Genetic drift outweighs balancing selection in shaping post-bottleneck major histocompatibility complex variation in New Zealand robins (Petroicidae)

The Chatham Island black robin, Petroica traversi, is a highly inbred, endangered passerine with extremely low levels of variation at hypervariable neutral DNA markers. In this study we investigated variation in major histocompatibility complex (MHC) class II genes in both the black robin and its nonendangered relative, the South Island robin Petroica australis australis. Previous studies have shown that Petroica have at least four expressed class II B MHC genes. In this study, the sequences of introns flanking exon 2 of these loci were characterized to design primers for peptide-binding region (PBR) sequence analysis. Intron sequences were comprised of varying numbers of repeated units, with highly conserved regions immediately flanking exon 2. Polymerase chain reaction primers designed to this region amplified three or four sequences per black robin individual, and eight to 14 sequences per South Island robin individual. MHC genes are fitness-related genes thought to be under balancing selection, so they may be more likely to retain variation in bottlenecked populations. To test this, we compared MHC variation in the black robin with artificially bottlenecked populations of South Island robin, and with their respective source populations, using restriction fragment length polymorphism analyses and DNA sequencing of the PBR. Our results indicate that the black robin is monomorphic at class II B MHC loci, while both source and bottlenecked populations of South Island robin have retained moderate levels of variation. Comparison of MHC variation with minisatellite DNA variation indicates that genetic drift outweighs balancing selection in determining MHC diversity in the bottlenecked populations. However, balancing selection appears to influence MHC diversity over evolutionary timescales, and the effects of gene conversion are evident.     

Gene duplication and gene conversion in class II MHC genes of New Zealand robins (Petroicidae)

In contrast to mammals, the evolution of MHC genes in birds appears to be characterized by high rates of gene duplication and concerted evolution. To further our understanding of the evolution of passerine MHC genes, we have isolated class II B sequences from two species of New Zealand robins, the South Island robin (Petroica australis australis), and the endangered Chatham Island black robin (Petroica traversi). Using an RT-PCR based approach we isolated four transcribed class II B MHC sequences from the black robin, and eight sequences from the South Island robin. RFLP analysis indicated that all class II B loci were contained within a single linkage group. Analysis of 3-untranslated region sequences enabled putative orthologous loci to be identified in the two species, and indicated that multiple rounds of gene duplication have occurred within the MHC of New Zealand robins. The orthologous relationships are not retained within the coding region of the gene, instead the sequences group within species. A number of putative gene conversion events were identified across the length of our sequences that may account for this. Exon 2 sequences are highly diverse and appear to have diverged under balancing selection. It is also possible that gene conversion involving short stretches of sequence within exon 2 adds to this diversity. Our study is the first report of putative orthologous MHC loci in passerines, and provides further evidence for the importance of gene duplication and gene conversion in the evolution of the passerine MHC.Nucleotide sequence data reported in this paper are available in the GenBank database under the accession numbers AY258333–AY258335, AY428561–AY428570, and AY530534–AY530535     

An assessment of the probability of secondary poisoning of forest insectivores following an aerial 1080 possum control operation

Assays for the toxin sodium monofluoroacetate (compound 1080) were undertaken on arthropods collected from toxic baits after a brushtail possum (Trichosorus vulpecula) control operation in Nothofagus forest in central North Island, New Zealand. The 1080 concentrations measured (mean 57 mu g per g, max 130 mu g per g) are considerably higher than those reported by other researchers who collected arthropods randomly after control operations. These data, together with published information on sensitivities to 1080, as well as diet and consumption rates, were used to calculate the median lethal doses of arthropods that have fed on 1080 baits for a number of vertebrate insectivores found in Nothofagus forest. The results indicate small insectivores that feed on, or close to, the ground (e.g., tomtit Petroica macrocephala, robin P. australis, hedge sparrow Prunella modularis, and the short-tailed bat Mystacina tuberculata) may be vulnerable to secondary poisoning. For instance, a tomtit will receive the median lethal dose of 1080 from 1.32 g (i.e., 14.7% of its daily food intake) of arthropods containing 57 mu g per g of 1080. Because of their greater sensitivity to 1080 poisoning, bats are at much greater risk; a short-tailed bat will receive the median lethal dose of 1080 from as little as 0.04 g (0.7% of its daily food intake) of arthropods containing 57 mu g per g of 1080.     

Is the black robin in genetic peril?

In 1980 the entire black robin species Petroica traversi comprised only five birds, and the current population of ≊ 200 individuals is known to be derived from a single breeding pair. We show here that levels of minisatellite DNA variation in the black robin are among the lowest reported for any avian species in the wild. Surprisingly, similarly bottlenecked control populations of a closely related species ( P. australis australis ) exhibit significantly higher levels of genetic variation. This suggests that the black robin's persistence in a single small population for the last 100 years, rather than the recent bottleneck itself, accounts for the low genetic variation observed. Despite apparent genetic impoverishment, survival and reproductive performance indicate that the black robin is viable under existing conditions. This example illustrates that significant levels of genetic variation are not a necessary prerequisite for endangered species' survival.     

Plant-Species Preferences of Birds in Lowland Rimu (

Plant species preferences of birds were determined by comparing the proportional bird use of plant species during direct observations with the proportions of plant species present on point-height intercepts in lowland rimu (Dacrydium cupressinum) forest in North Okarito, Westland. Plant species and bird use of plant species were divided into 5 m height classes, and rimu trees were divided into four age classes (sapling, pole, mature, and old). The frugivorous New Zealand pigeon (Hemiphaga novaeseelandiae) used mature and old rimu more than expected from the proportion of these age classes present, and it preferred the upper tiers of the forest. The omnivorous tui (Prosthemadera novaeseelandiae) had similar preferences to the pigeon. Other omnivorous species, viz., the bellbird (Anthornis melanura) and silvereye (Zosterops lateralis), shared preferences with both the pigeon and insectivorous species. Most insectivorous species, viz., the brown creeper (Mohoua novaeseelandiae), grey warbler (Gerygone igata), New Zealand fantail (Rhipidura fuliginosa), New Zealand tomtit (Petroica macrocephala), and rifleman (Acanthisitta chloris), used pole rimu more than expected and preferred the middle and lowest tiers. The insectivorous New Zealand robin (Petroica australis) had no preference for any plant species but had a strong preference for deadwood and the lowest tier of the forest. Of the 10 species sufficiently abundant to be monitored, the pigeon, bellbird, and tui are most likely to be detrimentally affected by selective-logging of mature and old rimu.     

Assessment of hybridisation between the endangered Chatham Island black robin (<Emphasis Type="Italic">Petroica traversi</Emphasis>) and the Chatham Island tomtit (<Emphasis Type="Italic">Petroica macrocephala chathamensis</Emphasis>)

Hybridisation between an endangered species and a more common species can facilitate population decline and extinction of the endangered species due to wasted reproductive effort, outbreeding depression and/or swamping of alleles due to widespread or complete admixture. The Chatham Island black robin (Petroica traversi) is an endangered songbird species, which was reduced to only five individuals in 1980. Intensive cross-fostering, whereby black robin offspring were placed into nests of the closely related Chatham Island tomtit (Petroica macrocephala chathamensis) to increase reproductive output, contributed to the rapid recovery of the species within 10 years. Several hybridisation events occurred and although those hybrids were successfully eliminated from the population, concerns remained for the possibility of introgression between the two species that may have gone unnoticed. In this study, we genotyped seven microsatellite loci in both species from the two islands where they coexist, to assess the level of hybridisation and the extent of introgression between the two species. The two species shared no alleles at five of the seven loci genotyped, and cluster analysis, AMOVA and admixture analysis of a total of 174 black robins and 78 Chatham Island tomtits showed no evidence of hybridisation or introgression on either of the two islands where they co-exist. As a result, there is no evidence that black robins are currently in any danger of population decline or extinction through hybridisation with tomtits, although small population size and skewed sex ratio, particularly in the smaller of the two populations, may facilitate future hybridisation events.     

Sign left by brushtail possums after feeding on bird eggs and chicks

Brushtail possums (Trichosurus vulpecula) were offered Japanese quail (Coturnix japonica) eggs and day-old domestic chickens (Gallus gallus) during a captive feeding trial. Differences in feeding sign left by possums of differing sex, age class, and hunger were slight or absent. Possum feeding trial remains were also compared with remains of North Island robin (Petroica australis longipes) and North Island tomtit (Petroica macrocephala toitoi) eggs and chicks preyed on by ship rats (Rattus rattus) at videoed nests. Eggs fed on by possums were frequently crushed or had crushed shell margins whereas eggs preyed on by ship rats often had jagged shell margins and separate small shell fragments. Possums that ate chickens mostly left partially eaten carcasses with torn flesh, of which 50% were at least partially skinned. Ship rats left partially eaten birds with chewed flesh and bones but did not skin carcases. Possums rarely spat out shell pellets but produced feather pellets on eight of 13 occasions. Egg shell remains left by possums were indistinguishable from those left by ship rats for 11% of 72 shell remains examined from the feeding trial. Characteristic sign should enable possums and ship rats to be differentiated as predators after most but not all predations.     

Identifying predators at nests of small birds in a New Zealand forest

Time-lapse video equipment was used to film continuously at nests of two small passerines, the New Zealand Robin Petroica australis and the Tomtit Petroica macrocephala , in an indigenous broadleaf/hardwood forest in central North Island, New Zealand. The nests were illuminated with infrared light to allow night-time observations of predator and parent bird behaviour, and signs left at nests were linked to predator identity. Introduced Ship Rats Rattus rattus and the small native owl or Ruru Ninox novaeseelandiae were filmed preying on eggs or chicks on 12 occasions, and Ship Rats scavenged on eggs on two occasions. Parent birds sometimes altered the signs left at nests after predation, which confused identification of the predator, while Ship Rat scavenger and predator signs were indistinguishable. This suggests that attempts to identify predators from nest signs could be misleading and potentially a widespread problem. Time-lapse video filming with infrared illumination is potentially the least biased method of identifying predators, but it is expensive and so is best used in conjunction with simpler methods. This study found no evidence that filming altered predation rates or that the predators or parent birds reacted strongly to the camera or lights, so we believe that filming is a valuable and safe technique to guide management for the recovery of critically endangered species that are threatened by predators.     

Impacts of introduced common wasps (Vespula vulgaris) on experimentally placed mealworms in a New Zealand beech forest

An introduced social wasp Vespula vulgaris may compete with native birds for honeydew and invertebrates in New Zealand forests. Experimentally hidden mealworms (Tenebrio molitor) persisted longer at two sites following wasp poisoning that at two sites where wasps were not poisoned. Mealworms persisted longer in the morning than in the afternoon within all study sites. An unusually low mealworm removal rate during a morning trial before wasp poisoning heavily influences the results of this experiment but we have no ecological reason to ignore it. Wasps may therefore be having a heavy impact on invertebrate abundance on very short time scales (within a day following dawn emergence). They may also remove cached food items that would otherwise be retrieved by the South Island robin (Petroica australis australis) during cold or dark feeding conditions.     

Mortality of North Island tomtits (

Aerial poisoning operations with carrot or cereal baits are used to control brushtail possum (Trichosurus vulpecula) populations in New Zealand forests for ecosystem conservation and to stop the spread of bovine tuberculosis to cattle and deer herds on adjacent farmland. Although various measures have been implemented to reduce the incidence of bird kills, dead birds continue to be found after poison operations. Colour- banded North Island tomtits (Petroica macrocephala toitoi) were monitored in treatment and non-treatment areas in Pureora Forest Park to determine the costs and benefits of aerial 1080 possum poisoning operations to tomtit populations. The August 1997 operation (carrot baits with very little chaff, 0.08 % w/w 1080, 10 kg ha(-1)), resulted in 11 (79%) of 14 tomtits disappearing, but none of nine from the non-treatment area. Whether the birds died of primary or secondary poisoning is unknown. No tomtits in either treatment or non-treatment areas disappeared following the August 1998 operation (cereal baits, 0.08% w/w 1080, 5 kg ha(-1)). The carrot bait operation resulted in almost all possums and rodents being killed, but a few possums and rodents survived the cereal bait operation, apparently because of a gap in bait distribution. During the 1997/98 nesting season, tomtit pairs in the 1997 treatment area had high nesting success (80% of nests fledged chicks, mean of four fledglings per nest). Even so, by the following spring it seemed that the population had not recovered to its pre-poison level. Further research on this topic is warranted, the priority being to monitor tomtit mortality during more aerial 1080-cereal bait operations in order to assess the likely risks of using those baits.     

Mitochondrial and nuclear DNA phylogenies reveal a complex evolutionary history in the Australasian robins (Passeriformes: Petroicidae)

The Australasian robins (Petroicidae) comprise a relatively homogeneous group of small to medium-sized insectivorous birds. Their center of diversity is Australia and New Guinea (40 species) but seven species have managed to colonize geographically distant islands such as Tanimbar, New Britain, New Zealand, New Caledonia, Norfolk Island, Vanuatu, Solomon Islands, Fiji and Samoa. To resolve the evolutionary relationships within the Petroicidae, we here present the results of a phylogenetic analysis of sequence data from two mitochondrial genes (ND2, CO1) and one nuclear intron (β-Fibrinogen intron 5) for all 14 genera and 40 of the 46 currently recognized species. All phylogenetic analyses identified six primary lineages, treated here as subfamilies, within the Petroicidae: (1) Eopsaltriinae comprising Eopsaltria (excluding E. flaviventris), Tregellasia, Peneothello, Melanodryas, Poecilodryas and Heteromyias; (2) Drymodinae comprising Drymodes; (3) Microecinae comprising Microeca, Monachella and Eopsaltria flaviventris; (4) Petroicinae comprising Petroica and Eugerygone; (5) Pachycephalopsinae comprising Pachycephalopsis; and (6) Amalocichlinae comprising Amalocichla. The genera Eopsaltria, Microeca, Peneothello and Poecilodryas were found to be paraphyletic. Based on assessments of phylogenetic branching patterns and/or DNA divergence it also was apparent that Eopsaltriaaustralis, Tregellasialeucops, Melanodryascucullata, Heteromyiasalbispecularis, Drymodessupercilious and Microecaflavigaster may each comprise more than one species. The Petroicidae display a complex biogeographical history involving repeated radiations both within, and across Australia and New Guinea. It appears that dispersal into smaller islands such as New Britain, Tanimbar and the South Pacific has only been undertaken by species with a "flycatcher" body form.     

Comparing methods for assessing mortality impacts of an aerial 1080 pest control operation on tomtits (

This study aimed to estimate the level of mortality of North Island tomtits (Petroica macrocephala toitoi) during an aerial 1080 possum poisoning operation in Tongariro Forest, New Zealand, and to evaluate transect-based alternatives to banding for monitoring tomtit populations. The operation used 12 g toxic (1080 at 0.15% weight/weight) cereal baits sown at 3 kg/ha. Transects were established at three neighbouring sites; two within the 1080 poison area, and one outside. The re-sighting of 14 out of 15 banded male tomtits at one site within the 1080 operation indicated that mortality was low. This was backed up by results from a before-after-control-impact (BACI) design to analyse density estimates from distance sampling along transects. We analysed the change in counts of territorial males before and after the operation based on the same transect surveys. This also showed little impact of poisoning on tomtits, and indicated that loss rates greater than 8.4% due to 1080 were incompatible with the data (95% one-sided confidence bound). Counts of territorial males gave a much tighter confidence bound than the banding or distance sampling results. Of the techniques applied, the counting of territorial males appears to have the most promise for providing high-precision estimates of short-term impacts, by taking full advantage of the territorial habits of male tomtits in spring. However, distance sampling shows potential for providing the basis for longer-term monitoring of tomtit populations. The transect-based approaches involved substantially fewer resources than banding for estimating short-term impacts, and offer a considerably less-intensive means of longer-term monitoring of tomtits.     

Effect of the blood-sucking mite

Pathological consequences of the blood-sucking mite Ornithonyssus bursa vary between species, with its impact ranging from no measurable effect, to significant blood loss and chick mortality. In New Zealand, where several bird species are known to be parasitised by O.bursa, the effect of this mite on host fitness is unclear, as few studies have been carried out. During a three-year study of the North Island robin Petroica longipes on Tiritiri Matangi Island, the prevalence of O. bursa in robin nests and on chicks and its impact on robin chick growth and survival was measured. The presence of mites was correlated with both time of the season and humidity of the habitat, with infestation being positively correlated with later nesting attempts and more humid microclimates. Robin chicks in infested nests were significantly smaller and fledged at an earlier age than chicks in nests where no mites were detected. Despite this effect, no significant difference in body size or survival was detected between the two groups at one month post-fledging. This was most likely because chicks from mite- infested nests compensated for their retarded growth once they left the nest environment. On mainland New Zealand, where ground-dwelling mammalian predators are present, chicks forced to leave the nest at an earlier age with less developed flying skills may be at an increased risk of predation.     

Decreased immunocompetence in a severely bottlenecked population of an endemic New Zealand bird

Inbreeding resulting from severe population bottlenecks may impair an individual's immune system and render it more susceptible to disease. Although a reduced immune response could threaten the survival of highly endangered species, few studies have assessed the effect of population bottlenecks on immunocompetence. We compared the counts of leucocytes and external, blood and gastrointestinal parasite loads in two populations of the endemic New Zealand robin Petroica australis to assess the immunocompetence of birds in a severely bottlenecked population relative to its more genetically diverse source population. Despite similar parasite loads in both populations, robins in the severely bottlenecked population showed lower counts of both total leucocyte and total lymphocyte numbers. When the immune system was experimentally challenged using the phytohaemagglutinin skin test, robins in the severely bottlenecked population exhibited a significantly lower immune response than the source population, suggesting that birds passing through a severe bottleneck have a compromised immunocompetence. Our results confirm that severe bottlenecks reduce the immune response of birds and highlight the need to avoid severe bottlenecks in the recovery programmes of endangered species.     

Controlling small mammal predators using sodium monofluoroacetate (1080) in bait stations along forestry roads in a New Zealand beech forest

A single five night pulse of sodium monofluroacetate (0.15% 1080) applied in bait stations at two different spacing intervals, 100 and 200 m, along forestry roads in New Zealand beech forest, killed all four of the resident radio-tagged stoats (Mustela erminea) and all three of the resident radio- tagged wild house cats (Felis catus) by secondary poisoning. Gut contents of predators indicated that house mice (Mus musculus), ship rats (Rattus rattus) and bushtail possums (Trichosurus vulpecula) were important sources of the toxin. High kills of predators, possums and rats at both 100 and 200 m spacing regimes suggest that greater efficacy of controlling these pests would be achieved with the latter method. Evidence suggests that routine management of possums and rats using 1080 and brodifacoum has resulted in widespread control of small mammalian carnivores by secondary poisoning in New Zealand forests. However, aerial application of poison can kill large numbers of tomtits (Petroica macrocephala) and robins (Petroica australis) and few other native bird species have been adequately monitored through such operations. Reducing risks to native wildlife is responsible ecological management. Use of bait stations along forestry roads or tracks may be fundamental in mounting cost-effective :Large-scale ground-based protection of native wildlife through safer predator controls.     

Bird Abundance in Different-Aged Stands of Rimu (

The abundance of birds in three different-aged stands (young, mature, and old) was examined at North Okarito, a lowland rimu (Dacrydium cupressinum) forest in Westland, using 5-minute counts, transect counts, and mist-netting. Most of New Zealand's common forest bird species were present in the study area, with relatively high numbers of brown creeper (Mohoua novaeseelandiae) and New Zealand robin (Petroica australis), and low numbers of kaka (Nestor meridionalis) and yellow- crowned parakeet (Cyanoramphus auriceps). Most insectivorous species were more abundant than expected (from sampling effort) in young and mature stands, the frugivorous New Zealand pigeon (Hemiphaga novaeseelandiae) was more abundant than expected in mature and old stands, and most omnivorous species, viz., bellbird (Anthornis melanura), silvereye (Zosterops lateralis), and tui (Prosthemadera novaeseelandiae), were more abundant than expected in young and old stands. North Okarito Forest provided an important source of seasonal foods (nectar, fruit, and seeds) for frugivorous, omnivorous, and introduced granivorous species, which tended to have greater changes in their seasonal abundance than did insectivorous species. Coupe- logging of old stands will affect all bird species because it will reduce the overall area of standing forest, but it will have a greater impact on the pigeon, bellbird, silvereye, robin, and tui because of their preference for old stands.     

Secondary poisoning of stoats (Mustela erminea), feral ferrets (Mustela furo), and feral house cats (Felis catus) by the anticoagulant poison,brodifacoum

Abstract

The extent of darkening of melanin‐based plumages in birds has previously been linked with increasing aggressive encounters between individuals. The North Island robin (Petroica longipes) is a territorial New Zealand endemic passerine that displays delayed plumage maturation (darkening of the plumage with age). Aggressive boundary interactions in the robin are relatively common during the breeding season, when territories are protected and juveniles are dispersing. This study tests the hypothesis of aggression‐mediated plumage darkening in a population of North Island robins by examining if males and older (darker) birds are either (1) involved in a higher number of aggressive interactions, or (2) are more often the aggressor than females and younger birds. When sex and age are accounted for, darker individuals will be either (3) involved in a higher number of interactions or (4) more often the aggressor in encounters with other individuals. Data were collected by scoring the plumage darkness of 32 individuals in the field, and observing (1) interaction behaviours, and (2) age and sex of the birds involved in each interaction. The results show no support for any aggression‐mediated plumage darkness in the robin; males and older birds were not involved in more aggressive interactions, and were not more often the aggressor; and neither the frequency of interactions or the number of aggressive interactions were correlated with a darker plumage. Other more complex mechanisms may explain delayed plumage darkness in the North Island robin.     

Losing anti‐predatory behaviour: A cost of translocation

Translocation of endangered species to habitats where exotic predators have been removed is now a common conservation practice around the world. Many of these translocated populations have thrived, and they are often used as sources for the harvesting of individuals for translocations to sites where exotic predators still exist, albeit at reduced densities. This study investigates how isolation from exotic predators affects the ability of individuals to recognize such predators using the North Island robin (Petroica longipes) as a model. The study was carried out in three robin populations in the North Island, New Zealand: a translocated population on Tiritiri Matangi Island, where exotic mammalian predators are absent; a population reintroduced from Tiritiri Matangi Island to Wenderholm Regional Park, a mainland site where these mammals are controlled to low densities; and a mainland population at Benneydale where exotic predatory mammals are common. The response intensity of robins to a model stoat was high at Benneydale and low at Tiritiri Matangi and Wenderholm. This result indicates that isolation from mammalian predators on Tiritiri Matangi has suppressed the ability of North Island robins to recognize these predators. It is possible that the low predatory mammal densities at Wenderholm have reduced robin contact with stoats, therefore reduced the opportunity for robins to learn to recognize stoats. Thus, translocation of individuals from populations without predators to places where key predators still exist could be unsuccessful if translocated individuals fail to perform appropriate anti‐predator behaviours.     

Using artificial nests to predict nest survival at reintroduction sites

Artificial nests are frequently used to assess factors affecting survival of natural bird nests. We tested the potential for artificial nests to be used in a novel application, the prediction of nest predation rates at potential reintroduction sites where exotic predators are being controlled. We collected artificial nest data from nine sites with different predator control regimes around the North Island of New Zealand, and compared the nest survival rates with those of North Island robin (Petroica longipes) nests at the same sites. Most of the robin populations had been reintroduced in the last 10 years, and were known to vary in nest survival and status (increasing/stable or declining). We derived estimates of robin nest survival for each site based on Stanley estimates of daily survival probabilities and the known incubation and brooding periods of robins. Estimates of artificial nest survival for each site were derived using the known fate model in MARK. We identified the imprints on the clay eggs in the artificial nests, and obtained different estimates of artificial nest survival based on imprints made by different potential predators. We then compared the value of these estimates for predicting natural nest survival, assuming a relationship of the form s = αpβ, where s is natural nest survival and p is artificial nest survival. Artificial nest survival estimates based on imprints made by rats (Rattus spp.) and brushtail possums (Trichosurus vulpecula) were clearly the best predictors (based on AICc), and explained 64% of the variation in robin nest survival among sites. Inclusion of bird imprints in the artificial nest survival estimates substantially reduced their predictive value. We suggest that artificial nests may provide a useful tool for predicting the suitability of potential reintroduction sites for New Zealand forest birds as long as imprints on clay eggs are correctly identified.     

INBREEDING INFLUENCES WITHIN‐BROOD HETEROZYGOSITY‐FITNESS CORRELATIONS (HFCS) IN AN ISOLATED PASSERINE POPULATION

Molecular estimates of inbreeding may be made using genetic markers such as microsatellites, however the interpretation of resulting heterozygosity‐fitness correlations (HFCs) with respect to inbreeding depression is not straightforward. We investigated the relationship between pedigree‐determined inbreeding coefficients (f) and HFCs in a closely monitored, reintroduced population of Stewart Island robins (Petroica australis rakiura) on Ulva Island, New Zealand. Using a full sibling design, we focused on differences in juvenile survival associated specifically with individual sibling variation in standardized multilocus heterozygosity (SH) when expected f was identical. We found that within broods, siblings with higher SH at microsatellite loci experienced a higher probability of juvenile survival. This effect, however, was detected primarily within broods that experienced inbreeding or when inbreeding had occurred in their pedigree histories (i.e., at the parents’ level). Thus we show, for the first time in a wild population, that the strength of an HFC is partially dependent on the presence of inbreeding events in the recent pedigree history. Our results illustrate the importance of realized effects of inbreeding on genetic variation and fitness and the value of full‐sibling designs for the study of HFCs in the context of small, inbred populations.