Mitigation of seabird mortality on factory trawlers: trials of three devices to reduce warp cable strikes

Experimental trials were conducted onboard a stern trawler to identify the relative efficacy of three emerging mitigation measures (tori lines, warp scarer and Brady baffler) designed to reduce seabird mortality caused by warp cable strikes. The use of mitigation measures was clearly shown to substantially reduce seabird mortalities from collisions between seabirds and warp cables. Based on an established significant relationship between contact rate and seabird mortality, when using contact rate as an index of mortality there was a clear performance hierarchy of the three measures. Tori lines and the warp scarer were significantly more effective at reducing contacts than the Brady Baffler, whilst tori lines represent a smaller, but still significant, improvement on the warp scarer. While further testing would be required under local environmental and operational conditions, our findings are likely to have application for many trawl fisheries around the world.

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Factors affecting the number and mortality of seabirds attending trawlers and long-liners in the Kerguelen area

The factors affecting the number and the mortality rates of seabirds attending long-liners and trawlers fishing in the Kerguelen area were studied during four successive seasons (1994–1997), based on observations carried out onboard by dedicated observers. Twenty-four species of seabirds were observed attending fishing vessels, representing an average of 591 birds/census. The total numbers attending varied mainly according to the year, the cloud cover and the presence of offal from long-liners. The dumping of offal increased the numbers of birds attending the vessel, especially when the offal could be easily handled by birds. The activity of the vessels also affected the numbers attending, birds being more abundant during line setting and trawl hauling. White-chinned petrels were the most abundant ship-following seabirds, followed by black-browed albatrosses, giant petrels and cape petrels. The number of white-chinned petrels, black-browed and grey-headed albatrosses attending fishing vessels increased in the time between spring and autumn, whereas it was the reverse situation for giant petrels and cape petrels. Four species of seabirds were caught by fishing gear, mainly by long-lines: white-chinned petrels, and black-browed, grey-headed and wandering albatrosses. Taking into account the number of birds from each species attending long-liners and known to be potential by-catch, some species appear to be more susceptible to being caught than others. White-chinned and grey-headed albatrosses are caught in much higher proportions than the numbers present, whereas black-browed albatrosses are caught in lower numbers. Giant petrels are abundant around long-liners but were never caught. In long-liners, most birds were killed when the lines were set during the day or when the deployment of the scaring device was not successful, with an overall figure of 0.47 birds/1000 hooks. Only one albatross was caught when the lines were set during the night. White-chinned petrels represented 92.2% of all birds killed by long-liners. The number of birds caught varied significantly among months and among years. The type of bait used also affected the catch rate. The catch rate was related to the number of birds attending the long-liner only for black-browed albatrosses. Most birds killed by trawlers were entangled by the netsonde cable. The efficiency of mitigation measures in order to reduce seabird mortality is discussed and it is stressed that night setting is the most efficient way to reduce mortality and should be enforced everywhere when possible. However, further methods should be developed to reduce the mortality of species active at night, especially white-chinned petrels whose populations in the Indian Ocean may by threatened by long-line fisheries. Accepted: 15 October 1999     

Reducing seabird strikes with trawl cables in the pollock catcher-processor fleet in the eastern Bering Sea

Effective mitigation measures were developed to reduce high levels of seabird mortality due to warp strikes in southern hemisphere trawl fisheries. However, in northern hemisphere trawl fisheries, little is known about the extent of cable strike seabird mortality or techniques to mitigate it. We compared the rate of heavy seabird strikes by third-wire cables and warps, using three mitigation measures compared to a control of no mitigation. Experiments were conducted aboard two catcher-processor vessels targeting walleye pollock (Theragra chalcogramma) in the eastern Bering Sea: one that rendered offal into fish meal and fish oil (Vessel R) and one that minced offal prior to discharge (Vessel M). More birds attended Vessel M, but the rate of seabird cable strikes was higher on Vessel R due to the greater aerial extent of its cables. Streamer lines significantly reduced heavy seabird strikes by both cable types regardless of discharge characteristics. Reducing the aerial extent of third wires also reduced third-wire strike rates, but this method was less effective than streamer lines. Warp booms designed to divert seabirds from warps failed to reduce seabird warp strikes, but this technique could be improved. These results show for the first time that seabird strikes with modern third-wire trawl sonar cable systems can be reduced through mitigation or gear modification and that warp strikes can be mitigated with techniques similar to those found successful in southern hemisphere fisheries. Mitigation measures and concepts identified in this study should be widely applicable.     

Estimates of population size of white-chinned petrels and grey petrels at Kerguelen Islands and sensitivity to fisheries

White-chinned petrels Procellaria aequinoctialis and grey petrels Procellaria cinerea are among the most frequently killed seabird species by accidental bycatch, and both species have received strong conservation concern. Data on population size are required to evaluate the impact of bycatch and to establish management plans. We estimated the population size of both species at Kerguelen, Southern Indian Ocean, from 2004 to 2006 by explicitly taking into account detection probability of burrows using distance sampling and burrow occupancy. A total of 31 line-transects were distributed across the eastern part of Kerguelen, representing a total length of 566 km. Detectability was low (from 0.19 to 0.54 for white-chinned petrels, 0.58 for grey petrels). Burrow densities varied from 1.37±0.67 to 25.77±5.23 burrows ha⁻¹ for white-chinned petrels and was 2.78±0.79 burrows ha⁻¹ for grey petrels. For white-chinned petrels, these densities were extrapolated to the entire surface area of vegetation and there were 234 000 (186 000–297 000) active burrows on Kerguelen. For grey petrels, the number of active burrows for the eastern part of Kerguelen was 3400 (1900–5600). Based on these estimates, the potential biological removal method suggests that the additional mortality on birds caused by the fisheries operating around Kerguelen can be considered a serious threat for the species at least at the regional scale of the Southern Indian Ocean, especially for grey petrels.     

Assessing the potential impact of wind turbines on the endangered Galapagos Petrel <Emphasis Type="Italic">Pterodroma phaeopygia</Emphasis> at San Cristóbal Island,Galapagos

We evaluated the collision risk of Galapagos Petrels Pterodroma phaeopygia with a wind energy development recently constructed in the highlands of San Cristóbal Island, Galapagos. Trained observers recorded the movements of petrels at dusk and dawn from the wind project site, and from control sites located along ravines that host nesting colonies. Collision mortality was also assessed by monitoring circular plots and transect lines located under human-made structures. Petrel flight activity showed a bimodal pattern, with the majority of the movements recorded in the hours previous to sunrise. Most petrels (96%) moved along major ravines that descend from the highlands to the south–southeastern coast of the island. Significant differences in passage rates were found between the project and control sites, with only five petrels recorded on the site selected for turbine installation. Although our data suggest that wind farms will not be more detrimental to petrels than other existing man-made structures, a word of caution is made because even very low levels of additional mortality might be significant for a species with such low productivity and slow maturation rates. Moreover, some other possible indirect effects on habitat change and disturbance might occur that were not assessed in our study. A post-construction monitoring program should be implemented to adequately assess long-term effects on petrels and to enable these uncertainties to be satisfactorily addressed.     

Multivariate effects on seabird bycatch in the legal Patagonian toothfish longline fishery around Crozet and Kerguelen Islands

The effects of temporal, spatial, environmental and operational effects on seabird incidental mortality in the legal Patagonian toothfish longline fishery operating, between 2003 and 2006, in French exclusive economic zones of Crozet and Kerguelen Islands were analysed. During the study period, the mean bycatch rate varied from 0.05 to 0.12 birds per 1,000 hooks. Two species were concerned by incidental mortality: white-chinned petrels (88%) and grey petrels (11.5%). Males of white-chinned petrel seemed more at a risk than females. Logbooks data tended to underreport mortality when compared with dedicated fishery observers. The results indicate that temporal (season or phenology) and spatial (area) factors reflecting mortality risk for seabirds played the most significant role in the incidental mortality of the two species. Operational (integrated weight mainline, number of scaring lines and number of hooks hauled) and environmental factors (wind/vessel angle, moon brightness) were also influential, although less significantly, in increasing this mortality risk. Our two steps analyses by separately modelling the probability of presence and the abundance given presence suggest that the decrease in seabird bycatch over the period was mainly due to an important decrease in probability (occurrence) of mortality.     

Attraction of petrels to artificial lights in the Canary Islands: effects of the moon phase and age class

The extent and intensity of artificial night lighting has increased with urban development worldwide. The resulting light pollution is responsible for mortality among many Procellariiformes species which show nocturnal activity on their breeding grounds. Here, we report light‐induced mortality of Procellariiformes during a 9‐year study (1998–2006) on Tenerife, the largest island of the Canary archipelago. A total of 9880 birds from nine species were found grounded, the majority being Cory’s Shearwaters Calonectris diomedea (93.4%). For this species the majority of grounded birds were fledglings (96.4%), which fall apparently while leaving their nesting colony for the first time; for the smaller species (storm‐petrels) adult birds were more often grounded than fledglings. For almost all species, grounding showed a seasonal pattern linked with their breeding cycle. Certain phases of the moon influenced grounding of Cory’s Shearwater, with the extent of grounding being reduced during phases of full moon. The percentage of fledglings attracted to lights in relation to the fledglings produced annually varied between species and years (0–1.3% for the Madeiran Storm‐petrel Oceanodroma castro; 41–71% for Cory’s Shearwater). Mean adult mortality rates also varied between species (from 0.4% for the European Storm‐petrel Hydrobates pelagicus and the Cory’s Shearwater, to 2.3% for the Manx Shearwater Puffinus puffinus). Here we show that light‐induced mortality rates are of concern, at least for petrels and small shearwaters. Thanks to efforts involving civil cooperation, 95% of grounded birds have been returned to the wild. To minimize the impact of artificial lights on petrels we recommend several conservation measures: continuing rescue campaigns, alteration of light signatures and reduction of light emissions during the fledging peaks. Furthermore, we recommend that a monitoring program for petrel populations be implemented, as well as further studies to assess the fate of released fledglings and continued research to address why petrels are attracted to lights.     

Diving behaviour of white-chinned petrels and its relevance for mitigating longline bycatch

The white-chinned petrel (Procellaria aequinoctialis) is the seabird species most commonly killed by Southern Hemisphere longline fisheries. Despite the importance of diving ability for mitigating longline bycatch, little is known of this species’ diving behaviour. We obtained data from temperature–depth recorders from nine white-chinned petrels breeding on Marion Island, southwestern Indian Ocean, during the late incubation and chick-rearing period. Maximum dive depth (16 m) was slightly deeper than the previous estimate (13 m), but varied considerably among individuals (range 2–16 m). Males dived deeper than females, and birds feeding chicks dived deeper than incubating birds, but dive rate did not differ between the sexes. Time of day had no significant effect on dive depth or rate. Our findings will help to improve the design and performance of mitigation measures aimed at reducing seabird bycatch in longline fisheries, such as the calculation of minimum line sink rates and optimum aerial coverage of bird-scaring lines.     

Can predation by invasive mice drive seabird extinctions?

The house mouse, Mus musculus, is one of the most widespread and well-studied invasive mammals on islands. It was thought to pose little risk to seabirds, but video evidence from Gough Island, South Atlantic Ocean shows house mice killing chicks of two IUCN-listed seabird species. Mouse-induced mortality in 2004 was a significant cause of extremely poor breeding success for Tristan albatrosses, Diomedea dabbenena (0.27 fledglings/pair), and Atlantic petrels, Pterodroma incerta (0.33). Population models show that these levels of predation are sufficient to cause population decreases. Unlike many other islands, mice are the only introduced mammals on Gough Island. However, restoration programmes to eradicate rats and other introduced mammals from islands are increasing the number of islands where mice are the sole alien mammals. If these mouse populations are released from the ecological effects of predators and competitors, they too may become predatory on seabird chicks.     

One House Two Families: Petrel Squatters Get a Sniff of Low‐Cost Breeding Opportunities

Burrowing is a widespread nesting behaviour, found in vertebrates and invertebrates. It is particularly common in small procellariiform seabirds such as blue petrels (Halobaena caerulea) and Antarctic prions (Pachyptila desolata), two closely related petrel species. However, digging a burrow is costly and alternative strategies may evolve. Accordingly, blue petrel males can adopt two alternative nesting strategies: digging a new burrow or squatting in an empty one. Importantly, a blue petrel squatter arriving at the colony to breed is more likely to find empty Antarctic prion burrows than empty blue petrel burrows, since the former species only start breeding a month later. However, squatting in a prion’s burrow is risky for blue petrels as the legitimate owner very often returns and claims the burrow back, thus ruining the squatter’s breeding attempt. We present here results of a survey of two sympatric colonies of blue petrels and Antarctic prions on Kerguelen Island. Our data show that blue petrel squatters preferentially occupy blue petrel empty burrows. To investigate potential underlying mechanisms behind this preference, we used a simple Y‐maze design to show that blue petrels can discriminate and prefer their specific odour over the prion odour. Our results confirm the existence of alternative burrowing strategies in blue petrels and suggest that squatters could use olfaction to avoid the less suitable Antarctic prion burrows.     

High power line collision mortality of threatened bustards at a regional scale in the Karoo,South Africa

Quantifying avian collisions with power lines at large spatial scales is difficult, but such mortality is of serious conservation concern for many bird species worldwide. To investigate effects on the Endangered Ludwig's Bustard Neotis ludwigii and two other bustard species, mortality surveys were conducted quarterly along high‐voltage transmission lines at five sites (total length 252 km) across the Karoo for 2 years and one low‐voltage distribution line site (95 km) for 1 year. Thirty bird species were found, with Ludwig's Bustards constituting 69% and other bustards a further 18% of carcasses (n = 679 birds). Significant explanatory variables of Ludwig's Bustard collisions were season (collisions more likely in winter), rainfall (less likely in drier areas) and year on transmission lines (highlighting variability between years). Season and proximity to roads were significant variables on distribution lines, with collisions more likely during winter and away from roads. Ludwig's Bustard collision rates (corrected for survey biases) were higher on transmission (1.12; 95% confidence interval (CI) 0.40–2.58 bustards/km/year) than on distribution lines (0.86; 95% CI 0.30–1.96), but these smaller lines are four times as extensive in South Africa and so probably kill more birds. Despite being much less abundant, Kori Bustards Ardeotis kori were the second most commonly recovered species, with collision rates of 0.10 (95% CI 0.05–0.19) on transmission lines in the Nama Karoo alone. Collision rates are highly variable but suggest mortality suffered by these two species is worryingly high. This adds to growing concern about the impacts of power lines on bustards globally, so given ongoing expansion to the power grid, collision mitigation measures should be implemented at all new power lines.     

Origins, phytogeny and taxonomy of the gadfly petrels Pterodroma spp

Taxonomic characters of gadfly petrels (Procellariidae: Pterodroma spp.) are reviewed and the genus is redefined. The structure of the upper intestines, which have become helicoidally twisted to varying degrees in most species, is an important character not hitherto used. Results of a phylogenetic study of the genus based mainly on the development of helicoidal intestines agree substantially with findings from studies of the Mallophaga parasitizing these petrels. One species, the Kerguelen Petrel Lugensa brevirostris, previously classified in Pterodroma, is shown to have closer affinity with some fulmar genera. The Tahiti Petrel Pseudobulweria rostrata and its rare or extinct relatives, formerly placed in a superspecies of Pterodroma, are more closely related to the Procellaria and Bulweria petrels, and may be derived from the link between the subfamilies Procellariinae and Fulmarinae. From consideration of the fossil record, anatomical characters and Mallophaga, a phylogeny of the Procellariidae is proposed which supports its monophyletic origin. Gadfly petrels apparently descended from the fulmars through the ancestral lines of Snow Petrels Pagodroma, the Kerguelen Petrel and finally the Blue Petrel Halobaena, which may have given rise separately both to gadfly petrels and to the prions Pachyptila. A late Pliocene origin of Pterodroma in the vicinity of southern New Zealand is possible. The genus Pterodroma is divided into four subgenera, representing four connected radiations, and 29 species are recognised. In probable chronological order, Proaestrelata (new subgenus) contains five species and is restricted to the Pacific Ocean, Cookilaria comprises six species restricted as breeders to the South Pacific, Hallstroma has seven species mainly in the tropics of the Pacific, Indian and South Atlantic Oceans, whereas Pterodroma includes 11 species which extend as breeders from the southwest Pacific west to the South Atlantic and into the North Atlantic. Ecological, physical and physiological adaptations in the evolution of gadfly petrels are discussed.     

Measuring global trends in the status of biodiversity: red list indices for birds

The rapid destruction of the planet's biodiversity has prompted the nations of the world to set a target of achieving a significant reduction in the rate of loss of biodiversity by 2010. However, we do not yet have an adequate way of monitoring progress towards achieving this target. Here we present a method for producing indices based on the IUCN Red List to chart the overall threat status (projected relative extinction risk) of all the world's bird species from 1988 to 2004. Red List Indices (RLIs) are based on the number of species in each Red List category, and on the number changing categories between assessments as a result of genuine improvement or deterioration in status. The RLI for all bird species shows that their overall threat status has continued to deteriorate since 1988. Disaggregated indices show that deteriorations have occurred worldwide and in all major ecosystems, but with particularly steep declines in the indices for Indo-Malayan birds (driven by intensifying deforestation of the Sundaic lowlands) and for albatrosses and petrels (driven by incidental mortality in commercial longline fisheries). RLIs complement indicators based on species population trends and habitat extent for quantifying global trends in the status of biodiversity. Their main weaknesses are that the resolution of status changes is fairly coarse and that delays may occur before some status changes are detected. Their greatest strength is that they are based on information from nearly all species in a taxonomic group worldwide, rather than a potentially biased subset. At present, suitable data are only available for birds, but indices for other taxonomic groups are in development, as is a sampled index based on a stratified sample from all major taxonomic groups.     

Technical mitigation to reduce marine mammal bycatch and entanglement in commercial fishing gear: lessons learnt and future directions

Fisheries bycatch is one of the biggest threats to marine mammal populations. A literature review was undertaken to provide a comprehensive assessment and synopsis of gear modifications and technical devices to reduce marine mammal bycatch in commercial trawl, purse seine, longline, gillnet and pot/trap fisheries. Successfully implemented mitigation measures include acoustic deterrent devices (pingers) which reduced the bycatch of some small cetacean species in gillnets, appropriately designed exclusion devices which reduced pinniped bycatch in some trawl fisheries, and various pot/trap guard designs that reduced marine mammal entrapment. However, substantial development and research of mitigation options is required to address the bycatch of a range of species in many fisheries. No reliably effective technical solutions to reduce small cetacean bycatch in trawl nets are available, although loud pingers have shown potential. There are currently no technical options that effectively reduce marine mammal interactions in longline fisheries, although development of catch and hook protection devices is promising. Solutions are also needed for species, particularly pinnipeds and small cetaceans, that are not deterred by pingers and continue to be caught in static gillnets. Large whale entanglements in static gear, particularly buoy lines for pots/traps, needs urgent attention although there is encouraging research on rope-less pot/trap systems and identification of rope colours that are more detectable to whale species. Future mitigation development and deployment requires rigorous scientific testing to determine if significant bycatch reduction has been achieved, as well as consideration of potentially conflicting mitigation outcomes if multiple species are impacted by a fishery.

     

Minimising mortality in endangered raptors due to power lines: the importance of spatial aggregation to optimize the application of mitigation measures

Electrocution by power lines is one of the main causes of non-natural mortality in birds of prey. In an area in central Spain, we surveyed 6304 pylons from 333 power lines to determine electrocution rates, environmental and design factors that may influence electrocution and the efficacy of mitigation measures used to minimise electrocution cases. A total of 952 electrocuted raptors, representing 14 different species, were observed. Electrocuted raptors were concentrated in certain areas and the environmental factors associated with increased electrocution events were: greater numbers of prey animals; greater vegetation cover; and shorter distance to roads. The structural elements associated with electrocutions were shorter strings of insulators, one or more phases over the crossarm, cross-shaped design and pylon function. Of the 952 carcasses found, 148 were eagles, including golden eagle (Aquila chrysaetos), Spanish imperial eagle (Aquila adalberti) and Bonelli's eagle (Aquila fasciata). Electrocuted eagles were clustered in smaller areas than other electrocuted raptors. The factors associated with increased eagle electrocution events were: pylons function, shorter strings of insulators, higher slopes surrounding the pylon, and more numerous potential prey animals. Pylons with increased string of insulators had lower raptor electrocution rates than unimproved pylons, although this technique was unsuccessful for eagles. Pylons with cable insulation showed higher electrocution rates than unimproved pylons, both for raptors and eagles, despite this is the most widely used and recommended mitigation measure in several countries. To optimize the application of mitigation measures, our results recommend the substitution of pin-type insulators to suspended ones and elongating the strings of insulators.     

Solving man-induced large-scale conservation problems: the Spanish imperial eagle and power lines

Background

Man-induced mortality of birds caused by electrocution with poorly-designed pylons and power lines has been reported to be an important mortality factor that could become a major cause of population decline of one of the world rarest raptors, the Spanish imperial eagle (Aquila adalberti). Consequently it has resulted in an increasing awareness of this problem amongst land managers and the public at large, as well as increased research into the distribution of electrocution events and likely mitigation measures.

Methodology/Principal Findings

We provide information of how mitigation measures implemented on a regional level under the conservation program of the Spanish imperial eagle have resulted in a positive shift of demographic trends in Spain. A 35 years temporal data set (1974–2009) on mortality of Spanish imperial eagle was recorded, including population censuses, and data on electrocution and non-electrocution of birds. Additional information was obtained from 32 radio-tracked young eagles and specific field surveys. Data were divided into two periods, before and after the approval of a regional regulation of power line design in 1990 which established mandatory rules aimed at minimizing or eliminating the negative impacts of power lines facilities on avian populations. Our results show how population size and the average annual percentage of population change have increased between the two periods, whereas the number of electrocuted birds has been reduced in spite of the continuous growing of the wiring network.

Conclusions

Our results demonstrate that solving bird electrocution is an affordable problem if political interest is shown and financial investment is made. The combination of an adequate spatial planning with a sustainable development of human infrastructures will contribute positively to the conservation of the Spanish imperial eagle and may underpin population growth and range expansion, with positive side effects on other endangered species.     

Phylogenetic relationships in Pterodroma petrels are obscured by recent secondary contact and hybridization

The classification of petrels (Pterodroma spp.) from Round Island, near Mauritius in the Indian Ocean, has confounded researchers since their discovery in 1948. In this study we investigate the relationships between Round Island petrels and their closest relatives using evidence from mitochondrial DNA sequence data and ectoparasites. Far from providing clear delimitation of species boundaries, our results reveal that hybridization among species on Round Island has led to genetic leakage between populations from different ocean basins. The most common species on the island, Pterodroma arminjoniana, appears to be hybridizing with two rarer species (P. heraldica and P. neglecta), subverting the reproductive isolation of all three and allowing gene flow. P. heraldica and P. neglecta breed sympatrically in the Pacific Ocean, where P. arminjoniana is absent, but no record of hybridization between these two exists and they remain phenotypically distinct. The breakdown of species boundaries in Round Island petrels followed environmental change (deforestation and changes in species composition due to hunting) within their overlapping ranges. Such multi-species interactions have implications not only for conservation, but also for our understanding of the processes of evolutionary diversification and speciation.     

SUBFOSSIL PETREL BONES FROM THE CHATHAM ISLANDS

The breeding community of petrels on the Chatham Islands has previously seemed curiously poor compared to that of analogous stations in the Indian Ocean or South Atlantic (14 species compared with 18 in the Tristan-Gough group). Examination of subfossil deposits from the Chatham Islands probably dating from the early stages of human colonization which occurred within the last few hundred years reveals remains of at least 20 petrels, all of which except one may well have bred in the past, without including storm petrels, of which two species are still known to breed while others may also have bred in the past. The grand total of at least 21 breeding species, many apparently in vast numbers, would probably make the archipelago the most important breeding station for petrels in the world at the time of the first human colonization. It seems possible that in addition to the present breeding species the following may have bred: at least one endemic species of gadfly petrel, the Magenta Petrel Pterodroma magentae , and local populations of at least two other gadfly petrels, two shearwaters of the genus Procellaria and two of the genus Puffinus and a sooty albatross of the genus Phoebetria . Small populations of these, and perhaps other undetected species as well, may still survive in inaccessible places.     

Methodologies for Surveying Herpetofauna Mortality on Rural Highways

Abstract: Road mortality can contribute to local and regional declines in amphibian and reptile populations. Thus, there is a need to accurately and efficiently identify hotspots of road-mortality for hazard assessment and mitigation. In 2002, we conducted walking and driving surveys throughout an extensive rural highway network in northern New York, USA, to evaluate survey methods and to quantify spatial and temporal patterns of herpetofauna road-mortality. In 2004, we repeated the surveys at a subset of locations to quantify interannual repeatability. Reptile and amphibian species had different peak periods of road-mortality because they differed in the causes of movements that resulted in crossings. Spatial locations of herpetofauna road-mortality were concentrated at a limited number of hotspots. Hotspots overlapped across species and were located at consistent locations across years. Results of walking and driving surveys were highly repeatable among survey teams, but driving surveys underestimated the density of road-mortality because many animals were missed. Detection failure was higher in some taxa (e.g., frogs) than others (e.g., turtles). Our results indicate that it is possible to design a valid, efficient methodology for locating hotspots of reptile and amphibian road-mortality along a road network and, thus, pinpoint priority sites for mitigation.     

Widespread gene flow between oceans in a pelagic seabird species complex

Global‐scale gene flow is an important concern in conservation biology as it has the potential to either increase or decrease genetic diversity in species and populations. Although many studies focus on the gene flow between different populations of a single species, the potential for gene flow and introgression between species is understudied, particularly in seabirds. The only well‐studied example of a mixed‐species, hybridizing population of petrels exists on Round Island, in the Indian Ocean. Previous research assumed that Round Island represents a point of secondary contact between Atlantic (Pterodroma arminjoniana) and Pacific species (Pterodroma neglecta and Pterodroma heraldica). This study uses microsatellite genotyping and tracking data to address the possibility of between‐species hybridization occurring outside the Indian Ocean. Dispersal and gene flow spanning three oceans were demonstrated between the species in this complex. Analysis of migration rates estimated using bayesass revealed unidirectional movement of petrels from the Atlantic and Pacific into the Indian Ocean. Conversely, structure analysis revealed gene flow between species of the Atlantic and Pacific oceans, with potential three‐way hybrids occurring outside the Indian Ocean. Additionally, geolocation tracking of Round Island petrels revealed two individuals travelling to the Atlantic and Pacific. These results suggest that interspecific hybrids in Pterodroma petrels are more common than was previously assumed. This study is the first of its kind to investigate gene flow between populations of closely related Procellariiform species on a global scale, demonstrating the need for consideration of widespread migration and hybridization in the conservation of threatened seabirds.