Space use and agonistic behaviour in relation to sex composition in large flocks of laying hens

Some authors have found indications of subgroup formation when domestic fowl are forced to live together in large flocks, while others have not. In this study experiments were carried out to test the hypothesis that hens in large flocks have home ranges in parts of the pen and that they form subgroups. We also studied if this is influenced by males. In a tiered aviary system (density averaged 16 hens/m(2) of floor area) eight flocks of 568+/-59 ISA Brown laying hybrids were kept in pens. Half of the pens contained 1 male per on average 24 females (mixed flocks). At peak production (36-53 weeks of age) four females roosting closely together for about 14 days and four females roosting far apart from each other were taken out from each flock and put together in separate groups in small pens. Their agonistic behaviour was studied for 2 days before they were put back. This was repeated with new birds, resulting in 16 small sample groups being studied. At 70 weeks, three groups of 10 females per flock roosting closely together in different parts of the pen were dyed with different colours and their locations were observed for 2 nights and 2 days.The incidence of aggressive pecks during day 1 among birds that had been roosting close to each other tended to be lower (P=0.05) than among birds that had been roosting far apart. This effect was not significant among birds from all-female flocks, but among birds from mixed flocks (P<0.05). However, this indicates a recognition of roosting partners and possibly also a rebound effect of the males' reduction of female aggressiveness towards strangers. Irrespective of sex composition in the flocks, birds marked while roosting at the ends of the pens were significantly more often observed within these areas than in other areas of the pen during daytime and came back to the same roosting sites at night (P<0.05-P<0.001). This was not the case for birds from the middle of the pens, where the distribution in the pen in most cases did not differ from random. These results show that laying hens in large groups are rather constant in their use of space, which indicate the presence of home ranges. However, environmental features that facilitate localisation may be important. In summary, we think that these findings indicate the existence of subgroup formation.     

Use of perches and nestboxes by laying hens in relation to social status, based on examination of consistency of ranking orders and frequency of interaction

Four groups of 15-19 adult ISA Brown hens were studied in pens to assess the relationship between social status and use of perches and nestboxes. This was to test the hypothesis that subordinate hens use these resources more by day, for avoiding dominants, but that dominants use perches more at night, for roosting. The experiment consisted of a 5-week pre-treatment period, when no perches were present, and a 4-week treatment period, when each group was tested with different perch treatments (No, Low, Medium, High). All groups were observed systematically in each week, when all interactions of three types (aggressive peck, non-aggressive peck, approach/avoidance) in a group were recorded by noting the instigator and recipient (from numbered wing tags) onto a matrix. Proportions of time that each bird spent using perches and nestboxes, by day and at night, were also recorded. The results indicate that social status of individual laying hens is relatively stable across time and can be based reliably on counts of either aggressive pecks or approach/avoidances, but not non-aggressive pecks. Aggressive pecks were the most frequent type of interaction observed, and were reduced by the presence of perches. Use of nestboxes, but not perches, was greater at night than by day. There were weak tendencies for perches, and to a lesser extent nestboxes, to be used more by lower ranking birds by day, but not at night. There was some evidence of increased use of these resources by higher ranking birds at night. It is concluded that provision of perches reduces bird density on the floor (where nearly all interactions occurred), allows subordinates a means of avoiding dominants by day, reduces frequency of agonistic interactions, and should thus benefit laying hen welfare.     

Group size and perching behaviour in young domestic fowl

To test the hypothesis that young domestic fowl perform less perch-related antipredator behaviour with increasing group size, White Leghorn pullets were reared in four replicate groups of 15, 30, 60 and 120 at a constant density of 5 birds/m(2). Each pen contained perches 20, 40 and 60cm above the ground. Perch space per bird per perch level was the same for all groups. It was predicted that, with increasing group size, domestic fowl would (1) spend less time on perches (i.e. more time down on the floor); (2) be less vigilant while perching; (3) spend relatively more time preening down on the floor. As predicted, the proportion of 3- to 18-week-old birds roosting on perches during scans throughout the photoperiod decreased with increasing group size, from 41+/-1.7% in groups of 15 birds to 33+/-1.6% in groups of 120 birds. This effect was due to reduced use of the lower perches; use of the highest perches was high at all group sizes. The proportion of birds vigilant on the highest perches of those present on that perch level decreased with increasing group size. The proportion of birds engaged in the vulnerable activity of preening down on the floor increased with group size. The frequency of transitions between floor and perches was not affected by group size but birds received more disturbances from other birds when on the top perch level in the larger groups. Thus, the decline in vigilance on the top perch level with increasing group size was not due to reduced disturbance from other birds. In conclusion, despite domestication and protection from non-human predators, changes in the use of perches by young domestic fowl with increasing group size were consistent with the antipredator hypothesis.     

Access to barrier perches improves behavior repertoire in broilers

Restriction of behavioral opportunities and uneven use of space are considerable welfare concerns in modern broiler production, particularly when birds are kept at high densities. We hypothesized that increased environmental complexity by provision of barrier perches would help address these issues by encouraging perching and enhancing use of the pen space across a range of stocking densities. 2,088 day-old broiler chicks were randomly assigned to one of the following barrier and density treatment combinations over four replications: simple barrier, complex barrier, or control (no barrier) and low (8 birds/m(2)), moderate (13 birds/m(2)), or high (18 birds/m(2)) density. Data were collected on focal birds via instantaneous scan sampling from 2 to 6 weeks of age. Mean estimates per pen for percent of observations seen performing each behavior, as well as percent of observations in the pen periphery vs. center, were quantified and submitted to an analysis of variance with week as the repeated measure. Barrier perches, density and age affected the behavioral time budget of broilers. Both simple and complex barrier perches effectively stimulated high perching rates. Aggression and disturbances were lower in both barrier treatments compared to controls (P<0.05). Increasing density to 18 birds/m(2) compared to the lower densities suppressed activity levels, with lower foraging (P<0.005), decreased perching (P<0.0001) and increased sitting (P = 0.001) earlier in the rearing period. Disturbances also increased at higher densities (P<0.05). Use of the central pen area was higher in simple barrier pens compared to controls (P<0.001), while increasing density above 8 birds/m(2) suppressed use of the central space (P<0.05). This work confirms some negative effects of increasing density and suggests that barrier perches have the potential to improve broiler welfare by encouraging activity (notably by providing accessible opportunities to perch), decreasing aggression and disturbances, and promoting more even distribution of birds throughout the pen space.     

Effects of density on perching behavior of broiler chickens

Exercise through perching has been suggested as a way to reduce the impact of leg problems in broiler chickens. It is possible that higher stocking densities may motivate birds to perch more, and perhaps reduce some of the detrimental effects to broiler health seen with high stocking densities. The goal of this research was to investigate the effects of density (10, 15, and 20birds/m(2)) and perch design on the frequency of perch utilization. Mixed sex broilers were assigned to 36 pens in a four perch treatmentxthree density factorial with three replications for each treatment/density combination in a randomized complete block design. Pens were assigned to one of four perch treatments: control (no perches), horizontal (three horizontal perches), angled (three 10 degrees angled perches), or mixed angle (one horizontal, one 10 degrees angled, and one 20 degrees angled perch), at each of the three densities. The results show that although the frequency of perch use was low, (2.6%+/-0.15), significant preferences were clear. Perching frequency was significantly higher when birds were raised at stocking densities of 15 (2.88+/-0.303) or 20birds/m(2) (2.76+/-0.211), as opposed to 10birds/m(2) (2.10+/-0.209) as indicated by a marginally significant main effect (p<0.0597), and a significant linear effect (P<0.0427). The birds used the horizontal perches the most, followed by 10 degrees angled and mixed angle perch treatments with decreasing frequency. An effect of age was found, in that perching increased during the first 4 weeks, and dropped off significantly at the end of the rearing period for all perch treatments. In general, perches closest to the hallway or outside of the house were used more than perches in the middle of the pen. Preferential use of the highest section of the 10 degrees angled perches was also found. The applied perch treatments or densities did not significantly affect final body weight or feed conversion. Percent mortality due to heat stress showed a significant increase with density, while mortality not caused by heat stress did not change with perch treatment or density.     

Welfare of organic laying hens kept at different indoor stocking densities in a multi-tier aviary system. II: live weight,health measures and perching

Multi-tier aviary systems, where conveyor belts below the tiers remove the manure at regular intervals, are becoming more common in organic egg production. The area on the tiers can be included in the net area available to the hens (also referred to as usable area) when calculating maximum indoor stocking densities in organic systems within the EU. In this article, results on live weight, health measures and perching are reported for organic laying hens housed in a multi-tier system with permanent access to a veranda and kept at stocking densities (D) of 6, 9 and 12 hens/m² available floor area, with concomitant increases in the number of hens per trough, drinker, perch and nest space. In a fourth treatment, access to the top tier was blocked reducing vertical, trough, and perch access at the lowest stocking density (D6x). In all other aspects than stocking density, the experiment followed the EU regulations on the keeping of organic laying hens. Hen live weight, mortality and foot health were not affected by the stocking densities used in the present study. Other variables (plumage condition, presence of breast redness and blisters, pecked tail feathers, and perch use) were indirectly affected by the increase in stocking density through the simultaneous reduction in access to other resources, mainly perches and troughs. The welfare of the hens was mostly affected by these associated constraints, despite all of them being within the allowed minimum requirements for organic production in the EU. Although the welfare consequences reported here were assessed to be moderate to minor, it is important to take into account concurrent constraints on access to other resources when higher stocking densities are used in organic production.     

Rearing without early access to perches impairs the spatial skills of laying hens

The effect of rearing with and without perches on the spatial ability of domestic hens (Gallus gallus domesticus) was investigated. No access or late access to perches during rearing has been shown to increase the later prevalence of floor eggs and cloacal cannibalism in loose-housed laying hens. This may be explained by either the birds reared without perches have difficulty using perches due to low muscle strength, lack of motor skills, and inability to keep balance, or they have impaired spatial skills necessary for moving around in three-dimensional space. These alternative explanations are not mutually exclusive.Thirty, day-old chicks were randomly allocated into two equal groups and reared in litter pens, one with access to perches (P+) and one without (P-). At 8 weeks of age, all birds were given access to perches, and by 15 weeks, all birds were using perches for roosting at night. At 16 weeks, 10 birds from each group were tested in pens where food was presented on a wire mesh tier 40 cm above the ground (T40). Three consecutive tests, with increasing difficulty for the bird to reach the food, were then performed. Firstly, the food was presented at 80 cm above the ground but with the tier at 40 cm still present; secondly, food was presented on the tier at 80 cm; and then, finally, with the food on a 160 cm high tier with the tier at 80 cm still present. All birds were food deprived for 15 h before each test and the time from the bird entering the pen until reaching the food was recorded. There was no difference in the time to reach the food between P+ and P- birds in the T40 test. But as the difficulty of the task increased, the difference between the P+ and P- birds became significant, with the P- birds taking a longer time to reach the food or not reaching it at all. Since there was no difference between P+ and P- in the T40 test, it seems reasonable to suppose that the later differences did not depend on differences in physical ability. Therefore, the results may imply that rearing without early access to perches, in some ways, impairs the spatial cognitive skills of the domestic hen.     

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.     

Daily energy expenditure and water turnover in two breeds of laying hens kept in floor housing

Laying hens are increasingly kept in barn or free-range systems, which not only allows birds to move freely but also potentially entails higher energy expenditures due to higher locomotor activity. Therefore, the aim of our study was to quantify the daily energy expenditure (DEE) and water turnover in freely moving laying hens. For that purpose, 10 Lohmann Selected Leghorn (LSL) and 10 Lohmann Brown (LB) hens were obtained from a conventional breeding company at 17 weeks of age. The trial started when birds reached an age of 34 weeks. All 20 birds were kept together in the same littered floor pen (12.1 m²). The pen was equipped with perches, a nest box, feeding and nipple drinkers. The DEE was determined individually for all experimental birds (n = 20) for a total of nine days using the doubly labelled water (DLW) method. Lohmann Brown hens were heavier than LSL hens, but laying rate did not differ between the two breeds, that is, one egg per hen and day during the study period. Average egg mass was 63.1 ± 0.20 g in LB and 61.7 ± 0.12 g in LSL hens, which converted to an egg energy content of 420 and 410 kJ/egg, respectively. Dilution spaces for oxygen and hydrogen differed between the breeds but not the respective turnover rates. Total body water as a percentage of body mass (LB: 54.4%, LSL: 53.8%; SEM = 0.7, F_1,18 = 0.41, P = 0.513) and total water intake (TWI) per day (LB: 275 ml/day, LSL: 276 ml/day; SEM = 20, F_1,17 = 0, P = 0.994) did not differ between LB and LSL hens. Individual DEE increased with body mass in LB but not in LSL hens. Average DEE did not differ between the two breeds (LB: 1 501 kJ/day; LSL: 1 520 kJ/day; SEM = 32.1, F_1,17 = 2.54, P = 0.131). However, when comparing the DEE on a metabolic mass basis, LSL hens expended with 984 kJ/kg^0.75 on average significantly more energy per day than LB hens (895 kJ/kg^0.75; SEM = 20.3, F_1,18 = 10.1, P = 0.005). Our results suggest that the DLW technique is a viable method to measure the energy expenditure and water turnover over several days in laying hens. Furthermore, we show that laying hens kept in floor pens fit into the general pattern of DEE among wild birds.     

Effect of rearing density on pecking behaviour and plumage condition of laying hens in two types of aviary

The objective of this experiment was to investigate the effect of rearing density on pecking behaviour and plumage during rearing and throughout the laying period in aviaries. Chicks were reared on sand at high (H; 13 m⁻²) or low (L; 6.5 m⁻²) density, in four rearing pens of 390 chicks and eight pens of 195 chicks, respectively, each pen measuring 30 m². Proportions of chicks per pen performing various types of pecking behaviour were recorded by scan sampling during 16 observation bouts in each rearing pen at 6 weeks of age and during 24 observation bouts at 12 weeks. Individual body weights and plumage condition were recorded. Later, these pullets were housed at 17 hens m⁻² in Tiered Wire Floor (TWF; 3 H and 3 L pens of 275 hens) and Laco-Volétage (2 H and 2 L pens of 275 hens) aviaries. At 35 weeks, two samples of eight hens from each aviary pen were observed for pecking behaviour in a test pen. Throughout the laying period, additional records were collected on pecking behaviour, body weight, plumage condition, egg production, and mortality. The L birds had better plumage condition at 6 weeks of age and throughout the laying period. These birds also ground pecked more frequently than H birds during rearing and the laying period. At 12 weeks, L birds feather pecked less than H birds, but no relationship was found between rearing density and feather-pecking behaviour during the laying period. Although TWF hens feather pecked more frequently than Volétage hens, there was no interaction between rearing density and type of aviary for the various pecking behaviours.     

Spatial distribution and behaviour of laying hens housed in an alternative system

The spatial distribution and behaviour of perchery housed laying hens were compared at a constant stocking density (18.5 birds/m(2)) in eight pens with colonies of five different sizes (323 birds (N=1), 374 birds (N=2), 431 birds (N=2), 572 birds (N=1) and 912 birds (N=2)). The birds were placed in the perchery when they were 12 weeks old. Observations began when they were 26 weeks old and continued at 8 week intervals until 61 weeks of age. Colony size did not appear to affect the spatial distribution of birds, but more standing behaviour and less feeding behaviour were observed in the smallest and largest colony sizes. Older birds spent more time on the floor areas and less time on perches. Young birds (26-28 weeks) spent more time feeding, foraging, drinking and preening, and less time standing idle than older birds. In the afternoons, there were fewer birds on the perches and more on the floor levels, corresponding with less time spent resting and more time spent performing active behaviours. Birds did not distribute themselves evenly throughout their pens: within specific areas of pens densities varied between 9 and 41 birds/m(2). This variation, which reflects the flux of birds from one part of the pen to another, was greatest for the larger colony sizes, and may have adverse implications for welfare in terms of crowding and hysteria.     

Factors influencing perch selection by communally roosting Turkey Vultures

ABSTRACT Many birds roost communally during at least part of their annual cycle, suggesting that for them the advantages of living in a group outweigh the disadvantages. However, perch sites within a roost may vary in quality because of differences in degree of exposure to the elements, predators, and fecal droppings. Individuals should select perches in the roost that minimize costs while enabling them to experience the benefits of communal roosting. We studied communally roosting Turkey Vultures (Cathartes aura) in northeastern Iowa (USA) from late August to mid‐October, when hatching‐year (HY) birds had joined the roost and were distinguishable from after‐hatching‐year (AHY) birds. On 82 d during our 4‐yr study (2004–2007), we noted the age class and perch position of vultures on two communication towers used as a preroost site. Perches used by vultures were classified as top‐level (with no perches above them) or lower‐level (with other perches above them). Top‐level perches were preferred by Turkey Vultures. Of 1713 birds recorded, 71% were on top‐level perches, even though only 39% of available perches were top‐level. Vultures did not use lower perches if top perches on that tower were unoccupied. The percentage of birds using lower perches increased as the number of vultures present increased, suggesting that top‐level perches were occupied first. AHY birds used top‐level perches more often than expected and HY birds used top‐level perches less often than expected, implying that age‐related dominance affected perch selection. On 61 of 82 d (74%), top‐level perches of both towers were occupied and, on 8 d (10%), only top perches on one tower were occupied. However, on 13 d (16%), both top‐level and lower‐level perches were occupied on one tower while no vultures perched on the other tower, suggesting that social attraction to other vultures can override a general preference for top‐level perches. Thus, our results provide evidence that social attraction, age‐related dominance, and preference for higher perches are proximate factors influencing perch selection in communally roosting Turkey Vultures. Ultimate factors that may be responsible for Turkey Vultures preferring higher roosting perches are reduced risk of predation, less exposure to fecal droppings that might reduce their plumage quality, and better visual information for locating food sources.     

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.     

Effectiveness of Avian Predator Perch Deterrents on Electric Transmission Lines

ABSTRACT A new high-voltage transmission line in north-central Nevada, USA, was considered a potential threat to greater sage-grouse (Centrocercus urophasianus) because avian predators are attracted to and hunt from elevated perches. As a mitigation measure, perch deterrents were installed on the transmission line towers at the time of construction; in addition, 2 existing high-voltage transmission lines were retrofitted with deterrents. Previous published studies have investigated the efficacy of perch deterrents in preventing or reducing electrocution of avian predators and fecal contamination of insulators, but none have evaluated deterrents as a means of eradicating perching on towers. We conducted point transect surveys and perching-duration observations of corvids and raptors and determined that although perch deterrents did not prevent perching, the perching duration of raptors on the deterrents was reduced compared to other perching substrates. Perching of raptors indicated that some hunting most likely took place from the towers; therefore, the deterrents did not completely obviate the threat that avian predators posed to greater sage-grouse. Although the deterrents reduced the probability of avian predators perching on the towers, avian predators overcame the deterrents to take advantage of the height of the towers where no other perches of similar height existed. The perch deterrents as designed did not have the desired short-term effect on avian predators, but further monitoring may reveal longer-term effects and distinguish perching behaviors specific to different species of avian predators.     

Do Bird Perching Structures Elevate Seed Rain and Seedling Establishment in Abandoned Tropical Pasture?

Lack of seed dispersal has been shown to be a major factor limiting tropical forest recovery in abandoned pasture land. The goal of this work was to determine whether bird perching structures serve to enhance seed dispersal and seedling establishment in an abandoned pasture in Costa Rica. Two types of perching structures (crossbar and branch) were tested. Bird visitation rates were significantly higher on branch than on crossbar perches. The number of animal-dispersed seeds was significantly higher below branch perches than below crossbar perches or in open pasture. Despite differences in seed rain, percent cover of animal-dispersed plants and the number of seedlings of animal-dispersed plant species were similar below both perch types and in open pasture. Baiting perches with bananas did not increase either bird visitation rates or seed rain. These results suggest that, although bird perching structures increase seed dispersal, they do not overcome other barriers to tropical forest recovery such as seed predation and low seed germination.     

The Effect of Cooled Perches on Immunological Parameters of Caged White Leghorn Hens during the Hot Summer Months

The objective of this study was to determine if thermally cooled perches improve hen immunity during hot summer. White Leghorn pullets at 16 week of age were randomly assigned to 18 cages of 3 banks at 9 hens per cage. Each bank was assigned to 1 of the 3 treatments up to 32 week of age: 1) thermally cooled perches, 2) perches with ambient air, and 3) cages without perches. Hens were exposed to natural ambient temperatures from June through September 2013 in Indiana with a 4 h acute heat episode at 27.6 week of age. The packed cell volume, heterophil to lymphocyte (H/L) ratio, plasma concentrations of total IgG, and cytokines of interleukin-1β and interleukin-6, plus lipopolysaccharide-induced tumor necrosis factor-α factor were measured at both 27.6 and 32 week of age. The mRNA expressions of these cytokines, toll-like receptor-4, and inducible nitric oxide synthase were also examined in the spleen of 32 week-old hens. Except for H/L ratio, thermally cooled perches did not significantly improve currently measured immunological indicators. These results indicated that the ambient temperature of 2013 summer in Indiana (24°C, 17.1 to 33.1°C) was not high enough and the 4 h heat episode at 33.3°C (32 to 34.6°C) was insufficient in length to evoke severe heat stress in hens. However, cooled perch hens had a lower H/L ratio than both air perch hens and control hens at 27.6 week of age and it was still lower compared to control hens (P < 0.05, respectively) at 32 week of age. The lowered H/L ratio of cooled perch hens may suggest that they were able to cope with acute heat stress more effectively than control hens. Further studies are needed to evaluate the effectiveness of thermally cooled perches on hen health under higher ambient temperatures.     

Raptor and Corvid Response to Power Distribution Line Perch Deterrents in Utah

Abstract: Increased raptor and corvid abundance has been documented in landscapes fragmented by man-made structures, such as fence posts and power lines. These vertical structures may enhance raptor and corvid foraging and predation efficiency because of increased availability of perch, nesting, and roosting sites. Concomitantly, vertical structures, in particular power distribution lines, have been identified as a threat to sage-grouse (Centrocercus spp.) conservation. To mitigate potential impacts of power distribution lines on sage-grouse and other avian species, the electrical power industry has retrofitted support poles with perch deterrents to discourage raptor and corvid use. No published information is available regarding efficacy of contemporary perch deterrents on avian predator use of lower-voltage power distribution lines. We evaluated efficacy of 5 perch deterrents mounted on support poles of an 11-km section of a 12.5-kV distribution line that bisected occupied Gunnison sage-grouse (Centrocercus minimus) habitat in southeastern Utah, USA. Perch deterrents were mounted on the line in November–December 2006 following a random replicated block design that included controls. During 168 hours and 84 hours of direct observation in 2007 and 2008, respectively, we recorded 276 and 139 perching events of 7 potential avian predators of sage-grouse. Golden eagles (Aquila chrysaetos) were the dominant species we recorded during both years. We did not detect any difference in perching events by perch deterrent we evaluated and controls (P > 0.05). Perch deterrents we evaluated were not effective because of inherent design and placement flaws. Additionally, previous pole modifications that mitigated avian electrocutions provided alternative perches. We did not record any raptor or corvid electrocutions or direct predation on Gunnison sage-grouse. The conclusions of this study can be applied by conservation groups and power companies to future management of power distribution lines within areas inhabited by species sensitive to man-made vertical structures.     

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.     

The effects of operant control over food and light on the behaviour of domestic hens

In intensive farming systems, the animals have little control over important elements in their environments. For instance, food of a pre-set type is delivered at set times, and the lighting schedule is controlled by the farmer. It has been suggested that low levels of environmental control over important events may reduce welfare by increasing passivity and stress. This study aimed to evaluate the effect of providing control over food and lighting additional to a restricted regime on the behaviour of small groups of laying hens (Gallus gallus domesticus). Twelve pens, each containing five birds, were paired to give six controlling and six non-controlling pens. These pairs of pens were yoked, such that birds in the controlling pens were able to make an operant response to gain access to extra food and light, whilst the yoked pens also received these outcomes but were unable to control their occurrence. The birds were kept continuously in the experimental conditions for 9 weeks. Records were made of general behaviour and activity, aggression and plumage damage scores, every 2 weeks. Data on key-pecking and egg production were continuously recorded throughout the experiment. The controlling birds used the operant keys to open the feeder for an average of 92min and to turn on the light for 46min per pen per day. The high number of key-pecks indicates that the birds were motivated to make use of the keys to control access to additional food and light. The non-controlling treatment pens showed significantly higher levels of preening and resting. Contrary to previous studies the use of operant feeders in this experiment did not induce a high level of feather pecking or aggressive interactions, as there was no significant difference between treatments. During the experiment the non-controlling hens laid significantly more eggs than the controlling hens. The results suggest that lack of control over these particular environmental events induced mild stress in the non-controlling pens of birds, and that further investigations into the effect of lack of control on welfare would be warranted.     

Accuracy of laying hens in jumping upwards and downwards between perches in different light environments

Eighty Lohmann Brown layer hens were reared in floor pens fitted with perches from 1 day of age. After the peak of lay (25 weeks of age), their ability to jump to and from perches in different light environments was assessed in two experiments using digital video techniques that allowed detailed measurements of take-off, flight and landing behaviours.In Experiment 1, birds jumped up or down (angles of 10 and 18°) between two horizontal perches that were separated by a gap of 60 cm under different lighting conditions (5, 10 or 20 lux; incandescent or high- or low-frequency fluorescent). In Experiment 2, the horizontal distance was increased to 80 cm and contrast between perch and background was varied. Fifty-two hens (65%) achieved the training criterion for Experiment 1: jumping a 60 cm gap five times of which three in a row. Thirty-two of these hens (62%) subsequently failed to achieve the 80 cm jump criterion for Experiment 2.In Experiment 1, birds took off sooner (P<0.001), turned their heads further downward relative to the landing perch (P<0.001), beat their wings more often during flight (P<0.001), and took longer to achieve balance (P<0.001) when jumping downward rather than upward. In Experiment 2, refusals to jump, and clumsy or missed landings, occurred more frequently on downward than upward jumps (P<0.001). These behaviours were unaffected by lighting conditions, or by the amount of contrast between the perch and its background.In conclusion, behaviours indicating inaccurate control of landing were more frequent on downward than on upward jumps (P<0.001). However, these behaviours were not affected by light intensity, light type or contrast. The results suggest that there is a difference between the two types of jumps in the risk of injury to hens housed in aviaries where perches must be used to gain access to resources.