth rate in the crèching age. Joining the crèche earlier can provide benefits that could have strong implications for the chicks’ future reproductive lives.     

Avian predation at a Southern Rockhopper Penguin colony on Staten Island,Argentina

We studied predation risk in relation to nest location and subcolony size in Southern Rockhopper Penguins (Eudyptes chrysocome chrysocome) during the chick-rearing period. Striated Caracaras (Phalcoboenus australis), the main predator, preferentially attacked from tussock grasses which are found in the periphery of all subcolonies (peripheral tussocks) and often scattered within them (central tussocks). The greatest numbers of predation and attempted predation events were observed on nests in the periphery of the subcolony next to peripheral tussocks, and on those nests next to central tussocks. Central tussocks offer Striated Caracaras an additional “edge” area from which to prey, much in the same way as do the peripheral tussocks. Predation rate per individual was not correlated with subcolony size possibly due to the presence of central tussocks which, by creating an extra edge area, change the subcolony shape. There is a suggestion (P = 0.06) of increased probability of nest success with subcolony size.     

DO NEST SITE CHARACTERISTICS AFFECT THE BREEDING SUCCESS OF RED BISHOPS EUPLECTES ORIX?

Summary

Ferguson, J.W.H. 1994. Do nest site characteristics affect the breeding success of Red Bishops Euplectes orix? Ostrich 65:274-280.

A colony of Red Bishop birds Euplectes orix in a reed bed near Pretoria was studied during two breeding seasons. Breeding activity was greater during the second year, following increased rainfall. Predation was the most important source of mortality with 25–30% of the nests yielding fledglings. Between 7 and 11% of the nests were parasitised by Diederik Cuckoos. Reed height and distance from the edge of the reed bed were strongly correlated with nest density. From a temporal perspective breeding success was highest in late January following the peak in breeding activity. These observations suggest that overall breeding success is higher when nest densities are low. The mean fledging rate per nest was lower in areas of high nest density. This was, however, a statistical artifact. Multivariate analyses could not identify any environmental factors as predictors of breeding success within a colony.     

Age and breeding success related to nest position in a White stork Ciconia ciconia colony

Coloniality is a breeding system that may produce benefits in terms of breeding success, although these advantages could vary according to factors such as colony size or nest position. We studied breeder's age in relation to nest position (peripheral or central) within the colony. In addition, we studied the relationship between breeding success and nest position, controlling for breeder's age, a highly correlated factor, in a White Stork Ciconia ciconia colony over a 7-year period. Our results show that central nests are mainly occupied by adult birds and had lower failure rates. However, controlling for breeder's age, nest position per se did not explain breeding success. The scarce predation and the lack of human disturbance in the study colony could explain the absence of differences in breeding success between different nest positions within the colony.     

Week-end bias at observatories

Capsule Although subject to human disturbance Turtle Doves do nest successfully in these olive and orange orchards.

Aim To investigate the breeding ecology of Turtle Doves in a man‐made agricultural habitat in central Morocco.

Methods Turtle Dove nests were monitored in orange and olive orchards over three years (2006, 2007 and 2008). Nest abundance, nest location, egg‐laying chronology, clutch size, nest survival rates and breeding success were determined and compared between orchard types.

Results The Moroccan population of Turtle Doves start breeding earlier than European populations. Clutch size, nest survival rates and breeding success were similar in orange and olive orchards. Nest location differed between orange and olive trees. Nest densities were 16 nests/ha in olive orchards and 45 nests/ha in orange orchards. Nest success rate averaged 48%. Daily nest survival rates did not vary according to orchard types, year and date. In the two orchards, no nest position variables were significant predictors of nesting success.

Conclusion Although highly frequented by people, fruit orchards seem to be suitable breeding habitats for Turtle Doves in this region.     

Causes and consequences of fine-scale breeding dispersal in a female-philopatric species

The potentially confounded effects of factors affecting breeding dispersal have rarely been simultaneously examined. The consequences of breeding dispersal are even less studied, presenting a paradox: breeding dispersal seldom seems to improve breeding success, despite its presumed adaptiveness. We studied the causes and consequences of breeding dispersal in female-philopatric eiders (Somateria mollissima) in relation to the spatiotemporal predictability of nest success. Previous nest fate, breeding experience, and breeding density simultaneously affected breeding dispersal. Dispersal distances were longer among inexperienced breeders and after failed breeding. Individual dispersal distances decreased with increasing nest-site-specific breeding density, whereas island-specific nesting success peaked at intermediate densities. The fate of neighbouring nests (‘public information’) did not influence dispersal. Breeding dispersal was unrelated to subsequent hatching success, controlling for individual quality (body condition, breeding experience, previous nest fate), while it delayed hatch date, which is likely to impair reproductive success. This delay may result from the loss of acquired information of local breeding conditions, prolonging nest prospecting and establishment, also helping explain why breeding dispersal did not increase at high breeding densities, despite a potential reduction in nesting success. In long-lived species, however, dispersal-induced reductions in reproductive output in one season could be offset by improved parental survival prospects. Careful nest prospecting may be profitable, because overall nest success had a strong island-specific component but showed weak temporal variation, and successive individual nest fates were predictable between years. Once a safe nest site is found, females may breed at the same place successfully for many years.     

Determinants of reproductive success and offspring sex in a turtle with environmental sex determination

Despite the importance of maternal effects in evolution, and knowledge of links among nest site choice, timing of nesting, offspring sex, and reproductive success in animals with environmental sex determination, these attributes have not been rigorously studied in a combined and natural context. To address this need we studied the relationships between three maternal traits (nest site choice, lay date, and nest depth) and two fitness‐related attributes of offspring (hatchling sex and embryonic survival) in the riverine turtle Carettochelys insculpta, a species with temperature‐dependent sex determination, for four years. Predation and flooding were the major sources of embryonic mortality in 191 nests. Embryonic survival was influenced by both lay date and nest site choice: in one year when nesting began later than average, nests laid later and at lower elevations were destroyed by early wet season river rises. In other years early nesting precluded flood mortality. However, turtles did not nest at the highest available elevations, and a field experiment confirmed that turtles were constrained to nest at lower elevations where they could construct a nest chamber. The principal determinant of hatchling sex in 140 nests was lay date, which in turn was apparently related to the magnitude of the previous wet season(s). Clutches laid earlier in the season (a female's first clutch) produced mainly males, while later clutches (her second clutch) yielded mostly females, due to seasonal increases in air temperatures. Accordingly, later nesting produced female‐biased hatchling sex ratios in 1996, while earlier nesting resulted in sex ratios near unity in the other years. However, all‐female nests were more likely to be flooded than mixed‐sex or all‐male nests in years when nesting was late. In conclusion, we found evidence that the position of two maternal trait distributions (elevation of the nest site and lay date), associated with the reproductive strategy of C. insculpta, reflect a combination of natural selection, physical constraints, and phenotypic plasticity. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 81 , 1–16.     

Correlates of Common Buzzard Buteo buteo density and breeding success in the West Midlands

Buzzard density and breeding success in relation to habitat and Rabbit Oryctolagus cuniculus abundance was studied in the West Midlands from 1994 to 1996. We found densities of 81 and 22 territorial pairs per 100 km² in two areas 40 km apart; the former is the highest density yet recorded in Europe. High Buzzard breeding densities were associated with high proportions of unimproved pasture and mature woodland within estimated territories. Buzzards laid earlier clutches at lower altitudes and with high proportions of unimproved pasture close to nests. Large clutches and high numbers of fledged young were associated with high Rabbit abundance close to nests. Most nest failures occurred during incubation and were probably mainly due to corvid predation. Brood reduction was associated with low proportions of deciduous woodland close to nests and small clutch sizes, although the causes of chick mortality were uncertain. Rabbits were the main prey item found at nests with passerines, especially young corvids, also appearing frequently.     

Lesser Scaup Nest Success and Duckling Survival on the Yukon Flats,Alaska

Abstract: Over the last 20 years scaup numbers have declined, and these declines have been greatest in the northern boreal forests of Canada and Alaska where most lesser scaup (Aythya affinis) nest. We studied nest success and duckling survival of lesser scaup over 3 field seasons, 2001–2003, on the Yukon Flats National Wildlife Refuge in northeastern Alaska, USA. Daily survival rate (DSR) of nests on our study area across all 3 years was 0.943 (n = 177 nests, 95% CI: 0.930–0.954), corresponding to a nest success of only 12.3%, considerably lower than published estimates of an average nest success as high as 57% for lesser scaup in the northern boreal forest. With Mayfield logistic regression, we investigated effects on nest survival of year, clutch initiation date, and nesting habitat type (large wetlands >10 ha, small wetlands <10 ha, and wooded creeks). Neither year nor clutch initiation date influenced nest survival; however, the odds of nest success on large wetlands was 49% lower than on wooded creeks (odds ratio = 0.512, 95% CI = 0.286, 0.918). Based on the model that used only habitat type for estimation, DSR on large wetlands was 0.931 (corresponding nest success = 7.6%), DSR on small wetlands was 0.941 (nest success = 11.1%), and DSR on wooded creeks was 0.963 (nest success = 26.2%). To estimate duckling survival, we monitored 10 broods (n = 75 ducklings) over 3 field seasons by radiotagging hens at nest hatch. Most duckling mortality (94%) occurred in the first 10 days after hatch. Average duckling survival during 1–10 days was 0.321 (95% CI: 0.122–0.772), during 11–20 days was 0.996 (95% CI: 0.891–1.040), and during 21–30 days was 0.923 (95% CI: 0.769–1.041). Three of 10 hens moved all or part of their broods overland between nesting and brood-rearing wetlands for distances of 0.3–1.6 km. Our estimates of lesser scaup nest success and duckling survival on the Yukon Flats were among the lowest ever reported for ducks nesting at northern latitudes, even though the study site was in pristine boreal forest. Estimating and comparing scaup demographic rates from different geographic areas can contribute to improved conservation. Given the scarcity of information on scaup nesting in the boreal forest, basic nesting parameters are important to those trying to model scaup population dynamics.