Crex crex

Crex crex

The corn crake or corncrake, landrail (Crex crex Linnaeus, 1758) is a bird belonging to the Rallidae family.

Systematic –
From a systematic point of view it belongs to:
Eukaryota domain,
Kingdom Animalia,
Subkingdom Eumetazoa,
Superphylum Deuterostomia,
Phylum Chordata,
Subphylum Vertebrata,
Infraphylum Gnathostomata,
Superclass Tetrapoda,
(clade) Amniote,
Aves class,
Subclass Neornithes,
Superorder Neognathae,
Order Gruiformes,
Rallidae family,
Genus Crex,
Species C. crex.
The term is basionym:
– Rallus crex Linnaeus, 1758.
The terms are synonymous:
– Crex pratensis Bechstein;
– Gallinula crex;
– Rallus spec Linnaeus, 1758.

Geographic Distribution and Habitat –
Crex crex is the only species of the genus Crex Bechstein, 1803, and is native to central and western Eurasia.
Its nesting range is quite large and goes from Europe to western Siberia; in detail it goes from Great Britain and Ireland, across Europe, to central and western Siberia. It has currently disappeared from much of its historical range; in the past this bird occupied all the areas favorable to it between 41 and 62° north latitude. A fairly large population is also present in western China, but the species breeds only rarely in the northern regions of Spain and Turkey. The old testimonies according to which the species also breeds in South Africa are incorrect.
This bird winters mostly in Africa, in an area from the Democratic Republic of Congo and the central regions of Tanzania from where it reaches eastern South Africa. North of this area, it is seen mainly as a migratory species, but it also rarely winters in North Africa and west and north of the typical wintering area of south-eastern Africa. The majority of the South African population, made up of around 2000 individuals, resides in KwaZulu-Natal and in what was formerly the Transvaal Province, but estimates regarding other African regions are uncertain. In the 19th century, when the species was much more numerous, large numbers of specimens were sighted in Western Europe, especially in Great Britain and Ireland, between December and February.
In Italy, this bird is present only in the central-eastern Alpine area, from Lombardy to Friuli-Venezia Giulia.
Its habitat is mainly a lowland species, but it nests up to altitudes of 1400 m, in the Alps, 2700 m, in China, and 3000 m, in Russia. As a nesting habitat in Eurasia, the species in the past preferred meadows along rivers, with tall, thick grasses, such as sedges and irises. Now it is generally found in the cold humid prairies used for the production of hay, especially where traditional agriculture is practiced, with not too excessive hay harvesting and a limited use of fertilizers. It also lives in treeless grassy areas of mountainous regions, taiga, coastal regions or where the latter have been created by fires. It can also be found on the edges of wetlands, but it never enters actual swamps, as well as open areas where the vegetation exceeds 50 cm in height or is too dense to prevent walking through it. Bushes or hedges can be used as decoy places. Grasslands where the grass is not cut by humans or grazing animals become too tangled to be used for nesting, but it sometimes also nests in fields of cereals, peas, rapeseed, clover or potatoes. After nesting, the adults move to areas where the vegetation is higher, such as reed beds or expanses of irises and nettles, to molt, and then return to the hay and fodder fields to brood a second time. In China, the species also nests in flax fields. Although males are often seen singing in overused hay fields or cereal fields, there is low reproductive success in such areas, and nesting is more likely to occur on the edges of fields or in nearby areas left fallow.
When it winters in Africa, it occupies dry prairies and savannas, where the vegetation measures 30–200 cm in height, including areas affected seasonally by fires and, more rarely, expanses of sedges or reed beds. It is also found in uncultivated and abandoned fields, in areas of uncultivated grass at airports and on the edges of cultivated fields. In South Africa it is present up to at least 1750 m altitude.
During migration it can also be found in wheat fields and around golf courses.

Description –
The Crex crex is a bird with evident sexual dimorphism, with a length of 27-30 cm, a wingspan of 42-53 cm, for an average weight of 165 grams in the male and 145 grams in the female.
This species is recognized for having a brown-tawny plumage, with a reddish iris. Head and chest are gray in the male, while the upper parts of the wing appear light and shiny brown, reminiscent of the color of hazelnuts.
The adult male has the top of the head and all the upper regions of brown-black colour, streaked with buff or grey. The coverts are a characteristic chestnut color, with some white stripes. The face, neck and chest are blue-grey, except for a light brown stripe extending from the base of the bill to above the eye, the abdomen is white, and the sides and undertail are marked by white and brown stripes. The strong beak is flesh-colored, the iris is light brown, and the legs and feet are light gray.
The female, on the other hand, has warmer toned upper regions and a thinner and less conspicuous supraocular stripe. Outside the mating season, the upper regions of both sexes become darker and the lower regions less grey.
Juveniles have a similar appearance to adults, but have a more yellowish upper region, while the gray of the lower regions is replaced by a buff-brown.
The chicks are covered in black down and all populations show great individual variation in colouration; as we move towards the eastern borders of the range, the birds gradually take on a lighter and grayer colour.
After nesting, the adults carry out a complete moult, which generally ends in late August or early September, before migrating towards south-eastern Africa. In Africa, before returning, the birds are subjected to a partial pre-nesting moult, which mainly involves the plumage of the head, body and tail. Young specimens molt their head and body feathers approximately five weeks after hatching.
The male’s warning call, in nesting habitats, is a deep, croaking and repetitive krek krek, generally emitted from a low perch with the head and neck held almost vertical and the beak open. This call can be heard from 1.5 km away, and serves to reaffirm possession of a certain territory, to attract females and to launch challenges to invading males. Since there are slight differences in the vocalizations emitted, it is possible to recognize each male by his call. At the beginning of the nesting season, the call is sounded almost continuously at night, but also during the day. It can be repeated more than 20,000 times per night, peaking between midnight and three o’clock.
In fact, due to the difficulty in spotting the species, the populations are surveyed by counting the calls of the males emitted between 11pm and 3am.
This call was developed to make the position of the male more visible, since the species lives in the thick vegetation. The frequency of calls reduces after a few weeks, but may intensify again towards the end of the egg-laying period, before ceasing altogether at the end of the breeding season.
The male also produces a sort of growl, emitted with the beak closed during aggressive displays.
The female can emit a call similar to that of the male, but in addition produces a characteristic bark, with a similar rhythm to the main call, but less shrill. She also produces a kind of chirp and a chirp, oo-oo-oo, to call the chicks. The latter emit a faint peeick-peeick of contact, and a peep used to request food.
In Africa the bird is always silent.
The eggs are oval, slightly shiny and cream in color or with green, blue or gray tones, speckled with red-brown. They measure 37×26 mm and weigh approximately 13-16 g, of which 7% is made up of the shell.

Biology –
The Crex crex is a bird that, like other species, uses song to attract the female and delimit its territory. The plumage itself is straightened and exhibited during the traditional “love dance” which takes place in spring, typically in the month of April.
However, it is a difficult bird to spot in its nesting sites: it generally remains hidden among the vegetation, but sometimes it can venture onto open terrain.
In Africa, it has more reserved habits.
Until 1995, it was believed to be monogamous, but males occupy territories with variable boundaries and mate with two or more females, moving away when spawning is almost complete. The territory of the males covers an area varying between 3 and 51 ha, but on average measures 15.7 ha. Females occupy smaller areas, covering only 5.5 ha. The male wards off intruders by emitting his call and assuming a particular posture, with his wings lowered and his head facing forward. This is usually enough to drive the intruder away; if it does not move, the two birds raise their heads and necks and lower their wings until they touch the ground. Then they run in circles making a cawing call and throwing themselves at each other. Sometimes it can lead to a real fight, with the birds throwing themselves at each other, hitting each other with their beaks and, sometimes, with their legs. The female does not take part in the defense of the territory.
During courtship the male can offer food to his partner. Sometimes he also performs a short parade, keeping his neck stretched out, his head facing downwards, his tail open like a fan and his wings open with the tips touching the ground. He then tries to approach the female from behind her, then climb onto her back and mate.
The nest is generally placed in the grass, sometimes in a safe place along a hedge, near an isolated tree or bush, or among dense vegetation. Where the grass is not long enough to begin the nesting season, the first nest may be built in a meadow or among marsh vegetation, while the second is built in tall grass. The second nest can also be placed at a higher height than the first, to take advantage of the grasses growing on the hill, which develop later. The nest, well hidden in the grass, is built in a depression or cavity in the ground. It is made of blades of dry grass and other plant substances woven together, and stuffed with finer tufts. In the past it was believed that nest building was the exclusive task of the female, but in a recent study carried out in captivity it was always the male who took care of this.
The size of the nest varies from 12 to 15 cm in diameter, with a depth of 3–4 cm. The clutch consists of 6-14 eggs, usually 8-12.
The eggs are laid every other day, but during the second clutch two eggs per day can be laid. Only the female takes care of the brooding; its tendency to remain immobile when it feels threatened, or to wait until the last moment to take flight, causes many deaths during haymaking and harvesting. The eggs hatch all together after 19-20 days, and the precocious chicks leave the nest within one or two days. They are fed by the female for three or four days, but then provide food for themselves. The young fledge after 34-38 days. The second brood is laid approximately 42 days after the first, but the incubation period is shorter, 16-18 days. The young, once grown, can remain in the company of the female until it is time to migrate to Africa.
In undisturbed sites, nesting success is high, 80-90%, but it decreases somewhat in lawns treated with fertilizers and in lands subject to ploughing. How and when haymaking is carried out is of crucial importance; agricultural machinery can kill 38-95% of the chicks on a given site: these losses concern 50% of the chicks of the first brood and just under 40% of those of the second. The influence of climate on the survival of the young is limited: since they develop rather quickly, in dry or hot periods, losses due to climate are relatively few. Unlike many other species where the chicks are precocial, the chicks are fed by their mother until they reach independence, and this can help them when the situation worsens. More than by time, the survival of chicks is influenced above all by the number of members of the brood: in fact, the survival rate decreases in broods that are too large. The annual survival rate in adults is less than 30%, but some specimens can live up to 5-7 years.

Ecological Role –
The Crex crex was described for the first time by Linnaeus in his Systema Naturae of 1758, with the name Rallus crex, but was later transferred to the genus Crex, created by the German naturalist and ornithologist Johann Matthäus Bechstein in 1803, and named Crex pratensis . The specific name crex, however, enjoyed priority over Bechstein’s pratensis, so the species was called Crex crex, the name by which it is still known today. The scientific name, Crex crex, derived from the ancient Greek κρεξ, is onomatopoeic and refers to the repetitive strident call of the animal.
This bird migrates to Africa via two main routes: a western one, through Morocco and Algeria, and a more important eastern one, through Egypt. In passing, it has been sighted in almost all countries located between the breeding and wintering range, including much of West Africa and those areas of southern Asia located between the eastern end of the breeding range and the ‘Africa. Sometimes nomadic specimens have been reported in Sri Lanka, Vietnam, Australia, Seychelles, Bermuda, Canada, United States, Greenland, Iceland, Faroe Islands, Azores, Madeira and the Canary Islands.
These birds do not move much during the night, while during the day they can wander up to 600 m: researchers could therefore count the same specimen twice. Counting males, however, underestimates the true size of a population by almost 30%, and this discrepancy can be even greater, since on a given night only 80% of the males present in a certain area can sing.
It is most active at dawn and dusk, after heavy rainfall or in periods of not too heavy rain. Its flight is generally weak and fluttering, although not as much as that of the African rail. Over long distances, such as during a migration, it is capable of a more powerful and resistant flight, during which it keeps its legs raised. It walks by raising its legs a lot, and can run quickly through the grass while keeping its body flattened laterally and horizontally. On occasion, it is also capable of swimming. When flushed out by a dog, it can make a short flight of less than 50 m, landing mostly behind a bush or thicket, and then curls up on the ground. If disturbed in an open area, it may run a short distance, with its body lowered and its neck facing forward, and then stop to look at its pursuer. When captured, it can play dead, then jump back up if it sees a way out.
In the wintering grounds it is solitary, and each specimen occupies a territory of 4.2-4.9 ha, although the exact total extension is rather doubtful, since these birds can move following floods or haymaking or to follow the plant growth. During migrations, flocks of up to 40 animals can form, sometimes associated with quail. Migrations take place at night, and in the best sites where the flocks rest during the day, several hundred specimens can gather. The ability to migrate is innate and is not learned by adults; chicks raised from birds raised in captivity for ten generations were able to migrate to Africa and return to their starting point just like young ones raised in the wild.
As regards nutrition, it is an omnivorous species, but feeds mainly on invertebrates, such as earthworms, slugs and snails, spiders, beetles, dragonflies, grasshoppers and other insects. In the nesting areas, it also devours harmful species such as weevils of the Sitona genus, which damage legume crops, tipules and Elateridae, which in the past were a real scourge for grassy expanses. Sometimes it also catches frogs and small mammals, while as vegetable substances it mainly consumes seeds of herbaceous plants and cereal grains. In the wintering grounds the diet is almost similar, but also includes typical local prey, such as termites, cockroaches and dung beetles. The preys are captured on the ground, between low plants and large tufts of grass; the bird may dig through leaf litter with its beak, or run in pursuit of more active prey. Generally it searches for prey in the thick vegetation, but, especially in the wintering areas, it can also hunt on grassy paths or dirt roads. Indigestible substances are regurgitated in the form of 1 cm wide wads. The chicks feed primarily on animal matter, and when fully developed they can fly with their parents up to 6.4 km away from the nest to visit additional foraging areas. Like other rails, this species ingests small pebbles to aid digestion.
Among its predators we remember the white stork which can kill chicks left exposed by early mowing.
Predators at its nesting sites include wild and domestic cats, American mink (introduced by humans), wild ferrets, otters, red foxes and various birds, such as buzzards and hooded crows. In Lithuania, the raccoon dog, introduced there by man, also hunts this bird.
In undisturbed sites, nests and nestlings are rarely attacked, as demonstrated by the greater reproductive success found in such areas. Once, during migration, a specimen was attacked and killed by a black goshawk.
Among the parasites that attack Crex crex we remember the widespread trematode Prosthogonimus ovatus (which lives in the oviducts of birds), the parasitic worm Plagiorchis elegans, the larvae of parasitic flies and the ticks of the Haemaphysalis and Ixodes genera.
The conservation status of this bird is significantly influenced by human activities.
The transition from traditional to mechanized haymaking techniques has caused serious damage to the European population of this species.
Until 2010, despite occupying a breeding area covering 12,400,000 km², the Crex crex was classified, on the IUCN Red List, among the «nearly threatened species», due to the decrease in the European population, but a monitoring carried out in Russia and Kazakhstan showed that in this area the number of specimens had remained stable or even increased. Currently, therefore, it is classified as a “species of minimal risk”, since the largest populations, those of Russia and Kazakhstan, do not appear to be threatened at all. The population of this bird is estimated in Europe at 1.3-2 million breeding pairs, three-quarters of which in European Russia alone, to which another 515,000-1,240,000 pairs present in Asian Russia must be added; the total population is estimated at 5.45-9.72 million specimens. In much of the western region of the breeding range, numbers have declined significantly, and the decline continues today, although conservation programs have enabled their recovery in some countries, such as Finland, where the population has increased fivefold , and in the United Kingdom, where it doubled. In the Netherlands, in 1996, there were 33 nesting sites, which had risen to at least 500 by 1998.
The breeding population began to decline in the 19th century, but this process particularly intensified after World War II. In much of Europe the main cause of this decline has been the loss of nests and chicks due to early hay mowing. In the last century the haymaking period has been brought forward more and more, due to the development of faster growing crops, made possible by land reclamation and the use of fertilizers, as well as by the replacement of traditional harvesting methods with scythes with the use of mechanical mowers, first pulled by horses, then by tractors. Mechanization has also made it possible to operate more quickly over large areas, such that couples who lose their first clutch are unable to find an alternative site to lay a second. Even the main technique with which haymaking is carried out, in a circular manner from the outside of the field towards the centre, offers little possibility of escape for the chicks, who thus remain exposed to attack by potential predators. Adults are able to escape from mowers, but during brooding some females do not leave the nest, with fatal results.
Another threat factor for this bird is habitat destruction, since reclaimed fields treated with chemical fertilizers are less suitable for nesting than traditional hay fields. In Western Europe, the conversion of grasslands into agricultural land was facilitated by state subsidies, while in Eastern Europe the collapse of collective agriculture led to the abandonment of agricultural land, in an area considered important for the breeding of the species. Other more localized threats include spring flooding and disturbance from roads or wind farms.
The meat of this bird is good to eat and, especially in the past, it was hunted for this reason,
A more significant impact than direct hunting is the indirect capture of many specimens, up to 14,000 per year, in Egypt, where migratory specimens remain trapped in nets positioned for quails, with whom they are often in company during migration. Although 0.5-2.7% of the European population is lost with this type of hunting, the losses recorded are lower than when the species being hunted were more numerous and predictable.
Most European countries have taken steps to ensure the survival of Crex crex and improve the management of natural resources; a specific action plan is also at work in which countries from all over Europe are collaborating. The objective of conservation programs is to monitor populations and their ecology and guarantee their survival, especially through the variation of hay harvesting periods and the techniques with which it is practiced. Haymaking carried out later allows the species to nest peacefully, while leaving undisturbed strips of hay at the edges of the fields and cutting from the center outwards reduces the risk of mortality. Population decline will stop if such measures are applied on a large enough scale. Even the reduction in illegal killing and the implementation of efficient protection measures in countries where hunting is still permitted could do a lot to benefit the species. Reintroduction programs have been carried out in England, and in many other countries nesting sites are carefully monitored. Where nesting sites impact urban areas, there are cost implications, estimated in a study in Germany at several million euros per individual. In the wintering sites, however, it is not at all threatened, on the contrary, it can benefit from deforestation processes, which create more open habitats.

Guido Bissanti

Sources
– Wikipedia, the free encyclopedia.
– GBIF, the Global Biodiversity Information Facility.
– C.Battisti, D. Taffon, F. Giucca, 2008. Atlas of nesting birds, Gangemi Editore, Rome.
– L. Svensson, K.Mullarney, D. Zetterstrom, 1999. Guide to the Birds of Europe, North Africa and the Near East, Harper Collins Publisher, United Kingdom.

Photo source:
– https://inaturalist-open-data.s3.amazonaws.com/photos/291238509/original.jpg