Nightjar Caprimulgus Research Articles

Resolving a heated debate: The utility of prescribed burning as a management tool for biodiversity on lowland heath

Abstract Lowland heath is a priority habitat for conservation, nowadays largely managed for biodiversity. Historically, prescribed burning has been the principal management tool, but there are increasing calls to substitute burning with cutting to improve biodiversity outcomes. However, poor understanding of potential impacts compromises decision making. Our study was carried out in the New Forest National Park, the largest area of lowland heath in Europe. Using a multi‐trophic approach, we compared the ecological impact of prescribed burning with two types of vegetation cutting (swiping and baling) as management tools for biodiversity outcomes for up to 20 years after management. Indicators included: common standards monitoring (CSM) assessment; vegetation species assemblage; below‐ and above‐ground invertebrate biodiversity; and available food resources for two characteristic heathland birds—the Dartford Warbler Sylvia undata and the Nightjar Caprimulgus europaeus. When compared with swiped sites, areas managed by prescribed burning resulted in: better habitat condition (assessed by CSM); higher cover of heathers; lower bracken cover; more areas of bare ground. We found no evidence that burning is detrimental for the investigated components of biodiversity. Cutting by swiping did not replicate the benefits of burning. Swiping supported grassland conditions that suit non‐heathland species. Baling resulted in habitat condition similar to prescribed burning but restricted replication of baled sites limited our conclusions. However, swiped sites supported high invertebrate abundance and diversity, including food resources for Dartford Warbler and Nightjar. Synthesis and applications. Removing burning from the management programme is likely to reduce heathland condition. Biodiversity is encouraged by a mosaic of management and more mobile species, such as birds, will exploit the resources provided by several management techniques. Including some cutting in a rotational regime is likely to be beneficial although prescribed burning should form the majority of the management programme, Lowland heathland differs fundamentally from upland heathland/moorland and it is not easy to transfer the results. Current heathland CSM does not adequately assess wider biodiversity on protected areas but is effectively an assessment of vegetation feature condition. Including invertebrates in surveys provides a more nuanced assessment of heathland condition.

Rush or relax: migration tactics of a nocturnal insectivore in response to ecological barriers

During their annual migration, avian migrants alternate stopover periods, for refuelling, with migratory flight bouts. We hypothesise that European Nightjars (Caprimulgus europaeus) adapt their daily migration tactics in association with biomes. We tracked the autumn migration of 24 European Nightjars, from breeding populations in Mongolia, Belgium and UK, using GPS-loggers and multi-sensor data loggers. We quantified crepuscular and nocturnal migration and foraging probabilities, as well as daily travel speed and flight altitude during active migration in response to biomes. Nightjars adopt a rush tactic, reflected in high daily travel speed, flight altitude and high migration probabilities at dusk and at night, when travelling through ecological barriers. Migration is slower in semi-open, hospitable biomes. This is reflected in high foraging probabilities at dusk, lower daily travel speed and lower migration probabilities at dusk. Our study shows how nightjars switch migration tactics during autumn migration, and suggest nightjars alternate between feeding and short migratory flight bouts within the same night when travelling through suitable habitats. How this may affect individuals’ fuel stores and whether different biomes provide refuelling opportunities en route remains to be investigated, to understand how future land-use change may affect migration patterns and survival probabilities.

Leucistic plumage as a result of progressive greying in a cryptic nocturnal bird

Leucism, broadly defined as the lack of melanin pigmentation, occurs in many animal species. Most studies on leucism and other colour aberrations are based on opportunistic observations or small cross-sectional samples, thus limiting our ability to produce reliable results and test theoretical predictions. This study combines cross-sectional and longitudinal data collected in 2016–2020 from a population of red-necked nightjars (Caprimulgus ruficollis). The goals of the study are (i) to investigate sex and age effects on partial leucism, (ii) to separate within-subject effects (progressive greying) from between-subject effects (selective disappearance), and (iii) to examine differences in body mass, structural size, and life span between leucistic and non-leucistic individuals. The probability of leucism in nightjars increased from juveniles to adults at similar rates in males and females. Our longitudinal analysis and life-span comparisons indicated a minor contribution of selective disappearance to age-related changes in leucism, but rather suggested that the loss of melanin from feathers can be attributed to progressive greying in ageing adults. Body mass and size were consistently smaller (5% and 1.5%, respectively) in leucistic than in non-leucistic nightjars, although the reason for this difference remains unclear. Our study sheds light on the sources and mechanisms of variation in leucism in natural populations and its relationship with important life-history traits, such as life span.

Moth biomass and diversity in coniferous plantation woodlands

Moths are a vital ecosystem component and key food source for many species, but have shown widespread and often severe declines. Multiple factors have been implicated in these declines, although the most important large-scale factors in the temperate zone are considered to be land use change and climate change. The majority of forest cover in the U.K. and elsewhere in Europe is dominated by intensively managed plantation woodlands, and studies have shown reduced broadleaved woodland cover can negatively affect moth diversity and biomass. However, few studies have examined how open habitats within the plantation forest matrix, which often represent a large proportion of the total forest area, are utilised by moth species. Here, we aimed to determine: (1) how moth biomass in open habitats within plantation forests varies seasonally and in response to management; and (2) how species diversity and Welsh conservation priority (“Section 7”) species respond to management at multiple spatial scales. We sampled moth communities in open habitats within five coniferous plantation forests across Wales, using light traps deployed in areas that ranged from < 1 to > 20 years post-felling. We found a significant non-linear relationship between space, time and moth biomass, with a significant peak in biomass in the summer months (∼29th June) suggesting important phenological effects with associated implications for dependent species. Biomass was also strongly affected by time since felling, with older habitats in general supporting a higher moth biomass, although this was dependent on the seasonal variation in habitat ‘greenness’ and productivity, as measured by NDVI. We also found that the abundances of Welsh priority species responded positively to increased extents of open habitats of ages 1–10 years post felling, but the amount of recent clear felling (0 years post felling) in the surrounding landscape had a negative correlation with both abundance and diversity. We conclude that habitat, seasonality/ productivity and short-term weather variations play a key role in determining moth biomass, species diversity and the presence of Welsh priority moth species within managed coniferous plantation woodland. This means there is an opportunity for forest management practices to adopt measures that can not only enhance moth biomass productivity, in turn supporting insectivorous species such as European nightjar Caprimulgus europaeus, but also deliver wider ecosystem services through the provision of habitat matrices that support invertebrate species of conservation concern.

Taxonomic revision of the Savanna Nightjar (Caprimulgus affinis) complex based on vocalizations reveals three species

BackgroundThe Savanna Nightjar (Caprimulgus affinis) is a widespread, polytypic species which was previously treated as two or three species. It is currently treated as a single species based on superficial similarity of their songs but no detailed comparisons of the songs in this complex have been made.MethodsA total of 15 acoustic variables were measured for the songs of 86 individuals representing 8 of the 10 subspecies in the complex.ResultsThree major groups can be distinguished based on univariate and multivariate analyses: a northern group consisting of the subspecies C. a. monticolus, C. a. amoyensis and C. a. stictomus; a southern group consisting of C. a. affinis, C. a. kasuidori, C. a. timorensis and C. a. propinquus; and a third group in the Philippines consisting of C. a. griseatus.ConclusionsIt is here argued that these groups are best treated as species, and that Franklin’s Nightjar (C. monticolus) and Kayumanggi Nightjar (C. griseatus) are reinstated as separate species.

Flight altitude dynamics of migrating European nightjars across regions and seasons.

ABSTRACTAvian migrants may fly at a range of altitudes, but usually concentrate near strata where a combination of flight conditions is favourable. The aerial environment can have a large impact on the performance of the migrant and is usually highly dynamic, making it beneficial for a bird to regularly check the flight conditions at alternative altitudes. We recorded the migrations between northern Europe and sub-Saharan Africa of European nightjars Caprimulgus europaeus to explore their altitudinal space use during spring and autumn flights and to test whether their climbs and descents were performed according to predictions from flight mechanical theory. Spring migration across all regions was associated with more exploratory vertical flights involving major climbs, a higher degree of vertical displacement within flights, and less time spent in level flight, although flight altitude per se was only higher during the Sahara crossing. The nightjars commonly operated at ascent rates below the theoretical maximum, and periods of descent were commonly undertaken by active flight, and rarely by gliding flight, which has been assumed to be a cheaper locomotion mode during descents. The surprisingly frequent shifts in flight altitude further suggest that nightjars can perform vertical displacements at a relatively low cost, which is expected if the birds can allocate potential energy gained during climbs to thrust forward movement during descents. The results should inspire future studies on the potential costs associated with frequent altitude changes and their trade-offs against anticipated flight condition improvements for aerial migrants.

Metabarcoding reveals selective dietary responses to environmental availability in the diet of a nocturnal, aerial insectivore, the European Nightjar (Caprimulgus europaeus)

Many bird species are vulnerable to environmental change, so knowledge of their diet and its variation can help understand population status and flexibility to respond to change. Insectivorous species are predicted to have a flexible diet within and between individuals, which can respond to naturally fluctuating prey abundance, thus allowing opportunistic exploitation of available resources. We analysed the diet of a nocturnal, aerial insectivore, the European NightjarCaprimulgus europaeus, using high‐throughput metabarcoding. We quantified diet diversity and composition of 130 faecal samples from nests and roosts on a northern breeding site in the UK from 2015 to 2018, and compared differences among individuals and years. Although dominated by moths, diet varied significantly between individual faecal samples and between years and months. Prey species composition varied between years, and was more variable between samples in 2017 than in other years. Faecal samples were significantly more likely to contain moth species with a wingspan of &gt; 60 mm and less likely to contain moth species of &lt; 25 mm wingspan. This indicated size‐selective foraging, which also varied between months and years. Diet was driven by interindividual variation, indicating population‐level flexibility in prey choice. Metabarcoding provided a valuable tool in the exploration of insectivorous diets, but efforts are needed to build comprehensive reference libraries in order to compile full prey species lists.

Body mass dynamics of migratory nightjars are explained by individual turnover and fueling

AbstractBody mass is a commonly used indicator of the energy stores of migratory animals and there is considerable evidence that it is a critical determinant of migration decisions and outcomes. Mean population mass often increases during the post-breeding period in most migratory species. Usually, this increase is interpreted as the result of fuel accumulation for migration based on the assumption that mean population mass mirrors mean individual mass. However, an empirical test of this assumption is lacking, and it is unknown whether the general increase in mean population mass is entirely the result of within-individual mass gain, or if it rather reflects a change in the nature of individuals in the population (mass-dependent turnover). We investigated changes in body mass during the post-fledging period of a migratory bird, the Red-necked Nightjar (Caprimulgus ruficollis), and combined longitudinal and cross-sectional data collected over 9 years to disentangle the relative contribution of individual-level (mass gain) and population-level (selective appearance and disappearance) processes. We found that the average body mass of fully-developed juveniles increased as the season progressed and that both individual mass gain and the selective disappearance of lighter individuals contributed to this increase. Contrary to the general expectations for migrants, the turnover of individuals contributed 3.5 times more to the seasonal increase in average body mass than individual mass gain. On a practical note, this differential contribution implied a discrepancy of over 40% between the time-average rates of mass gain (fuel deposition rates) estimated from population-level and individual-level data. Our study calls for caution in the use of population-level changes in body mass to make inferences about individual fuel deposition rates and, more generally, indicates that longitudinal and cross-sectional approaches need to be combined to uncover phenotype-time correlations in natural populations.

Biometrics, distribution, and breeding notes of Savanna Nightjar (Caprimulgus affinis) in several islands of Indonesia

Abstract. Widodo W, Sulistyadi E. 2021. Biometrics, distribution, and breeding notes of Savanna Nightjar (Caprimulgus affinis) in several islands of Indonesia. Biodiversitas 22: 2756-2762. The Savanna Nightjar Caprimulgus affinis Horsfield, 1821, a member of the family Caprimulgidae, is a sexually dimorphic, insectivorous nightjar species commonly found in Southeast Asia, including Indonesia. A least-concern species, Savanna Nightjar has diverse habitats from grasslands to shrubs to high-rise rooftops in the middle of the city. Yet, its breeding habits, particularly in urban areas, remain obscure. The purpose of the research is to discuss the biometric measurement, distribution pattern and notes of the breeding of Savanna Nightjar, through analyzing 50 specimens originating from Java, Sumatra, Billiton, Borneo, and Nusa Tenggara Islands belonging to the Museum of Zoology Bogor (MZB) in Cibinong and through a series of observation. The morphological measurements of specimens include the measurements of the length of the bodies, the wings, the tails, the bills, and the tarsi. One-way ANOVA analysis showed that the length of the body and the tail of Savanna Nightjar in Nusa Tenggara are significantly longer than those of Savanna Nightjar in Java, Sumatra, Billiton, or Borneo islands. The biometric differences could have been contributed to different habitat characteristics. Additionally, it was found the likelihood of breeding habit of Savanna Nightjar in urban areas with that of the countrysides because of the resemblance of semi-natural ecosystems in the city such as artificial rivers, small lakes, and parks to Nightjar’s open landscape natural habitats, which facilitates the breeding habits. Still, the migration of Savanna Nightjar from open country-landscapes to the metropolitan areas remains elusive and requires a more detailed study

Scientific data laundering: Chimeric mitogenomes of a sparrowhawk and a nightjar covered-up by forged phylogenies

In 2017, Gang Liu and colleagues published a paper in this journal in which they described the first mitochondrial genome of Japanese Sparrowhawk Accipiter gularis (Aves, Accipitriformes). The paper included two phylogenies (one based on full mitogenomes, the other on mitochondrial 12S/16S rRNA sequences) that placed this species among the goshawks and sparrowhawks (genus Accipiter). These phylogenies also included a previously published mitogenome of Grey Nightjar Caprimulgus indicus. Here, we show that the published mitogenome of A. gularis is a chimera of three species (a sparrowhawk, a buzzard and a dove), and that the published mitogenome of C. indicus is a chimera of two owl species. Phylogenetic re-analysis showed substantial differences from those published by Liu et al. (2017): the A. gularis sequence was placed among Streptopelia doves in the 12S/16S rRNA tree, and the C. indicus sequence was placed among Otus owls in the mitogenomic and mitochondrial 12S/16S rRNA trees. The phylogenies in Liu et al. (2017) showed several other peculiarities: (i) the inclusion of Javan Hawk-eagle Nisaetus bartelsi in the mitogenome tree (whereas no mitogenome is available of this species and no such sequence has been described in the literature), (ii) reciprocal monophyly of the genera Buteo, Leucopternis and Buteogallus (whereas multiple previous studies have shown these to be para- or polyphyletic), and (iii) the placement of Black-chested Buzzard Eagle Geranoaetus melanoleucus and Crane Hawk ‘Geranoaetus’ (=Geranospiza) caerulescens as sister species (whereas all previous studies have shown these to be distantly related). Close examination of the figures in Liu et al. (2017) revealed that both phylogenies have been manually prepared or modified. The evidence indicates that Liu et al. (2017) published phylogenies that were not based on existing data but were fabricated to reflect preconceived ideas about phylogenetic relationships. The phylogenies published by Liu et al. (2017) give the impression that the mitogenomic sequence described in their paper (A. gularis) and another one (C. indicus) described by Zhao et al. (2016) are authentic and correctly identified, whereas in reality these sequences are highly problematic chimeras. The term ‘scientific data laundering’ is proposed for the practice of hiding poor or erroneous research data with fabricated or falsified figures.

Using UAV‐mounted thermal cameras to detect the presence of nesting nightjar in upland clear‐fell: A case study in South Wales, UK

Abstract1. Confirming the presence and location of European Nightjar Caprimulgus europaeus nests is a significant fieldwork challenge in ecological monitoring. Nest sites can be located through direct observation or capture and radio tracking of breeding individuals; however, such work is time consuming, disturbing and costly.2. Unmanned aerial vehicles (UAV) equipped with thermal sensors may enable rapid survey over large areas by detecting nest locations based on the contrast of relatively warm nests and the surrounding cooler ground. The application of this concept using UAV‐mounted thermal sensors was trialled in two upland clear‐fell forestry sites in South Wales, UK.3. Detection trials were undertaken at five known nightjar nest sites to assess optimal timing and flight height for surveys. Nest heat signatures were clear during dusk and dawn, but not during the daytime. Nests were identifiable at flight heights up to 25 m, but flight heights of 12–20 m were optimal for the numbers of pixels per nest.4. This approach was tested in a field trial of a 17‐ha forestry site where the presence and position of nesting nightjars were unknown. An automated transect at dusk and dawn at 15 m flight elevation identified two active nightjar nests and four male nightjar roost sites. Without image analysis automation, the process of manual inspection of 2607 images for ‘hotspots’ of the approximate size and shape of nightjar nests was laborious.5. The UAV approach took around 18 h including survey time, processing and ground verification, whilst a nightjar nest finding survey would take 35 h for the same area. The small size of nightjars and the low resolution of the thermal sensors requires low altitude flight in order to maximize detectability and pixel coverage. Low flight elevation requires more consideration of the risk of collision with trees or posts. Consequently, the approach would not be suitable for covering areas of highly variable terrain.

Testing for effects of tail-mounted radio tags and environmental variables on European Nightjar Caprimulgus europaeus nest survival

ABSTRACT Capsule Monitoring of European Nightjar Caprimulgus europeaus nest sites over seven years produced no evidence of a negative effect of tail-mounted radio tag deployment on nest success. Aims To test whether nest success of European Nightjars was affected by radio tag deployment. Methods The breeding success of European Nightjars was monitored at the Brechfa West Wind Farm, Carmarthenshire, Wales, from 2013 to 2019. A total of 85 nests were located through a combination of capture and radio tracking of breeding individuals, and direct observation combined with focused searching. All located nests were subsequently monitored through a combination of visual checks and trail camera deployment until their natural conclusion. Results No evidence was identified to support a negative effect of tail-mounted radio tag deployment on the nest success of European Nightjars. However, nesting success (at least one chick fledged) was positively associated with mean temperature during the nesting period, although the strength of this effect varied through time. Conclusion The use of tail-mounted radio tags on European Nightjars had no significant negative effect on nest success.

A molecular analysis of the mysterious Vaurie’s Nightjar Caprimulgus centralasicus yields fresh insight into its taxonomic status

A molecular analysis of the mysterious Vaurie’s Nightjar Caprimulgus centralasicus yields fresh insight into its taxonomic status

Habitat Selection by the European Nightjar Caprimulgus europaeus in North-Eastern Poland: Implications for Forest Management

Research Highlights: Intensive forest management practices generally have a negative effect on biodiversity. However, the creation of new, open habitats as a consequence of timber harvesting within large areas of woodland may be favorable to some bird species. Background and Objectives: Habitat selection of the European Nightjar Caprimulgus europaeus in a coniferous woodland area in northeastern Poland was studied in order to specify management recommendations. Materials and Methods: To define the influence of various environmental parameters on territory occupation, 11 micro- and 3 macrohabitat factors were analyzed. Results: Denser vegetation in the ground layer deterred birds from nesting in clearings with such characteristics. Moreover, Nightjars preferentially inhabited sites adjacent to young stands of trees. Birds preferred plots with a higher number of clearings in the neighborhood, as this enabled them to enlarge their foraging area. Other microhabitat factors (e.g., the type, age and area of clearings), as well as macroscale factors like distances to the forest edge, nearest roads and human settlements, were of no importance. Conclusions: Knowledge of the Nightjar preferences may be useful in working out a compromise between an appropriate level of clear-felling and conservation of other bird species requiring preservation of old tree stands.

Identification of different song types in the European Nightjar Caprimulgus europaeus

ABSTRACT Capsule: Two distinct song types were identified for male European Nightjars Caprimulgus europaeus with their relative frequency of use changing through the breeding season, indicating a possible link to paired status. Aims: To test whether two song types could be defined in audio recordings and whether use differed in relation to the paired status of males. Methods: Unattended acoustic recording devices were placed at a Nightjar study site in Nottinghamshire, United Kingdom, and recordings of churring vocalizations were made during two periods of the breeding season. These recordings were then analyzed to identify the presence/absence of the song terminal phrase and associated audible features. Results: Two distinct song types were identified in the recorded audio data that differed in their terminal phrasing and overall song duration. The number of Nightjar songs with a terminal phrase increased significantly between the two sampling periods, from lower levels during the site arrival period, to higher levels during the first clutch initiation period. Conclusion: This study showed that the use of Nightjar song types appears to vary through the breeding season, with males being more likely to produce song with a terminal phrase during the first clutch initiation period, when they are more likely to be paired or in the presence of a female. The unattended acoustic recording method may provide a minimally intrusive means of assessing the number of Nightjar breeding pairs and not just singing males.

The avifauna, conservation and biogeography of the Njesi Highlands in northern Mozambique, with a review of the country’s Afromontane birdlife

Northern Mozambique’s ‘sky-island’ mountains have become increasingly recognised for their Afromontane birdlife. Despite growing ornithological coverage, however, several Mozambican mountains remain poorly known. We present results from a three-week survey of three such mountains: the Njesi Plateau, Mount Chitagal and Mount Sanga (collectively termed the Serra Jeci/Njesi highlands) in Niassa, north-western Mozambique. These mountains had received little/no previous biological surveys, but are the only known locality of the endangered Mozambique Forest-warbler Artisornis sousae (formerly Long-billed Tailorbird A. moreaui sousae). We recorded 159 species, including several range-extensions of both conservation and biogeographical importance (e.g. Dapple-throat Arcanator orostruthus), and 15 Afromontane biome-restricted species, including two species new for Mozambique (Montane Nightjar Caprimulgus poliocephalus and Dark Batis Batis crypta). We found good numbers of Mozambique Forest-warblers on all three mountains, extending the distribution of this little-known and highly range-restricted taxon. Combining our data with previous surveys (collectively totalling 184 species), we critically appraise the Njesi Important Bird Area (MZ015), based on the occurrence of 26 Important Bird Area (IBA) trigger species, correcting previous errors in its assessment and suggest extensions that include Mount Sanga to the north, and extensive miombo woodland to the west. The site also qualifies as a Key Biodiversity Area (KBA) and Alliance for Zero Extinction (AZE) site. Finally, we review all published ornithological literature from Mozambique’s mountains and discuss emergent biogeographical patterns in their Afromontane avifauna, while also highlighting key sites that require ornithological surveys. We find that the Njesi highlands are more biogeographically linked to Tanzania, than to mountains farther south in Mozambique and Malawi. Collectively, our results illustrate the critical value of even small Afromontane forests on remote highlands for some of Africa’s least known, and most threatened avifauna.

Correlates of individual variation in the porphyrin-based fluorescence of red-necked nightjars (Caprimulgus ruficollis)

Many nocturnal animals, including invertebrates such as scorpions and a variety of vertebrate species, including toadlets, flying squirrels, owls, and nightjars, emit bright fluorescence under ultraviolet light. However, the ecological significance of this unique coloration so attached to nocturnality remains obscure. Here, we used an intensively studied population of migratory red-necked nightjars (Caprimulgus ruficollis) to investigate inter-individual variation in porphyrin-based pink fluorescence according to sex, age, body condition, time of the year, and the extent of white plumage patches known to be involved in sexual communication. Males and females exhibited a similar extent of pink fluorescence on the under-side of the wings in both juvenile and adult birds, but males had larger white patches than females. Body condition predicted the extent of pink fluorescence in juvenile birds, but not in adults. On average, the extent of pink fluorescence in juveniles increased by ca. 20% for every 10-g increase in body mass. For both age classes, there was a slight seasonal increase (1–4% per week) in the amount of fluorescence. Our results suggest that the porphyrin-based coloration of nightjars might signal individual quality, at least in their first potential breeding season, although the ability of these and other nocturnal birds to perceive fluorescence remains to be unequivocally proven.

Nocturnal migration of night hunters

Ecology Bird migration is a vast global biannual phenomenon requiring food as fuel on a similar scale. Superimposed on these twice-yearly events are other regular occurrences, including tightly predictable lunar cycles. Norevik et al. wondered how the moon might influence migration of birds that hunt at night, such as the European nightjar Caprimulgus europaeus . These birds hunt insect prey by sight and are more active during moonlit nights, giving a monthly boost to their food intake. Using GPS-linked data loggers, the authors found that migration activity in these birds en route tends to peak after a full-moon feeding binge. The lunar cycle strongly synchronizes migration responses among individuals, which means a large proportion of a population migrates simultaneously. Such synchronized responses may make them vulnerable to climate change–related or other adverse events along their migration route. PLOS Biol. 10.1371/journal.pbio.3000456 (2019).

The trade-off between fix rate and tracking duration on estimates of home range size and habitat selection for small vertebrates.

Despite advances in technology, there are still constraints on the use of some tracking devices for small species when gathering high temporal and spatial resolution data on movement and resource use. For small species, weight limits imposed on GPS loggers and the consequent impacts on battery life, restrict the volume of data that can be collected. Research on home range and habitat selection for these species should therefore incorporate a consideration of how different sampling parameters and methods may affect the structure of the data and the conclusions drawn. However, factors such as these are seldom explicitly considered. We applied two commonly-used methods of home range estimation, Movement-based Kernel Density Estimation (MKDE) and Kernel Density Estimation (KDE) to investigate the influence of fix rate, tracking duration and method on home range size and habitat selection, using GPS tracking data collected at two different fix rates from a small, aerially-insectivorous bird, the European nightjar Caprimulgus europaeus. Effects of tracking parameters varied with home range estimation method. Fix rate and tracking duration most strongly explained change in MKDE and KDE home range size respectively. Total number of fixes and tracking duration had the strongest impact on habitat selection. High between- and within-individual variation strongly influenced outcomes and was most evident when exploring the effects of varying tracking duration. To reduce skew and bias in home range size estimation and especially habitat selection caused by individual variation and estimation method, we recommend tracking animals for the longest period possible even if this results in a reduced fix rate. If accurate movement properties, (e.g. trajectory length and turning angle) and biologically-representative movement occurrence ranges are more important, then a higher fix rate should be used, but priority habitats can still be identified with an infrequent sampling strategy.

Observation of nest visitation by multiple males in the European Nightjar Caprimulgus europeaus

ABSTRACTWe report observations of nest visitation of multiple males to three nests of European Nightjars Caprimulgus europeaus. In one case, we report the direct observation of two males apparently exhibiting parental behaviour at the same nest. In two other cases, second males visited nests. We consider the potential functions of nest visits by extra-pair males in the Nightjar.