Petroica Longipes Research Articles

Male New Zealand robins (Petroica longipes) cater to their mate\u2019s desire when sharing food in the wild

In many species that have bi-parental care, food-sharing males provide vital nutritional resources to their mates during reproduction. However, it is currently unknown whether females can signal specific desires to their mates, or if males can cater to female desire in the wild. Here we investigate whether and how wild male North Island robins (Petroica longipes) respond to changes in their mates’ desires and nutritional need when sharing food. We demonstrate that wild female robins’ desire for particular foods changes over short time periods; when given the choice between two types of insect larvae, females prefer the type they have not recently eaten. In our experiments, wild male robins preferentially shared the larvae type that their mate was most likely to desire and also increased the quantity of food shared if she had begun incubating. Males catered to their mates’ desire when female behaviour was the only cue available to guide their choices. This is the first evidence that females may behaviourally communicate their specific food desires to their mates, enabling males to cater to fine-scale changes in their mates’ nutritional requirements in the wild. Such a simple behaviour-reading mechanism has the potential to be widespread among other food-sharing species.

Commentary: Wild psychometrics: Evidence for ‘general’ cognitive performance in wild New Zealand robins, Petroica longipes

A commentary on Wild psychometrics: Evidence for ‘general’ cognitive performance in wild New Zealand robins, Petroica longipes by Shaw, R. C., Boogert, N. J., Clayton, N. S., and Burns, K. C. (2015). Anim. Behav. 109, 101–111. doi: 10.1016/j.anbehav.2015.08.001

Population responses of a native bird species to rat control

ABSTRACTInvasive‐predator control can be beneficial to native species, but it is important to quantify those benefits to ensure they justify the costs. In a previous study (2005–2011), a modified before‐after‐control‐impact (BACI) design was used to estimate the effect of rat control in farmland forest fragments on vital rates of North Island robins (Petroica longipes), a New Zealand native bird species often targeted in private restoration initiatives. Based on the results, continuous rat control was implemented in 5 fragments predicted to have a high probability of subpopulation growth. Here, I report subsequent abundance estimates; the number of robins in those fragments increased from 57 to 134, from 2011–2014, closely matching the prediction of 131 based on the previous vital rate estimates. In comparison, numbers declined or stayed relatively stable over this period in 8 non‐controlled fragments, except for 1 fragment that was adjacent to 1 of the controlled fragments and therefore would have received juveniles dispersing from it. Therefore, the results illustrate that where there is uncertainty about where to conduct control operations, short‐term data on survival and reproduction can be used to predict longer‐term effects, allowing predator‐control efforts to be done strategically. © 2016 The Wildlife Society.

Reasoning about “Capability”: Wild Robins Respond to Limb Visibility in Humans

Little comparative work has focused on what nonhumans understand about what physical acts others are capable of performing, and none has yet done so in the wild, or within a competitive framework. This study shows that North Island robins visually attend to human limbs in the context of determining who to steal food from. We presented 24 wild North Island Robins (Petroica longipes) with two experimenters. Robins could choose to steal a mealworm from one of two experimenters: one whose limbs were exposed and one who underwent a range of visual obstructions in two experiments. In most conditions, robins preferred to steal food located near the experimenter whose limbs were obscured by a cloth or board rather than food located near the experimenter whose limbs were not obscured. The robins’ responses indicate that human limb visibility is associated with reduced access to food. Current findings lay the groundwork for a closer look at the potential general use of causal reasoning in an inter-specific context of using limbs to perform physical acts, specifically within the context of pilfering. This study presents one of the first tests of the role of visual attendance of potential limb availability in a competitive context, and could provide an alternative hypothesis for how other species have passed tests designed to examine what individuals understand about the physical acts others are capable of performing.

A guide for banding North Island robin (Petroica longipes) nestlings

ABSTRACTMeasures of population productivity and individual survival are essential for effective conservation management and scientific investigations. In studies of birds, individuals are often marked with unique colour band combinations to enable estimates of population vital rates. If birds are banded in the nest this must be done at the correct stage in nestling development. If nestlings are banded too early it can lead to leg damage. If they are banded too late it can cause early fledging and reduced survival. Here, we use photographs to guide estimation of the best stage to band North Island robin (Petroica longipes), or toutouwai, nestlings, which is typically at 9–12 days of age.

Avian malaria in introduced, native and endemic New Zealand bird species in a mixed ecosystem

Avian malaria, caused by Plasmodium spp., has been reported as a cause of morbidity and mortality in New Zealand bird populations. The prevalence of Plasmodium lineages in the Waimarino Forest was evaluated in NZ robins (Petroica longipes), other passerines, blue ducks (Hymenolaimus malacorhynchos), and brown kiwi (Apteryx mantelli), using nested PCR. The presence of P. sp. lineage LINN1, P. (Huffia) elongatum lineage GRW06 and P. (Novyella) sp. lineage SYAT05 was demonstrated; Plasmodium (Haemamoeba) relictum lineage GRW4 was not found. The highest prevalence of infection was found in introduced European species (80.5%), followed by native (19%) and endemic species (3.5%), with a significant difference between these groups. All detected Plasmodium lineages have previously been identified in New Zealand and introduced species have been suggested as an important reservoir of infection. The results of this study will aid New Zealand conservation managers with disease risk management during bird translocations from the Waimarino forest.

Wild psychometrics: evidence for ‘general’ cognitive performance in wild New Zealand robins, Petroica longipes

In human psychometric testing, individuals' scores in tests of diverse cognitive processes are positively correlated, with a ‘general intelligence’ factor (g) typically accounting for at least 40% of total variance. Individual differences in cognitive ability have been extensively studied in humans, yet they have received far less attention in nonhuman animals. In particular, the development of a test battery suitable for quantifying individual cognitive performance in birds remains in its infancy. Additionally, implementing this approach in the wild, where the ecological significance of cognition can also be explored, presents considerable logistical challenges for most species. We developed a cognitive test battery for wild New Zealand North Island robins. Our battery comprised six tasks based on established measures of avian cognitive performance: a motor task, colour and shape discrimination, reversal learning, spatial memory and inhibitory control. Robins varied greatly in their ability to solve these tasks and we found weakly positive, nonsignificant correlations between most tasks. A principal components analysis of task performances yielded two factors with eigenvalues >1. The first component extracted explained over 34% of the variance in cognitive performance and all six tasks loaded positively on this first component. We show, using randomization tests, that these results are robust. Our results thus suggest that a general cognitive factor, analogous to human g, underpins cognitive performance in wild North Island robins tested in their natural habitat.

Wild robins (Petroica longipes) respond to human gaze.

Gaze following and awareness of attentional cues are hallmarks of human and non-human social intelligence. Here, we show that the North Island robin (Petroica longipes), a food-hoarding songbird endemic to New Zealand, responds to human eyes. Robins were presented with six different conditions, in which two human experimenters altered the orientation or visibility of their body, head or eyes in relation to mealworm prey. One experimenter had visual access to the prey, and the second experimenter did not. Robins were then given the opportunity to 'steal' one of two mealworms presented by each experimenter. Robins responded by preferentially choosing the mealworm in front of the experimenter who could not see, in all conditions but one. Robins failed to discriminate between experimenters who were facing the mealworm and those who had their head turned 90° to the side. This may suggest that robins do not make decisions using the same eye visibility cues that primates and corvids evince, whether for ecological, experiential or evolutionary reasons.

Strategic Rat Control for Restoring Populations of Native Species in Forest Fragments

Forest fragments have biodiversity value that may be enhanced through management such as control of non-native predators. However, such efforts may be ineffective, and research is needed to ensure that predator control is done strategically. We used Bayesian hierarchical modeling to estimate fragment-specific effects of experimental rat control on a native species targeted for recovery in a New Zealand pastoral landscape. The experiment was a modified BACI (before-after-control-impact) design conducted over 6 years in 19 forest fragments with low-density subpopulations of North Island Robins (Petroica longipes). The aim was to identify individual fragments that not only showed clear benefits of rat control, but also would have a high probability of subpopulation growth even if they were the only fragment managed. We collected data on fecundity, adult and juvenile survival, and juvenile emigration, and modeled the data in an integrated framework to estimate the expected annual growth rate (λ) of each subpopulation with and without rat control. Without emigration, subpopulation growth was estimated as marginal (λ = 0.95-1.05) or negative (λ = 0.74-0.90) without rat control, but it was estimated as positive in all fragments (λ = 1.4-2.1) if rats were controlled. This reflected a 150% average increase in fecundity and 45% average increase in adult female survival. The probability of a juvenile remaining in its natal fragment was 0.37 on average, but varied with fragment connectivity. With juvenile emigration added, 6 fragments were estimated to have a high (>0.8) probability of being self-sustaining (λ > 1) with rat control. The key factors affecting subpopulation growth rates under rat control were low connectivity and stock fencing because these factors were associated with lower juvenile emigration and higher fecundity, respectively. However, there was also substantial random variation in adult survival among fragments, illustrating the importance of hierarchical modeling for fragmentation studies.

Wild North Island Robins (Petroica longipes) respond to Prey Animacy

North Island robins of New Zealand are a food hoarding species, which is unique in that they almost exclusively cache highly perishable hunted insects for later retrieval. In order to do so, they either kill and dismember or paralyze their prey for caching, depending on the prey size and kind. The present study comprises two experiments, using a Violation of Expectancy (VoE) paradigm to examine variation in search behavior response to different prey conditions. The first experiment presents three different types of prey (mealworms, earthworms and locusts) in expected (present) and unexpected (absent) conditions. The second experiment presents prey in varying states of animacy (alive and whole, dead and whole, dead and halved, and an inanimate stick) and reveals prey in expected (same state) or unexpected (differing state) conditions. While robins did not respond with differential search times to different types of unexpectedly missing prey in Experiment 1, in Experiment 2 robins searched longer in conditions where prey was found in a differing state of animacy than initially shown. Robins also searched longer for prey when immediately consuming retrieved prey than when caching retrieved prey. Results indicate that North Island robins may be sensitive to prey animacy upon storage and retrieval of insect prey; such information could play a role in storage, pilfering and retrieval strategies of such a perishable food source.

Using radio-tracking data to predict post-release establishment in reintroductions to habitat fragments

Dispersal from release areas is a critical problem for reintroductions. Reliable methods are therefore needed for analysing post-release monitoring data to guide further releases. Radio tracking can greatly improve data quality by distinguishing dispersal from mortality. However, fates of animals continue to be uncertain if transmitters have short battery life and detection range, as is typically the case with small animals. We present an approach for simultaneously modelling probabilities of fidelity (remaining in release area), survival, detection and transmitter failure from post-release monitoring data, and illustrate how it was applied to translocations of North Island robins (Petroica longipes) to 17 forest fragments (5–56ha) over 5years. The modelling showed that fidelity probability depended on the sex (higher in females) and translocation date (higher in winter than autumn), and that variation among fragments was well explained by the “cost distance to nearest neighbour” (an index reflecting the amount of pasture and shrubland needing to be crossed to reach another forest area) and the area of the release fragment (higher in larger fragments). Combined with survival, the estimated probability of a bird remaining in its release fragment the next breeding season ranged from 0.02 to 0.39. As these estimates were refined, they could be used to assess suitability of fragments for further releases and numbers of each sex needing to be released to compensate for dispersal. The Bayesian framework underlying the approach potentially allows application to any amount of data by using informative priors derived from previous translocations or expert opinion.

The ability of North Island Robins to discriminate between humans is related to their behavioural type.

Animals are able to learn to identify persistent threats to themselves and their offspring. For example, birds are able to quickly learn to discriminate between humans that have previously threatened their nests from humans with whom they have had no prior experience. However, no study has yet examined whether a bird's ability to discriminate between humans is related to the bird's underlying behavioural type. In this study, we examined whether there were differences among North Island (NI) robins (Petroica longipes), based on their underlying behavioural type, in their abilities to discriminate between familiar and novel human observers. Using a simple feeding experiment, we timed how long it took birds to attack a food item placed next to an observer on each of 7 days. On the eighth day, a different observer timed the birds. We found that birds could be split into two behaviour types based on their attack behaviour: fast attackers (latencies <20 sec) and slow attackers (latencies >20 secs). Interestingly, the fast birds did not increase their attack latency in response to the novel observer whereas the slow attackers did. This result, for the first time, demonstrates that a bird's ability to discriminate between humans can vary among birds based on their behavioural type.

Coccidia species in endemic and native New Zealand passerines

New Zealand native passerines are hosts to a large variety of gastrointestinal parasites, including coccidia. Coccidian parasites are generally host-specific, obligate intracellular protozoan parasites. In passerine birds, members of the genus Isospora are most common. Under natural conditions, these parasites seldom pose a threat, but stressors such as quarantine for translocation, overcrowding, or habitat changes may cause an infection outbreak that can severely affect wild populations. Although coccidia are important pathogens and have caused mortalities in kiwi (Apteryx spp.) and hihi (Notiomystis cincta), their prevalence, epidemiology, life cycles, and taxonomic relationships are still widely unknown in native New Zealand songbirds. Over a period of 3years (2007-2009), we examined 330 fecal samples of six native passerine species: tui (Prosthemadera novaeseelandiae), North Island saddleback (Philesturnus carunculatus rufusater), North Island robin (Petroica longipes), silvereye (Zosterops lateralis), and fantail (Rhipidura fuliginosa). The overall prevalence by flotation of coccidian infection in the New Zealand bird species examined was 21-38%, 21% in North Island robin, 38% in tui, and 25% in saddleback. Similar to prior studies in other countries, preliminary sequencing results suggest that coccidia in passerines in New Zealand are members of the family Eimeriidae, unlike the phenotypically similar genus Cystisospora of mammals. Using molecular methods, we identified at least five new genetically distinct Isospora species in the examined birds (three in tui and one each in saddlebacks and North Island robins).

Predicting post-release establishment using data from multiple reintroductions

For any reintroduction it is important to maximise the probability of released individuals establishing in the target area (settling and surviving to breed). Factors influencing establishment have typically been studied at single sites, making it impossible to assess factors that vary at the site level (e.g. connectivity) or quantify unpredictable variation among sites. Using data from 14 reintroductions of the North Island robin (Petroica longipes) to native forest reserves, we show how Bayesian modelling can be used to identify general drivers of establishment and to account for site-to-site variation when making predictions for new sites. High landscape connectivity and high rat tracking rates (a density index) at reintroduction sites were key factors associated with lower individual establishment probabilities. Habitat similarity between source and release sites was also important, as robins sourced from native forest had higher establishment than those from exotic pine forest. Previous predator experience appeared to affect establishment in sites with mammalian predators, as founders sourced from sites with these predators had higher establishment than those from other sites. Our approach can be applied to a wide range of species that are being reintroduced to multiple sites, providing guidance on source and release site selection, efficacy of management interventions, and the numbers of individuals to release to achieve desired initial population sizes. The results are not only applicable to these particular species, but can be used to predict site suitability for reintroductions of species with similar dispersal behaviour or other ecological characteristics.

Simulating Retention of Rare Alleles in Small Populations to Assess Management Options for Species with Different Life Histories

Preserving allelic diversity is important because it provides the capacity for adaptation and thus enables long-term population viability. Allele retention is difficult to predict in animals with overlapping generations, so we used a new computer model to simulate retention of rare alleles in small populations of 3 species with contrasting life-history traits: North Island Brown Kiwi (Apteryx mantelli; monogamous, long-lived), North Island Robins (Petroica longipes; monogamous, short-lived), and red deer (Cervus elaphus; polygynous, moderate lifespan). We simulated closed populations under various demographic scenarios and assessed the amounts of artificial immigration needed to achieve a goal of retaining 90% of selectively neutral rare alleles (frequency in the source population = 0.05) after 10 generations. The number of immigrants per generation required to meet the genetic goal ranged from 11 to 30, and there were key similarities and differences among species. None of the species met the genetic goal without immigration, and red deer lost the most allelic diversity due to reproductive skew among polygynous males. However, red deer required only a moderate rate of immigration relative to the other species to meet the genetic goal because nonterritorial breeders had a high turnover. Conversely, North Island Brown Kiwi needed the most immigration because the long lifespan of locally produced territorial breeders prevented a large proportion of immigrants from recruiting. In all species, the amount of immigration needed generally decreased with an increase in carrying capacity, survival, or reproductive output and increased as individual variation in reproductive success increased, indicating the importance of accurately quantifying these parameters to predict the effects of management. Overall, retaining rare alleles in a small, isolated population requires substantial investment of management effort. Use of simulations to explore strategies optimized for the populations in question will help maximize the value of this effort..

Erratum to: Large quantity discrimination by North Island robins (Petroica longipes)

Erratum to: Large quantity discrimination by North Island robins (Petroica longipes)

Helminths in endemic, native and introduced passerines in New Zealand

The aim of the study was to obtain preliminary data on the occurrence of helminths in New Zealand endemic passerines. We also examined a small number of non-endemic native and introduced birds. Altogether, of 388 samples of faeces or dead birds, 5.4% contained evidence of trematode infections, 7.7% of cestode infections and 1.5% of Capillaria. Trematodes found in the gall bladders of saddlebacks and one song thrush were tentatively identified as belonging to the family Dicrocoeliidae but definitive identifications have yet to be made. The taxonomic position of the trematodes found in tui is unknown. However, these are the first records of trematodes in New Zealand endemic passerines. The presence of cestode infections in saddlebacks, tui and the North Island robin, and of Capillaria in tui, appears not to have been recorded previously.

Large quantity discrimination by North Island robins (Petroica longipes)

While numerosity-representation and enumeration of different numbers of objects-and quantity discrimination in particular have been studied in a wide range of species, very little is known about the numerical abilities of animals in the wild. This study examined spontaneous relative quantity judgments (RQJs) by wild North Island robins (Petroica longipes) of New Zealand. In Experiment 1, robins were tested on a range of numerical values of up to 14 versus 16 items, which were sequentially presented and hidden. In Experiment 2, the same numerical contrasts were tested on a different group of subjects but quantities were presented as whole visible sets. Experiment 3 involved whole visible sets that comprised of exceedingly large quantities of up to 56 versus 64 items. While robins shared with other species a ratio-based representation system for representing very large values, they also appeared to have developed an object indexing system with an extended upper limit (well beyond 4) that may be an evolutionary response to ecological challenges faced by scatter-hoarding birds. These results suggest that cognitive mechanism influencing an understanding of physical quantity may be deployed more flexibly in some contexts than previously thought, and are discussed in light of findings across other mammalian and avian species.

Memory for Multiple Cache Locations and Prey Quantities in a Food-Hoarding Songbird

Most animals can discriminate between pairs of numbers that are each less than four without training. However, North Island robins (Petroica longipes), a food-hoarding songbird endemic to New Zealand, can discriminate between quantities of items as high as eight without training. Here we investigate whether robins are capable of other complex quantity discrimination tasks. We test whether their ability to discriminate between small quantities declines with (1) the number of cache sites containing prey rewards and (2) the length of time separating cache creation and retrieval (retention interval). Results showed that subjects generally performed above-chance expectations. They were equally able to discriminate between different combinations of prey quantities that were hidden from view in 2, 3, and 4 cache sites from between 1, 10, and 60 s. Overall results indicate that North Island robins can process complex quantity information involving more than two discrete quantities of items for up to 1 min long retention intervals without training.

An Integrated Approach for Predicting Fates of Reintroductions with Demographic Data from Multiple Populations

We devised a novel approach to model reintroduced populations whereby demographic data collected from multiple sites are integrated into a Bayesian hierarchical model. Integrating data from multiple reintroductions allows more precise population-growth projections to be made, especially for populations for which data are sparse, and allows projections that account for random site-to-site variation to be made before new reintroductions are attempted. We used data from reintroductions of the North Island Robin (Petroica longipes), an endemic New Zealand passerine, to 10 sites where non-native mammalian predators are controlled. A comparison of candidate models that we based on deviance information criterion showed that rat-tracking rate (an index of rat density) was a useful predictor of robin fecundity and adult female survival, that landscape connectivity and a binary measure of whether sites were on a peninsula were useful predictors of apparent juvenile survival (probably due to differential dispersal away from reintroduction sites), and that there was unexplained random variation among sites in all demographic rates. We used the two best supported models to estimate the finite rate of increase (λ) for populations at each of the 10 sites, and for a proposed reintroduction site, under different levels of rat control. Only three of the reintroduction sites had λ distributions completely >1 for either model. At two sites, λ was expected to be >1 if rat-tracking rates were <5%. At the other five reintroduction sites, λ was predicted to be close to 1, and it was unclear whether growth was expected. Predictions of λ for the proposed reintroduction site were less precise than for other sites because distributions incorporated the full range of site-to-site random variation in vital rates. Our methods can be applied to any species for which postrelease data on demographic rates are available and potentially can be extended to model multiple species simultaneously.