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Concept: Chicken


Domestic chickens are members of an order, Aves, which has been the focus of a revolution in our understanding of neuroanatomical, cognitive, and social complexity. At least some birds are now known to be on par with many mammals in terms of their level of intelligence, emotional sophistication, and social interaction. Yet, views of chickens have largely remained unrevised by this new evidence. In this paper, I examine the peer-reviewed scientific data on the leading edge of cognition, emotions, personality, and sociality in chickens, exploring such areas as self-awareness, cognitive bias, social learning and self-control, and comparing their abilities in these areas with other birds and other vertebrates, particularly mammals. My overall conclusion is that chickens are just as cognitively, emotionally and socially complex as most other birds and mammals in many areas, and that there is a need for further noninvasive comparative behavioral research with chickens as well as a re-framing of current views about their intelligence.

Concepts: Psychology, Cognitive psychology, Sociology, Bird, Cognition, Chicken, Knowledge, Emotion


Coccidiosis, caused by species of the apicomplexan parasite Eimeria, is a major disease of chickens. Eimeria species are present world-wide, and are ubiquitous under intensive farming methods. However, prevalence of Eimeria species is not uniform across production systems. In developing countries such as Ethiopia, a high proportion of chicken production occurs on rural smallholdings (i.e. ‘village chicken production’) where infectious diseases constrain productivity and surveillance is low. Coccidiosis is reported to be prevalent in these areas. However, a reliance on oocyst morphology to determine the infecting species may impede accurate diagnosis. Here, we used cross-sectional and longitudinal studies to investigate the prevalence of Eimeria oocyst shedding at two rural sites in the Ethiopian highlands.

Concepts: Epidemiology, Disease, Infectious disease, Agriculture, Infection, Ethiopia, Apicomplexa, Chicken


To determine the contents of chicken nuggets from 2 national food chains.

Concepts: Chicken, Fast food, C-Bo


The Late Jurassic Lourinhã Formation is known for its abundant remains of dinosaurs, crocodylomorphs and other vertebrates. Among this record are nine localities that have produced either dinosaur embryos, eggs or eggshell fragments. Herein, we describe and identify the first crocodiloid morphotype eggs and eggshells from the Lourinhã Formation, from five occurrences. One clutch from Cambelas, composed of 13 eggs, eggshell fragments from Casal da Rola and Peralta, one crushed egg and eggshells from Paimogo North, and four crushed eggs as well as eggshell fragments from Paimogo South. We observed and confirmed diagnostic morphological characters for crocodiloid eggshells and which are consistent with a crocodylomorph affinity, such as the ellipsoidal shape, wedge-shaped shell units, triangular extinction under cross-polarized light, and tabular ultrastructure. This material is distinctive enough to propose two new ootaxa within the oofamily Krokolithidae, Suchoolithus portucalensis, oogen. and oosp. nov., for the material from Cambelas, the most complete clutch known for crocodiloid eggs, and Krokolithes dinophilus, oosp. nov., for the remaining material. These are the oldest crocodylomorph eggs known, extending the fossil record for this group to the Late Jurassic. Furthermore, except for the clutch from Cambelas, the material was found with theropod eggs and nests, in the other four occurrences, which seem to suggest some form of biological relationship, still unclear at this point.

Concepts: Egg, Bird, Reptile, Chicken, Fossil, Paleontology, Dinosaur, Archaeopteryx


In the United Kingdom, outbreaks of Campylobacter infection are increasingly attributed to undercooked chicken livers, yet many recipes, including those of top chefs, advocate short cooking times and serving livers pink. During 2015, we studied preferences of chefs and the public in the United Kingdom and investigated the link between liver rareness and survival of Campylobacter. We used photographs to assess chefs' ability to identify chicken livers meeting safe cooking guidelines. To investigate the microbiological safety of livers chefs preferred to serve, we modeled Campylobacter survival in infected chicken livers cooked to various temperatures. Most chefs correctly identified safely cooked livers but overestimated the public’s preference for rareness and thus preferred to serve them more rare. We estimated that 19%-52% of livers served commercially in the United Kingdom fail to reach 70°C and that predicted Campylobacter survival rates are 48%-98%. These findings indicate that cooking trends are linked to increasing Campylobacter infections.

Concepts: Microbiology, Infection, Pathogen, United Kingdom, Chicken, Preference, Campylobacter, Campylobacteriosis


Birds seem to use a light-dependent, radical-pair-based magnetic compass. In vertebrates, cryptochromes are the only class of proteins that form radical pairs upon photo-excitation. Therefore, they are currently the only candidate proteins for light-dependent magnetoreception. Cryptochrome 4 (Cry4) is particularly interesting because it has only been found in vertebrates that use a magnetic compass. However, its structure and localization within the retina has remained unknown. Here, we sequenced night-migratory European robin (Erithacus rubecula) Cry4 from the retina and predicted the currently unresolved structure of the erCry4 protein, which suggests that erCry4 should bind Flavin. We also found that Cry1a, Cry1b, and Cry2 mRNA display robust circadian oscillation patterns, whereas Cry4 shows only a weak circadian oscillation. When we compared the relative mRNA expression levels of the cryptochromes during the spring and autumn migratory seasons relative to the non-migratory seasons in European robins and domestic chickens (Gallus gallus), the Cry4 mRNA expression level in European robin retinae, but not in chicken retinae, is significantly higher during the migratory season compared to the non-migratory seasons. Cry4 protein is specifically expressed in the outer segments of the double cones and long-wavelength single cones in European robins and chickens. A localization of Cry4 in double cones seems to be ideal for light-dependent magnetoreception. Considering all of the data presented here, especially including its localization within the European robin retina, its likely binding of Flavin, and its increased expression during the migratory season in the migratory bird but not in chicken, Cry4 could be the magnetoreceptive protein.

Concepts: Gene expression, Messenger RNA, Bird, Chicken, European Robin, Erithacus, American Robin, Magnetoception


Although the temporal overlap between human dispersal across Australia and the disappearance of its largest animals is well established, the lack of unambiguous evidence for human-megafauna interactions has led some to question a human role in megafaunal extinction. Here we show that diagnostic burn patterns on eggshell fragments of the megafaunal bird Genyornis newtoni, found at >200 sites across Australia, were created by humans discarding eggshell in and around transient fires, presumably made to cook the eggs. Dating by three methods restricts their occurrence to between 53.9 and 43.4 ka, and likely before 47 ka. Dromaius (emu) eggshell occur frequently in deposits from >100 ka to present; burnt Dromaius eggshell first appear in deposits the same age as those with burnt Genyornis eggshell, and then continually to modern time. Harvesting of their eggs by humans would have decreased Genyornis reproductive success, contributing to the bird’s extinction by ∼47 ka.

Concepts: Human, Animal, Bird, Chicken, Australia, Megafauna, Megafauna of Australia, Australian megafauna


This paper investigates what “free-range” eggs are available for sale in supermarkets in Australia, what “free-range” means on product labelling, and what alternative “free-range” offers to cage production. The paper concludes that most of the “free-range” eggs currently available in supermarkets do not address animal welfare, environmental sustainability, and public health concerns but, rather, seek to drive down consumer expectations of what these issues mean by balancing them against commercial interests. This suits both supermarkets and egg producers because it does not challenge dominant industrial-scale egg production and the profits associated with it. A serious approach to free-range would confront these arrangements, and this means it may be impossible to truthfully label many of the “free-range” eggs currently available in the dominant supermarkets as free-range.

Concepts: Egg, Food, Chicken, Meat, Lutein, Factory farming, Egg white, Egg yolk


Optimality theory predicts that females tend to maximize their offspring survival by choosing the egg-laying site. In this context, the use of conspecific cues allows a more reliable assessment of the habitat quality. To test this hypothesis, Tetranychus urticae Koch is an appropriate biological model as it is a phytophagous mite living in group, protected against external aggression by a common web. Experiments were conducted to determine the respective influence of substrate (living substrate: bean leaf vs. non-living substrate: glass plate), silk and presence of conspecific eggs on the egg-laying behavior of T. urticae females. On both living and non-living substrates, the presence of silk positively influenced the probability of a female to lay an egg, but had no influence on the number of eggs deposited. The egg-laying behavior was mainly determined by the nature of the substrate with mites laying fewer eggs on a non-living substrate than on a living one. The presence of a conspecific egg had no impact on either the probability of laying an egg or on the oviposition rate. This study showed a high variability among females in their fecundity and egg-laying performance. The physiology of females (individual fecundity), the egg-laying substrate and to a lesser extent the presence of silk impacted on the decision of spider mites to lay eggs.

Concepts: Chicken, Acari, Arachnid, Tetranychus urticae, Spider mite, Tetranychus, Acariformes, Agricultural pest mites


The former use of chlordecone (CLD) in the French West Indies has resulted in long-term pollution of soils and of food chains. CLD may be transferred into eggs of hens reared outdoors, through polluted soil ingestion. Tropical volcanic soils display variable capacities of pollutant retention: CLD is less available and more persistent in andosol than in nitisol. The impact of soil type on CLD bioavailability to hens was tested through a relative bioavailability study. The deposition of CLD in egg yolk and in abdominal fat was measured in 42 individually housed laying hens fed with diets containing graded levels of CLD from polluted andosol, nitisol, or spiked oil during 23 days. Within each ingested matrix, the concentration of CLD in yolk and in abdominal fat linearly increased with the amount of ingested CLD (P < 0.001). However, the response to andosol diets and to nitisol diets was not different from the response to oil diets (P > 0.1), indicating that CLD was equally bioavailable to laying hens, irrespective of the matrix. This suggests that the hen’s gastrointestinal tract efficiently extracts CLD from the two tropical volcanic soils, regardless of their retention capacity. Thus, hens reared on polluted soils with CLD may lay contaminated eggs.

Concepts: Egg, Digestive system, Pollution, Chicken, Egg white, Egg yolk, Lecithin, Hen