Philip O’B. Lyver

Plasticity in above‐ and belowground resource acquisition traits in response to single and multiple environmental factors in three tree species

Functional trait plasticity is a major component of plant adjustment to environmental stresses. Here, we explore how multiple local environmental gradients in resources required by plants (light, water, and nutrients) and soil disturbance together influence the direction and amplitude of intraspecific changes in leaf and fine root traits that facilitate capture of these resources. We measured population-level analogous above- and belowground traits related to resource acquisition, i.e. “specific leaf area”–“specific root length” (SLA–SRL), and leaf and root N, P, and dry matter content (DMC), on three dominant understory tree species with contrasting carbon and nutrient economics across 15 plots in a temperate forest influenced by burrowing seabirds. We observed similar responses of the three species to the same single environmental influences, but partially species-specific responses to combinations of influences. The strength of intraspecific above- and belowground trait responses appeared unrelated to species resource acquisition strategy. Finally, most analogous leaf and root traits (SLA vs. SRL, and leaf versus root P and DMC) were controlled by contrasting environmental influences. The decoupled responses of above- and belowground traits to these multiple environmental factors together with partially species-specific adjustments suggest complex responses of plant communities to environmental changes, and potentially contrasting feedbacks of plant traits with ecosystem properties. We demonstrate that despite the growing evidence for broadly consistent resource-acquisition strategies at the whole plant level among species, plants also show partially decoupled, finely tuned strategies between above- and belowground parts at the intraspecific level in response to their environment. This decoupling within species suggests a need for many species-centred ecological theories on how plants respond to their environments (e.g. competitive/stress-tolerant/ruderal and response-effect trait frameworks) to be adapted to account for distinct plant-environment interactions among distinct individuals of the same species and parts of the same individual.

Intra-seasonal variation in foraging behavior among Adélie penguins (Pygocelis adeliae) breeding at Cape Hallett, Ross Sea, Antarctica

We investigated intra-seasonal variation in foraging behavior of chick-rearing Adélie penguins, Pygoscelis adeliae, during two consecutive summers at Cape Hallett, northwestern Ross Sea. Although foraging behavior of this species has been extensively studied throughout the broad continental shelf region of the Ross Sea, this is the first study to report foraging behaviors and habitat affiliations among birds occupying continental slope waters. Continental slope habitat supports the greatest abundances of this species throughout its range, but we lack information about how intra-specific competition for prey might affect foraging and at-sea distribution and how these attributes compare with previous Ross Sea studies. Foraging trips increased in both distance and duration as breeding advanced from guard to crèche stage, but foraging dive depth, dive rates, and vertical dive distances travelled per hour decreased. Consistent with previous studies within slope habitats elsewhere in Antarctic waters, Antarctic krill (Euphausia superba) dominated chick meal composition, but fish increased four-fold from guard to crèche stages. Foraging-, focal-, and core areas all doubled during the crèche stage as individuals shifted distribution in a southeasterly direction away from the coast while simultaneously becoming more widely dispersed (i.e., less spatial overlap among individuals). Intra-specific competition for prey among Adélie penguins appears to influence foraging behavior of this species, even in food webs dominated by Antarctic krill.

Incidence of plastic fragments among burrow-nesting seabird colonies on offshore islands in northern New Zealand

Marine plastic pollution is ubiquitous throughout the worlds oceans, and has been found in high concentrations in oceanic gyres of both the northern and southern hemispheres. The number of studies demonstrating plastic debris at seabird colonies and plastic ingestion by adult seabirds has increased over the past few decades. Despite the recent discovery of a large aggregation of plastic debris in the South Pacific subtropical gyre, the incidence of plastics at seabird colonies in New Zealand is unknown. Between 2011 and 2012 we surveyed six offshore islands on the northeast coast of New Zealands North Island for burrow-nesting seabird colonies and the presence of plastic fragments. We found non-research related plastic fragments (0.031 pieces/m(2)) on one island only, Ohinau, within dense flesh-footed shearwater (Puffinus carneipes) colonies. On Ohinau, we found a linear relationship between burrow density and plastic density, with 3.5 times more breeding burrows in areas with plastic fragments found. From these data we conclude that plastic ingestion is a potentially a serious issue for flesh-footed shearwaters in New Zealand. Although these results do not rule out plastic ingestion by other species, they suggest the need for further research on the relationship between New Zealands pelagic seabirds and marine plastic pollution.

Circumpolar analysis of the Adélie Penguin reveals the importance of environmental variability in phenological mismatch

Evidence of climate-change-driven shifts in plant and animal phenology have raised concerns that certain trophic interactions may be increasingly mismatched in time, resulting in declines in reproductive success. Given the constraints imposed by extreme seasonality at high latitudes and the rapid shifts in phenology seen in the Arctic, we would also expect Antarctic species to be highly vulnerable to climate-change-driven phenological mismatches with their environment. However, few studies have assessed the impacts of phenological change in Antarctica. Using the largest database of phytoplankton phenology, sea-ice phenology, and Adélie Penguin breeding phenology and breeding success assembled to date, we find that, while a temporal match between Penguin breeding phenology and optimal environmental conditions sets an upper limit on breeding success, only a weak relationship to the mean exists. Despite previous work suggesting that divergent trends in Adélie Penguin breeding phenology are apparent across the Antarctic continent, we find no such trends. Furthermore, we find no trend in the magnitude of phenological mismatch, suggesting that mismatch is driven by interannual variability in environmental conditions rather than climate-change-driven trends, as observed in other systems. We propose several criteria necessary for a species to experience a strong climate-change-driven phenological mismatch, of which several may be violated by this system.

One method does not suit all: variable settlement responses of three procellariid species to vocalisation playbacks

Abstract Attempts to establish seabird colonies at restoration sites using artificial visual and auditory social cues have had varying success rates, differing between sites and species. The biological mechanisms responsible for this variation are poorly understood. We used experimental call playback to test the attraction of three sympatric procellariid species to auditory social cues in northern New Zealand. To test whether the size of nearby breeding colonies affected the level of response to call playback, audio recordings were broadcast from three similar locations with varying densities of breeding conspecifics within 1 km. Grey-faced Petrel (Pterodroma gouldi) were attracted to conspecific vocalisation playbacks at all three sites and also to playbacks of other species. Fluttering Shearwater (Puffinus gavia) were attracted to playback at only two locations. Flesh-footed Shearwater (Puffinus carneipes) were not attracted to playbacks, broadcast from only one location. For Grey-faced Petrels and Fluttering Shearwaters, response to call playback increased with increasing densities of nearby breeding conspecifics, suggesting there may be a relationship between attraction and the size of nearby potential source populations. For some procellariid species call playback represents a cost-effective alternative to other active restoration approaches, such as translocation. However, we caution that its effectiveness for individual species at different sites should be assessed at the outset of restoration initiatives.

A representation of a Tuawhenua worldview guides environmental conservation

Indigenous peoples and local communities interact with approximately two-thirds of the world’s land area through their worldviews and customary tenure regimes and offer significant knowledge contributions and lessons about sustainability. We worked with Tuawhenua Māori to document domains, concepts, and mechanisms within the worldview representation in a way that could guide environmental conservation in New Zealand. We then applied the framework to a cultural keystone species for Tuawhenua, the kererū ([New Zealand pigeon [(Hemiphaga novaeseelandiae]) to elucidate this human–environment relationship. Whakapapa (genealogy), whenua (land), and tangata (people) were interconnected domains that formed the conceptual basis of our framework. Within these domains, the concepts of mauri (life essence), mana (authority), and ihi (vitality) guided the expression of the community’s relationship with the environment. Cultural expressions related to the kererū demonstrated the cultural significance of the bird to Tuawhenua that went well beyond the ecological and intrinsic value of the species. The Tuawhenua worldview representation also emphasized the human– nature relationship and the role that metaphor plays in expressing this relationship. Indigenous peoples and local community worldviews are important for establishing priorities, reconciling the human relationship with the environment, and facilitating the coproduction of knowledge in response to pressing local and global environmental conservation issues.

Deciding when to lend a helping hand: a decision-making framework for seabird island restoration

Following the removal of an introduced species, island restoration can follow two general approaches: passive, where no further intervention occurs and the island is assumed to recover naturally, and; active, where recovery of key taxa (e.g. seabirds) is enhanced by manipulating movement and demography. Steps for deciding between these techniques are: (1) outlining an explicit restoration goal; (2) building a conceptual model of the system; (3) identifying the most effective management approach; and (4) implementing and monitoring outcomes. After decades of island restoration initiatives, retrospective analysis of species’ responses to active and passive management approaches is now feasible. We summarize the advantages of incorporating these analyses of past restoration results as an initial step in the decision-making process. We illustrate this process using lessons learned from the restoration of seabird-driven island ecosystems after introduced vertebrate eradication in New Zealand. Throughout seven decades of successful vertebrate eradication projects, the goals of island restoration have shifted from passive to active enhancement of island communities, which are heavily dependent on burrow-nesting petrel population recovery. Using a comparative analysis of petrel response to past predator eradications we built a conceptual model of petrel recovery dynamics and defined key site and species characteristics for use in a stepwise decision tree to select between active or passive seabird population management. Active restoration techniques should be implemented when seabird populations are absent or declining; and on islands with no nearby source colony, small remnant colonies, highly altered habitat with shallow soil and slopes, and with competitive species pairs. As we continue to restore complex island communities, decision-making tools using a logical, step-wise framework informed by previous restoration successes and failures can aid in increasing understanding of ecosystem response.

Variation in productivity of Grey-faced Petrels (Pterodroma gouldi) with local burrow density and breeding island

Abstract For long-lived birds, estimates of productivity can be effective indicators of environmental change or responses to management. Such estimates are also valuable in modelling population growth. We report estimates of nest survival for burrow-nesting Grey-faced Petrels (Pterodroma gouldi) from four islands off the north-eastern coast of New Zealand. We surveyed the contents of breeding burrows for up to four breeding seasons and followed the fates of 1371 eggs. We used a logistic-exposure modelling approach to investigate the effects of island, year, local burrow density and occupancy rate on nest survival. Daily nest survival varied between years and islands but declined with increasing local burrow density across all islands. Local burrow occupancy rate had no detectable effect. We estimated overall rates of breeding success on our island groups of 11% (95% confidence interval 9–14%) to 28% (26–30%). The negative density-dependent relationships between local burrow densities and productivity add to the growing evidence for this effect in burrow-nesting seabirds worldwide, in contrast to trends in surface-breeding species. The variation in productivity between our study colonies may be linked to the restoration histories of the islands and suggests that data from one location should be used cautiously when guiding management of the same species elsewhere.

Grey-faced petrel (Pterodroma gouldi) productivity unaffected by kiore (Pacific rats, Rattus exulans) on a New Zealand offshore island.

Burrow-nesting seabird populations are vulnerable to predation by introduced rats, because of their nesting habits and slow life histories. We investigated whether control of kiore (Pacific rats, Rattus exulans) by removal trapping, and during an unsuccessful community-led island-wide eradication attempt, had any effects on nest survival of grey-faced petrels (Pterodroma gouldi) on Ririwha (Stephenson Island), northeastern New Zealand. We compared nest survival between two plots at which rats were trapped and six un-trapped plots in 2010, as well as at all plots during and after the poisoning programme in 2011–2012. Neither mean rates of breeding burrow occupancy nor nest survival differed between trapped and un-trapped plots in 2010. We found no significant differences between years or between plots throughout the poisoning programme. Extrapolation of daily nest survival rates to the full 172-day combined egg and chick period gave an estimate of mean annual productivity for all plots combined of 0.285 (95% confidence interval 0.252–0.318), which is higher than on comparable predator-free islands. Although the absence of a detectable effect of kiore on breeding grey-faced petrels on Ririwha is reassuring, we can be less sure that smaller burrow-nesting seabirds on the island are secure.