Nest Fidelity Research Articles

Null models confirm nest site fidelity by male smallmouth bass, Micropterus dolomieu

BackgroundMany animals appear to preferentially renest in proximity to a site they previously occupied. Evidence of nest fidelity is often inferred from a right skewed distribution of distances between the nests of individuals that breed in two consecutive reproduction episodes, where many individuals nest some arbitrarily close distance to their prior nest and others, in the extended right tail of the distribution, nest far from the nest they previously occupied. Because right skewed distributions of inter-nest distances can arise even when individuals choose nest locations randomly, however, such inferences are prone to error. The importance of null models—used to generate patterns of individual inter-nest distances by processes that do not involve site attachment—for inferences about site fidelity has been known for decades but is still often unappreciated or ignored.MethodsThe right skewed distributions of inter-nest distances observed in two earlier studies of male smallmouth bass (Micropterus dolomieu) suggest prima facie that males exhibit nest site fidelity between annual reproduction episodes, but patterns of inter-nest distances have yet to be compared to an adequate null model. Here, we evaluate the nest site fidelity of marked male M. dolomieu in a decade-long dataset, where we apply a randomization procedure based on the rencontre probability problem to generate null models. Eight observed distributions of individual, annual inter-nest distances are compared to a year-specific null model to determine whether random processes are sufficient to explain the observed distributions of inter-nest distances.ResultsThrough contrasts between observed annual inter-nest distances and results derived from null models that imposed realistic constraints on behavior, we show that some males were undoubtedly nest-site faithful. To reinforce the utility of null models and to make these kinds of models more accessible, we also provide a supplemental tutorial. The tutorial illustrates how random site choices, subject to common ecological and behavioral constraints, and even how distance is measured, can produce patterns of inter-nest distances that falsely imply nest site fidelity, or a lack of fidelity. The R code needed to reproduce these null models is included. The inference errors evident in our examples generalize to other forms of site fidelity, such as the apparent patch fidelity of certain sea bird foragers.ConclusionsThe comparisons of observed distributions of inter-nest distances with those generated by null models imply that, as suggested in prior studies, male M. dolomieu indeed exhibit annual nest site fidelity. Procedures like those we apply are necessary first steps in analyses when distributions of distances between the nests of individuals in consecutive reproduction episodes are used to infer nest-site fidelity. Why male M. dolomieu are site faithful is a question yet to be answered.

Divergent Circadian Foraging Strategies in Response to Diurnal Predation Versus Persistent Rain in Asian Weaver Ant, Oecophylla smaragdina, Suggest Possible Energetic Trade-offs.

The study of chronobiology of foraging behavior in social insects offers valuable models for the investigation of circadian rhythms. We scored hourly nest entries and exits of Oecophylla smaragdina (Asian weaver ant) workers in 9 active non-polydomous nests on days with and without rain and with and without a primarily diurnal predator present. After determining that Oecophylla display a high nest fidelity, we focused exclusively on analyzing nest entry counts: we found a significant decrease in overall entry counts of individual ants on rainy days compared with non-rainy days (p < 0.0001). They usually maintain a typical diurnal pattern of foraging activity; however, that regularity was often distorted during rainy periods but appeared to quickly revert to typical patterns following rain. This lack of compensatory foraging activity following a period of rain supports the hypothesis that these ants have enough food reserves to withstand a pure masking-induced suppression of foraging activity. Predation through bird anting, too, decreased foraging activity but appeared to cause a reversal in foraging activity timing from diurnal to nocturnal foraging. Daily periodicity of foraging was significantly disrupted in most nests during rain; however, daily foraging periodicity was disrupted in only one nest due to presence of predators. Thus, rain and predation both exert significant impacts on the overall foraging activity of Asian weaver ants, but while persistent pressure from rain seemed to primarily cause masking (diminution) of circadian foraging activity, predation restricted to the daytime resulted in phase-inversion to nocturnal foraging activity, with little diminution. This is consistent with different energetic strategies being used in response to different pressures by this species.

Naturalistic learning and reproduction in ring neck doves (Streptopelia risoria)

Successful reproduction in avian species requires considerable parental care, and for most species the efforts of both parents are necessary for the survival of offspring. Here we make the case that in these species reproductive interactions are enhanced when neurochemical activity reinforces critical stimuli and behaviors through associative learning. Drawing from research on several different species, we describe evidence for the role of associative learning in the reproductive behaviors of ring neck doves (Streptopelia risoria). A hypothetical mechanism involving a combination of classical and operant conditioning is proposed to explain the formation and maintenance of the pair bond, nest fidelity, and incubation behavior. The role of the opiate system in reinforcing various aspects of reproductive behavior in this and other species is discussed.

The architecture of assisted colonisation in sea turtles: building new populations in a biodiversity crisis

Due to changing environmental conditions, many species will have to migrate or occupy new suitable areas to avoid potential extinction in the current biodiversity crisis. Long-lived animals are especially vulnerable and ex-situ conservation actions can provide solutions through assisted colonisations. However, there is little empirical evidence on the process of founding new populations for such species or the feasibility of assisted colonisations as a viable conservation measure. Here, we combined genetics with reproductive data to study the rise of two wild populations of green turtles (Chelonia mydas) in the Cayman Islands as a possible outcome of a reintroduction program started 50 years ago. We show that both populations are highly related to the captive population but rapidly diverged due to genetic drift. Individuals from the reintroduced populations showed high levels of nest fidelity, within and across nesting seasons, indicating that philopatry may help reinforce the success of new populations. Additionally, we show that reintroduction from captive populations has not undermined the reproductive fitness of first generation individuals. Sea turtle reintroduction programs can, therefore, establish new populations but require scientific evaluation of costs and benefits and should be monitored over time to ensure viability in the long-term.

Editorial: Microbial Drivers of Sociality – From Multicellularity to Animal Societies

While sociality is present in a taxonomically diverse number of species, most animals remain solitary (Bourke, 2011). Over the last centuries, this apparent imbalance in social and non-social animals has led to a great deal of research aimed at shedding light on the biotic and abiotic factors explaining the emergence and maintenance of sociality in nature (West et al., 2015). Among them, microbes were quickly identified as a major problem for the evolution of social life, because frequent contact between group members typically facilitates the transmission of pathogens, high nest fidelity favours the establishment of microbial pathogens close to their social hosts and, finally, because social groups often exhibit limited genetic diversity and thus limited genetic resistance against certain pathogen strains (Schmid-Hempel, 1998; Cremer et al., 2007). However, this long-standing view has changed considerably over the last few years. Recent research indeed revealed that group living may be more effective than solitary living to Limit the risk of infection by pathogenic microbes because group living also allows the development of an additional layer of defence against pathogens in the form of social immunity (Cremer et al., 2007; Cotter and Kilner, 2010). Under strong pressure from pathogens, microbes could therefore promote, rather than hinder, the evolutionary transition from solitary to group Living (Meunier, 2015; Biedermann and Rohlfs, 2017). Moreover, we are increasingly aware that many microbes provide essential benefits to their hosts by performing critical digestive, physiological, and reproductive functions (Engel and Moran, 2013; McFall-Ngai et al., 2013). The need to Access beneficial microbes may thus have played a role in the expression of frequent and tight interactions between conspecifics and ultimately promoted social evolution (Wilson, 1971; Onchuru et al., 2018). Finally, a growing number of studies suggest that microbes could enforce the Aggregation and expression of cooperative behaviours of the hosts to increase their chance of reaching new hosts and may therefore be involved in the evolution of host sociality (Lewin-Epstein et al., 2017) (but see Johnson and Foster, 2018).

Understanding dispersal patterns can inform future translocation strategies: A case study of the threatened greater stick‐nest rat (Leporillus conditor)

AbstractDispersal behaviour and sociality are significant factors influencing survival at both the individual and population levels. In translocation and breeding programmes, social structure and sex‐biased philopatry and dispersal should be considered in order to maximise population viability and conservation outcomes. Here, we use the greater stick‐nest rat (Leporillus conditor), a native Australian rodent, as a case study to understand how knowledge of social structure and dispersal can inform conservation and translocation programmes. We combine high‐throughput DNA sequencing with field trapping data from a translocated population of greater stick‐nest rats at Arid Recovery Reserve, South Australia, to provide the first empirical evidence of female philopatry and male‐biased dispersal in this species. Males were found to disperse, on average, 1.5 km from the natal nest, while females typically did not disperse beyond 500 m. Further, recapture data showed that females demonstrated a higher degree of nest fidelity than males over time. Based on these findings, we make two key recommendations for future translocations of the species. Firstly, founders should be harvested in small groups at adjacent nest sites with groups separated by a minimum of 1.5 km allowing family group structure to be retained during translocation while simultaneously maximising genetic diversity. Secondly, translocated individuals should be released in family cohorts into patches of optimal habitat that contain adequate shelter substrates interspersed over short distances (~300–500 m, the maximum dispersal distance of females found in this study), thereby facilitating nest establishment and maintenance of family groups. The results of this study have implications for conservation and reintroduction biology as a whole; we highlight the importance of considering spatial genetic structure during all stages of translocations to improve outcomes, and the value of combining genetic and field data to better understand species’ social and spatial preferences.

The effect of biological and anthropogenic sound on the auditory sensitivity of oyster toadfish, Opsanus tau.

Many aquatic organisms use vocalizations for reproductive behavior; therefore, disruption of their soundscape could adversely affect their life history. Male oyster toadfish (Opsanus tau) establish nests in shallow waters during spring and attract female fish with boatwhistle vocalizations. Males exhibit high nest fidelity, making them susceptible to anthropogenic sound in coastal waters, which could mask their vocalizations and/or reduce auditory sensitivity levels. Additionally, the effect of self-generated boatwhistles on toadfish auditory sensitivity has yet to be addressed. To investigate the effect of sound exposure on toadfish auditory sensitivity, sound pressure and particle acceleration sensitivity curves were determined using auditory evoked potentials before and after (0-, 1-, 3-, 6- and 9-day) exposure to 1- or 12-h of continuous playbacks to ship engine sound or conspecific vocalization. Exposure to boatwhistles had no effect on auditory sensitivity. However, exposure to anthropogenic sound caused significant decreases in auditory sensitivity for at least 3 days, with shifts up to 8dB SPL and 20dB SPL immediately following 1- and 12-h anthropogenic exposure, respectively. Understanding the effect of self-generated and anthropogenic sound exposure on auditory sensitivity provides an insight into how soundscapes affect acoustic communication.

Relationship between salinity and sonic fish advertisement behavior in a managed sub-tropical estuary: Making the case for an acoustic indicator species

The Florida Everglades have been subjected to decades of human disturbance directly and indirectly related to freshwater management. As a result, intensive efforts directed at restoring water quality in the region have been congressionally mandated. Long-term hydrological monitoring of the Florida Bay Estuary has significantly improved scientific understanding of physical environmental processes within the southern portion of Everglades National Park. Linking environmental processes to ecosystem dynamics, however, requires a relevant metric of biological activity that 1) is representative of ecosystem interactions, 2) can be measured at the same temporal and spatial scales of hydrological data collection, and 3) is at sufficient resolution to provide an understanding of organismal, population, and community-level changes. Through changes in physiology, behavior, or ecology, fishes may respond to acute and chronic changes in their habitats. Passive acoustic detection of sonic fishes may provide an opportunity to link physical and ecosystem processes in estuarine systems. Gulf toadfish (Opsanus beta, family Batrachoididae) are a mid-trophic-level species with a widespread distribution throughout Florida Bay and the broader Gulf of Mexico. Advertising males call in both reproductive and agonistic contexts and exhibit high degrees of nest fidelity. As a result, their calls can be reliably used as an indication of animal presence, as well as behavioral state and reproductive condition. By investigating toadfish call occurrence across three hydrological monitoring stations in Florida Bay, we determined that Gulf toadfish have highest probability of acoustic occurrence at sites with lower salinity (Dunn’s test, p < 0.01), and that Gulf toadfish calling significantly changed with variation in salinity regimes at their nesting locations. For every one unit increase in salinity the probability of toadfish acoustic occurrence decreases by 16% (95% C.I. 7%–23%). This study indicated significant behavioral and acoustic heterogeneity over relatively short distances (7–30 km) within Florida Bay, and demonstrates that local environmental conditions are related to calling behavior in addition to seasonal or broader climatic conditions. Given that a great deal is known about the behavior, physiology, and life history of toadfishes, evidence that Gulf toadfish consistently responded to salinity between and within sites lends strong initial support for the use of Gulf toadfish calling behavior as an acoustic indicator of estuary conditions and environmental change in estuaries targeted for ecological restoration.

Factors Influencing Nest Survival in Florida Bass

AbstractAngling nesting Florida Bass Micropterus salmoides floridanus may influence the survival of the brood and could negatively affect bass populations. Our objectives were to estimate daily nest survival for Florida Bass and to examine factors that influence nest survival to the swim‐up fry stage. Snorkelers examined a total of 259 nests in a small, mesotrophic lake in north‐central Florida from 2010 to 2012. We compared nest survival rates with accumulated degree‐days, largest temperature drop following nest discovery, nest score, presence of a guarding male bass, and size of the guarding male. The most important factor in determining nest survival was the presence of a male bass. However, guarding male fish were only observed on 66% of active nests despite multiple visits to each nest, indicating a lower tendency to remain with the brood than has been reported in other Micropterus species. Florida Bass have displayed lower nest guarding behaviors in other studies; a prolonged spawning season and the presence of top predators in southern bass populations may influence decreased nest fidelity and nest guarding behavior. Individual nesting attempts may be less important for successful Florida Bass recruitment.Received September 28, 2016; accepted February 28, 2017 Published online May 12, 2017

Nest-site selection, nesting behaviour and spatial ecology of female Nile crocodiles (Crocodylus niloticus) in South Africa

Nesting biology and ecology have been investigated for Nile crocodiles (Crocodylus niloticus), but information on behaviour and movement patterns of nesting females during nest guarding is scant. Consequently, we investigated the home ranges, nest-site selection strategies, movement patterns, activity levels and nest fidelity of four nesting females using telemetry. Gravid females selected winter basking/breeding areas close (351±2m) to nest-sites. Mean home range and core-use areas of nesting females were 8539±4752m2, and 4949±3302m2 respectively. Mean home range (0.85ha) was significantly smaller than those of non-nesting females (108.4ha) during nesting season. Activity levels and mean daily movements while nesting were 8.1±2.5% and 213±64m, respectively, and increased to 47.9±11.7% and 2176±708m post-nesting. Overall levels of nest fidelity were 82.8±11.7%, (day 78.1±15.9%; night 87.3±7.8%). Highest nest fidelity recorded during incubation was 99.7% over 96days. Telemetry data from nesting females were helpful for elucidating spatial and behavioural patterns during the nest guarding period, and provided novel insights into this biologically important event.

Sex in the City: Breeding Behavior of Urban Peregrine Falcons in the Midwestern US.

Peregrine falcons (Falco peregrinus) were extirpated from most of the continental United States by widespread use of the pesticide DDT in the 1960s. Populations have rebounded with banning of the pesticide and successful implementation of captive breeding and hacking programs. An essentially new population of Midwestern peregrines now exists that is comprised almost entirely of urban-nesting birds. The new population is considered to be of mixed ancestry, occurs at relatively high densities, and has nest sites in close proximity, factors that could influence breeding behaviors including mate fidelity, nest-site fidelity, extra-pair paternity, and natal dispersal. We investigated these behaviors using a combination of field observations and DNA microsatellite genotyping. Data for eleven microsatellite DNA markers, including eight newly developed for the species, were analyzed from a total of 350 birds from nine Midwestern cities, representing 149 broods collected at 20 nest sites. To document breeding behavior, parentage was inferred by likelihood techniques when both parents were sampled and by parental genotype reconstruction when only one parent was sampled. In cases where neither parent was sampled, a sibship reconstruction approach was used. We found high mate fidelity and nest-site fidelity in urban peregrines; in 122 nesting attempts made by long-term breeders, only 12 (9.8%) mate changes and six (4.9%) nest-site changes occurred. Only one brood (of 35 tested) revealed extra-pair paternity and involved a male tending two offspring of a recently acquired mate. Natal dispersal patterns indicated that female peregrines dispersed on average 226 km, almost twice the distance of males (average 124 km). Despite the novel environment of cities, our results suggest that monogamous breeding, nest fidelity, and female natal dispersal are high in urban peregrines, not unlike other raptors living in non-urban habitats.

Nest fidelity is driven by multi-scale information in a long-lived seabird.

Although the reproductive success of most organisms depends on factors acting at several spatial scales, little is known about how organisms are able to synthesize multi-scale information to optimize reproduction. Using longitudinal data from a long-lived seabird, Monteiro's storm-petrel, we show that average breeding success is strongly related to oceanic conditions at the population level, and we postulate that (i) individuals use proximal information (their own reproduction outcome in year t) to assess the qualities of their mate and nest and to decide to retain them or not in year t + 1; (ii) the intensity of these responses depends on the quality of the oceanic environment in year t, which affects the predictability of reproduction outcome in year t + 1. Our results confirm that mate and nest fidelities are higher following successful reproduction and that the relationship between the success of a given pair and subsequent nest fidelity is stronger in years with unfavourable oceanic conditions, suggesting that individuals rely on distant information to modulate their use of proximal information and adjust their breeding strategy.

Response of burrowing owls to experimental removal of satellite burrows

Studies of habitat relationships indicate that burrowing owls (Athene cunicularia) often select nest sites with multiple burrows. This behavior may increase survival of post-emergent nestlings. We experimentally blocked access to burrows within 20m of nests (satellite burrows) within a large grassland in central California to evaluate the response by year-round resident burrowing owls to removal of satellite burrows. We compared reproductive performance and nest fidelity between owls whose access to potential satellite burrows was blocked and owls whose nests had similar numbers of naturally occurring burrows within 20m of the nest prior to manipulation. Adult owls and their young moved away from treatment nests, but reproductive rates between owls from treatment and control nests did not differ. Movements involved the entire family, occurred before young had fledged, and owls did not return to the natal nest burrow. Movements ranged from 25m to 120m and occurred at 5 of the 7 treatment nests with young. No such movement occurred at any of the control nests. Our findings support results from correlational studies that multiple nearby burrows influence nest site selection. 2014 The Wildlife Society

Quantification of Supercolonial Traits in the Yellow Crazy Ant,Anoplolepis gracilipes

Supercoloniality is a social structure displayed by many invasive ant species, but there has been surprisingly little research quantifying the extent to which individual species display traits underlying such social organisation. This study quantifies three traits for the yellow crazy ant, Anoplolepis gracilipes Smith (Hymenoptera: Formicidae): little or no aggression between workers from different nests; the exchange of workers among nests; and resource exchange among nests, as well as supercolony structure arising from patterns of distribution and density of detections. Supercolonies displayed a structural continuum from being small (< 10 ha) and “aggregated” with great continuity among detections through to being large (> 10,000 ha) and “diffuse” with little continuity among detections. Smaller supercolonies had greater ant densities than larger supercolonies. In laboratory trials, no aggression was observed between workers from different nests sourced from different supercolonies, and paired nests merged within 24 hours. Workers lacked nest fidelity by rapidly populating artificial nests containing alien queens. The daily worker turnover rate per nest was estimated to be below 20%. Resources were readily moved among nests, with a resource being detected up to 13 m away from a source within 24 hours, and as far as 32 m after four days. The rate and distance of resource movement increased with increasing worker and nest density. This research has demonstrated that A. gracilipes displays supercoloniality equivalent to that of the well-studied Argentine ant Linepithema humile. Quantification of these traits is required for other supercolonial species to improve our understanding of this social strategy, especially for invasive ants to aid in understanding factors that promote invasion success and to improve management.

An experimental study measuring the effects of a tarsus-mounted tracking device on the behaviour of a small pursuit-diving seabird

Miniaturized tracking devices are taking a rapidly increasing role in studies measuring animal movement and other aspects of behaviour, especially for wide-ranging species such as seabirds that are difficult to observe otherwise. A crucial, but questionable criterion of such migration research is assuming that effects of tracking devices on animal behaviour are negligible, to ensure results of tracking studies are biologically relevant. To address this concern, we experimentally quantified effects of a 2 g (ca. 1.1% of body mass) geolocation device on crested auklet (Aethia cristatella) behaviour, including return rate, activity on the colony surface, and measures of reproductive performance in a two-year, two-part field study. In experiment 1, we fitted tracking devices (or identical dummy devices) to one mate of a breeding pair in nesting crevices, to quantify effects on reproductive performance and nest fidelity. In experiment 2, we assigned dummy devices to birds captured at the colony site surface, to quantify effects on social activity, return rate and provisioning behaviour. For birds tagged in crevices, we detected no effect on fledging success, or chick growth rate (mass and wing length). However, mass at fledging age of chicks provisioned with one tagged parent was significantly lower than control, and low nest site fidelity (compared to control birds) was observed for tagged birds. Individuals tagged on the colony surface showed significantly reduced colony surface activity, return rates and provisioning behaviour. This study shows strong ‘observer effects’ of an attached device well below the recommended size limit for wildlife tagging. Future studies should both quantify effects of attached devices and consider the biological relevance of measures of the behaviour of interest.

Quantification of supercolonial traits in the yellow crazy ant, Anoplolepis gracilipes.

Supercoloniality is a social structure displayed by many invasive ant species, but there has been surprisingly little research quantifying the extent to which individual species display traits underlying such social organisation. This study quantifies three traits for the yellow crazy ant, Anoplolepis gracilipes Smith (Hymenoptera: Formicidae): little or no aggression between workers from different nests; the exchange of workers among nests; and resource exchange among nests, as well as supercolony structure arising from patterns of distribution and density of detections. Supercolonies displayed a structural continuum from being small ( < 10 ha) and “aggregated” with great continuity among detections through to being large (>10,000 ha) and “diffuse” with little continuity among detections. Smaller supercolonies had greater ant densities than larger supercolonies. In laboratory trials, no aggression was observed between workers from different nests sourced from different supercolonies, and paired nests merged within 24 hours. Workers lacked nest fidelity by rapidly populating artificial nests containing alien queens. The daily worker turnover rate per nest was estimated to be below 20%. Resources were readily moved among nests, with a resource being detected up to 13 m away from a source within 24 hours, and as far as 32 m after four days. The rate and distance of resource movement increased with increasing worker and nest density. This research has demonstrated that A. gracilipes displays supercoloniality equivalent to that of the well-studied Argentine ant Linepithema humile . Quantification of these traits is required for other supercolonial species to improve our understanding of this social strategy, especially for invasive ants to aid in understanding factors that promote invasion success and to improve management.

Reproductive performance of alternative male phenotypes of growth hormone transgenic Atlantic salmon (Salmo salar).

Growth hormone (GH) transgenic Atlantic salmon (Salmo salar) is one of the first transgenic animals being considered for commercial farming, yet ecological and genetic concerns remain should they enter the wild and interact reproductively with wild fish. Here, we provide the first empirical data reporting on the breeding performance of GH transgenic Atlantic salmon males, including that of an alternative male reproductive phenotype (i.e. small, precocially mature parr), in pair-wise competitive trials within a naturalised stream mesocosm. Wild anadromous (i.e. large, migratory) males outperformed captively reared transgenic counterparts in terms of nest fidelity, quivering frequency and spawn participation. Similarly, despite displaying less aggression, captively reared nontransgenic mature parr were superior competitors to their transgenic counterparts in terms of nest fidelity and spawn participation. Moreover, nontransgenic parr had higher overall fertilisation success than transgenic parr, and their offspring were represented in more spawning trials. Although transgenic males displayed reduced breeding performance relative to nontransgenics, both male reproductive phenotypes demonstrated the ability to participate in natural spawning events and thus have the potential to contribute genes to subsequent generations.

Selection of nest sites by wood mice Apodemus sylvaticus in a Mediterranean agro-forest landscape

One of the most important structures for an individual’s survival is a refuge, especially for species subject to significant predatory pressure or living in environments affected by severe climatic conditions. We studied how wood mice (Apodemus sylvaticus), inhabiting a Mediterranean environment, use nests and the factors that could be determining this use. Radio-tracking of 16 mice allowed us to detect 24 diurnal nests, which were used with a high fidelity rate (1.75 nests/animal). Nest sites that had been identified using radio-tracking were matched with 24 randomly selected non-nest sites (located within an area defined by the sum of all individual home ranges), and all sites were characterized according to their macro- and micro-habitat parameters. Using a generalized linear model, we tested three hypotheses: (1) a nest’s use is influenced by its proximity to food patches; (2) the degree of sheltering provided by each site influences its use; and (3) nest use is constrained by a combination of food- and shelter-related features. Females had higher nest fidelity than males, and the degree of sheltering provided by each site had a positive significant influence on its use. Nests offering higher protection (e.g., under thick vegetation), good drainage (e.g., sleep slopes), and lower human and predatory disturbance (far from orchards) were most often used. The proximity to food patches seemed to negatively influence nest use. Results indicate the need to preserve patches of natural dense vegetation near riparian habitats, which is in agreement with the focus of mammalian protection plans in Mediterranean agricultural landscapes. These patches are important areas for Apodemus sylvaticus, an acorn disperser species, which is preyed on by raptors and mammalian carnivores.

Nest use by western pygmy-possums (Cercartetus concinnus) (Marsupialia:Burramyidae) at Innes National Park, South Australia

We examined the nest use of 15 radio-tracked western pygmy-possums (Cercartetus concinnus) throughout one year for up to nine nights each at Innes National Park, South Australia. At least one pygmy-possum was followed in each of 12 months. Nest type and nest fidelity varied greatly; shallow burrows under debris were the most frequently used. Nest preferences of females with young remain unknown. The ability of C. concinnus to use a diversity of nest types over relatively short periods is likely to be an important survival strategy.

Not all who wander are lost: nest fidelity in Xylocopa virginica examined by mark recapture

Relocation to novel nests (sometimes called drifting) in flying Hymenoptera is often interpreted as the result of navigation error and guard bees erroneously admitting foreign individuals into the nest. We studied nest fidelity and nest relocation of both females and males in a nesting aggregation of Xylocopa virginica in southern Ontario, Canada, where females can nest either solitarily or socially. Adult female and male bees were trapped at nest entrances, individually paint marked, and then released. Subsequent recapture patterns were used to assess nest fidelity: that is, how faithful individuals were to their home nest and how often they moved to another nest. Bees were considered to have relocated if they were recaptured in a nest different from the one in which they were initially trapped, indicating that they had spent at least one night in a new nest. Some females were only captured in one nest, some occasionally moved to new nests, temporarily or permanently, and a few were never caught in the same nest twice. In addition, females relocated to nests that were further away in 2007 when population density was low, suggesting that they seek out and claim nesting spaces when they are available. Males relocated more frequently than females, with most drifting from nest to nest in no obvious pattern. This indicates that males spend the night wherever space is available or in nests nearest to their territories. This study reveals that for both female and male X. virginica, nest membership is not as stable as once thought.