The Effect of Human Presence and Human Activity on Risk Assessment and Flight Initiation Distance in Skinks

Antipredator behavior and risk assessment of many species are affected by the presence of humans and their activities. Previous studies have largely been conducted on birds and mammals and relatively less is known about human impacts on reptiles. We used flight initiation distance (FID) as a measure of risk assessment in inland blue‐tailed skinks (Emoia impar) and tested the direct and indirect effects of humans on risk assessment. We first examined the effects of varying levels and types of human disturbance and activity on skink FID. We found that skinks flushed at significantly longer distances in areas with the least human activity. We then tested the degree to which skinks are able to discriminate different numbers of humans by comparing FID across three different types of approaches. Skinks did not significantly differentiate between a single approacher and a single approacher coming from a group of two other people, but did flush at greater distances when approached by three people simultaneously. Although skinks are not directly harvested or harassed by humans, they have refined human discrimination abilities. Overall, skinks habituate to a variety of human activities and perceive a larger threat when the number of human approachers is greater.     

Waterbird responses to regular passage of a birdwatching tour boat: Implications for wetland management

Participation in outdoor recreation can increase support for wildlife conservation, but may also disturb wildlife. We examined responses of wintering waterbirds to the regular passage of a small boat specifically dedicated to birdwatching tours in a coastal Ramsar site in northern Spain. Disturbances were measured during two separate periods: 2006–2008 and 2012–2015. Incidence and magnitude of disturbance events were compared by grouping species based on their interest to birders (target vs. non-target) and compared across sectors of the tour route. Flight-initiation distances (FID) were used to estimate species-specific buffer zones, which can be used to manage recreational disturbance to waterbirds. We further examined relationships between species-specific traits and FID, time flying, and distance flying following disturbance. A single boat tour disturbed on average 0.3% of non-target and 2.8% of target wintering bird populations within the wetland, with the effect being more pronounced on target species due to their smaller populations. Wing loading was positively associated with distance flying after disturbance. Based on measured FIDs, we calculated an overall buffer zone for all species of 100 m, and species-specific buffer zones ranging from 41 to 211 m. Disturbance incidence and the number of birds disturbed per tour were both greatest in narrow tidal channels (<200 m), where boats were forced to pass within 100 m of waterbirds. We urge caution in allowing boat passage through tidal channels in which boat operators cannot effectively maintain recommended buffer zones between their boat and waterbirds.     

Managing human disturbance: factors influencing flight-initiation distance of birds in a West African nature reserve

Escape behaviour in response to perceived predators can be employed as a guide when designating protected areas around sensitive bird species to minimise the impact of human disturbance. A key measure of escape response is flight-initiation distance (FID), the distance at which a prey animal initiates its escape when approached by a potential predator. We tested the predictions of optimal escape theory by determining the factors that influence FID of bird species in a Nigerian reserved area and its surrounding habitats, and so the potential utility of FID in managing human disturbance on birds, for the first time within a West African context. We tested how FID varied with group size, proximity to vegetation acting as protective cover, levels of human use, and survival rate, and whether these relationships varied by species. We collected 504 FIDs for seven bird species in Amurum Forest Reserve and its surrounding habitats (Jos, Nigeria). The FID was lower in larger groups and when species were closer to protective cover. The FID was lower outside of the protected area because animals in sites with higher levels of human presence and use may become habituated. The FID was higher for species with higher survival, being consistent with predictions from life history theory. Overall, birds perceived humans as a potential threat and responded in accordance to the predictions of optimal escape theory, with FID increasing with increased cost of staying. Reserve managers in Africa could use species- and context-specific FIDs to designate buffer distances for the protection of wildlife from human disturbance.     

冬季水鸟对崇明东滩水产养殖塘的利用

自然湿地的丧失和退化给依赖湿地生存的水鸟带来了严重威胁,人工湿地作为水鸟栖息地的功能日益受到关注.水产养殖塘是人工湿地的重要类型之一.通过研究崇明东滩水产养殖塘冬季水鸟群落组成及其栖息地特征,发现大面积养殖塘比小面积养殖塘吸引更多种类和更高密度的水鸟.养殖塘在放水前水位较高时吸引更多游禽栖息,而在放水后水位较低时吸引更多涉禽;在放水过程中,养殖塘中水鸟的种类最多,密度最大.另外,在放水的不同时期,不同的环境因子对水鸟群落的影响不同:放水之前,养殖塘水面面积和平均水深是水鸟种类和数量的主要影响因子,其中游禽种类和数量受水面面积影响较大,涉禽种类和数量受平均水深影响较大;放水过程中,裸地面积、芦苇面积、干扰程度、平均水深和水深变异对水鸟、游禽和涉禽的种类和数量起主要作用;放水之后,水深变异对水鸟种类和数量的影响较大,而影响游禽种类和数量的主要因子是水面面积,影响涉禽种类和数量的主要因子是水深变异.研究表明,通过对影响水鸟栖息地利用的主要因子的有效管理,养殖塘在提供经济效益的同时也能为水鸟提供适宜的栖息地.     

Birds at a Southern California beach: seasonality, habitat use and disturbance by human activity

Use of a Santa Barbara beach by people and birds varied in both time and space. There were 100 birds, 18 people and 2 dogs per kilometer. Bird density varied primarily with the season and tide while human activity varied most between weekend and weekday. Bird distributions along the beach were determined mainly by habitat type (particularly a lagoon and exposed rocky intertidal areas) For crows and western gulls, there was some evidence that access to urban refuse increased abundance. Interactions between birds and people often caused birds to move or fly away, particularly when people were within 20 m. During a short observation period, 10% of humans and 39% of dogs disturbed birds. More than 70% of birds flew when disturbed. Bird species varied in the frequency that they were disturbed, partially because a few bird species foraged on the upper beach where contact with people was less frequent. Most disturbances occurred low on the beach. Although disturbances caused birds to move away from humans, most displacement was short enough that variation in human activity did not alter large-scale patterns of beach use by the birds. Birds were less reactive to humans (but not dogs) when beach activity was low.     

Human habituation reduces hyrax flight initiation distance in Serengeti

Many animal populations are exposed to disturbance originating from human activities. In response to human disturbance, certain animals display a variety of potentially costly behavioural responses, such as increased antipredator behaviour or relocation to new areas. In contrast, other animals seemingly thrive in the presence of humans and benefit from human-derived resources. Flight initiation distance (FID: the distance between predator and prey when prey starts to flee) is a measure commonly used to assess animals’ tolerance to humans. In this study, we tested how FID changes in relation to human presence in two hyrax species in Serengeti National Park. Hyraxes living on kopjes (rock outcrops) among human settlements showed a significantly shorter FID than hyraxes living on kopjes without human settlements. In addition, we found that hyraxes feeding before the experiment had shorter FID than hyraxes resting or being vigilant, and hyraxes disturbed during the early morning had shorter FID than hyraxes disturbed during late morning. We did not find any significant effects of group size or species composition on FID. Our results suggest that hyraxes living in the presence of humans are habituated and are not adversely affected by human settlements.     

鸟类惊飞距离及其影响因素

惊飞距离(FID)是指捕食者(包括人类)接近目标个体并导致其逃避时,捕食者与目标个体之间的距离。惊飞距离能很好地衡量动物个体在特定环境下的恐惧反应和风险权衡,是研究动物逃避行为的常用指标,并为物种保护提供科学依据。鸟类是研究逃避行为的理想对象,本文综述了影响鸟类惊飞距离的各种因素,可分为3类:栖息地因素(距隐蔽处的距离和生境开阔度等)、鸟类自身因素(生活史、体型和群体大小等)以及与捕食者相关的因素(捕食者的接近方向和速度等)。城市化也会影响鸟类的惊飞距离,导致城市中的鸟类通常比乡村生境的同种鸟类拥有更短的惊飞距离。习惯化、适应和生境选择是解释惊飞距离城乡差异的3种假说。研究鸟类的惊飞距离及其影响因素,有助于理解鸟类的逃避行为及其风险权衡机制,为物种保护中设立合理的缓冲区域及制定有效的保护管理措施提供科学依据。目前国内有关鸟类惊飞距离的研究多为行为观察和单一因素的影响,有待从不同因素的交互作用角度探讨鸟类的逃避行为并用于物种保护。     

Winter coexistence in herbivorous waterbirds: Niche differentiation in a floodplain,Poyang Lake,China

The classical niche theory supports the idea that stable coexistence requires ecological differences between closely related species. However, information on waterbirds coexistence in the entirely landlocked freshwater system of Poyang Lake is not well understood, especially when the available biomass of their food in the area decreases. In this study, we tested the ecological segregation mechanisms in the 2015/2016 and 2016/2017 wintering periods among eight herbivorous waterbirds (including the Siberian crane Grus leucogeranus, hooded crane Grus monacha, white‐naped crane Grus vipio, common crane Grus grus, greater white‐fronted goose Anser albifrons, bean goose Anser fabalis, swan goose Anser cygnoides, and tundra swan Cygnus columbianus) at Poyang Lake. Using field observations and species niche and foraging habitat selection models, we investigated the abundance, distribution, and food sources of these eight waterbird species to quantify and compare their habitat use and ecological niches. Our results showed that niche segregation among the waterbirds, with respect to food types, time, and spatial location, allow them to coexist and use similar resources. The water level gradually receded in the sub‐lakes of the Poyang Lake, which could provide food sources and various habitats for wintering herbivorous waterbirds to coexist. We demonstrated that the differences in habitat use could mitigate interspecific competition, which may explain the mechanism whereby waterbirds of Poyang Lake coexist during the wintering period, despite considerable overlap in the dietary niches of herbivorous waterbirds.     

Landscape approaches to studying the effects of disturbance on waterbirds

The internationally important populations of waterbirds that winter in the United Kingdom can face intense pressure from human disturbance as a result of the high urbanization found around many protected coastal or inland wetland sites. Here, I describe and evaluate an approach that has been used to investigate the spatial effects of human disturbance on waterbirds. Rather than directly investigating behavioural responses to individual disturbance events, the presence of features in the landscape associated with disturbance is instead used as a surrogate, with the essential aim being to demonstrate that bird numbers or densities are depressed or their behaviour altered in proximity to areas used by humans. This paper first describes case studies that demonstrate the limitations of the basic inference (i.e. that disturbance influences patterns of waterbird distribution or behaviour) and then how investigations might be strengthened. For conclusions to be sound, it is particularly important that other factors, such as food supply, that might also explain the spatial patterns observed are considered or other corroborative evidence presented. The approach is thus least applicable in the most heterogeneous environments where many factors, perhaps spatially autocorrelated, may explain variation in distribution or behaviour. However, greatest confidence in the validity of conclusions may be gained where studies are able to show (ideally by experimental manipulation) that species' distributions or behaviour vary temporally in line with the levels of human use of the features examined. Although its aim and scope are thus limited, the use of a landscape approach, provided that it takes into account other factors affecting spatial variation in bird abundance or behaviour, can provide a preliminary assessment of species avoidance of key sources of disturbance that may offer a framework for more detailed investigation.     

Behavioral responses of nesting birds to human disturbance along recreational trails

ABSTRACT The presence of recreational trails can impact breeding birds either indirectly by altering habitat or the movement patterns of predators or directly if the presence of humans disturbs birds. We examined the behavioral responses of nesting female Northern Cardinals (Cardinalis cardinalis) to human disturbance using both experimental and observational approaches. From April to August 2006 and 2007, we monitored Northern Cardinal nests in 18 riparian forests in Ohio, USA. Two experimental trials were conducted at each nest (N= 63), with Flight Initiation Distance (FID, the distance at which a bird flushed from the nest) recorded as we approached nests by walking directly toward them and by walking along trails located variable distances from nests. We also measured flight initiation distance (FID) when nests were approached during routine nest checks (N= 160). Cardinals were six times more likely to flush when nests were approached directly, and females on higher nests were less likely to flush regardless of distance to trail. FID was not significantly influenced by the distance of nests from trails. We found no association between nest survival and the tendency of birds to flush. Rather, nest survival was best explained by nest height. Thus, our findings suggest that the responses of birds to human use of recreational trails have only short‐term effects, with no apparent effects of on nest survival. Because the reaction of birds to humans in our study depended on how nests were approached, studies where FID is used as an indicator of sensitivity to human disturbance and is determined by direct approaches may overestimate the potential impact of trails on nesting birds.     

Beware the serpent: the advantage of ecologically-relevant stimuli in accessing visual awareness

Snakes and spiders constitute fear-relevant stimuli for humans, as many species have deleterious and even fatal effects. However, snakes provoked an older and thus stronger evolutionary pressure than spiders, shaping the vision of earliest primates toward preferential visual processing, mainly in the most complex perceptual conditions. To the best of our knowledge, no study has yet directly assessed the role of ecologically-relevant stimuli in preferentially accessing visual awareness. Using continuous flash suppression (CFS), the present study assessed the role of evolutionary pressure in gaining a preferential access to visual awareness. For this purpose, we measured the time needed for three types of stimuli - snakes, spiders (matched with snakes for rated fear levels, but for which an influence on humans but not other primates is well grounded) and birds - to break the suppression and enter visual awareness in two different suppression intensity conditions. The results showed that in the less demanding awareness access condition (stimuli presented to the participants' dominant eye) both evolutionarily relevant stimuli (snakes and spiders) showed a faster entry into visual awareness than birds, whereas in the most demanding awareness access condition (stimuli presented to the participants' non-dominant eye) only snakes showed this privileged access. Our data suggest that the privileged unconscious processing of snakes in the most complex perceptual conditions extends to visual awareness, corroborating the proposed influence of snakes in primate visual evolution.     

Visual artificial grammar learning: comparative research on humans, kea (Nestor notabilis) and pigeons (Columba livia)

Artificial grammar learning (AGL) provides a useful tool for exploring rule learning strategies linked to general purpose pattern perception. To be able to directly compare performance of humans with other species with different memory capacities, we developed an AGL task in the visual domain. Presenting entire visual patterns simultaneously instead of sequentially minimizes the amount of required working memory. This approach allowed us to evaluate performance levels of two bird species, kea (Nestor notabilis) and pigeons (Columba livia), in direct comparison to human participants. After being trained to discriminate between two types of visual patterns generated by rules at different levels of computational complexity and presented on a computer screen, birds and humans received further training with a series of novel stimuli that followed the same rules, but differed in various visual features from the training stimuli. Most avian and all human subjects continued to perform well above chance during this initial generalization phase, suggesting that they were able to generalize learned rules to novel stimuli. However, detailed testing with stimuli that violated the intended rules regarding the exact number of stimulus elements indicates that neither bird species was able to successfully acquire the intended pattern rule. Our data suggest that, in contrast to humans, these birds were unable to master a simple rule above the finite-state level, even with simultaneous item presentation and despite intensive training.     

Consistency in the flight and visual orientation distances of habituated chacma baboons after an observed leopard predation. Do flight initiation distance methods always measure perceived predation risk?

Flight initiation distance (FID) procedures are used to assess the risk perception animals have for threats (e.g., natural predators, hunters), but it is unclear whether these assessments remain meaningful if animals have habituated to certain human stimuli (e.g., researchers, tourists). Our previous work showed that habituated baboons displayed individually distinct and consistent responses to human approaches, a tolerance trait, but it is unknown if the trait is resilient to life‐threatening scenarios. If it were consistent, it would imply FIDs might measure specific human threat perception only and not generalize to other threats such as predators when animals have experienced habituation processes. We used FID procedures to compare baseline responses to the visual orientation distance, FID, and individual tolerance estimates assessed after a leopard predation on an adult male baboon (group member). All variables were consistent despite the predation event, suggesting tolerance to observers was largely unaffected by the predation and FID procedures are unlikely to be generalizable to other threats when habituation has occurred. FID approaches could be an important tool for assessing how humans influence animal behavior across a range of contexts, but careful planning is required to understand the type of stimuli presented.     

Variability in the area,energy and time costs of wintering waders responding to disturbance

Birds’ responses to human disturbance are interesting due to their similarities to anti‐predator behaviour, and understanding this behaviour has practical applications for conservation management by informing measures such as buffer zones to protect priority species. To understand better the costs of disturbance and whether it will impact on population size, studies should quantify time‐related responses as well as the more commonly reported flight initiation distance (FID). Using waders wintering on an estuarine area, we experimentally disturbed foraging birds on the Wash Embayment, UK, by walking towards them and recording their responses (FID, alert time, time spent in flight, time taken to resume feeding, and total feeding time lost). We present data for 10 species of conservation concern: Curlew Numenius arquata, Oystercatcher Haematopus ostralegus, Bar‐tailed Godwit Limosa lapponica, Grey Plover Pluvialis squatarola, Redshank Tringa totanus, Knot Calidris canutus, Turnstone Arenaria interpres, Ringed Plover Charadrius hiaticula, Sanderling Calidris alba and Dunlin Calidris alpina. Larger species responded more strongly, response magnitude was greater under milder environmental conditions, and responses varied over both small and large spatial scales. The energetic costs of individual responses, however, were low relative to daily requirements and disturbance events were unlikely to be frequent enough to seriously limit foraging time. We suggest, therefore, that wintering wader populations on the Wash are not currently significantly negatively impacted by human disturbance during the intertidal foraging period. This is also likely to be the case at other estuarine sites with comparable access levels, visitor patterns, invertebrate food availability and environmental conditions.     

Wintering waterbird assemblages in the central part of the Gulf of Gabès in southern Tunisia

Although the Gulf of Gabès is recognised as an Important Bird Area, several aspects of the ecology of waterbirds inhabiting this area still need to be investigated. We observed how waterbird foraging guilds varied among habitats. In total, 49 species belonging to 16 families were recorded. Winter visitors accounted for 73% of counts. The avifauna was dominated by shorebirds (52% of records), followed by large wading birds (25%), open-water birds (18%) and waterfowl (5%). However, the structure of local waterbird communities and their composition in terms of foraging guilds varied according to habitat type. The bird communities of sandy beaches were dominated by open-water birds, whereas large mudflats were dominated by shorebirds, and wadi estuaries showed a more even representation of foraging guilds. Locally rare species had narrow distributions, whereas locally abundant species were found widely within the gulf. For four species the 1% population level criterion of the Ramsar Convention was exceeded. Overall, our results show that the Gulf of Gabès hosts important numbers of waterbirds with different ecological requirements, which confirms the importance of this gulf as a wintering area for Palearctic waterbirds.     

Song switching and agonistic stimulation in the song sparrow (Melospiza melodia): five tests

Male song sparrows in southeastern Ontario have repertoires of five to 11 distinct song types. The singer repeats each song type a variable number of times before switching to another type. Analysis of territorial singing suggested that rate of switching song types is positively correlated with intensity of agonistic stimulation, where ‘agonistic’ signifies conflict-related. The song-switching hypothesis was tested with playback experiments which varied stimulus intensity in five different ways: (1) presence or absence of song stimuli; (2) addition of visual to auditory stimuli; (3) location of the song stimulus 20 m inside or outside territory; (4) nesting phases of the subjects; and (5) switching rate and rate of novel song type production of the playback (i.e. stimulus versatility). The subjects' switching rates and flight rates consistently increased with greater stimulation, although song rate tended to remain unaffected. The signalling of response intensity through adjustments in switching rate exemplifies how song repertoires function in agonistic communication.     

Asymmetries in stimulus comparisons by monkey and man

Similarity is a core concept in theories of object recognition, categorization, and reasoning. It is often conceptualized as a geometric distance in a multidimensional stimulus space. However, research in humans has revealed that similarity judgments involve more than a simple distance calculation and tend to be asymmetric when stimuli differ in factors such as prototypicality. For example, most people judge 99 to be more similar to 100 than 100 to 99. Up to now, it was not known whether such asymmetries might also occur in nonhuman subjects. This study reveals asymmetries in the pattern of errors made by four rhesus monkeys in a temporal same/different task. Monkeys usually perceived a smaller difference between two different stimuli when the first stimulus in a trial was less prototypical than the second, just as what was found previously for human subjects. The pattern of asymmetries differed between monkeys, and a control study showed that such variability is also present for human subjects. We propose that known neurophysiological mechanisms can account for asymmetry in the stimulus comparisons of both species. Thus, seemingly complex phenomena that occur when human subjects rate stimulus similarity are also present in macaques' similarity judgments and could be based on relatively simple mechanisms.     

EDITORIAL

Understanding breeding site preferences is important for management of colonial waterbirds. The number of active colonial waterbird nests at a series of four small constructed wetlands in Cape Town was counted monthly from 1999 to 2008. In total 491 pairs belonging to 11 waterbird species were involved. Between 1997 and 2004 a number of different artificial structures were used to attract colonial waterbirds to breed at one of the constructed wetlands. The changes in use of the different artificial structures, and of natural reedbeds, for nesting revealed the site preferences of different waterbird species. Structures that simulated flooded dead trees were most successful in attracting breeding waterbirds. Reedbeds were used for nesting when the number of such artificial structures was reduced. When the reedbeds were removed some birds returned to the artificial structures, whereas others moved to a more distant wetland. Some species were pioneers that provided public information about safety from predation that apparently encouraged birds in other species to settle. Safety from potential mammalian predators was clearly the prime consideration in breeding locality selection. Adverse winds and human disturbance were less important factors.     

Situational Specificity in Alpine-marmot Alarm Communication

We studied the degree to which alpine marmot (Marmota marmota L.) alarm calls function as communication about specific external stimuli. Alpine marmots emit variable alarm calls when they encounter humans, dogs, and several species of aerial predators. The first part of the study involved observations and manipulations designed to document contextual variation in alarm calls. Alarm calls varied along several acoustic parameters, but only along one that we examined, the number of notes per call, was significantly correlated with the type of external stimulus. Marmots were more likely to emit single-note alarm calls as their first or only call in response to an aerial stimulus, and multiple-note alarm calls when first calling to a terrestrial stimulus. This relationship was not without exceptions; there was considerable variation in the number of notes they emitted to both aerial and terrestrial stimuli, and a single stimulus type — humans — elicited a wide range of acoustic responses. The second part of the study involved playing back three types of alarm calls to marmots and observing their responses. Marmots did not have overtly different responses to the three types of played-back alarm calls. Our results are consistent with the hypotheses that: 1. Alarm calls do not refer to specific external stimuli; 2. Alarm calls function to communicate the degree of risk a caller experiences; and 3. Alarm calls require additional contextual cues to be properly interpreted by conspecifics.     

Sources and extent of human disturbance to waterbirds in the UK: an analysis of Wetland Bird Survey data, 1995/96 to 1998/99

Capsule Less than 32% of counters record disturbance at their site, with differences in causes between coastal and inland sites.

Aim Wetland Bird Survey (WeBS) data were reviewed to investigate the sources and scale of potential disturbance to waterbirds in the UK.

Methods Between 1995/96 and 1998/99, WeBS volunteer counters recorded human activity and perceived waterbird disturbance during co-ordinated counts at wetland sites across the UK.

Results Over 68% of counters recorded no disturbance at their site and only a small proportion of these (< 2%) indicated very high levels. The frequency of disturbance peaked during the late summer. Just over 26% of disturbance events were attributed to human activities. The most perceived human-related disturbance was caused by people using motor-driven machines and shooters. Coastal waterbirds were more likely to be disturbed by walkers, shooters and large aircraft whereas those inland were more likely to be disturbed by motor-driven machines and unpowered boats.

Conclusions Volunteer-based surveys can be useful in monitoring the sources and distribution of potentially disturbing activities over large spatial scales.