Perch Height Research Articles

The establishment of Anolis wattsi as a naturalized exotic lizard in Trinidad

Trinidad has a single native Anolis species (A. chrysolepis) and several introduced exotics (A. aeneus, A. extremus, A. trinitatis, and A. wattsi). Anolis wattsi is the latest introduction, being first observed in the Waterloo area in 1992. This paper describes the distribution of this species in 2000 and 2004, by which time it had become established as a naturalized exotic lizard in western Trinidad. The species was verified as A. wattsi in the strict sense (formerly A. wattsi wattsi), differentiated from sibling species (other former subspecies of A. wattsi). A. wattsi is currently distributed in five discontinuous urban localities within an area of about 15 × 5 km, which suggests jump dispersal across unsuitable habitat (sugar cane fields). The rate of spread was about 100 m yr−1 within urban areas, and >1 km yr−1 for jump dispersal. A. wattsi occurred in the same habitat as the larger A. aeneus in gardens, parks and vacant lots. The two species differed significantly in perch height (but not in perch diameter) and substrate use. A. wattsi used lower perches, and replaced aeneus along the series trees (94% aeneus), posts and bushes, walls and fences, and ground (87% wattsi). Perch height of A. aeneus did not differ between locations with and without A. wattsi, and there was no correlation between numbers of the two species among sites. Possible interactions among introduced and native Anolis species on Trinidad are discussed.

Foraging behavior of tyrant flycatchers (Aves, Tyrannidae) in Brazil

In this paper we present data on the foraging maneuvers and substrates used to capture preys by 28 species of tyrant flycatchers (Tyrannidae) in Brazil. For six species: Arundinicola leucocephala Linnaeus, 1764, Fluvicola nengeta Linnaeus, 1766, Machetornis rixosa Vieillot, 1819, Myiozetetes similis Spix, 1825, Pitangus sulphuratus Linnaeus, 1766, and Tyrannus melancholicus Vieillot, 1819 -, we go further to investigate perch height, search time, sally distance, and sally angle. With a few exceptions, sally strike was the most frequent foraging maneuver. Living foliage and air were the most frequent substrates used to capture preys. Among the six species studied in detail we found three distinct groups of perch heights: F. nengeta and M. rixosa foraged on the ground, A. leucocephala with P. sulphuratus were medium-height foragers, and T. melancholicus and M. similis form the third group for which prey attacks usually start from perches from the ground up to 3 m. With the exception of P. sulphuratus, which had the longest search time, the other five species did not differ in this aspect of the foraging behavior. Three groups were also discernible in relation to sally distance: F. nengeta and M. rixosa usually attacked prey close (< 2 m) to them, A. leucocephala, P. sulphuratus and M. similis form a medium-distance (3-4 m) group, and T. melancholicus had the longest sally distances (up to 12 m). Birds differ in details of the sally angle that, together with other subtle differences in the foraging behavior, may render important differences in prey selection.

Lizard habitat partitioning on islands: the interaction of local and landscape scales

AbstractAim This study addresses how species resolve environmental differences into biological habitats at multiple, interacting spatial scales. How do patterns of local habitat use change along an elevation gradient? How do patterns of local habitat partitioning interact with partitioning at a landscape scale?Location Northern and southern Lesser Antilles islands, West Indies.Methods We document howAnolisDaudin, 1802 lizards partition habitat locally at sites along a landscape‐scale elevation gradient. We examine habitat partitioning both with and without interspecific interactions in the predominately flat northern Lesser Antilles islands and in the more mountainous southern islands.Results Anoles partition local habitat along perch‐height and microclimate axes. Northern‐group sympatric anoles partition local habitat by perch height and have overlapping distributions at the landscape scale. Southern‐group sympatric anoles partition local habitat by microclimate and specialize in particular habitats at the landscape scale. In both the northern and southern groups, species use different perch heights and microclimates only in areas of species overlap along the elevation gradient.Main conclusions We demonstrate the interaction between local‐ and landscape‐scale habitat partitioning. In the case of microclimate partitioning, the interaction results from the use of thermal physiology to partition habitat at multiple scales. This interaction prompts the question of whether habitat partitioning developed ‘local‐out’ or ‘landscape‐in’. We pose this dichotomy and present a framework for its resolution.

Ecomorphological variation in foraging behaviour by Puerto Rican Anolis lizardsAnolislizard ecomorphs

Ecomorphs of Anolis lizards evolved convergently via niche partitioning in separate radiations. Each ecomorph has a suite of traits including body size, morphology, microhabitat, anti-predatory behaviour, and foraging, but foraging movements of ecomorphs have not been characterized quantitatively. Data are presented on aspects of foraging for seven species representing four ecomorphs in the cristatellus series from Puerto Rico. Using these and published data for Jamaican and Hispaniolan anoles, an examination is made of predictions based on definitions of ecomorphs by Williams (1972, 1983). Grass-bush and trunk-crown anoles exhibited higher movement rates than trunk-ground anoles. Data for other radiations agree and support a prediction of relatively high movement rates for twig and trunk ecomorphs. All the species studied were ambush foragers and all used the head-down survey posture, indicating phylogenetic stability of these traits. Arboreal species adopted survey posture in about 75% of observations, and grass-bush species used it when on elevated perches. Rates of foraging movements increased as perch height decreased in grass-bush ecomorphs owing to visual obstruction by vegetation limiting the scanning area close to the ground. A similar relationship occurred unexpectedly in a trunk-crown II species, A. stratulus, whereas movement increased marginally with perch height in a trunk-crown I species, A. evermanni. Perch height and movement rates were unrelated in three trunk-ground species. Movements per minute and per cent time moving were highly correlated among species owing to the brevity of individual movements. Data from other Greater Antillean radiations are needed to separate the effects of ecology and phylogeny on anole foraging.

Visual fixation of a landing perch by chickens

Chickens were video recorded while making jumps or flights toward a landing perch, to test hypotheses about visual fixation behaviour. In the first experiment, varying the height above the landing perch of the food container providing the incentive to jump had no effect on head orientation, indicating that the birds were not fixating this object. In the second experiment, hens jumped over six combinations of perch height and distance, and a linear relationship was found at take-off between head orientation and the angular distance of the perch from the horizontal at the eye. This relationship is consistent with fixation of the perch by a linear combination of head and eye rotations, with the head component contributing 73% of the total response. The image of the perch is fixated 20 masculine below that of the bill tip, outside any region of the chicken retina specialised for high acuity vision. Fixation of the perch before jumping must therefore have some function other than inspection with high acuity, such as providing a constraint that enables precise visual control of trajectory and landing manoeuvres.

Evolutionary correlations among morphology, habitat use and clinging performance in Caribbean Anolis lizards

A central issue in evolutionary biology concerns whether morphology, performance and habitat use have coevolved. We investigated evolutionary relationships among the size of the subdigital toepad, clinging ability and perch height in 12 species of Caribbean Anolis lizard. Specifically, we predicted that: (1) because larger anole species tend to perch high in the canopy, both toepad area and clinging ability should scale with positive allometry to enable small and large lizards to possess approximately similar ratios of both variables relative to mass; (2) anole species with relatively larger toepads (i.e. size-adjusted) should be relatively better clingers compared with species with relatively small toepads; (3) species that perch high in the canopy should possess relatively large clinging abilities (either on an absolute or a size-adjusted basis). Our first hypothesis was refuted, as both toepad area and clinging ability scaled close to isometry (0.67) relative to mass, indicating that large lizard species have low ratios of clinging ability to mass compared with small lizard species. However, our second and third predictions were confirmed. Anole species with relatively larger toepads were relatively better clingers compared with species with relatively smaller toepads. Anole species that perched high in the canopy (either on an absolute scale or relative to size) tended to have relatively larger toepads and greater clinging capacities compared with species that perched lower in the canopy. These data provide indirect comparative evidence that the evolution of increased toepad size in some anole species is adaptive, by facilitating the occupation of perches high in the canopy. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 83, 389–398.

Seasonal foraging ecology in a forest avifauna of northern Kenya

We studied the avian foraging ecology in a single montane forest of northern Kenya, analysing the pattern of seasonal variation (wet vs. dry period) and its relationship with habitat structure. The foraging behaviour of 28 species was described in terms of four major dimensions (i.e. foraging technique, food substrate, perching site and perching height). Seasonal rainfall produced an increase in vegetation growth in the lower vegetation layers, while fruiting and flowering peaked in the dry season. We did not find much seasonal variation in foraging ecology when we analysed our data at the species or at the community levels. At the guild level, however, we found some seasonal shifts in perching height, food substrate and foraging technique. Some of these shifts seemed to be determined by food availability and distribution, as omnivores increased fruit consumption when this resource was more abundant, and nectarivores tracked the vertical distribution of flowers. The vertical biomass distribution of this avian community seemed to be largely determined by food. However, seasonal variation in the total biomass of some guilds was probably related to factors not considered in this study, such as breeding, or intra-African migratory movements. Altogether, despite marked seasonal variation in vegetation structure and food resources, the bird assemblage showed little change in its feeding ecology and micro-habitat use. Hence, we suggest that changes in habitat structure and resource levels were coped with primarily by adjusting population density and food requirements through seasonal breeding or migration.

Effects of artificial perches and interspecific interactions on patch use by wintering raptors

We used an experimental approach to investigate the effects of woody vegetation and interspecific interactions on patch use by three wintering raptor species in the coastal prairie in south Texas. We manipulated perch type and density by the addition of artificial perches to patches of coastal prairie grasslands, varying perch height in the first year and canopy density in the second year. American Kestrels (Falco sparverius) used areas with artificial perches more often than they used natural woody vegetation and areas without woody perches. Northern Harrier (Circus cyaneus) patch use did not vary with treatment type. Loggerhead Shrikes (Lanius ludovicianus) used areas of natural woody vegetation more than patches with artificial perches and patches with no perches. Patch use by Loggerhead Shrikes was also influenced by the presence of complex woody vegetation and interspecific interactions, whereas American Kestrel use was limited by landscape matrix and ground cover density. We believe that predation by Northern Harriers limited Loggerhead Shrikes to patches with escape cover, while competition from American Kestrels prevented Loggerhead Shrikes from concurrent patch use.

Size‐dependent predator–prey relationships between perch and their fish prey

Size‐dependent interactions between piscivorous perch Perca fluviatilis (age ≥1 year) and their fish prey age 0 year perch, pikeperch Sander lucioperca and roach Rutilus rutilus in the biomanipulated Bautzen Reservoir indicated that the highest ratio of prey total length (LT) to predator LT was 59%. Perch LT and prey fish LT were positively and linearly related. Perch LT was strongly related with both gape width and gape height. Within the range 80–110 mm LT, the gape height of perch exceeded gape width, while beginning at 120 mm LT the gape width exceeded gape height. The minimum, maximum and mean prey LT and prey body depths of all three prey species increased with increasing predator size, but the increases in mean sizes of perch and pikeperch as prey were less than that of roach. The low limit of the ‘predation window’ observed in this study coupled with results of previous studies on perch in the Bautzen Reservoir indicated that perch had a major impact on the population dynamics of both perch and pikeperch.

Ecomorphological Differences in Toepad Characteristics between Mainland and Island Anoles

Abstract Anoles (Anolis, Chamaeleolis, Chamaelinorops, Phenacosaurus) differ greatly in size and shape of their subdigital toepads. We sampled 79 anole species to address two issues. First, is toepad size significantly related to habitat use? Second, do anoles from mainland Central and South America differ from Caribbean anoles in either the size of their toepads or in the relationship between toepad shape and habitat use? Among all anoles, toepad size increases with both perch height and diameter, although when the effects of body size are removed, these relationships are weakened. Morphological differences exist between toepads of anoles from the two regions. Caribbean anoles have larger toepads relative to snout–vent length and wider pads at larger body sizes compared to mainland species. Relationships between toepad morphology and habitat use characteristics do not differ significantly between the two groups of anoles. However, with effects of size removed, Caribbean anoles have larger and wider toepa...

Patterns of microhabitat use in a sympatric lizard assemblage

The distribution of animals among habitats and microhabitats has frequently been used to examine patterns of niche overlap. We characterized microhabitat differences within an assemblage of four phrynosomatine lizard species (Sceloporus graciosus, Sceloporus undulatus, Urosaurus ornatus, and Uta stansburiana) that are commonly syntopic in the pinyon pine – juniper woodland habitat on the elevated mesas of western Colorado. We censused lizard populations and recorded microhabitat characteristics of areas surrounding capture sites within Colorado National Monument, U.S.A. Discriminant function analysis of microhabitat features extracted two significant roots, explaining 89% of the microhabitat variation observed among species. Planned comparisons of canonical scores revealed two significant microhabitat niche differences. First, the microhabitat niche of U. ornatus was distinguished from those of all the other species by higher perch height and more vertical substrate, indicating this species' arboreality. Second, the microhabitat niche of S. graciosus was distinguished from those of the other species by having more flatland and less rock, indicating the use of more open flat sandy areas within the pinyon pine – juniper woodland by this terrestrial species. Although the observed differences in microhabitat may influence the coexistence of these ecologically similar species, changes in relative abundance of the species over time suggest alternative mechanisms of coexistence.

Guidelines for the design and management of artificial raptor perches and nest-tree stands on forestry estates in South Africa

Synopsis The aim of this paper is to provide timber growers with silvicultural guidelines for the establishment of raptor perches and nest stands on forestry estates. Rodents do extensive damage to young saplings and as an ecologically friendly alternative to rodenticides, we provide guidelines on perch height and densities that can be implemented to facilitate rodent-eating, perch-hunting raptors. For example, if eight, 2-m high, even spaced poles are erected per hectare, the raptors will be able to hunt the entire area. The aim of creating nest stands on forestry estates is to establish 3-6 small (625m2) designated areas where raptors can breed separately from commercial forestry activities. Guidelines for small, tree-nesting raptors include dense stands (1000 treeslha) to hide nests from predators, whereas stands for intermediate size raptors must be thinned to 163 trees/ha to allow an increase in trunk diameter that, in turn, allows the trees to support bigger nests. Cultivating large trees for large ...

PREDATION ON A COMMON ANOLIS LIZARD: CAN THE FOOD-WEB EFFECTS OF A DEVASTATING PREDATOR BE REVERSED?

We artificially invaded a set of small islands with the large lizard Leioce- phalus carinatus to determine effects on food-web elements including an intermediate predator, the lizard Anolis sagrei; the latter was previously found to have major, mostly direct effects on web spiders, as well as detectable indirect effects on aerial arthropods (including parasitoids) and leaf damage. In addition to these food-web elements, we mon- itored ground-surface arthropods; they are expected to be affected directly, as well as indirectly via A. sagrei ,b yL. carinatus. Five islands were randomly selected for invasion while six others served as controls. In addition, four islands without A. sagrei were mon- itored to determine the natural state of the sagrei-free food web. We also monitored a variety of A. sagrei's traits, from behavioral through physiological and demographic to morphological, to elucidate the mechanisms whereby L. carinatus might affect the smaller lizard and to evaluate trait-mediated as well as density-mediated effects. Comparison of unmanipulated islands with and without A. sagrei showed that A. sagrei appeared to be affecting web-spider density and diversity, numbers of small aerial arthro- pods, number of large ground-surface arthropods, and two types of leaf damage, scars and mines. All effects were negative save one: Small aerial arthropods were more abundant with A. sagrei; this variable and parasitoid abundance were negatively related to web-spider density, implicating an indirect effect pathway from A. sagrei via web spiders. Introduction of L. carinatus had major and immediate effects on A. sagrei density and perch height; effects on perch diameter, percentage hatchlings, and the width of the body- size distribution followed over time. Behavioral shifts in habitat use continued to the end of the experiment, after changes in population density had mostly leveled off. Adult-male body condition became poorer after introduction of L. carinatus. Among islands, percentage use of the ground was correlated negatively with percentage vegetated area of the island and positively with premanipulation relative hindlimb length. We hypothesize that longer- legged individuals do better on the ground because they are faster there. Conditional ev- idence for an increase in adult-male relative hindlimb length suggested that, when the ground-inhabiting L. carinatus was introduced, such individuals were differentially able to escape predation. Introduction of L. carinatus significantly reversedA. sagrei's effect on number of species and density of web spiders but had no other major effects on lower level food-web elements. Thus, a relatively short-chained (two links) effect, with a relatively strong second link ( A. sagrei on spiders), showed the greatest indirect effect of the manipulation. Another poten- tially strong indirect effect, that on large ground-surface arthropods, did not occur, possibly because of compensatory (direct) predation by L. carinatus. Thus presence of omnivory may also be relevant to whether reversal of effects occurs. Although most A. sagrei effects were not reversed in the time available for the experiment, this may be typical, as natural L. carinatus colonizations can dwindle away to extinction over about the same time span, producing at best only short-term indirect effects. Population-density estimates from other sites and comparisons to other experimental studies suggest that, in general, predators on Anolis may have erratic effects in space and time.

Sexual and age differences in ecological variables of the lizard Microlophus atacamensis (Tropiduridae) from northern Chile

ABSTRACT Microlophus is a lizard genus of South-America which has many species with sexual size dimorphism. An ecologicalstudy was performed on M. atacamensis, a species inhabiting the intertidal zone of the coast of northern Chile. Thefollowing questions were addressed: (1) does M. atacamensis exhibit sexual dimorphism? (2) do individuals of differentage and sex segregate spatially? (3) do individuals of different age and sex use different type of microhabitat? and (4)do individuals of different sexes exhibit differences in thermoregulatory characteristics? The study was conducted indifferent localities from northern Chile, which include two types of rocky systems used by this species, a high and alow type. At the moment of lizard capture, type of microhabitat, height of perch, body, air and substrate temperatures,were recorded. Individuals were then measured and weighted, and separated by age class and sex. Results indicate thatthis species exhibits sexual dimorphism, males being larger. There were no intersexual differences in microhabitat usedand height of perch in the high type system, although adults and subadults were spatially segregated from juveniles. Inthe low type system adult females shared microhabitat with juveniles, a probable consequence of behaviors related tothe burying of eggs. There were no differences between sexes in thermal characteristics, and body temperature of lizardsshowed independence from external thermal conditions.Key words: Tropiduridae, Microlophus atacamensis , sexual dimorphism, thermoregulation, spatial segregation,Chile.

Foraging behaviour of brown-hooded kingfishers (Halcyon albiventris) in the East UsambaraMountains, Tanzania

We report metrics of foraging behaviour of the brown-hooded kingfisher (Halcyon albiventris) at field sites near Amani, Tanzania. We also test whether the relationships between perch height, search time, sally distance and handling times are consistent with predictions of opportunistic foraging. The time spent at a perch when the bird attempts prey capture should be shorter than give-up times when birds are taking the first thing detected. Hence, survival distribution functions and non-parametric rank statistics were used to test for differences between give-up and attempt perches. Since an exponential model appropriately described the perch survival distribution function, the time that a bird leaves a perch is independent from time already at the location. At any given time during a search for prey items, the probability that a kingfisher stayed at a perch was significantly lower when the bird made an attempt at the item than if it gave up on a location. Additionally, there were no relationships between search time and perch height, sally distance and handling times. This may be explained by an energetic trade-off with large prey handling costs, opportunistic feeding of the more abundant small prey items, or prey-specific familiarity by local kingfishers.

Correlates of active body temperatures and microhabitat occupation in nine species of central Australian agamid lizards

Body temperatures of active lizards and their correspondence with microhabitat occupation were studied for nine species of agamid lizards in the central Australian arid zone. Thermoregulatory behaviour was also documented using several measures, such as the use of shade and perch height. The effects of thermal environ- ment on lizard habitat occupation were hypothesized to be significant, because desert regions experience daily and seasonal extremes of temperature that are well in excess of a lizard's preferred temperature range. All species, except Ctenophorus isolepis and Diporiphora winneckei, were found to have body temperatures that corresponded closely to ground and surface temperatures. Thermoregulatory behaviour was also found to be important through- out a lizard's daily activity; all study species, other than Ctenophorus isolepis, were found to increase their perch height in the middle of the day. Ctenophorus isolepis was shown to be a strictly terrestrial species that uses the shade of spinifex in its thermoregulatory behaviour. Species exhibited a non-random selection of microhabitats and a preference for a particular set of thermal and structural factors. In this study, it was shown that structural factors were particularly important in microhabitat occupation. Thermal factors accounted for a smaller proportion of variance in microhabitat occupation, but still played a considerable role in the microhabitat use in central Australian agamids.

Differential degradation of antbird songs in a neotropical rainforest: adaptation to perch height?

Habitat characteristics that affect transmission and degradation of acoustical signals should influence strongly the evolution of bird songs. In this study propagation properties of songs of five antbird species were measured in a rainforest in southern Venezuela. The investigated species (Myrmothera campanisona, Thamnophilus aethiops, Thamnophilus amazonicus, Myrmotherula axillaris, and Herpsilochmus dorsimaculatus) use different song post heights at all levels of the rainforest. Because there is a height-specific pattern in degradation, it is hypothesized that their songs are adapted to species-specific transmission paths. To test this assumption, transmission parameters (excess attenuation, signal-to-noise ratio, and blur ratio) were measured for the songs at five different heights and at three different distances. In three of the five species, the results indicate a strong influence of environmental conditions on the design of the vocalizations. Degradation was minimized by the concentration of the signal to a narrower frequency range, the usage of lower frequencies, or a slower time structure for the songs near the ground. The results are discussed in relation to acoustical models of sound propagation and physiology, and it is suggested that height-dependent degradation within a forest is an important selection pressure for transmissibility in avian communication.

Flush Responses of Mexican Spotted Owls to Recreationists

Mexican spotted owls (Strix occidentalis lucida) occupy narrow canyons on the Colorado Plateau, some of which are subject to high levels of recreational activity. These activities represent a potential threat to owls, yet due to the confines of canyon walls spatial restrictions on recreational activities would likely eliminate all activity within these canyons. We assessed factors that influenced flush responses (flush or no flush), flush distances, distances of avoidance flights, and behavioral changes of owls in response to a single hiker that approached roosting owls. Increased perch height decreased the likelihood that adults (odds ratio = 0.09) and juveniles (odds ratio = 0.17) would flush in response to the presence of a hiker; having flushed previously the same day increased the likelihood of adults flushing on subsequent approaches (odds ratio = 6.83). Juveniles and adults were unlikely to flush at distances ≥ 12 m and ≥24 m from hikers, respectively, and neither age class was likely to alter its behavior in response to the presence of a hiker at distances ≥55 m. Based on these response thresholds, placing a 55-m buffer zone around roosting sites would eliminate virtually all behavioral responses of owls to hikers, but would restrict hiker access to 80% of canyons occupied by owls. A less conservative 12-m buffer zone would eliminate 95% of juvenile and 80% of adult flush responses, and restrict hiker access to 25% of canyons occupied by owls.

Selection of habitat and perches by the Great Grey Shrike Lanius excubitor and the effects of snow layer and prey type

Field observations on Great Grey Shrikes Lanius excubitor were performed in four study areas in SW Finland (60°N, 22°E). The relation between habitat use, perch selection, prey type and the presence of a snow layer was evaluated. The mean yearly (± SE) territory size was 144 ha ± 14.3. The habitat selection depended on if snow cover was present, reflecting the favouring of vegetation-scarce arable fields when hunting invertebrates and vegetation-rich habitats when mainly vertebrates were available. Consistent with theories on optimal perch height, the shrikes chose higher perches when mainly vertebrates were hunted and also increased the time/perch, probably reflecting that vertebrate prey occur less frequently than invertebrate prey. The selection of lower perches when hunting invertebrates was evident in mild winter periods but not in the autumn; the reasons for this is discussed. The appearance of snow increased the distance to mammalian prey but the average capture frequency of mammals remained unchanged. In accordance with optimal foraging theory the shrikes preferred to hunt invertebrates when these were available rather than to adopt a hunting strategy that would optimise the encounter rate with vertebrates. However, the average hunting rate of ground-living prey decreased as the snow depth increased whereas energetically costly types of hunting behaviour, like rate of movements, hovering and hunting of birds remained unchanged.

Response of American kestrels and gray-tailed voles to vegetation height and supplemental perches

We tested the behavioral and demographic responses of American kestrels, Falco sparverius, and gray-tailed voles, Microtus canicaudus, to vegetation height and addition of perches. We conducted our experiment in sixteen 0.2-ha rodent enclosures with four replicates assigned to each of the following treatments: tall vegetation without perches, tall vegetation with perches, short vegetation without perches, and short vegetation with perches. The enclosures were stocked with 20 gray-tailed voles in early November 1998. Before perches were erected during the 12th week of the experiment, kestrels showed a preference for short-vegetation enclosures (P < 0.05). After perches were erected, kestrels used enclosures with perches, showing the greatest preference for short-vegetation enclosures with a perch. Vole populations and recruitment rates were higher in tall-vegetation enclosures than in short-vegetation enclosures, but supplemental perches did not affect vole populations or recruitment. In many agricultural areas where perches are not available, providing supplemental perches may increase accessibility to prey species that cause crop damage. Facilitating predation by raptors may reduce vole populations and reduce the need to use potentially harmful chemicals in pest population management.