Lower Perches Research Articles

Roosting and breeding behaviour of Tawny Frogmouths Podargus strigoides in central-coastal Queensland

The roosting and breeding behaviour of a pair of Tawny Frogmouths Podargus strigoides was observed on the central Queensland coast over a period of 4 years (2018–2021). The study was conducted in a subtropical climate near Rockhampton, and provides data from a different geographical and climatic area compared with previous studies that were conducted in temperate southern Australia (New England Tablelands, Moree, and Sydney, New South Wales, and the Australian Capital Territory). Breeding data matched other studies: breeding in November–December, incubation of 28–30 days, fledging at 27–31 days, care of fledglings from 1–3 months, nests located in a horizontal fork of a tree on the edge of a clearing. Breeding success was high at 80% (8 of 10 nestlings survived). Roost sites were generally in tree species with a fibrous dark bark that provided camouflage, and were mostly within the leafy canopy (average height 9.11 m above ground), which provided protection from high daytime temperatures in both winter and summer. Only early in the morning on very cool days in winter did Frogmouths seek lower perches where sun exposure was greatest. These findings are consistent with other studies identifying thermoregulation and camouflage as important determinants of roost selection, although the need for greater sun exposure in winter was much lower in this study, reflecting the generally warm winter days. Fidelity to roost trees was high (90% of roosts were in four trees) and Frogmouths nested in a different tree each year. Both roosts and nests were confined to a home range of 1.6 ha. The frequency of feeding increased with nestling age, and was higher during the early part of the night. Overall, these findings advance understanding of the breeding biology of the Tawny Frogmouth in subtropical Australia.

Parameters of the adhesive setae and setal fields of the Jamaican radiation of anoles (Dactyloidae: Anolis): potential for ecomorphology at the microscopic scale

Abstract The subdigital adhesive pads of Caribbean Anolis lizards are considered to be a key innovation that permits occupation of novel ecological niches. Although previous work has demonstrated that subdigital pad morphology and performance vary with habitat use, such investigations have only considered the macroscale aspects of these structures (e.g. pad area). The morphological agents of attachment, however, are arrays of hair-like fibres (setae) that terminate in an expanded tip (spatula) and have not been examined in a similar manner. Here we examine the setal morphology and setal field configuration of ecologically distinct species of the monophyletic Jamaican Anolis radiation from a functional and ecological perspective. We find that anoles occupying the highest perches possess greater setal densities and smaller spatulae than those exploiting lower perches. This finding is consistent with the concept of contact splitting, whereby subdivision of an adhesive area into smaller and more densely packed fibres results in an increase in adhesive performance. Micromorphological evidence also suggests that the biomechanics of adhesive locomotion may vary between Anolis ecomorphs. Our findings indicate that, in a similar fashion to macroscale features of the subdigital pad, its microstructure may vary in relation to performance and habitat use in Caribbean Anolis.

Anti-predatory sleep strategies are conserved in the agamid lizard Monilesaurus rouxii

Sleep is an essential part of animal biology, yet its ecological aspects such as predator avoidance remain understudied, especially in the wild. Sleep behaviour is likely to be subject to selection pressure and evolution, leading to sleep strategies to ensure survival during this vulnerable state. How sleep strategies of animals respond to alteration of macro-habitat has been largely unexplored. This study aimed to determine the effect of habitat type on the sleep ecology of the agamid lizard Monilesaurus rouxii. We carried out field work in the Western Ghats (India) biodiversity hotspot, in two differing habitat types—natural wet evergreen forests and human—modified Areca catechu plantations. We collected data on perches used by lizards for sleep, both in terms of their structural characteristics and their use (e.g. lizard head direction). To determine perch selection, we compared perch use with perch availability in both habitat types. Habitat type had limited influence on sleep perch selection of M. rouxii, with lizards selecting only unstable narrow-girthed plants, suggesting a highly conserved sleep strategy driven by predator avoidance. The majority of sleeping lizards displayed an ‘inward’ head direction, towards the potential path of a predator approaching from the ground. However, this strategy to select for narrow-girthed plants constrained lizards to use lower, unsafe sleep perches in plantations (driven by availability), which could have consequences for their survival. To our knowledge, our study is the first to examine in detail the effect of habitat alteration on sleep strategies in lizards. Sleep strategies of animals in the wild could affect their chances of survival and their performance during active behaviours. ‘Where’ and ‘how’ animals sleep are important aspects of their sleep strategy. However, it is unexplored if these choices would change in response to human modification of the natural habitat. We compared sleep site selection in the semi-arboreal agamid lizard Monilesaurus rouxii in two different habitats (natural and human-modified). Lizards always chose narrow, unstable perch plants to sleep, as they allow for early detection of an approaching predator. In the human-modified habitat (Areca catechu plantations), opting for narrow unstable perches led to lizards using significantly lower perches, probably leaving them vulnerable to predators approaching from the ground. Our results show that exploring sleep strategies in the wild is necessary to properly assess the effects of habitat modification on species.

Linear Space Requirements and Perch Use of Conventional Layer Hybrids and Dual-Purpose Hens in an Aviary System.

Roosting on elevated perches is a behavioral priority in laying hens, which is well-investigated in both experimental and commercial settings. However, little is known about perching behavior and perch requirements of alternative hybrids, such as dual-purpose hens. The aim of the present study was to gain basic knowledge on linear space requirements and perching patterns of dual-purpose hens (Lohmann Dual, LD) by comparing them to a conventional layer line (Lohmann Brown plus, LB+). About 3,700 hens per genetic strain were housed in two consecutive batches in four compartments of an aviary system with metal perches at different heights above a grid tier. As an indicator for required perching space, the body widths of a sample of individual hens was determined by image analyses. In addition, the use of five differently located perches and one cross-brace (structural element of the aviary system) was assessed by photo-based observations during the light and the dark phase. The LD hens measured an average body width of 15.95 ± 0.08 cm, and thus occupied about 7% more linear space than the LB+ hens (14.77 ± 0.08 cm body width; P < 0.05). Overall perch use was higher during the dark compared to the light phase, both in the LB+ (3.89 ± 0.08 vs. 0.79 ± 0.03 hens/m, P < 0.05) and the LD hens (2.88 ± 0.06 vs. 0.86 ± 0.03 hens/m, P < 0.05). With a maximum of 8.17 hens/m, the LB+ hens preferred to roost on the highest perches available at night. In contrast, the LD hens also rested on the lowest perches, and showed a more even use of all perches provided. During the day, the LD hens seemed to need lower perches for easy access to the feeders, whereas more LB+ hens used the higher perches, presumably to avoid threatening conspecifics. The present results show that preferences for certain perch locations differed between conventional layers and dual-purpose hens, whereas diurnal patterns of perch use were similar in both hybrids. Therefore, perches should be designed and located in an aviary system to meet the specific preferences and behavioral needs of the hybrid housed.

Partitioning of Foraging Habitat by Three Kingfishers (Alcedinidae: Cerylinae) along the South Llano River, Texas, USA

Current northward expansion of Ringed Kingfisher (Megaceryle torquata) and Green Kingfisher (Chloroceryle americana) into central Texas places them in aquatic systems with the temperate Belted Kingfisher (Megaceryle alcyon). Recent contact among the three species provides an opportunity to assess resource partitioning. A 23.5 km stretch of the South Llano River near Junction, Texas, USA was surveyed to determine seasonal abundance and compare foraging perch characteristics among the species. Data were collected on 7 foraging perch characteristics for 250 kingfisher observations across 26 surveys. Mean encounter rate for Green, Belted, and Ringed kingfishers per river kilometer was 0.48, 0.22, and 0.09, respectively. Green Kingfishers were present year-round, while the Belted and Ringed kingfishers were absent or rare from mid-spring to mid-summer. Characteristics of foraging perches were similar among the species with the exception of perch height, with Green Kingfisher having lower perches (142.3 cm ± 126.6 SD) than both Belted (550.8 cm ± 449.4 SD) and Ringed kingfishers (551.1 cm ± 422.7 SD). Mean perch heights of Green Kingfishers averaged higher during surveys when Belted Kingfishers were absent (210.5 cm ± 191.0 SD, n = 36) compared to surveys when Belted Kingfishers were present (124.0 cm ± 89.1 SD, n = 129).

Raptor Use of Artificial Perches in California Rangelands in Fall

Author(s): Kross, Sara; Chapman, Renata; Craig, Andrea; Kelsey, T. Rodd | Abstract: Most raptor species rely on perches for hunting, resting, preening and roosting and in many agricultural areas the availability of adequate perches can limit raptor abundance and diversity. This has negative implications for both raptor conservation and the natural pest control services they can provide for farmers. Installing artificial perches on agricultural lands can therefore benefit both raptors and farmers. However, installing perches under current guidelines is difficult on California’s 38 million acres of rangelands, where rocky soil can be restrictive to anchoring poles belowground. We developed a novel method for modifying existing fenceposts to support raptor perches. These raptor perches are relatively light, easy to construct, can be transported in multiple pieces and assembled in the field. We installed 16 artificial raptor perches in four representative habitats on a California ranch to 1) determine if raptors will use artificial perches in each habitat; 2) test raptor preferences for different perch configurations; and 3) observe which raptor species utilize perches. Here, we share our perch design as well as our results from monitoring perches between August and November 2017. We found that American kestrels, great horned owls, barn owls, and red-tailed hawks utilized perches, as did a number of non-raptor species. Perch use by raptors was highest in an irrigated pasture and at a mid-elevation grassland site located on a hill. Perches at a low-elevation, unirrigated pasture with no slope and perches located in higher elevation oak woodland sites were used significantly less. In all habitats raptors preferred to utilize 15-foot perches over 20-foot perches. Raptors rarely utilized a lower perch when two were available on a single pole, suggesting that this added feature is not necessary to attract the species we observed.

A multivariate approach to understanding shifts in escape strategies of urban lizards

Escape strategies of animals are economic decisions, expected to vary as a function of both intrinsic (e.g., performance ability) and extrinsic factors (e.g., level of threat and microhabitat). Anthropogenic disturbance, especially urbanization, changes a range of environmental factors including habitat characteristics and predation risk. As a consequence of differences in microhabitat structure and repeated exposure to anthropogenic disturbance, we hypothesize that animals in urban environments will be less risk averse than those in rural environments. Here, we examined the importance of extrinsic and intrinsic factors to understand the escape strategies of Psammophilus dorsalis across an urban-rural gradient. First, urban lizards used lower perches and chose refuges that were closer to their perches compared to rural lizards. Flight initiation distance (FID) of urban lizards in the field was shorter than that of rural lizards, but only for males. In response to a second attack, only rural males decreased their FIDs, whereas urban males showed low and invariable FIDs. Laboratory measures of sprint performance showed expected differences between the sexes, but no significant difference between urban and rural populations. Unlike the strong differences between males across habitats, escape strategies of females were similar in urban and rural areas, most likely because females generally rely on crypsis to minimize predation risk and are resistant to flee when approached. In sum, urban lizards have access to a more complex structural environment, with greater perch and refuge options, and have habituated to non-lethal anthropogenic disturbance. These extrinsic and intrinsic factors combine to result in lower risk aversion and may explain the ability to tolerate urban environments. Significance statement Rapid urbanization is at its peak globally, and many animals are forced to adjust to the associated environmental changes or face local extinction. Some species, however, seem to persist in urban areas, and we hypothesize that they behaviorally respond by being less risk averse. We used a multivariate approach to understand the escape strategies of the peninsula rock agama across an urban-rural gradient. Lizards in urban areas use a more complex structural environment, with greater perch and refuge options, compared to rural lizards. Urban lizards also allow closer approaches. Because of the differences in body coloration and size, escape strategies of females were less affected by urbanization as they use crypsis to minimize predation risk. All these extrinsic and intrinsic factors combine to result in lower risk aversion by urban lizards and may explain their tolerance of human altered environments.

Sexual differences in behavioral thermoregulation of the lizard Scelarcis perspicillata

Temperature determines all aspects of the biology of ectotherms. Although sexual differences in thermal ecology are not the rule in lizards, some species exhibit such differences. We studied the effect of sex and reproductive condition on the thermoregulation of an introduced population of Scelarcis perspicillata during the summer in Menorca (Balearic Islands, Spain). These lizards live in the wall surfaces of a limestone quarry, where the sun is scarce because of the narrowness of the quarry walls. The population is sexually dimorphic, with larger males than females. We measured body temperature (Tb) of adult males and females in the field, and air (Ta) and substrate temperature (Ts) at the capture sites, and recorded exposure to sunlight, height of the perch, and type of substrate. We also recorded operative temperatures (Te) as a null hypothesis of thermoregulation. Finally, we studied the thermal preferences of adult males and females in a laboratory thermal gradient. Thermal preferences were similar for pregnant and non-pregnant females, and sex did not affect the thermal preferences of lizards, even after controlling for the effect of body size. However, in the field, females achieved higher Tb than males, and occupied microhabitats with higher Ta and Ts and lower perch heights than males. Furthermore, females selected perches in full sun at a higher frequency than males. As a consequence, females achieved a higher accuracy and effectiveness of thermoregulation (0.89) than males (0.84). Thus, all else being equal, females would achieve a higher performance than males. The observed results are attributable to sexual differences in behaviour, probably in relation with the reproductive season.

The use of perches and platforms by broiler chickens

Perching is considered an integral part of chicken behaviour, and is suggested to alleviate leg problems and enhance mobility in broilers, as it stimulates diversification of locomotion. The use of perches is, however, low in broilers. There is a need for investigation of elevated structures that are better accepted by meat type chickens.We compared elevated plastic platforms with wooden perches on a commercial farm. The data comprises 4 flocks with perches and 6 flocks with platforms, as well as control flocks for both. The use of these structures and the activity of broilers were recorded from video. Activity was measured as bouts of movements in an area with no platforms. The behaviour of the birds was analysed at 3 ages, during both day and night.The use of platforms exceeded the use of perches. Broilers used low perches (10cm) more than high perches (30cm) at the age of 32days (P=0.001). Platforms were used more during day time than during nights especially in younger broilers (P=0.046). Broilers became more inactive as they got older and were less active during the nights. The presence of platforms had no effect on general activity. Because the perches were mostly unused their effect on bird activity was not analysed.The frequent use of platforms indicates they are better suited for broilers than perches. However, platforms did not appear to stimulate general activity. The fact that the broilers used platforms to a high degree indicate that broilers are motivated to use elevated structures or driven by high animal densities. It might be that the low perch use is due to physical challenges and not to a lack of motivation to use elevated structures.

Use of space by domestic chicks housed in complex aviaries

To improve the understanding of the development of locomotor capacity in layer hens, we measured how female laying hen chicks (n=120) of four different strains (LSL-lite, Hyline Brown, Dekalb White, Lohmann Brown; 3 groups of 10 chicks per line) utilized the ground, the air, elevated horizontal (platforms and perches) and inclined surfaces (ramps and ladders) in an aviary until 9 weeks of age. We used infra-red video recordings to perform all-occurrences sampling of locomotive behavioural and perching events that occurred on the ground—where bedding material, food and water were provided, in the air, and on elevated horizontal and inclined surfaces within weekly 30-min sampling periods. Chicks preferred level ground during the first week of life compared to weeks 5–9 (P<0.0001) and performed 52% of all behavioural events in this section. Elevated surface use began at 2 weeks of age and increased over time (P=0.003), where most behaviour was performed in S2 (45% of all events). Chicks preferred horizontal to inclined surfaces, which were used from weeks 2–5 with maximum use occurring during weeks 2 and 3. Lohmann LSL chicks used the space above the ground most frequently (P=0.05) and performed more aerial ascent/descent behaviour than other lines (P<0.0001). Overall activity levels declined with age (P<0.0001). In summary layer chicks almost exclusively locomoted on the ground but utilized elevated horizontal surfaces (perch, first platform) as early as 2 weeks. These results provide information for improving space use in rearing aviaries by introducing lower perches, platforms and ramps/ladders to accommodate age-dependent locomotor abilities.

Age- and sex-specific variations in microhabitat and macrohabitat use in a territorial lizard

Animals should select microhabitats with features that enhance fitness. However, the fitness benefits of different habitats may vary across ages and between sexes. By quantifying microhabitat choice in relation to age or sex, as well as the specific fitness consequences of habitat selection, we can better understand the factors that shape the way organisms distribute themselves across landscapes. Studies of Anolis lizards have provided critical insights into population and community structure, but most studies have focused on interspecific variation in habitat use, rather than intraspecific patterns. We quantified habitat use of Anolis sagrei at two scales (microhabitat and macrohabitat) for males and females of two distinct age classes (juvenile vs adult). We show that age, sex, size, and macrohabitat have significant effects on how A. sagrei utilize available microhabitat and that age, sex, size, and season influence macrohabitat use. In addition, large individuals of both age classes had increased survival during the breeding season. However, body size did not influence overwinter survival, but lizards that used relatively low perches had increased overwinter survival. Overall, this study demonstrates that the complex variation in habitat use by A. sagrei is explained by interactions among age, sex, size, season, and habitat scale. Habitat choice behaviors can have important effects on fitness, yet optimal habitat may vary across ages and between sexes. In this paper, we quantified microhabitat and macrohabitat use of the brown anole lizard (Anolis sagrei) and subsequently estimated selection on these behaviors via mark recapture. We show that the complex variation in habitat use by A. sagrei is explained by interactions among age, sex, size, season, and habitat scale. In addition, body size influenced survival of both age classes during the breeding season but not over winter. However, lizards that used relatively low perches had increased overwinter survival. These findings provide new insights into the factors that shape the way these organisms distribute themselves across landscapes and provide a rare assessment of selection on behavioral traits.

Exposure to Increased Environmental Complexity during Rearing Reduces Fearfulness and Increases Use of Three-Dimensional Space in Laying Hens (Gallus gallus domesticus).

The complexity of the rearing environment is important for behavioral development and fearfulness. The aim of this study was to test the hypothesis that laying hens reared in a complex aviary system with exposure to mild intermittent stressors would be less fearful, less sensitive to stress, and would use elevated areas of the pen more often as adults than hens reared in a barren cage environment. Laying hens (N = 160) were housed in the same rearing house; half of the birds (n = 80) in an aviary and the other half (n = 80) in cages. At 16 weeks of age, the birds were transported to the experimental facilities. Their behavior was recorded at 19 and 23 weeks of age and analyzed by analysis of variance on individual scores for a fearfulness-related principal component generated using principal component analysis. The results indicate that aviary-reared birds have lower levels of fearfulness compared with cage-reared birds both at 19 weeks and at 23 weeks of age. When comparing the response induced by initial exposure to a novel object at 19 and 23 weeks of age, more aviary-reared birds tended to fly up at 19 weeks compared to the cage-reared birds, indicating a tendency toward a more active behavioral response in the aviary-reared birds than in cage-reared birds. There was no difference between treatments in the flight response at 23 weeks. The groups did not differ in defecation frequency or the concentration of fecal corticosterone metabolites at either age. At 19 weeks, observation of the spatial distribution in the home pens indicated that more aviary-reared birds spent time on the low perch, the elevated platform, and the upper perch, compared to the cage-reared birds. However, at 23 weeks of age, these differences were no longer detected. The results of this study support the hypothesis that increased environmental complexity during rearing reduces fearfulness of adult laying hens.

Effect of Perch Height and Position on the Usage in Enriched Colony Housing Systems for

In order to determine the utility of different perches in enriched colony housing systems for laying hens, the use of perches and an effect of the type and location in the system was examined in this behavioral study. Laying hens of the line Lohmann Selected Leghorn were housed in four different enriched colony housing systems which differed particularly in the alignment and arrangement of the functional areas. For analysis, perches were grouped into three types: low, low underneath the drinking trough and high. To evaluate the use of the perch types, video recordings were taken for 48 hours during three observation periods. These recordings were analyzed hourly at daytime and twice at nighttime. Through scan sampling, the overall number of hens using the perches and the fraction of hens per meter on a specific perch type were assessed. At nighttime, an average 62% of the laying hens used the perches. On average, 24% of the laying hens used the perches at daytime, with no significant difference between the different systems. Low perches that were not installed underneath the drinking trough were less commonly used than high perches. However, the hens used low perches that were positioned underneath the drinking trough more than other perch types during the day. At nighttime, high perches were used frequently and, depending on the system, more than the low perches. It should be considered that the hens used the low perches underneath the drinking trough during the day not to rest but rather to have better access to the drinking trough. It can be recommended that a sufficient number of high perches should be offered, so that all hens have access to these obviously preferred perches. If perches are installed underneath the drinking trough, it should be considered if additional perch space should be offered.

Advertisement call of Dendropsophus microps (Anura: Hylidae) from two populations from southeastern Brazil

In anurans, acoustic communication is a major mechanism of pre-zygotic isolation, since it carries information about species recognition. Detailed descriptions of the acoustic properties of anuran advertisement calls provide important data to taxonomist and to the understanding of the evolution of the group. Herein we re-describe the advertisement call of the hylid frog Dendropsophus microps (Peters, 1872) after analyzing a larger sample than that of previous descriptions. We also compare the acoustic properties of the call in two populations and discuss the effect of the presence of the sister species, Dendropsophus giesleri (Mertens, 1950), a potential competitor, in one of the populations. Additionally, we provide information on calling sites and size of males. Males of D. microps emit two types of calls, which differ mainly in pulse repetition rate. Type A call has a mean frequency band varying from 4574 to 5452 Hz, (mean dominant frequency = 4972 Hz). Type B call has a mean frequency band varying from 4488 to 5417 Hz (mean dominant frequency = 4913 Hz). The calls of D. microps and D. giesleri are the only in the D. parviceps species group that have harmonic structure. The spectral properties of the call showed low intra-individual variation, being considered static, while the temporal properties were highly variable. Compared with males from the Boraceia population, males from the Ribeirao Grande population called from lower perches, and their calls had slightly lower frequency bands and significantly higher pulse rates in their type B calls. Inter-populational differences in acoustic properties, body size and use of calling sites could be related to selective forces associated with the presence of the sister species, a potential competitor for the population from Ribeirao Grande.

Foraging behaviour of insectivorous migrants and a resident songbird at a stopover site

AbstractDuring their staging at stopover sites, migrants compete with resident species over food resources. This ‘resource competition hypothesis’ has often been examined in breeding areas of songbirds, but little is known about resource competition between migrants and resident species at stopover sites. We studied foraging behaviour and microhabitat of the endemic resident species Cyprus Wheatear Oenanthe cypriaca in comparison to eleven migrating species of the same genus or of the same flycatching guild during spring migration on Cyprus, a Mediterranean stopover site. We characterized microhabitats of congeneric Oenanthe species by less cover overhead and low perches and distinguished them from migrating Ficedula hypoleuca, Ficedula albicollis and Phoenicurus phoenicurus, which preferred high cover overhead and medium perches. In a hierarchical cluster analysis, O. cypriaca clustered together with three shrike species Lanius and the flycatcher Muscicapa striata, with less cover overhead, but high perches. During foraging, hopping behaviour discriminated best among the Oenanthe species. Multidimensional scaling on foraging behaviour showed that O. cypriaca is clearly distinct from the other species. Direct competition (aggressive encounters) between the resident species and migrants was rarely observed. Our results provide support for niche partitioning and coexistence between migrants and a resident species at a stopover site.

Vigilance and roosting behaviour of laying hens on different perch heights

Laying hens prefer roosting on high compared to low perches during night time. According to the antipredator hypothesis, hens on high perches can afford to be less vigilant while roosting at night. A total of 120 LSL hens in groups of five were presented a single perch, which was varied in height throughout two subsequent experiments each. In experiment 1, an acoustic noise was played back in the middle of the night. Hens’ latencies until reaction and their roosting behaviours shown before disturbance were analysed depending on perch height (30, 90, or 150cm). In addition, roosting behaviours were recorded throughout the entire experimental nights and differences were analysed in relation to perch height. Experiment 2 focussed on night-time use of single perches offered at ten different heights ranging from 20cm to 180cm. In experiment 1, perch height and hens’ body orientation towards the source of acoustic noise did not influence reaction latencies (P>0.05). Surprisingly, hens resting with their head forward immediately before playbacks showed a slower reaction (LS-means=1.27s) to the acoustic noise than hens resting with their head under the wing (LS-means=0.71s, P=0.004). In contrast, the percentage of hens perching with their head forward during the entire night was higher on low (LS-means=55.48%) compared to high perches (LS-means=33.44%, P=0.001) in experiment 1. In both experiments, perch use increased with rising height up to 90cm. In experiment 2, hens did not show a preference for roosting on the perch compared to resting on the floor at a perch height of 80cm or lower. Although hens showed a clear preference to roost on perches higher than 90cm, their reactions to an acoustic disturbance during night time did not clearly support the antipredator hypothesis. Possibly, perch height may be a crucial factor when hens are searching for an appropriate roosting place before the dark period but may have limited influence on roosting behaviour during the night.

Remedies for a high incidence of broken eggs in furnished cages: Effectiveness of increasing nest attractiveness and lowering perch height

Two remedial treatments to reduce the high incidence of broken eggs in the furnished cages of our experimental layer farm were investigated: lining the nest floor with artificial turf (to increase nest acceptance) and lowering perch height (to reduce the chance of egg breakage of outside-nest eggs). A 2 × 2 factorial design was used with low (7 cm) or high (24 cm) perches, and with nest floors lined with artificial turf or plastic mesh. Eight cages, each housing 8 hens initially (aged 40 to 56 wk), were used per treatment. Egg location and percentage of broken eggs were recorded. Hen position (cage floor, nest, or perch) was recorded by direct scan-sampling observations. In addition, 8 cages (4 high + 4 low) each containing 8 hens (aged 54 to 56 wk) were videorecorded to determine perch use and behavior during the light period. Data were mainly analyzed using logistic regression and mixed models with cage as the experimental unit. Nest floor material did not influence the percentage of eggs broken or laid outside the nest. The proportion of outside-nest eggs (2.6 vs. 10.6%, P = 0.004), and consequently also of total eggs (2 vs. 4.6%, P = 0.016) broken, was lower for low than high cages. Perch use increased during the observation period, more so for the high cages during the light period and the low cages during the dark period. Perch bout duration (P < 0.001), the likelihood of ending a perching bout voluntarily (P = 0.013), and time spent sitting during perching (P = 0.007) were lower in low vs. high cages. In this study, replacing plastic mesh nest floor lining with artificial turf was not an effective remedy for the already-high rate of broken eggs, but the prevalence of broken outside-nest eggs was lower in cages with low versus high perches. However, perching behavior during the light period was more disturbed in cages with low perches.

Ultraviolet radiation influences perch selection by a neotropical poison-dart frog.

Ambient ultraviolet-B radiation can harm amphibian eggs, larvae and adults. However, some amphibians avoid UV-B radiation when given the opportunity. The strawberry poison dart frog, Oophaga pumilio, is diurnal and males vocalize throughout the day in light gaps under forest canopies that expose them to solar radiation. Previous studies have demonstrated that males calling from high perches are more successful at mating than those at lower perches. We investigated whether frogs at higher perches receive more ultraviolet-B than those calling from lower perches. We also investigated whether frogs on perches receiving relatively low ultraviolet-B levels maintained their positions for longer compared to individuals calling from perches receiving higher levels of ultraviolet-B. Finally, since it has been hypothesized that some animals utilize levels of UV-A as a visual cue to avoid UV-B damage, we artificially elevated ultraviolet-A levels to examine whether males exposed to artificially elevated ultraviolet-A abandoned their perches sooner compared to males exposed to visible light. We found that frogs called from perches receiving low ultraviolet-B regardless of perch height, and that frogs maintain their positions longer on perches receiving low ultraviolet-B compared to perches receiving even slightly higher ultraviolet-B levels. Exposing the frogs to artificially elevated levels of ultraviolet-A radiation caused males to move off of their perches faster than when they were exposed to a control light source. These experiments suggest that ultraviolet radiation plays an important role in frog behavior related to perch selection, even in rainforests where much of the solar radiation is shielded by the forest canopy.

Weather conditions and sexual differences affect the foraging behaviour of the insectivorous Cyprus Wheatear, Oenanthe cypriaca (Aves: Passeriformes: Muscicapidae)

Weather conditions (temperature, cloudiness, wind strength and precipitation) had an infl uence on the foraging behaviour of the Cyprus Wheatear (Oenanthe cypriaca). Under cloudy weather conditions the perch-pounce technique from low perches was used more often while under sunny conditions aerial sallying was used more often. A possible reason is the limited visual range from higher perches during high cloudiness. During higher temperatures and low wind speed aerial sallying from higher perches was preferred presumably because the activity of the ectothermic arthropods is strongly infl uenced by temperature and wind speed. Sexual differences existed in foraging behaviour. Females used hop-and-peck on the ground more often than males, and males preferred higher perches. This can be explained by a lower exposure to predators and hence lower predation risk that is especially important for females during the breeding season. Furthermore, males and females may occupy different niches during pre-breeding and incubation.

Escape Decisions by the Syntopic Congeners Sceloporus jarrovii and S. virgatus: Comparative Effects of Perch Height and of Predator Approach Speed, Persistence, and Direction of Turning

Many predation risk factors operate similarly in closely related taxa, but ecological and other differences among prey species may expose them to different risks in similar circumstances. We compared escape responses by the syntopic lizards Sceloporus jarrovii and S. virgatus to similar risk factors: perch height, predator approach speed, predator persistence, and direction of predator turning. Flight initiation distance (predator–prey distance when escape begins) decreased as perch height increased in both species but was shorter in S. virgatus. Sceloporus jarrovii fled except when perch height was above 2 m., but S. virgatus often did not flee even at low perch heights. These differences may reflect lower detectability of S. virgatus, which is difficult to detect on shaded sides of tree trunks and typically escapes without climbing out of reach. Flight initiation distance was greater for the faster and second of two approaches in both species. Sceloporus jarrovii fled more frequently than S. virgatus when a nearby investigator turned away from, but not toward, a lizard. At low perch heights and when a nearby predator moves, the larger S. jarrovii is warier than S. virgatus, which may rely relatively more on crypsis than escape. Similarity of responses to some risks by both species might reflect retention of ancestral behaviors or convergence. Escape differences seem to occur when risk operates differently due to ecological differences, suggesting that aspects of escape may be molded by natural selection with at least partial independence, resulting in escape strategies suitable to the ecologies of each species.