Thermoregulation in male western cicada killers (Sphecius grandis Say) in the Chihuahuan desert

(1) Male western cicada killers (Sphecius grandis) had elevated, apparently regulated, thorax temperatures during territorial patrolling. (2) Abdomen temperature increased steeply with increasing ambient temperature, approaching thorax temperature when ambient temperature exceeded 35 °C. (3) Both indirect evidence and heating experiments demonstrated the apparent ability to shunt heat from thorax to abdomen. (4) Dead, dry wasps reached lethal temperatures when placed in full sunlight on the bare ground, and substantially lower temperatures on plants. (5) The percentage of males perching was extremely low, occurring primarily during early morning hours. Most perching occurred on plants, and very little on the ground. (6) In contrast to what has been reported for eastern cicada killers (Sphecius speciosus), S. grandis males did not appear to use sophisticated behaviors to regulate body temperature during territorial defense, relying primarily on physiological mechanisms. (7) This strategy may be more appropriate for S. grandis in the hotter, drier environment of the lowland Chihuahuan desert.     

Postural Changes Accompany Perch Location Changes in Male Butterflies (Asterocampa leilia) Engaged in Visual Mate Searching

Males of the nymphalid butterfly Asterocampa leilia perch and wait during the morning at places where females are likely to appear. Males leave their perches to court passing females and chase away intruding males. As air and ground temperatures rise during the morning, males switch from perching on the ground to perching off the ground (average height = 0.87 m) for thermoregulatory reasons. To evaluate how this switch in perch location might affect mate detection, I have investigated how the three-dimensional posture of the male's body and head varies with perch location and how conspecifics fly through male perching areas. The body posture of males varies with perch location, as measured by pitch and roll relative to gravity, and yaw relative to the sun. Moreover, the pitch and roll of the head relative to the body is adjusted in a way that compensates for variation in body pitch and roll. These results, along with information on conspecific flight altitudes, suggest that when a male is perched on the ground his visual system is positioned in such a way that he is less likely to detect conspecifics flying nearby than when he is perched off the ground. Hence, it appears that early in the morning visual detection of mates and intruding males may be compromised by thermoregulatory concerns.     

Visual coverage and scanning behavior in two corvid species: American crow and Western scrub jay

Inter-specific differences in the configuration of avian visual fields and degree of eye/head movements have been associated with foraging and anti-predator behaviors. Our goal was to study visual fields, eye movements, and head movements in two species of corvids: American crow (Corvus brachyrhynchos) and Western scrub jay (Aphelocoma californica). American crows had wider binocular overlap, longer vertical binocular fields, narrower blind areas, and higher amplitude of eye movement than Western scrub jays. American crows can converge their eyes and see their own bill tip, which may facilitate using different foraging techniques (e.g., pecking, probing) and manufacturing and handing rudimentary tools. Western scrub jays had a higher head movement rate than American crows while on the ground, and the opposite between-species difference was found when individuals were perching. Faster head movements may enhance the ability to scan the environment, which may be related to a higher perceived risk of predation of Western scrub jays when on the ground, and American crows when perching. The visual field configuration of these species appears influenced mostly by foraging techniques while their scaning behavior, by predation risk.     

Auditory prey location in a pause--travel predator: search height, search time, and attack range of Tengmalm's owls (Aegolius funereus)

We studied the nocturnal hunting and diurnal roosting behaviorof 17 radio-equipped Tengmalm's owls (Aegolius funereus), 12males and 5 females, in coniferous forest during their nestingseason. The owls perched lower when hunting than when roosting,probably because hunting perches were selected to minimize thepredator-prey distance or to obtain unobstructed access to theground-dwelling small mammal prey, whereas roosting percheswere selected to minimize the probability of being detectedby an avian predator. There was no difference between perchingheights associated with giving up and prey attack, nor werethere any differences between perching heights, perching times,and attack distances associated with successful and unsuccessfulattacks. There were no sexual differences in perching heightduring hunting or roosting. However, giving-up times tendedto be longer for females than for their mates, which is expectedbecause females are larger than males, and the relative costof flight increases with body mass. The instantaneous attackrate was independent of perching time. The owls gave up theirperches at a constant rate and independently of the amount oftime already spent on the perch in an exponentially decayingpattern. The owls perched longer, however, before launchingan attack than before giving up, probably in order to observedetected prey until the right moment for an attack. Attack distancewas independent of both perching height and perching time. Perchingtime was inversely related to perching height, which fits thetheoretical expectation that the search area will decrease withincreasing height in birds that locate prey auditorily.     

Effect of larval food stress on male adult behaviour, morphology and reproductive investment in the butterfly Pararge aegeria

Males of several animals increase their reproductive success by territorial behaviour. In butterflies, males may defend a territory (i.e., territorial perching tactic), but this is assumed to be an energetically costly way to locate mates. Limitations of the energy budget may affect fight performance, and may, consequently, force males to adopt an alternative non-territorial searching behaviour (i.e., patrolling tactic) to maximize reproductive success. In this study, we tested to what extent behavioural tactics adopted by adult males of the butterfly Pararge aegeria (L.) were affected by the nutritional conditions during the larval stage. We compared the occurrence of territorial versus patrolling behaviour, lipid mass, flight muscle ratio, metabolic rate and spermatophore production of low quality males that were reared as a larva on drought-stressed host plants and control, high quality males. Low quality males were less likely to adopt the territorial perching tactic and emerged as adults with lower lipid mass than high quality males, but they were able to restore their lipid mass through adult feeding (and perhaps the breakdown of flight muscles). Host plant quality also affected spermatophore size. Independent of the larval food treatment, territorial perching males metabolised more lipids than non-territorial males, produced larger spermatophores and copulated for longer than males adopting non-territorial behaviour. We discuss the results relative to the co-existence of the behavioural tactics (perching and patrolling).     

Perching of Tengmalm's Owl (Aegolius funereus) Nestlings at the Nest Box Entrance: Effect of Time of the Day,Age, Wing Length and Body Weight

The behaviour of the nestlings of nocturnal cavity-nesting species has relatively rarely been studied in detail because of problems connected with use of the technical devices required to provide long-term monitoring of individuals. However, long-term observation of nestling behaviour is crucial in order to identify different types of behaviour which may be caused by sibling competition at the end of nesting period. We studied behaviour of 43 Tengmalm''s owl (Aegolius funereus) nestlings at 14 nests using a camera and a chip system. The nestlings perched at the nest box entrance from an average age of 28 days from hatching (range 24–34 days) until fledging, spending around 2 hours per day here in total, in periods ranging from a few seconds to 147 min (7.6±10.9 min, mean ± SD). We found that individual duration of perching at the nest box entrance was significantly influenced by nestlings'' age and wing length and that the duration of perching at the nest box entrance significantly decreased with time of night. However, during daylight hours, time of day had no effect on either probability or duration of nestlings'' perching. We suggest daylight perching at the nest box entrance results from nestlings'' preparation for fledging, while individuals perching here during the night may gain an advantageous position for obtaining food from the parents; another possibility at all times of day is that nestlings can reaffirm their social dominance status by monopolizing the nest box entrance.     

Ornithophilous canopy species in the Atlantic rain forest of southeastern Brazil

ABSTRACT.   In tropical ecosystems, birds play a relevant role in plant reproduction. Although hummingbirds are regarded as the most important vertebrate pollinators in the Neotropics, the possible role of perching birds as pollinators has been neglected. From 2003 to 2005, we observed 68 species of plants visited by birds in an Atlantic rainforest in southeastern Brazil, including three canopy species: Spirotheca rivieri (Malvaceae, Bombacoidea), Schwartzia brasiliensis (Marcgraviaceae), and Psittacanthus dichrous (Loranthaceae). Flowers of these three species were visited by 15 different species of perching birds and by hummingbirds. The flowers of these three plants are colorful, ranging from deep red or purple to orange. Spirotheca rivieri blooms during the austral winter and Schwartzia brasiliensis during the summer. The flowers of these two species produce copious amounts of dilute nectar in easily accessible structures and both species appear to depend primarily on perching birds as pollinators, with hummingbirds being secondary or minor pollen vectors. The tubular, narrow flowers of P. dichrous are produced during the austral summer and are visited primarily by hummingbirds. Perching birds also visit the flowers, but destroy them. Our results suggest that previous estimates of the number of perching birds that feed on nectar may be too low and that flowers pollinated by perching birds may be more common in the canopy of Neotropical forests than previously thought.     

Lipid economy,flight activity and reproductive behaviour in the speckled wood butterfly: on the energetic cost of territory holding

Insect flight is a highly energy demanding type of locomotion. In butterflies, males may locate females by different behavioural tactics. The tactics correspond to different flight types that, in turn, are assumed to reflect different energetic costs. Costs need to be considered to fully understand the pay‐offs of co‐existing alternative tactics relative to the environmental context and the phenotypes of the individuals. We addressed the issue in the speckled wood Pararge aegeria, in which males either adopt a territorial wait‐and‐fight tactic (i.e. territorial perching) in a sunlit patch on the forest floor, or a fly‐and‐search tactic to locate females in a wider area of the forest (i.e. patrolling). Perching corresponds to high frequency of take‐off flights and aerial combats with high levels of manoeuvrability and is assumed to be energetically more costly than longer, continuous flights at lower speed in patrollers. We tested the effect of different flight activity levels and of the behavioural tactics on lipid reserves and lipid use in males by laboratory and outdoor cage experiments. Low‐activity males that had access to honey water were capable of synthesizing lipids; their lipid reserves increased with age. The effect disappeared in males that actively flew in the outdoor cages. Lipid reserves decreased significantly faster in territorial perching males compared to non‐perching males, but resting metabolic rate did not differ between the alternative behavioural tactics. Territorial perching males had larger flight muscle ratio (i.e. thorax/body mass) than non‐perching males. We discuss the evidence of the physiological costs of perching relative to the co‐existence of perching and patrolling tactics.     

Physical Health Problems and Environmental Challenges Influence Balancing Behaviour in Laying Hens

With rising public concern for animal welfare, many major food chains and restaurants are changing their policies, strictly buying their eggs from non-cage producers. However, with the additional space in these cage-free systems to perform natural behaviours and movements comes the risk of injury. We evaluated the ability to maintain balance in adult laying hens with health problems (footpad dermatitis, keel damage, poor wing feather cover; n = 15) using a series of environmental challenges and compared such abilities with those of healthy birds (n = 5). Environmental challenges consisted of visual and spatial constraints, created using a head mask, perch obstacles, and static and swaying perch states. We hypothesized that perch movement, environmental challenges, and diminished physical health would negatively impact perching performance demonstrated as balance (as measured by time spent on perch and by number of falls of the perch) and would require more exaggerated correctional movements. We measured perching stability whereby each bird underwent eight 30-second trials on a static and swaying perch: with and without disrupted vision (head mask), with and without space limitations (obstacles) and combinations thereof. Video recordings (600 Hz) and a three-axis accelerometer/gyroscope (100 Hz) were used to measure the number of jumps/falls, latencies to leave the perch, as well as magnitude and direction of both linear and rotational balance-correcting movements. Laying hens with and without physical health problems, in both challenged and unchallenged environments, managed to perch and remain off the ground. We attribute this capacity to our training of the birds. Environmental challenges and physical state had an effect on the use of accelerations and rotations to stabilize themselves on a perch. Birds with physical health problems performed a higher frequency of rotational corrections to keep the body centered over the perch, whereas, for both health categories, environmental challenges required more intense and variable movement corrections. Collectively, these results provide novel empirical support for the effectiveness of training, and highlight that overcrowding, visual constraints, and poor physical health all reduce perching performance.     

The influence of providing perches and string on activity levels,fearfulness and leg health in commercial broiler chickens

The aim of this study was to assess the effect of providing environmental enrichment in the form of perches and string on the behaviour and welfare of commercial broiler chickens. Houses containing ~23 000 broiler chickens were assigned to one of four treatments in a 2×2 factorial design. Treatments involved two levels of access to perches (P) (present (24/house) ‘+P’ or absent ‘−P’) and two levels of access to string (S) (present (24/house) ‘+S’ or absent ‘−S’). All houses contained windows, and 30 straw bales were provided from day 10 of the rearing cycle. Treatments were applied in one of four houses on a single farm, and were replicated over four production cycles. Behaviour and leg health were observed in weeks 3 to 5 of the rearing cycle. Production performance and environmental parameters were also measured. There was an interaction between perches and age in the percentage of birds observed lying, with higher percentages of birds observed lying in the +P treatment than in the −P treatment during weeks 4 and 5. There was also a significant interaction between string and age in the percentage of birds observed in locomotion, with higher percentages observed in locomotion in the −S treatment than in the +S treatment during weeks 4 and 5. There was also an interaction between string and age in average gait scores, with lower gait scores in the +S treatment than in the −S treatment during weeks 3 and 5 but not within week 4. Daytime observations showed that perches and strings were used frequently, with one bout of perching occurring approximately every 80 s/perch, and one bout of pecking at string occurring every 78 s/string on average. There was a significant effect of age on use of perches (P<0.001) and string (P<0.001), with perching peaking during week 5 and string pecking peaking during week 3. We conclude that commercial broilers in windowed houses with access to straw bales display an interest in additional enrichment stimuli in the form of perches and string, and therefore that these stimuli have the potential to improve welfare. In addition, provision of string as a pecking device appeared to positively influence walking ability. However, this effect was numerically small, was only shown in certain weeks and was not reflected in the other leg health measure (latency to lie). The results also showed an apparent negative effect of string and perches on the activity levels of birds (recorded away from the immediate vicinity of these enrichments) towards the end of the production cycle. These results emphasise the need for further research into optimum design and layout of enrichment stimuli for modern broilers in windowed houses to ensure that their provision leads to clear welfare benefits.     

城市公园植被特征对陆生鸟类集团的影响

城市公共绿地是城市生态系统中重要的鸟类栖息地,其植被特征对鸟类集团存在显著影响。在通过分析植被特征对陆生鸟类集团的作用,从而为公园合理配置植被来提高其作为野生动物栖息地的生态服务功能提供理论基础。2009年10月至2011年10月,采用样线法对上海滨江森林公园进行鸟类调查,利用主成分分析划分鸟类集团,用高度定义植被层次,用卡方检验分析鸟类行为在植被层次上的差异。结果表明,滨江森林公园陆生鸟类群落在乔木层的栖息行为和运动行为频次显著多于其在灌木层和地被层的行为频次,在地被层的取食行为频次显著多于其在乔木层和灌木层的行为频次。陆生鸟类可划分为8个鸟类集团,鸟类集团之间存在栖息、运动和取食空间生态位的重叠。食虫拾取集团、杂食拾取集团、食肉飞取集团和植食拾取集团在栖息、运动和取食空间生态位上均存在较高的重叠度,其通过食性分离各自空间生态位。食虫探取集团和食虫飞取集团互为栖息空间生态位重叠度最高集团,其通过取食方式的不同来实现生态位的分离。根据公园植被特征对鸟类集团的影响结果对上海市公园绿地植被配置提出了建议。     

Thermoregulatory differences between phenotypes in the speckled wood butterfly: hot perchers and cold patrollers?

Males of the speckled wood butterfly Pararge aegeria L. (Satyrinae), actively search for females (“patrolling”) or wait for them at particular places (“perching”). Darker males are more likely to patrol than pale ones, which are mainly territorial perchers. We studied whether this morphological variation relates to thermoregulatory differences. The relationship between thoracic temperature and ambient temperature differed between the colour types under natural conditions: darker males had on average lower body temperatures than paler males. Different activities (e.g. resting, flying) and behavioural strategies (perching or patrolling) were associated with differences in thoracic temperature: patrolling males which mainly engaged in long flights and periods of basking afterwards, had lower thoracic temperatures than perching males which engaged in very short flights, fights and basking. When resting for a while thoracic temperatures did not differ between males practising different strategies. Under laboratory conditions, darker males heated up faster than pale males but there was no difference in the thoracic temperature at which they started to fly. These results indicate that thermal requirements (or general conditions) differ between the behavioural strategies, and that behavioural differences between phenotypes (colour types) relate to differences in thermal ecology. This supports the idea that darker males are better adapted to patrolling. There is no evidence that one mate-locating strategy is always superior to the other, which coincides with the observation that both strategies co-exist. More generally, this study shows that relatively small differences in colour can have a considerable effect on thermoregulation and hence on the behavioural strategies a heliothermic insect will adopt. Received: 15 August 1997 / Accepted: 15 December 1997     

舟山眼镜蛇对光暗周期加热光源反应所导致的体温变化

用 7条舟山眼镜蛇 (Najaatra)研究动物对光暗周期加热光源反应所导致的体温变化。设计两项实验 ,每项实验历时 9d。实验一光照期覆盖整个白天 ,实验二光照期覆盖整个晚上。眼镜蛇仅在加热光源开启期间进行体温调节 ,但光照期内任何阶段都未发现所有个体同时处于热活动状态。两项实验中热活动个体百分比的时间变化显著 ,实验二热活动个体百分比波动相对大于实验一。在加热光源开启期间 ,实验一热活动眼镜蛇的百分比总体上大于实验二。在两项实验中 ,热活动眼镜蛇体温的时间变化都不显著。实验一热活动眼镜蛇的体温高于实验二 ,而两项实验中不处于热活动状态的眼镜蛇的平均体温无显著差异。实验一热活动眼镜蛇 (31 1±0 8°C)选择的体温上限高于实验二眼镜蛇 (2 6 0± 0 9°C)。在两项实验的任何时间段内 ,眼镜蛇的体温都不低于环境温度。     

Depth of artificial Burrowing Owl burrows affects thermal suitability and occupancy

Many organizations have installed artificial burrows to help bolster local Burrowing Owl (Athene cunicularia) populations. However, occupancy probability and reproductive success in artificial burrows varies within and among burrow installations. We evaluated the possibility that depth below ground might explain differences in occupancy probability and reproductive success by affecting the temperature of artificial burrows. We measured burrow temperatures from March to July 2010 in 27 artificial burrows in southern California that were buried 15–76 cm below the surface (measured between the surface and the top of the burrow chamber). Burrow depth was one of several characteristics that affected burrow temperature. Burrow temperature decreased by 0.03°C per cm of soil on top of the burrow. The percentage of time that artificial burrows provided a thermal refuge from above‐ground temperature decreased with burrow depth and ranged between 50% and 58% among burrows. The percentage of time that burrow temperature was optimal for incubating females also decreased with burrow depth and ranged between 27% and 100% among burrows. However, the percentage of time that burrow temperature was optimal for unattended eggs increased with burrow depth and ranged between 11% and 95% among burrows. We found no effect of burrow depth on reproductive success across 21 nesting attempts. However, occupancy probability had a non‐linear relationship with burrow depth. The shallowest burrows (15 cm) had a moderate probability of being occupied (0.46), burrows between 28 and 40 cm had the highest probability of being occupied (>0.80), and burrows >53 cm had the lowest probability of being occupied (<0.43). Burrowing Owls may prefer burrows at moderate depths because these burrows provide a thermal refuge from above‐ground temperatures, and are often cool enough to allow females to leave eggs unattended before the onset of full‐time incubation, but not too cool for incubating females that spend most of their time in the burrow during incubation. Our results suggest that depth is an important consideration when installing artificial burrows for Burrowing Owls. However, additional study is needed to determine the possible effects of burrow depth on reproductive success and on possible tradeoffs between the effects of burrow depth on optimal temperature and other factors, such as minimizing the risk of nest predation.     

Thermal biology of Pacific cicada killers,Sphecius convallis Patton,in the Upper Sonoran Desert

A comprehensive investigation of the Pacific cicada killer, Sphecius convallis Patton, was undertaken to examine the behavioral and physiological mechanisms by which they are able to complete their life cycle in the thermal extremes of the Upper Sonoran Desert. S. convallis were endothermic, exhibiting elevated and relatively constant thorax temperatures during many activities. Males basked in trees at dawn to warm up, then used a variety of behaviors and perching strategies to maintain thorax temperature during territorial behavior. The thorax temperature of females was highest during provisioning and orientation flights, somewhat lower while investigating burrows, and lowest while digging burrows. The optimal thorax temperature for flight was about 40 °C, which was approximated most closely by males resting in the shade during the afternoon. In mating clusters, the mated male was the hottest, the female was coolest and the other males were intermediate. Wasps lost about 5% of body mass during heating treatments, and may use evaporative water loss for cooling. Pacific cicada killers use a complex suite of behavioral and physiological adaptations to regulate body temperature during their nesting season.     

Effects of radio transmitters on the behavior of Red-headed Woodpeckers

ABSTRACT.   Previous studies have revealed that radio-transmitters may affect bird behaviors, including feeding rates, foraging behavior, vigilance, and preening behavior. In addition, depending on the method of attachment, transmitters can potentially affect the ability of cavity-nesting birds to use cavities. Our objective was to evaluate effects of transmitters on the behavior of and use of cavities by Red-headed Woodpeckers ( Melanerpes erythrocephalus ). Using backpack harnesses, we attached 2.1-g transmitter packages that averaged 3.1% of body weight (range = 2.5–3.6%) to Red-headed Woodpeckers. We observed both radio-tagged ( N = 23) and nonradio-tagged ( N = 28) woodpeckers and determined the percentage of time spent engaged in each of five behaviors: flight, foraging, perching, preening, and territorial behavior. We found no difference between the two groups in the percentage of time engaged in each behavior. In addition, we found that transmitters had no apparent effect on use of cavities for roosting by radio-tagged woodpeckers ( N = 25). We conclude that backpack transmitters weighing less than 3.6% of body weight had no impact on either their behavior or their ability to use cavities.     

Seeing sunlit owls in a new light: orienting Snowy Owls may not be displaying

Snowy Owls Bubo scandiacus often face the sun when sitting on the ground or when perched. Such sun‐orienting has been suggested to represent a visual display to conspecifics but other explanations have not been thoroughly examined. We observed the orientation of wintering Snowy Owls to both the sun and the wind, and their perching behaviour during two winters in central Saskatchewan, Canada. We proposed three new explanations for sun orientation in addition to the display hypothesis: thermoregulation, hunting and defence against predators. On sunny days, 44% of 710 Owls faced the sun; this was non‐random because few did so on overcast days. Sun‐ as opposed to wind‐orienting was strongly associated with weather conditions. Logistic regressions indicated that at temperatures below –13 °C and at wind speeds greater than about 18 km/h, Owls tended to orient to the wind rather than to the sun. The likelihood of wind‐orienting increased if the Owl perched above the ground, whereas the likelihood of sun‐orientating increased slightly when the Owl was sitting on the ground. There was no difference between the sexes in orienting behaviour. Snowy Owls seemed to prioritize wind‐orienting for thermoregulation but the results are also consistent with the idea that sun‐orientation can reduce heat loss. Facing into the sun did not support the hunting explanation because the birds would have been blinded and not able to see prey, but was consistent with the protection explanation if it helps to increase vigilance against enemies. Although we cannot completely rule out the display explanation, the spatial context of sunning Owls and a lack of a sex effect makes it unlikely that this is the main function. Instead, Owls seem to trade‐off wind‐ vs. sun‐orienting according to the prevailing weather conditions and do so mainly to thermoregulate and perhaps to maintain vigilance.     

SEXUAL SELECTION AND BUTTERFLY DESIGN—A COMPARATIVE STUDY

Temperate butterflies of 44 species were examined to determine if their mating system (perching and patrolling) affected flight design. To control for spurious effects due to ancestry, 25 of these species were assigned to eight contrasts within which a change in mating system had occurred. In perching species sexual selection was predicted to favor traits associated with high acceleration ability and speed, while in patrolling species traits associated with flight endurance were predicted. In conformance with these expectations males of perching species had larger thorax/body mass ratios, higher wing loadings, and higher aspect ratios than patrolling species. The male mating system affected females in the same direction in the same variables as males. This could be explained by a genetic correlation with males. When removing the covariance between the sexes, only male design was explained by the mating system. The mating system was also associated with different degrees of sexual dimorphism in wing size. This supported the hypothesis that male design was affected by the mating system.     

Double kerneled fruits in almond (Prunus dulcis Mill.) as related to pre-blossom temperatures

A ten year study on the influence of pre-blossom temperatures on the percentage of double kerneled almond fruits, under warm climatic conditions, showed a negative correlation between the percentage of fruits with double kernels and mean temperatures during the pre-blossom months. When mean temperatures for single pre-blossom months were correlated with double-kernel production, mean temperatures in December showed a much larger correlation (r = -0.78) than those of November (r = -0.51) or January (r = -0.31). Artificially induced 3–4°C daytime increases in pre-blossom temperature on the variety ‘Malagueña’ which commonly produces double kernels, caused a marked fall in the percentage of double kerneled fruits, although it did not affect the percentage fruit set. Our results may indicate an important influence of pre- blossom temperatures on ovule viability.     

Behaviour, physiological states and thermal characteristics of aggregating male Hybomitra illota (Diptera: Tabanidae)

Male Hybomitra illota (Osten Sacken) were found aggregating in clearings in wooded areas in Rondeau Provincial Park, Ontario, Canada. At these sites they perched on a variety of substrates, and made frequent flights in pursuit of insects flying overhead. We know that these pursuit flights were part of the mating behaviour because some pursuits of female H. illota resulted in copulation. We call the aggregation sites 'mating arenas' and the behaviour exhibited by males 'perch-and-pursue'. Aggregation occurred only on sunny days, when ambient temperatures exceeded 18 degrees C. Males perched in sunny areas, except during hot afternoons, when some males were found in dappled shade. Some marked males remained at or returned to sites for up to 13 days, but most males did not remain at the same area within a site, even during the same day. The contents of the oesophageal diverticula of males were depleted daily. Concentration of diverticular carbohydrates changed through the season. Thoracic temperatures of males were high (c. 37 degrees C) and were regulated, probably both behaviourally and physiologically. The sites and behaviour of male H.illota at aggregation arenas bear some resemblance to lek sites and lekking in vertebrates. Males are aggregated in an arena but, within the perching component of the behaviour, we saw no evidence of male territoriality, display, or female choice. However, competition, display, or mate choice could occur within the pursuit-flight component.