Precocial Chicks Research Articles

Development of early foraging behaviour of domestic chicks in varying social contexts

Two aspects of foraging development might be crucial to learning in precocial chicks: what food particles look like and what food sites look like. Previous research indicates that there are innate dispositions for particle preferences and for preferring the type of food sites experienced between day 3 and 5 of age, both of which are likely to be socially modified. The aim of the present work was to investigate how chicks and their foster hens coordinate discovering food caches (N=24) during the first week of life in a foraging arena and, in a second study, how preferences for particles and food sites develop in groups of domestic chicks that were housed together with a foster hen or not, and whether a chick that is three days older than its group mates might substitute some of the foster hen's tutor effects for these preferences (16 groups in each of the three treatments). Particle preferences were tested on day 9 of age in the second study without hen, tutor or tutor control chicks in a test apparatus where an array of particle types was offered in differently coloured food pens. Chicks of foster hens were less likely than chicks of the other two treatments to peck at novel particles that most closely resembled known food particles (gravel). No difference between treatments was found for known food particles, particles of the home pen's ground substrate or another novel type of particle. In contrast to this tutor effect that was only found in chicks fostered by a hen, both chicks of a mother hen and chicks that were reared with an older and food trained chick, but not chicks with an additional naïve control chick of the same age, showed a first choice preference for types of food locations experienced on day 3 and 5 of age as opposed to types of food location experienced on day 2 and 7. It is concluded that the development of early learning in domestic chicks of what to forage on and where is adapted to naturally composed groups were the type of food sites are unlikely to be demonstrated by clutch mates during the first week of life and where only the mother hen shows specific displays for small scale aspects of foraging, such as in regard of food particles.

The role of landscape features and density dependence in growth and fledging rates of Piping Plovers in North Dakota, USA

ABSTRACT For species with precocial young, survival from hatching to fledging is a key factor influencing recruitment. Furthermore, growth rates of precocial chicks are an indicator of forage quality and habitat suitability of brood-rearing areas. We examined how growth and fledging rates of Piping Plover (Charadrius melodus) chicks were influenced by landscape features, such as hatchling density (hatchlings per hectare of remotely sensed habitat [H ha−1]), island vs. mainland, and wind fetch (exposure to waves) at 2-km segments (n = 15) of Lake Sakakawea, North Dakota, during 2007–2008. Hatchling growth was comparable with published estimates for other habitats. Models for fledging rate (fledged young per segment) assuming density dependence had more support (wi = 96%) than those assuming density independence (wi = 4%). Density-dependent processes appeared to influence fledging rate only at densities >5 H ha−1, which occurred in 19% of the segments we sampled. When areas with densities >5 H ha−1 were exc...

Evaluating Methodological Assumptions of Catch-Curve Survival Estimation for Unmarked Precocial Shorebird Chicks

Abstract. Estimating productivity for precocial species can be difficult because young birds leave their nest within hours or days of hatching and detectability thereafter can be very low. Recently, a method for using a modified catch-curve to estimate precocial chick daily survival for age based count data was presented using Piping Plover (Charadrius melodus) data from the Missouri River. However, many of the assumptions of the catch-curve approach were not fully evaluated for precocial chicks. We developed a simulation model to mimic Piping Plovers, a fairly representative shorebird, and age-based count-data collection. Using the simulated data, we calculated daily survival estimates and compared them with the known daily survival rates from the simulation model. We conducted these comparisons under different sampling scenarios where the ecological and statistical assumptions had been violated. Overall, the daily survival estimates calculated from the simulated data corresponded well with true survival...

Heterochronic Protein Expression Patterns in the Developing Embryonic Chick Cerebellum

The advantages of the embryonic chick as a model for studying neural development range from the relatively low cost of fertilized eggs to the rapid rate of development. We investigated in ovo cerebellar development in the chick, which has a nearly identical embryonic period as the mouse (19-22 days). We focused on three antigens: Calbindin (CB), Zebrin II (ZII), and Calretinin (CR), and our results demonstrate asynchronous expression patterns during cerebellar development. Presumptive CB+ Purkinje cells are first observed at embryonic day (E)10 in clusters in posterior cerebellum. At E12, corresponding with global expression of CB across the cerebellum, Purkinje cells began to express ZII. By E14-E16, Purkinje cells disperse into a monolayer and develop a pattern of alternating immunopositive and immunonegative ZII stripes. CR is initially expressed by clusters of presumptive Purkinje cells in the nodular zone at E8. However, this expression is transient and at later stages, CR is largely confined to the granule and molecular layers. Before hatch (E18-E20), Purkinje cells adopt a morphologically mature phenotype with complex dendritic arborizations. Comparing this data to that seen in mice, we found that the sequence of Purkinje cell formation, protein expression, and development is similar in both species, but these events consistently begin ∼5-7 days earlier in the precocial chick cerebellum, suggesting an important role for heterochrony in neurodevelopment.

Daily energy expenditure in precocial shorebird chicks: smaller species perform at higher levels

AbstractWe measured daily energy expenditure (DEE) during the development periods of precocial chicks of five species of Arctic shorebirds spanning a broad range in size, in order to investigate the relationships between DEE, body size, and growth rate. We also quantified the effect of weather conditions on the energy expenditure of chicks to establish the impact of cold arctic weather on their time and energy budgets. We used the doubly labeled water method to measure DEE at ambient temperatures in an outside enclosure on the subarctic tundra at Churchill, Manitoba, Canada. Growth rate was highest in the smallest species, and in general decreased with adult size, as shown by the decrease in growth rate constant and later inflection point with increasing adult body mass. DEE ranged from 14 kJ day−1in young chicks of the smaller species to 365 kJ day−1in older chicks of the larger species. From hatching onward, DEE of shorebirds was high compared to DEE of chicks of altricial species, reflecting the high costs of locomotion and thermoregulation, and mass-specific DEE increased rapidly to adult levels. Chicks of smaller species metabolized more energy per unit mass and functioned at higher multiples of resting metabolic rate than chicks of larger species. As chicks of smaller species also had higher growth rates, and thus simultaneously invested in growth and mature function, it seems that shorebird chicks can adjust total metabolizable energy as well as its relative allocation between investment in growth and mature function. DEE was similar to cold-induced peak metabolic rates achieved by shivering thermogenesis. Because chicks were motionless during laboratory metabolism measurements, the relatively high level of DEE compared to these metabolic rates suggests that locomotion produces similar amounts of heat as shivering. Ambient temperature did not affect DEE in outdoor pens, although higher wind speed resulted in slightly increased energy expenditure. Heat produced by locomotion is possibly sufficient to sustain thermoregulation under local environments. Furthermore, when ambient temperatures are low, chicks spend more time brooding and less time foraging, which presumably counters the tendency to increase thermogenesis in response to cold.

Transgenerational effects of early experience on behavioral, hormonal and gene expression responses to acute stress in the precocial chicken

Stress during early life can profoundly influence an individual's phenotype. Effects can manifest in the short-term as well as later in life and even in subsequent generations. Transgenerational effects of stress are potentially mediated via modulation of the hypothalamic–pituitary–adrenal axis (HPA) as well as epigenetic mechanisms causing heritable changes in gene expression. To investigate these pathways we subjected domestic chicken (Gallus gallus) to intermittent social isolation for the first three weeks of life. The early life stress resulted in a dampened corticosterone response to restraint stress in affected birds and in their male offspring. Stress-specific genes, such as early growth response 1 (EGR1) and corticotropin releasing hormone receptor 1 (CRHR1), were upregulated immediately after restraint stress, but not under baseline conditions. Treatment differences in gene expression were also correlated across generations which indicate transgenerational epigenetic inheritance. In an associative learning test early stressed birds made more correct choices suggesting a higher coping ability in stressful situations. This study is the first to show transgenerational effects of early life stress in a precocial species by combining behavioral, endocrinological, and transcriptomic measurements.

How did the Great Auk raise its young?

The extant auks show three strategies of chick rearing--precocial (chicks leave the nest site when a few days old), intermediate (young raised to a mass of around 20% of adult mass) and semi-precocial (young raised to a mass of around 65% of adult mass). It is not known which strategy the extinct Great Auk used. In this paper, we investigate this issue by a novel combination of a time and energy budget model and phylogenetic comparison. The first approach indicates that for reasonable estimates of the equation parameters, the Great Auk could have followed an intermediate strategy. For a limited range of parameters, the Great Auk could have followed the semi-precocial strategy. Phylogenetic comparison shows that it is unlikely that the Great Auk followed a precocial strategy. The results suggest that the Great Auk followed an intermediate strategy as does its presumed closest extant relative the Razorbill.

Colony kin structure and host‐parasite relatedness in the barnacle goose

Conspecific brood parasitism (CBP), females laying eggs in the nest of other 'host' females of the same species, is a common alternative reproductive tactic among birds. For hosts there are likely costs of incubating and rearing foreign offspring, but costs may be low in species with precocial chicks such as waterfowl, among which CBP is common. Waterfowl show strong female natal philopatry, and spatial relatedness among females may influence the evolution of CBP. Here we investigate fine-scale kin structure in a Baltic colony of barnacle geese, Branta leucopsis, estimating female spatial relatedness using protein fingerprints of egg albumen, and testing the performance of this estimator in known mother-daughter pairs. Relatedness was significantly higher between neighbour females (nesting < or = 40 metres from each other) than between females nesting farther apart, but there was no further distance trend in relatedness. This pattern may be explained by earlier observations of females nesting close to their mother or brood sisters, even when far from the birth nest. Hosts and parasites were on average not more closely related than neighbour females. In 25 of 35 sampled parasitized nests, parasitic eggs were laid after the host female finished laying, too late to develop and hatch. Timely parasites, laying eggs in the host's laying sequence, had similar relatedness to hosts as that between neighbours. Females laying late parasitic eggs tended to be less related to the host, but not significantly so. Our results suggest that CBP in barnacle geese might represent different tactical life-history responses.

Foraging in precocial chicks of the black‐tailed godwitLimosa limosa: vulnerability to weather and prey size

Self‐feeding precocial development is associated with high energy requirements and potentially vulnerable to short‐term reductions in food availability, yet few studies have investigated development of foraging in precocial chicks and its sensitivity to environmental conditions. We studied time budgets and foraging behaviour during the 25‐d prefledging period in the insectivorous chicks of a grassland shorebird, the black‐tailed godwitLimosa limosa. Until 8–10 d old, parental brooding was the main determinant of chicks’ daily foraging time. Brooding decreased with age and temperature and increased during rainfall. Foraging time increased to 70–90% of the daylight period in chicks older than a week, during which distances of 3–12 km d−1were covered. Chicks took 98% of their arthropod prey from the grassland vegetation. Prey ingestion rates increased in the first week and slowly declined thereafter, modified by wind speed, temperature and time of day. Chicks in poor body condition were brooded more than chicks growing normally and hence had less feeding time, potentially leading to a negative condition spiral under adverse conditions. However, we found no effect of condition on prey ingestion rate that would preclude recovery when conditions improve. Combining behavioural observations with data on energy expenditure revealed that mean prey size was small (1–4.5 mg), necessitating a high feeding rate, but increased notably after 7–10 d of age. This coincided with a decrease in walking speed, suggesting that chicks fed more selectively. Prey of older chicks approached the upper limit of sizes available in exploitable densities in the grassland vegetation, and this enhances the chicks’ sensitivity to variation in prey availability due to weather and agricultural practice.

Effects of color banding, radio tagging, and repeated handling on the condition and survival of Lapwing chicks and consequences for estimates of breeding productivity

Color bands and radio tags are widely used to facilitate individual recognition and relocation of precocial chicks in studies of prefledging survival. However, the accuracy of data collected and subsequent estimates of survival rates rely on the assumption that such techniques do not affect the parameters under study. We compared the body condition and survival of color-banded and radio-tagged Lapwing (Vanellus vanellus) chicks with noncolor-banded and nonradio-tagged individuals using a 10-year dataset (N = 3174 chicks, with 205 color banded and 700 radio tagged). Color bands did not adversely affect chicks. However, radio-tagged chicks and their untagged broodmates were handled more frequently because these broods were more readily encountered than those without a tagged member. Chicks disturbed and handled more frequently had lower body condition indices and higher mortality rates. Simulations of the impact of tagging and handling on breeding productivity under two scenarios indicated a 26% reduction in productivity in situations where nest and chick survival rates were low (as in our study), but only a 7% reduction in productivity for a simulated population with the higher levels of nest and chick survival associated with a stable population. The frequent disturbance associated with radio-tracking and recapturing chicks, rather than the attachment of a tag or physical handling of chicks, may affect body condition. Frequent handling and disturbance may affect body condition by reducing foraging time, increasing stress levels, or increasing pr?dation risk. Because our results suggested that the negative impact of handling could last up to a week, we recommend that investigators avoid disturbance of shorebird chicks more frequently than every 8 d.

Estimating survival of precocial chicks during the prefledging period using a catch-curve analysis and count-based age-class data

Estimating reproductive success for birds with precocial young can be difficult because chicks leave nests soon after hatching and individuals or broods can be difficult to track. Researchers often turn to estimating survival during the prefledging period and, though effective, mark-recapture based approaches are not always feasible due to cost, time, and animal welfare concerns. Using a threatened population of Piping Plovers (Charadrius melodus) that breeds along the Missouri River, we present an approach for estimating chick survival during the prefledging period using long-term (1993–2005), count-based, age-class data. We used a modified catch-curve analysis, and data collected during three 5-day sampling periods near the middle of the breeding season. The approach has several ecological and statistical assumptions and our analyses were designed to minimize the probability of violating those assumptions. For example, limiting the sampling periods to only 5 days gave reasonable assurance that population size was stable during the sampling period. Annual daily survival estimates ranged from 0.825 (SD = 0.03) to 0.931 (0.02) depending on year and sampling period, with these estimates assuming constant survival during the prefledging period and no change in the age structure of the population. The average probability of survival to fledging ranged from 0.126 to 0.188. Our results are similar to other published estimates for this species in similar habitats. This method of estimating chick survival may be useful for a variety of precocial bird species when mark-recapture methods are not feasible and only count-based age class data are available. RESUMEN Estimar el exito reproductivo de aves con polluelos precociales puede ser dificil debido a que los polluelos dejan el nido poco despues de eclosionar y los individuos o nidadas pueden ser dificiles de seguir. Los investigadores a menudo estiman la supervivencia durante el periodo pre-volanton y aunque son efectivos, los metodos de marcaje y recaptura no son siempre factibles por razones del costo, tiempo y bienestar del animal. Usando una poblacion amenazada de Charadrius melodus que se reproduce sobre el Rio Missouri, presentamos un metodo para estimar la supervivencia de polluelos durante el periodo pre-volanton usando datos de largo plazo (1993–2005) con clases de edades, basados en conteos. Utilizamos un analisis de curva de captura modificada y datos colectados durante tres periodos de muestreo de cinco dias cada uno, cerca del medio de la epoca reproductiva. Este metodo tiene algunos supuestos ecologicos y estadisticos y nuestros analisis fueron disenados para minimizar la probabilidad de violar dichos supuestos. Por ejemplo, limitando los periodos de muestreo a solo cinco dias dio el resultado razonable de que el tamano de la poblacion fue estable durante el periodo de muestreo. Las estimaciones de la supervivencia diaria anual variaron entre 0.825 (DE = 0.03) y 0.931 (0.02), dependiendo del ano y periodo de muestreo. Estas estimaciones dependieron de la suposicion de una supervivencia constante durante el periodo pre-volanton y de ningun cambio en la estructura de la edad de la poblacion. El promedio de la probabilidad de supervivencia en la etapa pre-volanton vario desde 0.126 hasta 0.188. Nuestros resultados son similares a otras estimaciones publicadas para esta especie en habitats similares. Este metodo de estimar la supervivencia de los polluelos podria ser util para una variedad de especies de aves precociales cuando los metodos de marcaje y recaptura no son factibles y cuando solo estan disponibles datos con clases de edades basados en conteos.

Non-precocial grey-faced petrel chicks ( Pterodroma macroptera gouldi) show no age-related variation in corticosterone responses to capture and handling

Development patterns in birds range from precocial species, which hatch chicks largely capable of independent existence, to altricial species, chicks of which are highly dependent on their parents for extended periods. Previous work indicates precocial chicks have a robust corticosterone response from hatching whereas non-precocial and altricial chicks have a small response that increases through development. Grey-faced petrels are characteristic of most burrowing procellariiform seabirds with non-precocial chicks that are unable to locomote and are dependent on adults for food, although chicks have well developed downy plumage and can thermoregulate at or soon after hatching. Initial plasma corticosterone concentrations and corticosterone responses to handling were measured during development in semi-precocial grey-faced petrel ( Pterodroma macroptera gouldi) chicks to determine whether they showed a precocial or altricial corticosterone response pattern. Chicks were sampled at six intervals through development from shortly after hatching until close to fledging. Mean corticosterone responses to handling after 30 min were high (115.9 ± 10.7 ng/ml) from 2 to 4 d after hatching and remained high throughout development (70–110 ng/ml). Contrary to expectations for non-precocial chicks, this pattern of corticosterone responses to handling indicates that grey-faced petrel chicks are able to perceive and respond to potential stressors from hatching, a response previously only demonstrated for precocial birds.

Pre-fledging energy requirements of the nocturnally fed semi-precocial chicks of the Spotted Thick-knee (Burhinus capensis)

Studies of pre-fledging growth and energetics in precocial (self-feeding) shorebird species have shown that chicks expend large amounts of energy on thermoregulation and activity. We investigated the pre-fledging growth and energetics of Spotted Thick-knee (Burhinus capensis) chicks, which are semi-precocial (fed by their parents), near Cape Town, South Africa, to determine whether semi-precocial development would reduce the energy expenditure of chicks and enable them to grow faster. In addition, because Spotted Thick-knees are nocturnally feeding shorebirds, we hypothesised that their more limited foraging time (compared with diurnal feeders) would negatively influence growth and energy expenditure of chicks during their spring-summer breeding season. The growth-rate coefficient, resting metabolic rate, peak daily metabolisable energy and total metabolisable energy of Spotted Thick-knee chicks were similar to the values predicted for birds of their size. Therefore, the potential negative impact of nocturnal feeding on growth of chicks may be being countered by reduced chick energy expenditure on thermoregulation and activity owing to parental feeding, and adults potentially extending their foraging time into the day as their chicks become larger. The relative energy requirements of growing Thick-knee chicks were greater than those of precocial shorebird chicks in the same climate of the Western Cape, but lower than those of shorebirds breeding in temperate or arctic zones. The semi-precocial mode of development of Spotted Thick-knees did not result in reduced energy expenditure or faster growth than anticipated for shorebirds in general, but their relative growth was greater than that of precocial species at the same latitude. Therefore, semi-precocial development benefits the growth of Spotted Thick-knees.

Alarm responses are maintained during captive rearing in chicks of endangered kaki

AbstractThe maintenance of species‐specific behavioural repertoires and traditions is an important but often implicit goal of conservation efforts. When captive rearing is used as a conservation practice, it becomes critical to address its possible implications for the social and behavioural traits of developing individuals. In particular, animals must retain or acquire many of their behavioural abilities to increase the likelihood of survival upon release into the wild. This study investigated the behavioural development of critically endangered kaki (black stilt: Himantopus novaezelandiae) chicks reared without live adult conspecifics. The captive rearing programme included playbacks of adult kaki alarm calls during cleaning and handling of precocial chicks housed as groups. We used videotaped observations and playback experiments to address the following questions: do kaki chicks respond differentially to (1) familiar versus unfamiliar adult kaki alarm calls and (2) conspecific alarm versus heterospecific control vocalizations. Adult‐naïve kaki chicks exhibited a varied behavioural repertoire over their early development. In multivariate analyses, when age was statistically controlled, chicks showed responses to familiar and unfamiliar alarm calls that were similar in magnitude. In contrast, following conspecific alarm calls chicks had longer average latencies to resume pre‐playback activities than following heterospecific vocalizations. Although the generality of these conclusions is limited by experimental constraints stemming from working with an endangered species, the findings suggest that current management techniques produce captive‐reared kaki for release into the wild that possess many of the behavioural and auditory recognition skills that are required for survival.

Timing of incorporation of docosahexaenoic acid into brain and muscle phospholipids during precocial and altricial modes of avian development

We investigated the possibilities that the proportion of docosahexaenoic acid (DHA) in phospholipids of brain and skeletal muscle at hatch, and the ontogenetic timing of the DHA accretion spurt in these tissues, might serve as indices of neonatal functional maturity that discriminate between precocial and altricial avian developmental modes. Comparison of the fatty acid profiles of the initial and residual yolks of two free-living altricial species, the swallow ( Hirundo rustica) and the sparrow ( Passer domesticus), reveals that, in contrast to precocial birds, there is no preferential uptake of DHA from the yolk during embryonic development. At hatch, the proportions of DHA in brain phospholipid (wt.% of fatty acids) of the swallow and sparrow, at 8.1% and 5.0%, respectively, are far lower than the values (16.9–19.6%) reported for non-altricial species. This reflects a marked difference in the timing of the brain DHA accretion spurt, which occurs during the first half of the embryonic period of precocial birds, but is largely delayed until after hatching in the altricial species. By the time of fledging, the proportion of DHA in the swallow brain phospholipid has increased to 14.3%. For non-altricial birds, the brain DHA concentration at hatch shows little interspecies variation, despite major differences in yolk DHA content. The proportions of DHA in leg muscle phospholipid of the newly hatched swallow and sparrow, at 2.9% and 2.5%, respectively, are far lower than the value (6.7%) for the precocial chicken. Again, this relates to differences in developmental timing, with muscle DHA accretion occurring in the first half of the chicken's embryonic period, whereas, in the swallow, this increase is delayed until after hatching. By the time of fledging in the swallow, DHA forms 9.3% of muscle phospholipid fatty acids, equivalent to the level attained in chicken muscle at the mid-embryo stage. The results indicate a clear distinction between altricial and non-altricial avian species in the timing of tissue DHA accretion during development, presumably reflecting differences in neonatal functional maturity.

Chic chicks: the evolution of chick ornamentation in rails

Competition over access to food has led to the evolution of a variety of exaggerated visual and vocal displays in altricial nestling birds. Precocial chicks that are fed by their parents also vary widely in appearance ranging from those with inconspicuous coloration to those with brightly colored bills, fleshy parts, and plumes. These ornaments are lost by the end of the period of parental dependence, suggesting they function in competition over parental care. We use a comparative approach to evaluate which ecological or life-history variables may have favored the evolution of conspicuous ornamentation in precocial chicks. We compiled data on chick morphology, ecology, and social organization of species in the Family Rallidae, a group with highly variable downy chicks. Chick ornamentation in the form of brightly colored bills, fleshy patches, or plumes is observed in 36 of 97 species for which downy chicks are described. Phylogenetic reconstructions suggest that nonornamentation is the ancestral state. Chick ornamentation has evolved multiple times within the Rallidae and is significantly associated with large clutch sizes and polygamous mating systems. Chick ornamentation was also weakly associated with adult ornamentation and adult dimorphism. We argue that these results support the hypothesis that lineages with higher levels of sibling competition are more likely to evolve ornamented chicks. Key words: chick coloration, precocial chicks, Rallidae, sibling competition, signaling. [Behav Ecol 15:946–951 (2004)]

SIBLINGS SET THE SOCIAL SCENE

Brush-turkeys probably won't win the `most doting parent' prize. Abandoning their newly laid eggs to develop in enormous compost heap incubators, the parents return to the Australian bush ready to resume their solitary existence. So brush-turkey chicks must be resourceful from the start,scratching around without a mother's example to guide them; `brush-turkey chicks are probably the most precocial chicks there are' explains Ann Göth. But it wasn't clear whether these abandoned hatchlings had the same social skills as other precocial chicks, which imprint on their mothers. Göth wondered whether brush-turkey chicks could imprint on other brush-turkey chicks instead. Working with Christopher Evans, she decided to test whether newly hatched brush-turkey chicks could recognise each other, and what attracts a hatchling to another chick shortly after it emerges from its decomposing incubator (p. 2199).But getting hold of brush-turkey eggs was far from straightforward. Göth had to brave leeches as she manually excavated the bird's enormous leaf litter incubators and transferred the eggs to soil incubators in the lab at Macquarie University. Having got some eggs, Göth also knew she had to keep the newly hatched chick's contented and unaware of their unnatural surroundings when they hatched, which meant constructing large net aviaries in an area of native forest on the University's campus.Having ensured that the chicks' Macquarie home was as natural as possible,Göth had one final test to do before putting newly hatched chicks through their social paces. The chick robots, which she and Evans had built, looked fine to human eyes, but would the real chicks fall for their doubles?Tentatively she tested five newly hatched youngsters' reactions to the pecking impostors, and was delighted when all of the chicks began acting socially,copying the robot's pecking action. Happy that the chicks were none the wiser about the chick-doubles, Göth was ready to test their preferences.Suspecting that the chicks would be most attracted to pecking actions,Göth allowed the newly hatched youngsters to choose between either a pecking robot or a robot involved in some other activity. But no matter which choice the chicks were offered, they always seemed to prefer spending time with the pecking robot chick, even trying to steal the food that the automated model appeared to dine on. The chicks were very sociable, despite their parents antisocial reputation.Göth wondered whether any other aspects of a brush-turkey chick's appearance attracted the youngsters and found that UV wavelengths reflected from brush-turkey's legs and beak were essential if the chick was to mimic its pecking actions. The team suspect that the chick's spectral properties could form part of a secret signal visible only to the UV sensitive chicks, but invisible to mammalian predators and airborne hunters.So even though they don't have a mother to imprint on, newly hatched brush-turkey chicks seem to have well developed social responses, despite the lack of parental guidance.

Brood sex ratio in the Kentish plover

How and why do the mating opportunities of males and females differ in natural population of animals? Previously we showed that females have higher mating opportunities than males in the Kentish plover Charadrius alexandrinus. Both parents incubate the eggs, and males provide more brood care than females; thus it is not obvious why the females find new mates sooner than the males. In this study we investigated whether the sex-biased mating opportunities stem from biased offspring sex ratios. We determined the sex of newly hatched, precocial chicks using CHD gene markers. Among fully sexed broods, 0.461 6 0.024 (SE) of chicks (454 chicks in 158 broods) were male, and this sex ratio was not significantly different from unity. The proportion of males at hatching decreased significantly over the breeding season, which occurred consistently in all 3 years of the study. Large chicks were more likely to be males than females. Neither parental age nor body size of male and female parents was related to brood sex ratio. We also sexed a number of chicks that were caught after they left their nest (range of estimated ages 0–17 days) and found that the proportion of males increased with brood age. This relationship remained highly significant when controlling statistically for hatching date. As brood size decreased due to mortality after the chicks left their nest, these results suggest that the mortality of daughters was higher than that of the sons shortly after hatching. Taken together, our results show that the female-biased mating opportunities in the Kentish plover are not due to biased brood sex ratio at hatching but, at least in part, are due to female-biased chick mortality soon after hatching. Key words: Charadrius alexandrinus, Kentish plover, mating opportunities, parental care, seasonal trends, sex allocation, sex ratio. [Behav Ecol 15:58–62 (2004)]

Effects of weather on the survival and growth of CorncrakeCrex crexchicks

Weather conditions during the early life of precocial chicks of some bird species have marked effects on survival and may also cause changes in adult population size. In this paper, we use data from broods with radiotagged mothers to examine correlations of growth rates and survival of CorncrakeCrex crexchicks in Scotland and Ireland with temperature and rainfall. The loss of whole broods before they reached independence was infrequent and not correlated with temperature or rainfall. Loss of some chicks from broods before independence usually occurred and multiple regression analysis indicated that the proportion of chicks that survived increased with decreasing initial brood size, increasing temperature and decreasing rainfall. However, the magnitude of the effects of weather on survival were quite small. The rate of weight gain of chicks varied considerably within and among broods. The mean daily weight gain rate of broods decreased significantly with increasing rainfall, and variation in the weight of chicks within broods was greater for broods whose mean rate of weight gain was low.

CHICKS ARE COOL ABOUT STAYING WARM

![Figure][1] Most chicks spend their young lives being waited on by their parents; all they have to do is eat and grow. But precocial chicks are much more independent. Within hours of breaking out of their shells, the youngsters are foraging for themselves. Which is fine in temperate climes,