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.     

Influence of environmental variability on breeding effort in a long-lived seabird, the yellow-nosed albatross

The provisioning parameters, breeding success, adult mass, andsurvival of yellow-nosed albatrosses were studied over 7 successiveyears at Amsterdam Island, southern Indian Ocean. We examinedthe ability of this long-lived seabird to adjust its breedingeffort under different environmental conditions and the fitnessconsequences in terms of survival and quality of offspring produced. Provisioning rate and adult mass varied extensivelybetween years, and the lowest and highest values were associatedwith sea surface temperature anomalies. When waters aroundthe island were colder, adults were in good condition and broughtlarge meals at short intervals, whereas warmer waters resultedin lower provisioning rates, lower adult mass, and lighter chicksat fledging. Adult survival and fledging success were not affectedby sea surface temperature anomalies. Yellow-nosed albatrossesappear to be unable to adjust their breeding effort every season,and their differential breeding investment probably primarilyreflects different levels of food availability. Yellow-nosedalbatrosses are able to regulate their provisioning behavior according to the nutritional status of their chick only whenconditions are favorable. Birds appear to invest primarilyin their own future maintenance rather than in provisioning.They have a wide safety margin in body mass that limits mortalityrisks during good years as well as during poor years. However,during unfavorable seasons adults continue to provision chicksthat have a poor prospect of survival to breeding, withoutadditional survival costs for the parents. Favorable seasonstherefore have a high value in terms of fitness because ofthe high quality of the chick produced. We suggest that understandinghow long-lived animals optimize their provisioning behaviorand lifetime reproduction can only be achieved through studiesencompassing several contrasted seasons.     

Cladistic analysis of cassiduloid echinoids: trying to see the phylogeny for the trees

Using DNA fingerprinting we estimated the reproductive success of 49 adult birds belonging to 16 breeding groups of the sexually monomorphic brown skua (Calharacta lonnbergi) from the Chatham Islands (New Zealand). This population has a variable mating system, breeding in both monogamous and polyandrous groups. The parentage of 45 chicks produced over three breeding seasons was unequivocally determined using the multilocus probes 33.15 and 33.6. We found no evidence of either extra-pair or extra-group fertilization and there was no evidence to suggest egg dumping by females in any breeding group. Consequently, in the case of pairs, parentage of all chicks was assigned to the resident adult birds. In addition, band sharing analysis indicated that members of communal groups were not close relatives. In the 10 communally breeding groups examined, multiple paternity within a clutch was recorded on two of the 12 occasions in which two chicks were reared. Analysis of the parentage of offspring belonging to different groups, from different years, demonstrated that the number of chicks produced by some adult males varied considerably between seasons. In contrast, the reproductive success of other individuals was constant; for example, one male produced two chicks in each of the three seasons it was studied, while other males in communal groups did not produce any chicks during the course of this study. Fitness is a lifetime parameter, and any assessment of it requires studies over at least the average lifetime of an individual. The findings presented in this study suggest that, for brown skuas, there are significant differences in the reproductive success of some adult males in different breeding seasons. These results indicate that estimates of reproductive fitness based on only a single breeding season's data can be seriously inaccurate. Should temporal changes in paternity (and/or maternity) be shown to be common phenomena in other species, then such results would have major implications for the interpretation of parentage studies.     

Effects of predation and weather on the breeding success of Avocets Recurvirostra avosetta

We investigated breeding success of Avocets Recurvirostra avosetta on the Wadden Sea coast of Schleswig-Holstein, Germany, during the years 1988–1997. Annual variations in hatching success were mainly determined by the presence of Red Foxes Vulpes vulpes in an embanked part of the study site and by the occurrence of storm tides on the saltmarshes. Hatching success did not correlate with the population size of avian egg predators. Annual chick survival rates were positively associated with June temperatures. The influence of predators on chick survival rates was not detectable. Annual breeding success (number of fledglings per number of breeding pairs) was significantly correlated with June temperature and chick survival, but not with hatching success.     

Maternal androgens in eggs of communally breeding guira cuckoos (Guira guira)

Variation of maternal androgens in avian eggs may be a mechanism of maternal influence on offspring development, growth, and/or behavior. We studied yolk androgen concentrations in eggs of guira cuckoos (Guira guira) to understand how females might enhance the success of offspring in a complex communal breeding system. We measured concentrations of androstenedione, 5alpha-dihydrotestosterone, and testosterone in yolks and identified eggs and clutches of individuals in joint nests by yolk protein electrophoresis. Androstenedione had the highest yolk concentration, at least 10 times higher than that of testosterone and 5alpha-dihydrotestosterone. The first eggs of individual females that laid two or three eggs in a joint nest had lower androstenedione concentrations than their second and third eggs, the latter having a lower probability of being ejected from the nest. This implies that guira cuckoo females may influence offspring survival and competitiveness in communal nests by means of differential allocation of androstenedione and laying tactics. There was significant variation in yolk androstenedione among females, but the order in which females entered laying in the communal clutch had no effect on the concentrations. Androstenedione yolk concentrations increased with communal clutch size, which may indicate that higher levels of competition in larger groups lead to higher yolk androgen concentrations. Finally, androstenedione concentrations were higher in clutches in the later wetter periods of the rainy season than during the earlier drier period. This may be explained by the high frequency of large clutches in the later periods, with more females contributing to a joint clutch.     

Reproductive success and helper effects in the cooperatively breeding grey-crowned babbler

Cooperative breeding, where some individuals help to raise offspring that are not their own, is a relatively rare social system in birds. We studied the breeding biology of a declining cooperative breeder, the grey-crowned babbler Pomatostomus temporalis , with the aim of isolating the social factors that affect its reproductive success. Most breeding pairs were assisted by philopatric offspring, although pairs could breed successfully without helpers. Females laid up to four clutches (usually three eggs per clutch) per season. Male (but not female) helpers increased the number of young fledged from individual nests and the likelihood of re-nesting, resulting in higher seasonal fledgling production. Helper effects on brood size and fledgling production were greater in the second year of the study, which was also characterized by higher nest failure. This suggests that helpers enhance reproduction more in poor conditions. Our study demonstrates the interacting effects of social and ecological factors on reproductive success, and that retention of offspring is not always beneficial for the breeders in cooperative species.     

The timing of breeding and offspring size in Great Tits Parus major

The relationship between the timing of breeding, offspring weight and offspring recruitment was investigated in two populations of Great Tits Parus major. In two of six seasons a significant negative correlation was found between laying date and fledgling weight, in three seasons the opposite was true and in one season no significant correlation existed between these variables. Offspring recruitment was quantified in five seasons, and late-nesting birds were found to produce significantly fewer recruiting offspring in two of these, the same two seasons when late fledglings had significantly lower weights. No significant correlation existed between the number of recruits and laying date in the three seasons when late fledglings were as heavy as or heavier than early fledglings. The potential detriment to reproductive success of lateness thus was offset when late-nesting parents managed to produce heavy young. Between-year variations in the seasonal pattern of reproductive success has previously been suggested to contribute to the maintenance of variability in the timing of breeding in Great Tits. In this paper we suggest that producing heavy offspring late in the season might be a proximate factor influencing the seasonal patterns of reproductive success. Producing heavy offspring late in the season is probably not a "strategy" but rather an effect of chance differences between years in the seasonal availability of food or the seasonality of other factors important for the nesting birds.     

Differential maternal investment counteracts for late breeding in magpies Pica pica: an experimental study

Reproductive success in many avian populations declines throughout the breeding season. Two hypotheses have gained attention to explain such a decline: the "timing" hypothesis proposes that deteriorating food availability causes the decline in reproductive success (causal effect of breeding time), whereas the "quality" hypothesis proposes that individuals of lower phenotypic quality reproduce at the end of the breeding season, causing the correlation between breeding time and breeding success. We tested both of these hypotheses in a monogamous single breeder, the magpie Pica pica , by experimentally inducing some pairs to lay a replacement clutch, after removal of the first clutch. The first clutch was left in the nest of another magpie pair (matched by laying date and clutch size), and incubated and raised by these foster parents. In this way we obtained two clutches from the same magpie pair with full siblings raised in conditions of the first and second reproductive attempts. High quality pairs (with laying dates in the first half of the breeding season) reached similar breeding success in replacement clutches as compared to first clutches of the same female. In addition, experimental pairs reared significantly more offspring of similar quality in their replacement clutches as compared to late-season first clutches, thereby suggesting that late season first clutches were produced by pairs of lower phenotypic quality. Results indicate that high quality pairs trade-off clutch size for larger eggs in replacement clutches, which could help magpie pairs to partly compensate for poorer environmental conditions associated with a delayed breeding attempt.     

Effect of polygyny on female reproductive success in the mandarin vole, <Emphasis Type="Italic">Microtus mandarinus</Emphasis> (Rodentia,Arvicolinae)

Indices of reproductive success were compared in monogamous and polygynous groups (MGs and PGs) of female mandarin voles kept under different laboratory conditions: in small cages, with frequent handling disturbance (30 MGs and 15 PGs), and in large glass tunnel systems, without disturbance (20 MGs and 16 PGs). MGs consisted of unrelated male-female pairs, and PGs consisted of two female sibs and an unrelated male each. No reproductive skew was observed within PGs; moreover, there was a positive correlation between the sibling females in the presence/absence of offspring, its total size, and the number of litters produced over 90 days. Regardless of keeping conditions, the proportion of parous females recorded over 45 days and the number of successfully reared offspring per female were greater in MGs than in PGs. Among groups kept in cages, reproductive success in PGs was lower because of a delay in breeding, reduced size of the first litter, and increased pup mortality during the first days of life. Observations on voles in tunnel systems were performed to quantify aggressive interactions and reveal the causes of pup mortality. In general, the level of aggression in both types of groups was low, but the frequency of female-female conflicts in PGs drastically increased during several days before and after the birth of the litter. Nevertheless, the sibling females in PGs used the common breeding nest and regularly fed reach other’s offspring. The causes of high pup mortality in PGs and probable advantages of communal breeding in mandarin voles are discussed.     

The social system of the Pale Chanting Goshawk Melierax canorus; monogamy v polyandry and delayed dispersal

The social organization and reproductive strategy of the Pale Chanting Goshawk Melierax canorus were investigated in four southern African study areas. Territories supporting adults additional to the breeding pair were observed in two study areas. Within one of these areas, these additional adults were either non-breeders staying in their natal territory but actively excluded from the nesting area during the breeding season or a male cobreeder participating fully in reproductive activities with the breeding pair. Polyandrous trios were, however, observed in only one vegetation type in this area, Broken Veld. The annual number of offspring fledged per group did not differ significantly between vegetation types nor between polyandrous trios and monogamous pairs within Broken Veld. Pale Chanting Goshawks lay predominantly two-egg clutches. In 2 out of 5 years, breeding groups succeeded in laying, hatching and even fledging a second brood of young after successfully fledging their first brood. Double brooding occurred more frequently in Broken Veld and most frequently in polyandrous trios in this vegetation type. To accommodate their relatively long breeding cycle (>115 days) in this temperate study area with its limiting summer breeding period, double-brooding Pale Chanting Goshawks laid the first clutch in midwinter and the second, on average, 24 days after the offspring from the first brood left the nest.     

Parental Investment Theory and Nest Defence by Imperial Shags: Effects of Offspring Number,Offspring Age,Laying Date and Parent Sex

Nest defence is a common form of parental care employed by birds to improve the survival of their offspring. Theory predicts that parents should adjust their nest defence according to the value of the brood at stake, defending more intensively broods with high survival and reproductive prospects. We evaluated the influence of offspring number, offspring age, laying date and parent sex on nest‐defence intensity (NDI) of the Imperial Shag Phalacrocorax atriceps, a sexually dimorphic seabird with seasonal decline in offspring survival and very limited renesting potential. We also evaluated whether NDI was correlated within pairs and whether NDI of both members of the pair was correlated with incubation and breeding success. To elicit defensive behaviour, we simulated predation attempts using a Kelp Gull Larus dominicanus model. As predicted by theory, NDI was positively correlated with the number of offspring in the nest and offspring age. NDI during chick rearing was higher than that at early and late incubation, while no differences were found between incubation stages. Contrary to our prediction, we did not find differences in NDI according to laying date. NDI for males was higher than females, while NDI was also positively correlated within pairs. NDI was not statistically related to incubation or breeding success. These results suggest that other factors, such as laying date or parental quality and age, play a much larger role in determining the outcome and productivity of a nesting attempt. Our results provide partial support for parental investment theory; while parental defence increased with brood value according to offspring number and age, parental defence was not related to laying date, a factor strongly affecting offspring survival and recruitment probabilities in this species.     

Responses of breeding common loons to human activity in upper Michigan

Breeding populations of the common loon (Gavia immer) in Michigan have declined in the past several decades, resulting in classification of this species as threatened under state law. Factors responsible for the decline are unknown, but may include toxic contaminants, mortality in commercial fish nets, and human disturbance of breeding sites. To assess the latter possibility, 960 hours of observation were devoted to observing human-loon interactions on two sets of lakes, one with restricted human use (minimal or no shoreline development and open to canoe use only), and another with unrestricted use (varying amounts of shoreline development and motorboat traffic). Six mated pairs of loons on six restricted use (r-u) lakes were compared to eight loon pairs on seven open-use (o-u) lakes. The number of nests that hatched young per nest started was not significantly different between the two sets of lakes (7 of 13 (0.62) on r-u lakes vs 8 of 17 (0.47) on o-u lakes), despite significantly more human activity on o-u lakes. Chicks hatched per pair of loons were likewise not significantly different (1.1 vs 1.2 on r-u and o-u lakes, respectively). Fledging success was significantly lower on r-u lakes (7 chicks fledged of 11 hatched) than on o-u lakes (13 fledged of 13 hatched). Human activity on o-u lakes was 2–3 times that on r-u lakes during chick rearing, but time spent by adult loons tending and feeding chicks was not significantly different between the two types of lakes. The larger size of most o-u lakes may have allowed loons a greater opportunity to avoid human disturbance. Higher levels of human activity did not affect production of chicks by loons under the conditions observed, but these results should not be extrapolated to lakes experiencing much higher human use.     

Extrapair paternity in the Hoopoe Upupa epops: an exploration of the influence of interactions between breeding pairs, non-pair males and strophe length

Previous studies of the Hoopoe Upupa epops have shown that the strophe length of male songs influences female mate choice, and is correlated with female reproductive rates and male production of fledglings in the male’s own brood. However, frequent interactions between breeding pairs and non‐pair males suggests that extrapair copulations could occur and could affect the real number of fledglings sired by males, and therefore the relationship between strophe length and breeding success. Here we analyse the incidence of interactions between breeding pairs and non‐pair males, and of extrapair paternity, the interrelation of these parameters, the influence of male strophe length on them, and whether extrapair fertilizations affect the correlation between strophe length and breeding success of males, in a colour‐ringed population of Hoopoes in south‐eastern Spain. Multilocus DNA‐fingerprinting revealed that 10% of the broods contained offspring sired by extrapair males, representing 7.7% of the chicks. However, the interactions between pairs and non‐pair males were more frequent, with more than 25% of broods being visited by non‐pair males, and about 10% being helped (fed or defended) by males other than the nest owner. Most of these relationships were apparently attempts by visitor males to obtain copulations with paired females, or to obtain access to such females or nests in future breeding attempts. However, there was no significant link between the detection of interactions with alien males in a nest and the occurrence of extrapair paternity in it, indeed extrapair paternity was found in only 30% of the nests with interactions, and therefore the detection of visits or helping by non‐pair males cannot be considered evidence of extrapair paternity in visited or helped broods. Males that sang with long strophes never suffered losses of paternity within their broods, while 25% of males that sang with short strophes did. However, these differences were not significant. Nevertheless, strophe length of males was significantly positively correlated with per brood and seasonal production of fledglings after accounting for losses of paternity within their own broods.     

Habitat preference, breeding success and the effect of primary productivity on Tawny Eagles Aquila rapax in the tropics

Breeding success of 176 Tawny Eagle pairs nesting on basalt (4724 km²– 92 pairs) and kalahari sand (9876 km²– 84 pairs) was monitored from 1973 to 1984 in Hwange National Park, Zimbabwe. Flat-topped trees were preferred for nesting but kalahari sand pairs used round-crowned trees more often, probably due to tree availability. Mean inter-nest distances on both biomes were significantly different (3–5 km on basalt, 59 km on kalahari sand). Clutch size and frequency of one-egg clutches in both biomes were similar and many more one-egg clutches were laid in the drier period of the study (1979–1984). There was no correlation between laying date and breeding success. More basalt pairs laid synchronously, probably due to the smaller inter-nest distances. Breeding success in both biomes was similar and significantly more chicks were reared during 1973–1978 than during 1979–1984 (wet and dry periods, respectively). Some districts produced more chicks than others, suggesting good and marginal areas within both biomes. The greater inter-nest distances and ability to breed successfully in round-crowned trees by kalahari sand Tawny Eagles resulted in a similar number of chicks reared per breeding attempt as basalt pairs, in spite of the lower primary production of the sand area.     

Pair bond and breeding success in Blue Tits Parus caeruleus and Great Tits Parus major

Data from 939 nests of the Blue Tit Parus caeruleus and 1008 nests of the Great Tit P. major from nestboxes provided in superabundance in mixed forest study sites between 1976 and 2001 were analysed to examine the effects of mate retention on breeding success and the relationship between mate fidelity and site fidelity. Most birds retained their former partner (76% in Great Tits and 65% in Blue Tits). The probability of a pair divorcing was affected by male age in Great Tits, divorce being more likely in pairs with first‐year males. Great Tit pairs breeding together for a second season bred earlier, but had no higher breeding success than pairs breeding together for the first time. In Blue Tits laying date and start of incubation tended to be earlier in pairs breeding together for a second season, but hatching and fledging dates were not earlier than in other pairs. Great Tit pairs breeding together for two consecutive seasons bred earlier in the second season than in the first, but breeding success did not differ significantly between years. In both species, breeding performance did not differ between pairs that divorced after a season and pairs that stayed together. Thus breeding success did not determine whether a pair divorced or bred together again. Neither Blue Tits nor Great Tits improved their breeding performance through divorce. Blue Tit females even had fewer fledglings in the year after divorce than in the year before. Mate retention affected breeding site fidelity. Blue Tit females had greater breeding dispersal distances between consecutive years when re‐mating than when breeding again with the same mate. In Great Tits both males and females dispersed more when re‐mating than when retaining the former partner, suggesting that mate retention increased the chance of retaining the breeding site. In both species, breeding dispersal distances did not differ between pairs that divorced and pairs in which one mate disappeared. Because no major advantage of mate retention was evident, we suggest that mate retention evolved under different conditions than those found in study sites with high breeding densities and a superabundance of artificial nesting sites.     

Effects of housing density on nasal pathology of breeding mice housed in individually ventilated cages

The 2011 edition of the Guide for the Care and Use of Laboratory Animals includes new recommendations for the amount of floor space that should be provided to breeding mice. When pairs or trios of continuously breeding mice are housed in shoebox cages, they may have less than this recommended amount of floor space. High housing densities may adversely affect animal health, for example, by compromising air quality inside the cage. Hence, some institutions are carefully reevaluating the microenvironments of breeding cages. The use of individually ventilated cages (IVCs) to house research mice allows for greater control over the quality of the cage microenvironment. The authors evaluated the microenvironments of shoebox cages in an IVC rack system housing breeding and non-breeding Swiss Webster mice. Ammonia concentrations were significantly higher in cages housing breeding trios with two litters. Histopathologic lesions attributable to inhaled irritants such as ammonia were found in mice housed in breeding pairs and trios. The authors conclude that the microenvironments of cages in an IVC rack system housing breeding pairs and trios may be detrimental to animal health.     

Effects of a trawling moratorium on the breeding success of the Yellow-legged Gull Larus cachinnans

The establishment of a two month commercial fishing moratorium, which overlapped each year with different stages of the breeding cycle of the Yellow-legged Gull Larus cachinnans at the Ebro Delta, Spain, provided the opportunity of testing the effects of food limitation on the breeding success of this species. The study was carried out in 1993, when the chick rearing stage occurred with normal commercial fishing activity and in 1994, when the chick rearing stage overlapped with the trawling moratorium. We recorded diet of the chicks, breeding phenology, clutch size, egg volume, hatching success and productivity of adult birds. There was a highly significant difference in the diet of the chicks between the two years and significantly lower productivity in 1994, whilst the other parameters examined did not change. These results show that a dependence on discards from commercial fishing activities may be a limiting factor in the breeding success of this seabird.     

Optimal conditions for breeding of captive humboldt penguins (Spheniscus humboldti): A survey of British zoos

We surveyed 16 British zoos and bird gardens to assess the optimal conditions for breeding of captive Humboldt penguins (Spheniscus humboldti). We obtained information on population, enclosure, and husbandry characteristics and related these variables to three measures of per capita breeding success, namely, per capita egg productivity, chick productivity, and hatching success (measured as the proportion of eggs laid that hatched). All three fitness measures increased with an increasing number of breeding pairs and total population size but were not related to population density. Once the effect of number of breeding pairs was removed statistically, chick productivity was found to be highest when nesting boxes were lined with sand and gravel instead of alternative substrata such as twigs or vegetation. Hatching success increased with increasing pool size and was highest in enclosures with concrete floors. Adult mortality in zoos was generally low and appeared related to the use of chlorine in freshwater pools and to the presence of other penguin species in Humboldt penguin displays. Several enclosure and husbandry parameters were not variable enough to assess their impact on reproduction of captive Humboldt penguins. Recommendations for optimising conditions for captive breeding of Humboldt penguins include keeping as large a population as possible in a concrete enclosure with a large pool area, while providing sand and gravel as nesting material. Bird density may be important but we did not detect detrimental effects on breeding for densities up to 0.25 birds m^–2. Adult mortality can be minimised by exhibiting Humboldt penguins in single‐species display and avoiding chlorination of pool water. An experimental approach is recommended to confirm the results of this correlational study. Zoo Biol 20:545–555, 2001. © 2002 Wiley‐Liss, Inc.     

Investigator disturbance reduces reproductive success in Short‐tailed Shearwaters Puffinus tenuirostris

Research procedures can have a detrimental effect on the reproductive success of the study species. In this study, the frequency of investigator disturbance on Short‐tailed Shearwaters Puffinus tenuirostris was examined experimentally throughout the incubation period to assess whether disturbance influences hatching success, pre‐fledging chick survival and chick body size. Handling of incubating birds every day, every 3 days and once a week reduced hatching success by 100, 61 and 39%, respectively, compared with pairs that were not disturbed. Most failures resulted from egg abandonment by the parents, particularly during the early stage of incubation. Chick survival did not differ between treatment groups, but control chicks were significantly heavier and had larger bill depths and longer wings. The difference in chick body mass and size observed between the control and disturbed chicks might be due to physiological or behavioural mechanisms in adults or carry‐over effects from the incubation stage to the next life‐history stage. Reduced offspring quality has the potential to affect post‐fledging survival and recruitment. These findings are significant in broader terms because any investigator disturbance that reduces reproductive success, survival and offspring fitness could interfere with the accurate assessment of demographic parameters and exacerbate population declines.     

The effect of parental age,experience and historical reproductive success on wandering albatross (Diomedea exulans) chick growth and survival

Growth and survival of altricial young are influenced by their parents’ abilities to invest in a breeding attempt. As a result, chick growth and survival in one breeding season may be indicative of their parents’ long-term reproductive potential. To determine whether variation in long-term reproductive success is driven by differential breeding investment, parental care and chick growth in wandering albatrosses (Diomedea exulans) were correlated with parental historical reproductive success. Effects of age and breeding experience (determined from past breeding attempts) and pre-laying body condition (mass–size indices) on chick growth and survival also were tested. Longer brooding of chicks increased their survival, but length of chick brooding did not differ between historically unproductive and successful breeders. Past reproductive success also was not correlated with chick growth rates or fledging mass or size. Chick brooding period, chick growth rates, final mass and size were independent of parental body condition. Older and more experienced parents brooded chicks for longer and their chicks grew faster, supporting previous findings that breeding competence is a learnt skill. Chick care and growth characteristics differed more between than within pairs, suggesting that differences in these characteristics are driven by variation among pairs.