Instruct: Given a question, retrieve relevant documents that can help answer the question.
Query: What bird lays the smallest egg?
The largest recorded egg is from a whale shark, and was 30cm ×14cm ×9cm (11.8in ×5.5in ×3.5in) in size.[1] Whale shark eggs typically hatch within the mother. At 1.5kg (3.3lb) and up to 17.8cm ×14cm (7.0in ×5.5in), the ostrich egg is the largest egg of any living bird,[2] though the extinct elephant bird and some dinosaurs laid larger eggs. The bee hummingbird produces the smallest known bird egg, which weighs half of a gram (around 0.02oz). Some eggs laid by reptiles and most fish, amphibians, insects and other invertebrates can be even smaller.
In birds, ornithologist David Lack carried out much research into regulation of clutch size. In species with altricial young, he proposed that optimal clutch size was determined by the number of young a parent could feed until fledgling. In precocial birds, Lack determined that clutch size was determined by the nutrients available to egg-laying females. An experimental study in Black Brent Geese (Black Brant), which rarely lay more than 5 eggs, found that the probability of an egg successfully leading to a fledged gosling declined from 0.81 for two-egg clutches to 0.50 for seven-egg clutches, whilst the nesting period increased with the increasing number of eggs laid. This suggests that there is no benefit for female Black Brant to lay more than five eggs.
Over fifty species in this family of birds practice brood parasitism; the details are best seen in the common cuckoo ("Cuculus canorus"). In a season the female lays one egg in 15–20 other bird nests. She removes some or all of the host's clutch of eggs, and lays an egg which closely matches the host eggs. In Britain the cuckoo lays small eggs that match the size of the smaller host's. The eggs are thick-shelled as a defense to protect the egg if the host detects the fraud.
Since their domestication, a large number of breeds of chickens have been established, but with the exception of the white Leghorn, most commercial birds are of hybrid origin. In about 1800, chickens began to be kept on a larger scale, and modern high-output poultry farms were present in the United Kingdom from around 1920 and became established in the United States soon after the Second World War. By the mid-20th century, the poultry meat-producing industry was of greater importance than the egg-laying industry. Poultry breeding has produced breeds and strains to fulfil different needs; light-framed, egg-laying birds that can produce 300 eggs a year; fast-growing, fleshy birds destined for consumption at a young age, and utility birds which produce both an acceptable number of eggs and a well-fleshed carcase. Male birds are unwanted in the egg-laying industry and can often be identified as soon as they are hatch for subsequent culling. In meat breeds, these birds are sometimes castrated (often chemically) to prevent aggression. The resulting bird, called a capon, has more tender and flavorful meat, as well.
Varricchio et al. (1997) described the exact structure of the nests. They were built from sediments, they were dish shaped, about 100 cm in internal diameter, and with a pronounced raised rim encircling the eggs. The more complete nests had between 16 (minimum number in MOR 246) and 24 (MOR 963) eggs. The eggs are shaped like elongated teardrops, with the more tapered ends pointed downwards and imbedded about halfway in the sediment. The eggs are pitched at an angle so that, on average, the upper half is closer to the center of the nest. There is no evidence that plant matter was present in the nest.
Varricchio et al.(1997) were able to extract enough evidence from the nests to infer several characteristics of troodont reproductive biology. The results are that they appear to have had a type of reproduction that is intermediate between crocodiles and birds, as phylogeny would predict. The eggs are statistically grouped in pairs, which suggests that the animal had two functional oviducts, like crocodiles, rather than one, as in birds. Crocodiles lay many eggs that are small proportional to adult body size. Birds lay fewer, larger, eggs. The Two Medicine troodont was intermediate, laying an egg of about 0.5 kg for a 50 kg adult. This is 10 times larger than reptiles of the same mass, but two troodont eggs are roughly equivalent to the 1.1 kg egg predicted for a 50 kg bird.
Northern gannets lay one egg that on average weighs , which is light for such a large seabird. The egg is around long by wide and the shell is pale blue and translucent initially before fading to a chalky white surface that is easily stained. Where two eggs are found in a nest this is the result of two females laying an egg in the same nest or one egg being stolen from another nest. Northern gannets will lay a replacement egg if the first is lost. Incubation takes 42 to 46 days, during which time the egg is surrounded by the brooding bird's warm, webbed feet. Just before hatching begins, the brooding bird releases the egg from its feet to prevent the egg from breaking under the adult's weight as the chick breaks it open. This is a frequent cause of death for chicks of birds that are breeding for the first time. The process of breaking the eggshell can take up to 36 hours. The webbed feet are also used to cover the chicks, which are only rarely left alone by their parents. Chicks that are left unattended are often attacked and killed by other northern gannets.
Bird eggs are laid by the females and incubated for a time that varies according to the species; a single young hatches from each egg. Average clutch sizes range from one (as in condors) to about 17 (the grey partridge). Clutch size may vary latitudinally within a species. Some birds lay eggs even when the eggs have not been fertilized; it is not uncommon for pet owners to find their lone bird nesting on a clutch of infertile eggs, which are sometimes called wind-eggs.
Many cuckoos are obligate brood parasites, meaning they only lay eggs in other birds' nests and never take care of their own young. Birds that do this, such as the common cuckoo or the brown-headed cowbird, lay relatively small eggs because their expected hosts are usually smaller birds. Cuckoos in the genus "Coccyzus", lay relatively large eggs even though they still parasitize smaller birds. Yellow warblers are the smallest birds recorded caring for black-billed cuckoo eggs. In experiments, these wood warblers were found to accept the cuckoo eggs 63% of the time even though their own eggs are only a quarter of the size. Even with the size difference, the warbler parent is often still able to raise the cuckoo as long as it can provide the chick with sufficient nutrition and incubation.
The black-billed cuckoo was originally placed in genus "Cuculus". This genus comprises Old World cuckoos that are all obligate brood parasites. Upon further genetic testing, it was placed into genus "Coccyzus" that comprises nine species of New World cuckoos. The black-billed and yellow-billed cuckoos are the only two that migrate into North America while the other seven are permanent residents of either Central or South America. Even though these two cuckoos overlap in range, they are not sister taxa. This suggests that the two species invaded North America separately. Although family Cuculidae is monophyletic, the genus "Coccyzus" was found to be polyphyletic.
The Jos Plateau indigobird ("Vidua maryae") is a species of bird in the family Viduidae. It is endemic to Nigeria. It lays its eggs in the nest of the rock firefinch which is also restricted to Nigeria. Because of their inability to incubate their eggs, they lay their eggs in the nest of the rock firefinch and then take away the exact number of laid eggs from the host bird in order to avoid suspicion from the host bird . After hatching they exhibit dominance against the hatchlings of the rock firefinchers. Their breeding seasons are all round the year but more pronounced during the cold Harmattan period between July and December.
Brood parasitism, in which an egg-layer leaves her eggs with another individual's brood, is more common among birds than any other type of organism. After a parasitic bird lays her eggs in another bird's nest, they are often accepted and raised by the host at the expense of the host's own brood. Brood parasites may be either "obligate brood parasites", which must lay their eggs in the nests of other species because they are incapable of raising their own young, or "non-obligate brood parasites", which sometimes lay eggs in the nests of conspecifics to increase their reproductive output even though they could have raised their own young. One hundred bird species, including honeyguides, icterids, and ducks, are obligate parasites, though the most famous are the cuckoos. Some brood parasites are adapted to hatch before their host's young, which allows them to destroy the host's eggs by pushing them out of the nest or to kill the host's chicks; this ensures that all food brought to the nest will be fed to the parasitic chicks.
All dinosaurs lay amniotic eggs with hard shells made mostly of calcium carbonate. Eggs are usually laid in a nest. Most species create somewhat elaborate nests, which can be cups, domes, plates, beds scrapes, mounds, or burrows. Some species of modern bird have no nests; the cliff-nesting common guillemot lays its eggs on bare rock, and male emperor penguins keep eggs between their body and feet. Primitive birds and many non-avialan dinosaurs often lay eggs in communal nests, with males primarily incubating the eggs. While modern birds have only one functional oviduct and lay one egg at a time, more primitive birds and dinosaurs had two oviducts, like crocodiles. Some non-avialan dinosaurs, such as "Troodon", exhibited iterative laying, where the adult might lay a pair of eggs every one or two days, and then ensured simultaneous hatching by delaying brooding until all eggs were laid.
Kiwi ( ) or kiwis are flightless birds native to New Zealand, in the genus Apteryx and family Apterygidae. Approximately the size of a domestic chicken, kiwi are by far the smallest living ratites (which also consist of ostriches, emus, rheas, and cassowaries), and lay the largest egg in relation to their body size of any species of bird in the world.
The shape, structure, and arrangement of eggs of "Protoceratopsidovum" and its relatives provide some insight into the palaeobiology of fossil eggs. Their asymmetrical shape (resembling bird eggs) suggests that the process of egg formation was similar to that of birds. Unlike bird eggs (which are laid one at a time), "Protoceratopsidovum" eggs were laid in pairs because the mother would have two functioning oviducts which would both lay a single egg simultaneously, contrasting with modern birds, which have only one functional oviduct. Though no fossils of parents incubating "Protoceratopsidovum" eggs have been found, their identification as maniraptoran eggs would imply that they were incubated.
Egg tossing or egg destruction is a behaviour observed in some species of birds where one individual removes an egg from the communal nest; which is related to infanticide. This behaviour is observed in avian species, most commonly females, who are involved with cooperative breeding or brood parasitism. Among colonial non-co-nesting birds, egg-tossing is observed to be performed by an individual of the same species. Tossing of eggs is non-accidental: the intruder rolls the egg to the edge of the nest by repeatedly flicking it with its beak. During co-nesting, before a bird starts laying its own eggs, it tosses out other eggs laid previously by another female. As a result, the last egg-layers may contribute more eggs to the common nest: this will increase the chances that newly laid eggs bearing the genetic material of that female will have a better chance of survival. In some species, egg-tossing is a strategy of clutch coordination: eggs are tossed until all birds in the common nest are ready to proceed with brooding. Preventing early egg-layers from dominating reproduction. Laying eggs late can be detrimental to the offspring once the egg is hatched since it will be smaller than their siblings thus increasing the risk of death. Performing this behaviour increases the offspring per individual compared to those in single pairs and many species have learnt to adapt to increase the chances of their offspring to survive.
The birds are then moved to broiler breeder "laying houses" or production barns. The birds are typically placed into crates, and transported by truck to a separate facility. Males and females are raised together at this point. Outwardly the laying house will resemble the rearing house. Inside, about one-half of the floor might consist of raised 'slats.' During the production run, manure will drop through the slats and accumulate in the pit underneath the slats. The birds are not generally caged, especially since the roosters must mate with the hens to fertilize the eggs. Nests are provided for laying hens. Both automatic and manual (example) nesting systems exist. Manual nests are usually stuffed with straw or shavings and eggs are hand-collected. Automatic systems usually have a plastic carpet lining, with a belt for egg collection. Careful layout and attention to bird behavior is required to avoid 'floor eggs'.
The common cuckoo, a brood parasite, provides examples of mimesis both in the adult and in the egg. The female lays her eggs in nests of other, smaller species of bird, one per nest. The female mimics a sparrowhawk. The resemblance is sufficient to make small birds take action to avoid the apparent predator. The female cuckoo then has time to lay her egg in their nest without being seen to do so. The cuckoo's egg itself mimics the eggs of the host species, reducing its chance of being rejected.
The female penguin lays one 460–470g (1.01–1.04lb) egg in May or early June;[65] it is vaguely pear-shaped, pale greenish-white, and measures around 12cm ×8cm (43⁄4in ×31⁄4in).[63] It represents just 2.3% of its mother's body weight, making it one of the smallest eggs relative to the maternal weight in any bird species.[67] 15.7% of the weight of an emperor penguin egg is shell; like those of other penguin species, the shell is relatively thick, which helps minimize risk of breakage.[68]
The number of eggs laid in a single brood is referred to as the clutch. Clutch size is usually within a small range of variation. Some birds respond to the accidental loss of eggs by laying a replacement egg. Others will stop laying based on the apparent size of the clutch. According to whether they respond to addition, removal, or both addition and removal of eggs, birds are classified as determinate layers (number of eggs laid is predetermined and do not respond to change) or as indeterminate layers. In general birds, birds with small clutch size tended to be indeterminate.
Sometimes hosts are completely unaware that they are caring for a bird that is not their own. This most commonly occurs because the host cannot differentiate the parasitic eggs from their own. It may also occur when hosts temporarily leave the nest after laying the eggs. The parasites lay their own eggs into these nests so their nestlings share the food provided by the host. It may occur in other situations. For example, female eiders would prefer to lay eggs in the nests with one or two existing eggs of others because the first egg is the most vulnerable to predators. The presence of others’ eggs reduces the probability that a predator will attack her egg when a female eider leaves the nest after laying the first egg.
Many females laid eggs on the rims of nests where the eggs could not survive without help. Human conservationists pushed the eggs back into the nests where they were incubated and hatched successfully. The maladaptive gene causing this behaviour spread until over 50% of females laid rim eggs. Humans stopped pushing eggs back in time to prevent the gene spreading to all birds which could have made the birds dependent on humans indefinitely. After human intervention stopped rim laying became less frequent, but 9% of birds still laid rim eggs as of 2011. Conservationists have faced some criticism that they may inadvertently do harm if they allow organisms with deleterious traits to survive and perpetuate what is maladaptive.
While many reptiles lay eggs with flexible, calcified eggshells, there are some that lay hard eggs. Eggs laid by snakes generally have leathery shells which often adhere to one another. Depending on the species, turtles and tortoises lay hard or soft eggs. Several species lay eggs which are nearly indistinguishable from bird eggs.
Birds which build in trees generally have blue or greenish eggs, either spotted or unspotted, while birds that build in bushes or near or on the ground are likely to lay speckled eggs.
Caprimulgiform birds typically lay small clutches: frogmouths and potoos lay only one egg, with exceptions such as the Australian Tawny Frogmouth which lay two to three and Marbled Frogmouth which lay one to two; nightjars one or two, and the Oilbird usually three. With the exception of the Oilbird, which nests colonially in tree hollows, caprimulgiform birds do not build a nest but lay their egg or eggs directly onto the ground or branches. Both parents usually incubate, and for camouflage the semialtricial chicks, covered with down at hatching but immobile, are often coloured white like the eggs.
Cowbirds eat insects, including the large numbers that may be stirred up by cattle. In order for the birds to remain mobile and stay with the herd, they have adapted by laying their eggs in other birds' nests. The cowbird will watch for when its host lays eggs, and when the nest is left unattended, the female will come in and lay its own eggs. The female cowbird may continue to observe the nest after laying eggs. If the cowbird egg is removed, the female cowbird may destroy the host's eggs to dissuade further removals, according to the Mafia hypothesis.
The female common ostrich lays her fertilised eggs in a single communal nest, a simple pit, 30to 60cm (12–24in) deep and 3m (9.8ft) wide,[53] scraped in the ground by the male. The dominant female lays her eggs first, and when it is time to cover them for incubation she discards extra eggs from the weaker females, leaving about 20 in most cases.[7] A female common ostrich can distinguish her own eggs from the others in a communal nest.[54] Ostrich eggs are the largest of all eggs,[55] though they are actually the smallest eggs relative to the size of the adult bird — on average they are 15cm (5.9in) long, 13cm (5.1in) wide, and weigh 1.4 kilograms (3.1lb), over 20 times the weight of a chicken's egg and only 1 to 4% the size of the female.[56] They are glossy cream-coloured, with thick shells marked by small pits.[17]