Climate fluctuation effects on breeding of blue penguins (Eudyptula minor)

Abstract

El Niño and La Niña climate perturbations alter sea currents and food availability for seabirds in many areas of the world. This changes their breeding success and mortality. Blue penguin (Eudyptula minor) breeding success is dependent upon whether one or two clutches per season are laid, and the hatching and fledging success of these clutches. This study uses six years of data from five blue penguin breeding colonies, three from Taiaroa Head, Otago Peninsula and two from Oamaru, to examine whether annual variation in breeding success correlates with El Niño/La Niña perturbations. When La Niña conditions prevailed, penguins started breeding later, and there was a lower proportion of double breeders than in El Niño and normal years. The probability of a newly hatched chick surviving to fledging was also dependent on whether large‐scale climatic conditions prevailed, whereas hatching success and overall breeding success (number of fledged chicks per breeding pair) showed no correlation with climate perturbations.     

Viral infections of little blue penguins (Eudyptula minor) along the southern coast of Australia

Serum antibodies to strains of avian paramyxovirus and flavivirus were detected in little blue penguins sampled at Port Campbell and Phillip Island, Victoria, Australia. No antibody to Newcastle disease virus (NDV) was detected in 267 sera collected, although one penguin captured for experimental studies had a hemagglutination-inhibition antibody titer of 2(4) to this virus. Experimental studies showed that the avian paramyxovirus designated APMV-IM and strain V4 of NDV were non-pathogenic for penguins, although the penguins could have been previously infected with these or similar virus strains. A flavivirus designated Saumarez reef virus, and an unnamed virus isolated from ticks on Macquarie Island, Southern Ocean were pathogenic causing disease and mortality in penguins inoculated with the viruses.     

Diet segregation between two colonies of little penguins Eudyptula minor in southeast Australia

We studied foraging segregation between two different sized colonies of little penguins Eudyptula minor with overlapping foraging areas in pre‐laying and incubation. We used stomach contents and stable isotope measurements of nitrogen (δ¹⁵N) and carbon (δ¹³C) in blood to examine differences in trophic position, prey‐size and nutritional values between the two colonies. Diet of little penguins at St Kilda (small colony) relied heavily on anchovy while at Phillip Island (large colony), the diet was more diverse and anchovies were larger than those consumed by St Kilda penguins. Higher δ¹⁵N values at St Kilda, differences in δ¹³C values and the prey composition provided further evidence of diet segregation between colonies. Penguins from each colony took anchovies from different cohorts and probably different stocks, although these sites are only 70 km apart. Differences in diet were not reflected in protein levels in the blood of penguins, suggesting that variation in prey between colonies was not related to differences in nutritional value of the diet. Anchovy is currently the only available prey to penguins throughout the year and its absence could have a negative impact on penguin food supply, particularly at St Kilda where the diet is dominated by this species. While it is difficult to establish whether diet segregation is caused by inter‐ or intra‐colony competition or spatial differences in foraging areas, we have shown that colonies with broadly overlapping foraging ranges could have significant differences in trophic position, diet composition and prey size while maintaining a diet of similar nutritional value.     

Reproductive performance of little penguins Eudyptula minor in relation to year, age, pair-bond duration, breeding date and individual quality

We measured breeding performance of little penguins Eudyptula minor at Phillip Island, Victoria, Australia, during a 21-year period. All birds considered in this paper (n=307) were of known age (2–22 y) and sex, and most were of known, or closely-estimated, pair-bond status (1–8 mates per bird; pair-bond durations 1–13 y). Breeding dates and breeding performance varied markedly from year to year; measures of annual performance were not associated with early breeding. Measures of individual breeding performance (clutch-size, hatching success, chick masses and productivity) were related to early laying, parental age, and duration of pair-bond. Dependence of breeding performance on parental age was curvilinear, levelling off at about 8 y of age. Productivity declined significantly among birds older than 8 y; this decline was not due to events in the last year of breeding ("terminal illness"). Breeding performance increased with duration of pair-bond at least through y 5. Early breeding was significantly related to age and duration of pair-bond. Most of these relationships were stronger among males than among females, and many of them were not significant when females were considered alone. After controlling for other factors, breeding performance varied significantly among birds, but autocorrelations were low and limited to intervals of one year. Parental quality (defined for birds studied in six or more years as the individual bird term in a GLM for productivity controlling for other factors) was not correlated with lifespan or other demographic parameters, but high-quality birds were less prone to change mates and burrows than low-quality birds. We know of no previous study in which simultaneous effects of laying date, age and pair-bond duration on breeding performance were measured, while controlling for year, individual quality and terminal illness.     

Acoustic properties of male advertisement and their impact on female responsiveness in little penguins Eudyptula minor

We examined the relationship between acoustic properties of male advertising calls, male body size and female responses in little penguins Eudyptula minor . Larger males produced calls of lower frequency. Playback experiments indicated that females were more likely to respond to low or medium pitched calls, than to high ones (although only 28% of females responded vocally to playback). This may reflect the interest of unmated females in large to medium sized senders as potential mates, or indicate a stronger territorial response to large intruders.     

Stable isotope analysis as a tool to monitor dietary trends in little penguins Eudyptula minor

Long‐term dietary monitoring of seabirds can be used to relate population fluctuations to at‐sea events. Stomach flushing is a conventional dietary monitoring technique, but has a number of disadvantages. Stable isotope analysis (SIA) is a less invasive method that provides unbiased dietary information over a longer period. We evaluated stable isotope analysis as a potential tool for monitoring long‐term little penguin Eudyptula minor diet. We determined diet composition during the chick feeding stage using stomach flushing and SIA at three separate colonies, using spatial variation in diet as a surrogate for potential temporal variation. Bayesian isotopic mixing models were generated for blood and feathers to evaluate their ability to discriminate broad‐scale (fish, squid, crustaceans) and fine‐scale (individual prey species) diet composition. Differences in stable carbon and nitrogen isotope ratios were found between colonies: broad‐scale isotopic mixing models predicted different proportional contributions of broad taxa (fish, cephalopod, crustacean) to diet than was indicated by stomach samples, reflecting the bias incurred by one‐off stomach contents analysis. Fine‐scale isotopic mixing models predicted proportional contributions of prey items with less certainty. Blood isotopic mixing models had narrower confidence intervals than models for feathers, but trends in δ¹⁵N for feathers mirrored those for blood. Our results suggest that relying on stomach contents analysis to detect shifts in prey consumption in little penguins could be very misleading, resulting in a less‐than‐complete idea of total prey consumption. SIA of little penguin tissues could be used to monitor dietary shifts across dissimilar taxa that may affect population numbers, but would fail to detect shifts between fish species.     

Increased survival and breeding performance of double breeders in little penguins Eudyptula minor,New Zealand: evidence for individual bird quality?

The little penguin Eudyptula minor is unique among penguin species in being able to fledge chicks from two clutches in one breeding season. Pairs laying two clutches in a given season make a higher reproductive investment, and may be rewarded by a higher reproductive success as they may raise twice as many chicks as pairs laying one clutch. The higher effort made by pairs laying two clutches could correlate negatively with survival, future reproductive performance or offspring survival, indicating a cost of reproduction. Conversely, a positive relationship between the number of clutches produced in a given breeding season and survival, future reproductive performance or offspring survival would indicate that birds laying two clutches belonged to a category of birds with higher fitness, compared to birds laying only one clutch in the season. In this study we used a long‐term data set taken from an increasing population of little penguins in Otago, SE New Zealand. We modelled the relationship between the number of clutches laid in a breeding season and survival probability, reproductive performance in the next breeding season and first year survival of offspring using capture‐recapture modelling.
Birds laying two clutches produced 1.7 times more fledglings during a breeding season than pairs laying one clutch. We found that birds laying two clutches had a higher probability of breeding in the following breeding season, a higher probability of laying two clutches in the following breeding season and a higher survival probability. There was no overall difference in post‐fledging survival between the young of birds producing one clutch and the young of birds producing two clutches. However, the survival of young of single clutch breeders declined with laying date, whereas the young of double clutch breeders had the same survival rate irrespective of laying date. For a subset of data with birds of known age, we found evidence that the probability of laying two clutches increased with age. However, there were also indications for differences among birds in the tendency to lay two clutches that could not be attributed to age. We tentatively interpret our results as evidence of quality difference among little penguin breeders.     

Comparison of barometric and pneumotachographic measurements of resting ventilation in the little penguin (Eudyptula minor)

1. We compared the use of the barometric method and pneumotachography for measurement of ventilation in the little penguin Eudyptula minor. 2. Simultaneous use of both techniques showed the barometric method to give a reliable estimate of tidal volume. 3. Comparison of birds with and without masks for pneumotachography showed wearing masks to produce a significant increase in ventilation, principally through a raised respiratory frequency.     

Foraging behaviour of the little penguin, Eudyptula minor: initial results and assessment of instrument effect

We investigated the foraging behaviour of little penguins using a new archival electronic activity recorder which simultaneously measures speed and depth against time. We present the first integrated data of foraging behaviour of two little penguins, from which we were able to distinguish between several types of travelling and foraging behaviours. The little penguins foraged mainly within 15 m of the surface and travelled at speeds between 8 and 9 km h^-1. Using attachments ranging between 1.4 and 11.8% penguin cross-sectional area (0.1 and 6% penguin mass), and isotopic water, we also assessed the effects of carrying devices while foraging. Both water influx and metabolic rates were significantly lower in penguins carrying devices, compared to penguins foraging without devices attached. Even the relatively small attachments resulted in a decreased foraging efficiency and we suggest that there is no simple or fixed relationship between size of device and the effect on the bearer.     

Few genetic differences between Victorian and Western Australian blue penguins,Eudyptula minor

Abstract

Blue penguins, Eudyptula minor, breeding on Penguin Island, Western Australia are considerably larger than other blue penguins in Australia. If genetic isolation is the cause, it may have implications for the conservation status of some blue penguin populations. We compared the sequences of two mitochondrial gene regions (cytochrome‐b and the control region) from Western Australian blue penguins with other populations of blue penguins from Australia and New Zealand. We found few differences between sequences from Western Australia, Phillip Island, Victoria and Otago, New Zealand, although all three differed considerably from other New Zealand blue penguins. Sequences for the control region from the Western Australian blue penguins and 30 more birds breeding at various Australasian sites provided further support for two major clades within Eudyptula; an Australian clade (including Otago) and a New Zealand clade.     

Sex-biased disruptive behaviour in breeding crested penguins

Colonial breeding is common in seabirds, and may provide individuals with benefits such as increased protection from predators by joint defence, improved information exchange and enhanced access to mates. However, the presence of large numbers of individuals in breeding colonies may also lead to interference, especially where conspecific behaviour disrupts the normal chick-rearing routine. Using standardised video recordings, we describe and quantify for the first time such disruptive behaviour by conspecifics in penguins. This disruptive behaviour appeared to be common in chick-feeding Southern rockhopper penguins Eudyptes chrysocome and its occurrence did not differ significantly among the colony areas where observations were made. Females were commonly (77 % of 111 observation sessions) disrupted by other adults when attempting to feed chicks alone during the crèche stage. They consequently reduced the time spent with their chicks. Disrupted chicks compensated by begging more intensely when their female parents were present, and they did not eat significantly less often than undisrupted chicks. In contrast, disruptive behaviour towards chick-feeding males or pairs was never observed. This study supplements knowledge about a disruptive behaviour that appears to be common but for which the function remains unclear in penguins, as the intruders did not appear to gain any visible benefits.     

Gastrointestinal helminths of little blue penguins,Eudyptula novaehollandiae (Stephens), from Otago,New Zealand

Data regarding helminth communities can provide insights into health, feeding interactions, behaviour and evolution of their host organisms. Penguins (Spheniscidae) are important components of marine food webs and tracking their helminth communities can be indicative of ecosystem health. New Zealand is home to 5 of the world's 19 penguin species and little is known about their gastrointestinal helminths. Here, we provide the first study on the gastrointestinal helminths of little blue penguins from south-eastern South Island, New Zealand. The helminth community consisted of two species of tapeworm; Tetrabothrius lutzi and Tetrabothrius sp.; three nematode species, Contracaecum eudyptulae, Capillaria sp. and Stegophorus macronectes; two acanthocephalans, Andracantha sigma and Bolbosoma balaenae; and one trematode, Galactosomum otepotiense. The most prevalent parasites were T. lutzi, A. sigma, and C. eudyptulae. This work includes three new host records and five new geographic records. This is the first report of B. balaenae occurring in a host other than a marine mammal. This study adds to our knowledge about the helminth community of New Zealand little blue penguins, and includes new genetic data on helminth species, providing a baseline against which future studies may be compared.     

Haematology and metabolism of the blood of the little penguin, Eudyptula minor

1. We studied the haematology of the little penguin, Eudyptula minor, and measured red cell enzymes, and the rate of O2 and glucose consumption and CO2 and lactate production of whole penguin blood. 2. Little penguins have a very low RBC count (1.66 x 10(12) l-1) and very large red cells (MCV = 229 microns 3), resulting in a normal haemoglobin and haematocrit. 3. Despite the lower body temperature of penguins, the rate of O2 consumption by whole blood is close to that predicted from studies on other birds.     

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.     

Diving patterns of female macaroni penguins breeding on Marion Island, South Africa

Despite the large biomass of macaroni penguins Eudyptes chrysolophus in the Southern Ocean, their feeding ecology is poorly known at some important breeding localities. We investigated the diving behaviour and diet of female macaroni penguins feeding small chicks on Marion Island (46o52′S, 37o5′E), South Africa, one of the species’ most northerly breeding sites, supporting 4% of their global population. We then compared our results with similar studies from other localities. In December 2008, we collected information on 12 foraging trips from 6 individuals using time-depth recorders, as well as diet from 42 individuals. Median trip duration was 22.8 h (5.6–80.8 h). Penguins performed 42.8 ± 15.9 dives per hour at sea, with dive depths averaging 24.6 ± 8.6 m and lasting 40.8 ± 12.1 s, although 74.3% of dives were <10 m. Euphasids dominated their diet (86% by mass), mainly Thysanoessa vicina. A second peak in dive depths at 55–80 m might reflect the 12% of fish in their diet. The substantial proportion of shallow night dives (30% of total dives) suggests some foraging occurs at night. Differences in diving patterns of individual macaroni penguins in this study confirmed the behavioural flexibility of these birds reported from other breeding localities. However, most other studies assumed that dives <3–5 m were commuting dives whereas our study suggests that at least some prey are caught during shallow dives. We highlight how different analytical methods can change the outcome of studies. Despite macaroni penguins’ apparent flexibility in foraging behaviour during the breeding season, their numbers are decreasing globally. Further investigations of their foraging behaviour are needed to assess potential competition with other predators and krill fisheries.     

The foraging behaviour of Little Penguins Eudyptula minor at different light levels

The role of vision in the prey-catching behaviour of Little Penguins Eudyptula minor was tested using four captive penguins in a swimming pool. A live fish was placed in the pool with a penguin at various light intensities before and after dawn and dusk. The penguins' behaviour in the morning was the same as in the evening. As the light decreased, the percentage of fish chased by the penguins decreased, and no fish were caught at a light level less than 0.01 μeinstein/m²/s (which occurs approximately 25 min before sunrise and after sunset at latitude 37̀S). The time the penguins spent searching for the fish also decreased with decreasing light. The probability of a penguin pursuing a fish was found to be dependent on the amount of light, such that log,( p /1 - p ) = 6.323 + 2.08 × log,(light level), where p = the probability of pursuing a fish.     

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.