The individual nest box as a super-stimulus for domestic hens

Following reports of inconsistent nest choice by hens in groups, choice of nest boxes by solitary hens was investigated. Thirty-two hens of a White Leghorn strain were each isolated with six nest boxes while they laid six eggs. From 16 hens, eggs were collected daily. Only one of these birds laid all her eggs in one nest box, and others used up to four boxes. The other 16 were allowed to accumulate eggs, and these were significantly more consistent in nest choice. Five used only one box. However, the other 11 of this group showed incomplete consistency.An explanation for inconsistent nest choice was suggested by a second experiment. The importance of enclosure in nest-site selection was tested in hens of White Leghorn and Rhode Island Red strains. Individuals about to lay their first egg were isolated with a choice of two types of nest box, selected from five types of different enclosure. Exposed nests, of similar dimensions to natural nests, were rarely used by either strain. By contrast, more enclosed nests were strongly selected. These results indicate that enclosure is an important stimulus in nest-site selection, and that artificial nest boxes, which are more enclosed than natural sites, act as super-normal stimuli (or “super-stimuli”). Choices between super-stimuli are likely to be equivocal, which accounts for inconsistency in the use of nest boxes and other features of the nesting behaviour of domestic hens.     

Egg-laying behaviour and nest-site selection of domestic hens kept in small floor-pens

The development of egg-laying behaviour and nest-site choice is described in seven flocks of White Leghorn hens housed in small floor-pens. Special interest was directed towards social dominance and the effect of the presence of a cock on the hen's nest-site choice. In the weeks before the hens came into lay, they frequently examined the nests. Nest-entries only occurred some days before, or in the hours preceding, the first oviposition. Some hens were very conservative in their nest-site choice within clutches as well as between clutches. A number of hens only persevered in their nest-site choice within clutches, while a third category did not show any consistency in their choices. Individual hens were consistent in using either the floor or a nest-box as a nesting site.No relationship was found between social status and nest-site choice, nor between social status and floor-laying. Some evidence was provided that the presence of a cock could reduce the number of floor-eggs in a flock provided with roll-away boxes.It is postulated that the nest-examinations in the weeks before laying may serve for the selection of a suitable nest-site.     

Selection through predation, snowfall and microclimate on nest-site preferences in the Water Pipit Anthus spinoletta

Nest-site characteristics can have a strong impact on reproductive success in birds. Nest sites should simultaneously protect from predators, offer shelter and provide a favourable microclimate. We studied the relationship between three agents of natural selection (predators [i.e. Adders and birds/mammals], snowfall and microclimate), nest-site characteristics and reproductive success to determine whether these influenced preference for specific nest-site characteristics in the Water Pipit Anthus spinoletta . Pooled over all nests, the relative importance as agents of natural selection decreased from mammalian/avian predation (15% of all nests) through Adder predation (12%) to snowfall (7%), but there were clear differences in space and time. Predation by Adders selected for nest sites surrounded by few medium-sized shrubs. Selection by mammalian and avian predators favoured no specific nest-site characteristics. Protection from snowfall was best in nests surrounded by relatively few medium-sized shrubs. Microclimate had a strong influence on nestling survival and duration of nestling period. In nests on ENE-facing slopes, where maximum temperatures were reached in the morning, nestling survival was higher than on WSW-facing slopes, where temperature maxima occurred in the afternoon. Our results indicate that weak, but significant, directional selection is acting on preference for certain nest-site characteristics through effects on survival and development of nestlings. As predation and snowfall are unpredictable, the evolution of an optimal nest placement strategy is unlikely on a small scale. On a larger scale, however, choice of one breeding area over another may be favoured because of predictable differences between locations in terms of survival and nestling development.     

Habitat Selection in Birds and the Role of Early Experience

The role of early experience in habitat selection in linnets (Acanthis cannabina) was tested in automatic habitat cages. Young linnets were kept in groups under three different habitat conditions: spruce-, foliage- and plastic-perches. In a choice test the members of the spruce- and the foliage-group preferred their familiar habitat whereas the “plastic”-group showed this preference only on the first experimental day and then behaved at random on the following days. In a further aviary experiment the females of the spruce-group constructed nests in small spruce trees, whereas the females of the foliage-group constructed nests in small foliage bushes. The early habitat experience seems strongly to influence later habitat and nest-site selection in the linnets.     

Nest preference of laying hens (Gallus gallus domesticus) and their motivation to exert themselves to gain nest access

In connection with the development of a test method for the attractiveness and appropriateness of nests for laying hens, we carried out an investigation by using a preference test and motivation measuring with the help of push doors. Hens were offered two different nest sites either consisting of a tray filled with wood shavings (litter tray) or a wooden nest box plus wood shavings (nest box). Hens were individually housed in pens (2.0 m × 2.0 m) and had free access to the nest sites until they laid their 15th egg. From that day the hens had to overcome a push door to reach the nest sites. Resistance for entrance was also increased stepwise at the door leading to the hens’ nest. The experiment ended when a hen stopped to lay in her usual nest site for four consecutive days (postexperimental period). The behaviour during the last hour before oviposition was video taped at a level of resistance of 3.5, 6.0, 7.5 and 10.0 N.The hens were categorized into nest and litter layers depending on nest choice. All but one hen pushed maximum resistances between 11.5 and 18.0 N with no differences between nest and litter layers. Behaviour did not significantly change with increasing levels of resistance, but there were significant differences between nest and litter layers. Nest layers spent more time nesting than litter layers while the latter showed a strong tendency to more exploring behaviour. For litter layers, more entries through the push door leading to their nest site and more unsuccessful pushes were detected than for nest layers. According to our results, two types of layers could be distinguished whereas the two were equally motivated to access their nest site.     

Assessment of lighting needs by W-36 laying hens via preference test

Light intensity, spectrum and pattern may affect laying hen behaviors and production performance. However, requirements of these lighting parameters from the hens’ standpoint are not fully understood. This study was conducted to investigate hens’ needs for light intensity and circadian rhythm using a light tunnel with five identical compartments each at a different fluorescent light intensity of <1, 5, 15, 30 or 100 lux. The hens were able to move freely among the respective compartments. A group of four W-36 laying hens (23 to 30 weeks of age) were tested each time, and six groups or replicates were conducted. Behaviors of the hens were continuously recorded, yielding data on daily time spent, daily feed intake, daily feeding time, and eggs laid under each light intensity and daily inter-compartment movement. The results show that the hens generally spent more time in lower light intensities. Specifically, the hens spent 6.4 h (45.4%) at 5 lux, 3.0 h (22.1%) at 15 lux, 3.1 h (22.2%) at 30 lux and 1.5 h (10.3%) at 100 lux under light condition; and an accumulation of 10.0 h in darkness (<1 lux) per day. The 10-h dark period was distributed intermittently throughout the day, averaging 25.0±0.4 min per hour. This hourly light-dark rhythm differs from the typical commercial practice of providing continuous dark period for certain part of the day (e.g. 8 h at night). Distributions of daily feed intake (87.3 g/hen) among the different light conditions mirrored the trend of time spent in the respective light intensity, that is, highest at 5 lux (28.4 g/hen, 32.5% daily total) and lowest at 100 lux (5.8 g/hen, 6.7%). Hen-day egg production rate was 96.0%. Most of the eggs were laid in <1 lux (61.9% of total) which was significantly higher than under other light intensities (P<0.05). Findings from this study offer insights into preference of fluorescent light intensity by the laying hens. Further studies to assess or verify welfare and performance responses of the hens to the preferred lighting conditions and rhythm over extended periods are recommended.     

Influence of nest-floor slope on the nest choice of laying hens

Group nests in alternative housing systems for laying hens primarily fulfil the hen's needs for seclusion and protection. Commercial nests used in Switzerland are built according to the provisions of the Swiss Animal Welfare Legislation. However, nest types can differ in aspects, such as floor slope, that could have an impact on egg-laying behaviour. Floor slope has to be designed so that eggs roll away without breaking and so that hens feel comfortable laying their eggs. In commercial nests, the slope is usually between 12% and 18%. The aim of this study was to investigate the effect of floor slope on the hen's nest preference and laying behaviour. We predicted that hens would prefer nests with a lower sloped floor for evolutionary reasons and for reasons related to comfort.Eight pens, each with 17-18 white laying hens (LSL), were equipped with two roll-away nests (0.54 m²) having different floor slopes (12% and 18%). Eggs were collected each day (from approximately 20 weeks of age until 28 weeks of age); the number of eggs in each nest and on the floor of the pens was recorded. Behaviour inside the nest was filmed for two consecutive days during the main egg-laying time from the second hour to the fifth hour (4 h) after lights came on in week 27/28. The following data were recorded: number of hens in each nest, the nest visits/egg number ratio, the number of sitting events, the body alignment of hens sitting in the nest and the number and duration of nest visits. Data were analysed with a repeated-measures ANOVA. There was no difference between the numbers of eggs in the two nests, but more hens were counted in nests with a 12% slope (p = 0.027). The ratio between the number of nest visits and number of eggs did not differ significantly between the nests. However, we counted more sitting events in the nest with 12% slope (p = 0.007). The percentage of body alignment towards the back (p = 0.044) and towards the front (p = 0.028) of the nest differed between the nests. Furthermore, for nest visits lasting between 10 and 90 min, we found significant differences in the total number of nest visits (p = 0.039). For visits in this range of duration, we also found significant differences for nest visits with sitting (p = 0.025) and for the number of nest visits with egg laying (p = 0.049). All of these differences favoured the 12% nest.Both nests were generally accepted by the hens. However, because of the higher number of hens counted in the 12% nest and the higher amounts of nest visits and sitting events found in these nests, we recommend to use nests with a floor slope of 12% rather than 18%.     

Reproductive behavior and spawning success of female Amblyglyphidodon leucogaster (Pisces: Pomacentridae) from the Red Sea

The reproductive behavior of female whitebelly damselfish, Amblyglyphidodon leucogaster, was investigated in the Gulf of Aqaba, Red Sea over two breeding seasons. Females were promiscuous, mating with 7–10 different males throughout the season. Females lay eggs in distinct batches, defined as the total number of eggs laid in a day. Generally females deposit a batch of eggs with one male (87.2%) and are capable of laying a new batch every other day. Egg batch size averaged 4009 eggs and females laid from 2 to 22 egg batches per season. The variation in spawning success was not correlated to body size. Females preferred to deposit eggs in nests that already contained early stage eggs (0–2 days old). Within a nest, females chose to lay eggs contiguous to the youngest egg batch, regardless if the nest contained either a single batch or multiple batches of different ages. Female within-nest spawning patterns appear to be a consequence of between nest preferences for nests with young eggs. It is proposed that the strong within-nest preference is a consequence of mate selection where females may use new egg batches as a visual cue as part of a copying style. Such a style may reduce the risk of predation and increase feeding opportunities, because less time is expended in mate selection, which would provide additional resources for egg production and ultimately increase female spawning success over the breeding season. This revised version was published online in July 2006 with corrections to the Cover Date.     

Neuroendocrine control of reduced persistence of egg-laying in domestic hens: evidence for the development of photorefractoriness.

Egg-laying in hens exposed for more than 11 months to photostimulatory daylengths was intermittent and associated with a reduction in numbers of yellow-yolky ovarian follicles. Old laying hens (105 weeks) had lower concentrations of luteinizing hormone (LH) in the pituitary gland and plasma and reduced pituitary gland responsiveness to chicken LH-releasing-hormones (LHRH-I and II) in vivo when compared with young laying hens (28 weeks). Four weeks after transfer from 14 to 8 h light/day, egg production almost stopped in old, but not in young hens, although plasma LH concentrations decreased in all birds. After transfer from 14 to 20 h light/day, plasma LH increased in young, but not in old, hens, without a change in the rate of egg production. Reproductive function was enhanced in old hens returned to long days after induction of a moult and ovarian regression by reducing daylength and dietary restriction. Moulted hens had a greater rate of egg production, higher concentrations of plasma LH and a greater pituitary-gland responsiveness to LHRH-II in vivo than unmoulted control hens. After transfer from 14 to 8 h light/day, egg-laying decreased more rapidly in unmoulted than in moulted hens; transfer to 17 h light/day increased egg production in moulted, but not in unmoulted, birds. Induction of ovarian regression in old hens by dietary restriction alone also enhanced reproductive function after the dietary restriction was relaxed. Egg-laying was more persistent in hens brought into lay for a second year by transferring them from 3 to 11 h light/day than in hens transferred from 3 to 20 h light/day. Egg production was stimulated in hens maintained on 3 or 11 h light/day for 42 weeks, after transfer to 20 h light/day. Egg production ceased in hens maintained on 20 h light/day for 46 weeks, after transfer to 3 h light/day. These observations are consistent with the view that poor persistence of laying in hens less than 2 years old and exposed continuously to long days is caused, in part, by a reduction in hypothalamic-gonadotroph function. This reduction in neuroendocrine function may be due, in part, to the development of relative photorefractoriness.     

Female preference for nests with many eggs: a cost-benefit analysis of female choice in fish with paternal care

In several fish species with paternal care, females prefer malesguarding many eggs in their nest. This preference might be advantageousbecause the presence of many other eggs dilutes the risk ofnewly laid eggs being eaten by the father. To evaluate thishypothesis quantitatively, we constructed a simulation modelthat mimics the breeding biology of the blenny Aidablenniussphynx. In contrast to earlier verbal models, the costs of choiceare explicitly taken into account We systematically varied factorssuch as the stringency of choosiness and the level and natureof the costs of choice. For realistic parameter values femalechoosiness may result in a fitness advantage of more than 50%.The optimal choice strategy created a distribution of eggs overthe nests which resembles that found in the field for A. sphynx.Our model shows that the relative fitness of a choice strategyis not constant but frequency dependent in a complicated way.If most females are choosy, a bimodal distribution of eggs overthe nests results, with many nests containing few and some nestscontaining many eggs. In such a situation choosiness is profitable,since randomly laying females will often lay their eggs in nestswith few eggs, producing a high mortality per egg due to filialcannibalism. If, on the other hand, only few choosers are present,their influence on the egg distribution is limited. A unimodaldistribution results which is profitable for nonchoosers, sincethe average egg mortality is low and nonchoosers do not bearthe costs of choice. The positive relation between chooser frequencyand chooser fitness makes it easy to understand why choosinessis evolutionarily stable. However, it is not obvious how thetrait is established by selection in the first place.[BehavEcol 7: 353–361 (1996)     

Retirement investment theory explains patterns in songbird nest-site choice

When opposing evolutionary selection pressures act on a behavioural trait, the result is often stabilizing selection for an intermediate optimal phenotype, with deviations from the predicted optimum attributed to tracking a moving target, development of behavioural syndromes or shifts in riskiness over an individual''s lifetime. We investigated nest-site choice by female golden-winged warblers, and the selection pressures acting on that choice by two fitness components, nest success and fledgling survival. We observed strong and consistent opposing selection pressures on nest-site choice for maximizing these two fitness components, and an abrupt, within-season switch in the fitness component birds prioritize via nest-site choice, dependent on the time remaining for additional nesting attempts. We found that females consistently deviated from the predicted optimal behaviour when choosing nest sites because they can make multiple attempts at one fitness component, nest success, but only one attempt at the subsequent component, fledgling survival. Our results demonstrate a unique natural strategy for balancing opposing selection pressures to maximize total fitness. This time-dependent switch from high to low risk tolerance in nest-site choice maximizes songbird fitness in the same way a well-timed switch in human investor risk tolerance can maximize one''s nest egg at retirement. Our results also provide strong evidence for the adaptive nature of songbird nest-site choice, which we suggest has been elusive primarily due to a lack of consideration for fledgling survival.     

Cuckoos versus reed warblers: Adaptations and counteradaptations

At study sites in Cambridgeshire, England, the percentage of reed warbler, Acrocephalus scirpaceus, nests parasitized by cuckoos, Cuculus canorus, in 2 years was 22·5% and 9·1%. The warblers rejected cuckoo eggs at 19% of parasitized nests. Parasitized clutches suffered less predation than unparasitized clutches, suggesting that the cuckoo itself was the major predator, plundering nests too advanced for parasitism so that the hosts would re-lay. The cuckoos laid a mimetic egg, parasitized nests in the afternoons during the host laying period, usually removed one host egg, laid a remarkably small egg and laid very quickly. Nests were experimentally parasitized with model eggs to study the significance of this procedure. Experiments showed that host discrimination selects for: (1) egg mimicry by cuckoos (poorer matching model eggs were more likely to be rejected); (2) parasitism during the laying period (mimetic eggs put in nests before host laying began were rejected); (3) afternoon laying (mimetic eggs were less likely to be accepted in the early morning than in the afternoon, when hosts were more often absent from the nest); (4) a small egg (large eggs, typical of non-parasitic cuckoos, were more likely to be rejected); (5) rapid laying (a stuffed cuckoo on the nest stimulated increased rejection of model eggs), and (6) sets a limit to host egg removal by cuckoos (if more than one or two are removed desertion may occur). Mimicry may also be selected for because it reduced the chance that second cuckoos can discriminate the first cuckoo's egg from the host's clutch. Predation did not select for mimicry; nests with a non-mimetic egg did not suffer greater predation than those with a mimetic egg. Host rejection of model eggs did not depend on: (1) stage of parasitism once host egg laying had begun (nevertheless cuckoos were more likely to lay early in the host laying period probably to increase the chance the cuckoo chick hatched); (2) removal of a host egg (however, this reduced the incidence of unhatched eggs so cuckoos may remove a host egg so as not to exceed the host incubation limit). There were two costs of rejection, an ‘ejection’ cost (own eggs ejected as well as the cuckoo egg) and, with mimetic eggs, a ‘recognition’ cost (own eggs ejected instead of the cuckoo egg). Reed warblers did not discriminate against unlike chicks (another species) and did not favour either a cuckoo chick or their own chicks when these were placed in two nests side by side. Possible reasons why the hosts discriminate against unlike eggs but not unlike chicks are discussed.     

Nest-site preference and maternal effects on offspring growth

Maternal preferences for oviposition sites are assumed to beadaptive, but offspring fitness is not always higher at preferredsites and, thus, further study of the selection pressures thatinfluence oviposition behavior is warranted. Among birds, predationis regarded as the primary agent of selection on nest-site microhabitatpreferences, but alternatives are rarely considered. We testedthe hypothesis that avian nest-site preferences are an adaptiveresponse to fitness costs imposed by variation in nest-sitemicroclimate. We documented that Chestnut-collared Longspurs(Calcarius ornatus) strongly preferred to orient nests towardsthe southeast and showed that this preference influenced microclimate:nests facing southeast had the highest midday temperatures.Yet, preferences were not adaptive because nestlings in nestswith the preferred orientation gained mass at a slower rate,had retarded skeletal growth, and reached a smaller final size.We experimentally tested this result by altering orientationof nests and confirmed, for the first time, that variation innestling growth was causally linked to variation in nest microclimatearising from nest-orientation preferences. Adults respondedto the high temperatures at preferred southeast-facing nestsby spending more time shading young from the sun, apparentlyattempting to ameliorate heat costs. This response, however,resulted in parents spending less time feeding young, potentiallyexplaining slower growth in these nests. Direct effects of highertemperatures may also play a role in slower growth. Althoughwe lack an explanation for this apparently maladaptive preference,these results demonstrate that nest-site choices of birds canyield fitness costs imposed by variation in nest microclimate.     

Are Cuckoos Maximizing Egg Mimicry by Selecting Host Individuals with Better Matching Egg Phenotypes?

Background

Avian brood parasites and their hosts are involved in complex offence-defense coevolutionary arms races. The most common pair of reciprocal adaptations in these systems is egg discrimination by hosts and egg mimicry by parasites. As mimicry improves, more advanced host adaptations evolve such as decreased intra- and increased interclutch variation in egg appearance to facilitate detection of parasitic eggs. As interclutch variation increases, parasites able to choose hosts matching best their own egg phenotype should be selected, but this requires that parasites know their own egg phenotype and select host nests correspondingly.

Methodology/Principal Findings

We compared egg mimicry of common cuckoo Cuculus canorus eggs in naturally parasitized marsh warbler Acrocephalus palustris nests and their nearest unparasitized conspecific neighbors having similar laying dates and nest-site characteristics. Modeling of avian vision and image analyses revealed no evidence that cuckoos parasitize nests where their eggs better match the host eggs. Cuckoo eggs were as good mimics, in terms of background and spot color, background luminance, spotting pattern and egg size, of host eggs in the nests actually exploited as those in the neighboring unparasitized nests.

Conclusions/Significance

We reviewed the evidence for brood parasites selecting better-matching host egg phenotypes from several relevant studies and argue that such selection probably cannot exist in host-parasite systems where host interclutch variation is continuous and overall low or moderate. To date there is also no evidence that parasites prefer certain egg phenotypes in systems where it should be most advantageous, i.e., when both hosts and parasites lay polymorphic eggs. Hence, the existence of an ability to select host nests to maximize mimicry by brood parasites appears unlikely, but this possibility should be further explored in cuckoo-host systems where the host has evolved discrete egg phenotypes.     

Gregarious nesting in relation to floor eggs in broiler breeders

Gregarious nesting has often been observed in laying hens, where hens prefer to visit a nest already occupied by other hens over empty nests. This may result in overcrowding of the nests which is considered a welfare issue and, moreover, can increase the economic issue of floor eggs. This study aimed to describe gregarious nesting and spatial behavior in broiler breeders and how this relates to genetic background, fearfulness and mating behavior. Five commercially available genetic lines of broiler breeders were housed in 21 pens of 550 females and 50 males (six pens for lines 1 and 2, five pens for line 3 and two pens for lines 4 and 5) during the ages 20–60 weeks. Every 10 weeks, the plumage condition and wounds were assessed of 50 random hens per pen. Avoidance distance and novel object tests were performed to assess fearfulness at four time points. Distribution of eggs over nests was observed for 6 weeks at the onset of egg production at 26 weeks of age, and use of space was recorded at four time points, while (floor) egg production was noted daily per pen. We found differences between genetic lines over time in plumage condition and prevalence of wounds. Fear of humans was highest at the earliest age tested and did not correlate with general fearfulness as assessed by the novel object test. The distribution of eggs over nests was related to genetic background and was more uneven at the earliest age compared to later ages, and a more uneven distribution was correlated with an increased percentage of floor eggs. Distribution of birds over the litter area differed between the genetic lines, and less use of the litter area was correlated with an increased fear of humans and presence of wounds, suggesting an association with aggressive mating behavior. This difference in distribution of the birds could also explain the correlation between increased presence of wounds and decreased percentage of floor eggs. It is concluded that broiler breeders do show gregarious nesting, which is affected by genetic background. Both increased gregarious nesting and wounds are related to increased floor egg percentage, which should be studied further in broiler breeder research. Genetic selection for even use of the available nests and of the litter and slatted area would therefore support both broiler breeder welfare and performance.     

Ablenkungsman?ver bei der Eiablage des H?herkuckucks(Clamator glandarius)

Summary A pair of the Great Spotted Cuckoo exhibited reproductive behaviour during the years 1968–72. Until 1971 the female laid the eggs in nests of Magpies or Blackbirds which were placed in the aviary. Birds which could serve as hosts at these times were not in the aviary. The female Cuckoo visited the nests before laying an egg quite often and stayed at or in the nests for longer periods.1972 two Rollers were kept together with the Cuckoos and one Roller laid four eggs into a cave of a beech-stump. Now the female Cuckoo tried to deposit its eggs into the Roller's nest and was successful doing so several times. As soon as the female Cuckoo was ready to lay, the male Cuckoo diverted the Roller and so made it possible for the female to get into the Rollers nest. The laying of the egg took only a few seconds.     

Proteomic analysis of hypothalamic proteins of high and low egg production strains of chickens

Two slow-growth local chicken strains, derived from a common base population, were bi-directionally selected over twenty generations for carcass traits (B strain) and egg production (L2 strain). The objective of the present study was to identify hypothalamic proteins associated with high egg production (by taking advantage of the similar genetic background of these two strains). Prior to and during egg laying, hypothalamic proteins of B and L2 hens were analyzed with two-dimensional gel electrophoresis (2-DE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Approximately 430 well-resolved spots, ranging from 10 to 40 kDa, pH 5-9, were quantified by image processing. Eight protein spots differed in quantity between B and L2 strains at either stage. Using LC-MS/MS, we identified six of eight protein spots, including proteins known for regulating gene expression, signal transduction and lipid metabolism. The mRNA expression levels of these six proteins were then evaluated by quantitative RT-PCR in five strains of hens, including B, L2 and another three commercial strains; heterogeneous nuclear ribonucleoprotein H3 (HNRPH3) was higher in L2 than in the B strain (consistent with the findings in 2-DE). Increased levels of HNRPH3 mRNA were also present in the hypothalamus of high-egg-yield White Leghorn layers, but were absent in other domestic commercial strains with low egg production rates. In conclusion, the expression level of HNRPH3 may be a new molecular marker to screen for high egg production in slow-growth local chickens.     

Early rearing enrichments influenced nest use and egg quality in free-range laying hens

In Australia, free-range egg production pullets are typically reared indoors, but adult layers get outdoor access. This new environment may be challenging to adapt to, which could impair egg production and/or egg quality. Adaptation might be enhanced through rearing enrichments. We reared 1386 Hy-Line Brown® chicks indoors with three treatments across 16 weeks: (1) a control group with standard litter housing conditions, (2) a novelty group providing novel objects that changed weekly, and (3) a structural enrichment group with custom-designed structures to partially impair visibility across the pen and allow for vertical movement. Pullets were transferred to a free-range system at 16 weeks of age with daily outdoor access provided from 25 until 64 weeks. Daily egg production at different laying locations (large nests, small nests and floor), weekly egg weights and egg abnormalities were recorded from 18 to 64 weeks old. External and internal egg quality parameters of egg weight, shell reflectivity, albumen height, haugh unit, yolk colour score, shell weight and shell thickness were measured at 44, 52, 60 and 64 weeks. There was a significant interaction between rearing treatment and nest box use on hen-day production from weeks 18 to 25 (P < 0.0001) with the novelty hens laying the most eggs and the control hens the fewest eggs in the nest box. Similarly, from 26 to 64 weeks, the novelty hens laid more eggs in the large nest boxes and fewer eggs on the floor than both the structural and control hens (P < 0.0001). Egg weight and abnormalities increased with age (P < 0.0001), but rearing treatment had no effect on either measure (both P ≥ 0.19). Rearing treatment affected shell reflectivity and yolk colour with the control hens showing paler colours across time relative to the changes observed in the eggs from enriched hens. The novelty hens may have established nest box laying patterns as they were more accustomed to exploring new environments. The differences in egg quality could be related to stress adaptability or ranging behaviour. This study shows that enriching environments during rearing can have some impacts on production parameters in free-range hens.     

利用天然树洞繁殖的五种鸟的巢位特征及繁殖成功率

对吉林省左家自然保护区次生阔叶林中的大山雀 ( Parusmajor)、沼泽山雀 ( Paruspalustris)、普通跓( Sitta europacea)、白眉姬? ( Ficedula zanthopygia)和灰椋鸟 ( Sturnus cineraceus) 5种利用天然树洞繁殖的次级洞巢鸟进行了巢位选择和繁殖成功率研究。本研究中共发现 1 41巢。五种鸟对树洞类型的选择存在种间差异 ,普通跓不利用裂洞 ,沼泽山雀不利用啄洞 ,其它 3种鸟对 3种洞均有利用 ,但有一定的倾向性。对 5种鸟 9个巢位变量的比较中 ,只有洞口方向差异不显著 ( p >0 .0 5 ) ,其它 8个变量均差异显著 ( p<0 .0 5 ) ,该结果说明 5种次级洞巢鸟对巢位的选择具有其各自的需求。洞口横径、洞口纵径、洞处树直径、洞内径、巢距地高是巢位选择重要变量 ,它们决定不同种类对树洞的利用。巢损失多数出现在产卵之前和孵化阶段 ,44个繁殖失败的巢中有 35个在这两个阶段损失。大山雀的巢成功率最低 ,灰椋鸟的巢成功率最高。 5种鸟的孵化率都超过 90 %。人为破坏和动物捕食是繁殖失败的主要原因 ,占总数的 61 .4%。洞巢鸟巢位选择中的重要变量影响繁殖成功。普通跓繁殖是否成功受洞口横径和巢高影响 ,沼泽山雀受洞口纵径、树胸径和洞内径影响 ,大山雀受洞口横径、巢高和洞内径影响 ,灰椋鸟受洞内径和洞深影     

MODE OF SEXUAL SELECTION DETERMINED BY RESOURCE ABUNDANCE IN TWO SAND GOBY POPULATIONS

We used field observations and experiments to show that sexual selection in two populations of sand gobies, Pomatoschistus minutus (Pisces, Gobiidae), was affected by differences in resource availability. Male sand gobies rely on empty mussel shells for nest building and spawning. The two populations differed considerably in nest-site abundance and sexual-selection regimes. In one population nest sites were scarce, leading to stronger male-male competition over nests, a higher nest site colonization rate and reduced potential for female choice compared with the other population that had a surplus of nests. In the high-competition population, males were larger than females, perhaps as a response to selection, whereas the other population was not sexually size dimorphic. The results from the field were confirmed in a pool experiment that demonstrated the effect of nest abundance on nest occupancy and male reproductive success. Larger males were more successful in obtaining nest sites in both high and low nest availability treatments. Larger males were also favored by females as mating partners, but only in the treatment with surplus nest sites. Nest shortage was associated with an increased potential for intrasexual selection (measured as the coefficient of variation), whereas the potential for intersexual selection was increased when nests were common. In conclusion, nest-site abundance can influence the relative contribution of intrasexual competition and mate choice in a population. Hence, resource availability can contribute to within-species variation in mating patterns.