by Marina KOLOTOVA, laboratory researcher, the Oka State Preserve of the Biosphere, Russian Federation
This place is a habitat of cranes. Here and there you can hear the whoops of these majestic, royal birds. Their voices have silvery overtones to them, sad and solemn at the same time. A marriage song whereby the crane asserts its right to live among other creatures. This graceful bird inspires artists and story-tellers. In some African countries it is still pictured on sundry emblems as a symbol of victory. From time out of mind human beings have revered cranes and admired their exquisite dances and plumage. These wonderful birds, alas, are dying out. Hence the saying: to go the way of the whooping crane. To save cranes from extinction, a bird sanctuary was set up at the Oka nature preserve in March 1979. Here in Russia we have these crane species, seven in all: the white, common and black cranes; the Canadian crane; the white-naped crane; the Japanese and the demoiselle crane.
These species are found in many parts of Russia. For instance, the white crane (Grus Leucogeranus) inhabits the taiga wilderness in Siberia's northeast, a land rich in lakes, swamps and cedar forests. This bird is about four to five feet tall. It nests in Yakutia's north and in the lower reaches of the Ob (Tyumen Region). One population of the white crane hibernates in China, and the other - in India and in Northern Iran.
Another species, the white-naped crane (Grus vipio) used to live in the Trans-Baikal and Amur territories, as well as in the lowlands next to Lake Khanka in the Primorye (Maritime) Territory. Today it occurs only in the south of the Trans-Baikal territory along the river Agutsa (Chita Region), in the Khingan nature preserve (southeast of the Amur Region) and in the northeastern districts of Mongolia and China. It nests in the marsh - and wetlands along river valleys and lakes, amidst birch and aspen forests found here and there. For wintertime this bird migrates to Korea and Japan. Adult cranes are about four and a half feet tall, and weigh 5.6 to 7.2 kg (11-15 pounds).
What concerns the black crane (Grus niger), its habitats are spotty. It mates in Yakutia and in the Amur Region, and hibernates in Japan. These birds are considered small, slightly above three feet and weighing 3.2-4.8 kg (6 to 9 pounds). They build their nests in dwarf-birch and larch copses about 50 to 100 meters from open moss bogs.
Yet another species, the Japanese crane (Grusjaponensis), lives along the middle and lower reaches of the Amur, in the lowlands off Lake Khanka and on the Kunashir island (Kuriles). It nests in wet- and boglands overgrown with sedge and related plants. This bird winters in Korea and perhaps in China. This is the largest among the cranes, over five feet tall and weighing 20 to 24 pounds.
The smallest species is represented by the demoiselle crane (Anthropoides virgo), just a little over three feet tall, and five to seven pounds in weight. Compared with the above species, it is less choosy and accommodates to rather diverse landscapes. Its population is rather large; in the past it inhabited the entire zone of southern steppes and some of the semi-deserts from the Black Sea in the west to the Trans-Baikal territory in the east. Today the demoiselle crane is found only in small habitats north of the Sea of Azov, in the Crimea, north of the Caucasus, in lowlands north of the Caspian Sea and in Kazakhstan. In winter it flies south as far as Africa, India, Burma and China. These cranes reach puberty in their third year and build nest in open places with sparse vegetation, not far from bodies of water.
Next, the common crane (Grus grus), also known as the gray crane. Today we can find it in Western Europe (in Scandinavia for the most part) and in taiga forests in Russia's north. Few, if any, cranes of this kind now occur in Russia's southwest. It is a rather large bird (four feet in height and about 9 pounds in weight). Its population winters in Turkey, Iran, Iraq, on the Arabian Peninsula, in Egypt, India and China. The common crane will always nest in marsh- and wetlands, be it moss- overgrown swamps or flood-lands and water-meadows.
The hilly terrain of the bushy tundra on the Chukot Peninsula is the haunt of the Canadian crane (about 3.5 feet tall and weighing from 8 to 10 pounds). The bulk of its population is found in Canada and the United States. The
Canadian crane hibernates on the coast of the Gulf of Mexico. Its nesting landscapes are varied; but the presence of bogs, rivers or well-drained intermontane lowlands is a must.
So much for the crane species. The threatened species, unfortunately. The threat is real: half of the crane populations are entered in the Red Data Book; these are the Asiatic white crane, the Japanese, the white-naped and the black crane. Years ago, the demoiselle crane was entered in the USSR Red Data Book. Although the common (gray) cranes are not in it yet, their population is shrinking.
This disastrous situation is related to the inability of cranes to adjust to the human environment and its inevitable aftereffects, such as pollution, poaching, the draining of water bodies, feed scarcities and the like. The worst menace comes from land improvement projects when boggy land tracts are drained and plowed up for farming uses. Add to this pesticides, cattle in pasturelands, and irrigation schemes upsetting the hydrological regime. All that causes the crane nesting grounds to contract. To rear progeny, he-and she-crane need a good nesting ground, sometimes a few square kilometers large. The mates will defend their territory against encroachments from other cranes. Should such territories shrink, some of the cranes will be unable to rear offspring.
The crane is a very cautious and shy bird. If disturbed, it will leave the nest with eggs in it; the eggs will be exposed to cold or else become an easy prey to vultures.
True, if worst comes to worst and the eggs are gone, a she-crane is capable of another laying. But hatching takes a whole month. And it takes all of the warm season to raise fledgelings and make them strong enough for a long flight to warmer latitudes before the onset of winter. That is why another egg laying will not keep the population from decreasing.
Besides, it takes a rather long time for a female crane to reach puberty-three, four and sometimes even five or six years. Her fertility rate is low, she lays but two eggs in a season; one of them is often not fertilized. Even if both eggs hatch, only one nestling survives at best.
Raising the brood is no easy job. First, both eggs do not hatch simultaneously, but two days apart.
The nestlings of some crane species are very aggressive toward each other-the older one takes advantage of the younger and robs it of food.
The brood of the Asiatic white and of the common crane are particularly vicious: from the very first hours of their life the little things start harassing each other. Kids of the white crane are most cruel in their first two or three weeks. But with the common crane fledgelings this tough period taking only a few days, from 30 to 50 percent of the family couples manage to rear two fledgelings.
The more the callow birdies depend on their parents, the more aggressive they are in their ways, and vice versa. The point is that in the first two and three weeks they are unable to get their food by themselves. As a matter of fact, adult cranes feed on small animals,
insects, fish, amphibians and rodents when they can get ones. Otherwise they are vegetarians hunting for every sort of seeds, tubers, corms and grain left in the fields after harvesting. But little cranes need animal protein to grow up and take to the air for a long journey south. Since some nesting territories are poor in animal feed, adult cranes are unable to supply a sufficient amount of it to their offspring. This may explain the bitter rivalry among the callow fledgelings. If one of the two dies, the other will get the benefit of extra feed to grow strong and sturdy. So, the sooner one of the two dies, the better it will be for the other.
Hence their aggressive behavior, which appears to be of evolutionary origin. You may ask: why do then cranes (white cranes in particular) lay two eggs? One will be well enough... But they have to - what if one egg is barren? So another one is needed for the species to survive.
Many bird experts have described the aggressive ways of white crane nestlings. But man tends to underrate the abilities of this cute bird. One of our ornithologists, I. Dyachkovsky, has observed two fledgelings reared in a white crane family. The survival chances of both depend on the wits of their parents. Some couples rear their progeny apart from each other. As soon as the first nestling hatches, one of the parents takes it away from the nest, while the other keeps brooding the other egg. The little ones are raised apart until their aggressive period is over, and the family is reunited then.
All things considered, we have set up a bird sanctuary cum nursery at the Oka nature preserve. Our aim is to save the crane from extinction and conserve its gene pool. We also aim to study the biology of rare crane species and develop methods for their upkeep in open-air cages and pens. Our crane sanctuary is part of the Russian-American program to rehabilitate the outgoing endemic species in Russia, the Asiatic white crane. Some of the cranes bred on the sanctuary's grounds are set free to join their kin flock in Western Siberia.
It is very important to get cranes to mate and breed in pens and open-air cages. Unfortunately, for a long time we in this country did not attach due attention to this matter. Even though by January 1, 1979, the Soviet Union's thirty zoos had 177 cranes of seven species, only a few egg-laying cases were reported, and those were unfertilized eggs. Only as late as 1983 and 1984 the Novosibirsk and Moscow zoos obtained a brood of white-naped, Indian and demoiselle cranes. So breeding cranes in sanctuaries was an altogether new job to us at the Oka preserve. Our experiments have enabled us to check on many notions, for one, that cranes reared by man do not pair and mate in captivity. But this is wrong, and now we know it: our people have raised two Canadian cranes and one Japanese (male) right from their birth; growing up, they have paired into quite worthy couples.
Being monogamous, cranes stay in wedlock for the rest of their life. Legend has it: should one of the partners die, the other would remain single until death. But this is an overstatement. According to our observations, the survivor will marry again, though not at once.
We in our sanctuary can raise far more crane nurslings from a crane couple than it occurs under natural conditions. Our ornithologists capitalize on the ability of cranes to lay eggs for a second time in a breeding season. All eggs-except those laid anew-are placed into a hatchery. The second lay is entrusted to parents only if they have shown exemplary behavior in hatching. This way we manage to obtain from 10 to 15 eggs from each couple in one breeding season. Even if some eggs happen to be barren or damaged, we manage to rear a brood of 5 to 7 at least.
Something else just as important: cranes reach their pubescence earlier in captivity (given good upkeep, of course). For instance, a couple of Canadian cranes produced offspring at age two (instead three or four); a Japanese crane male was virile enough as progenitor at three years (instead of three to four in a natural environment). And it took a white crane male 4 years (instead of 5 to 6) to become able to father progeny.
We must clarify a lot of things to have cranes mate and breed in captivity. For instance, the matter of food, and concentration of vitamins and mineral substances in it. We should know what kind of feed is good for adult cranes, and what is good for nestlings. We had to find out optimal incubation regimes in hatcheries (temperature and humidity, egg-turning frequency). Upkeep and maintenance conditions had to be optimized as well. We coped with this job somehow, and obtained a brood from the first couple of Canadian cranes already in the second year of our sanctuary.
The Canadian crane gave us a welcome opportunity for devising maintenance and breeding techniques. In 1981 they produced nine eggs, with only three fertilized. It looked like a poor result to us. Probably it came in consequence of artificial insemination we tried on the female of this couple. The fertilization rate of this technique- artificial insemination-is rather low; but it is often indispensable in a sanctuary for lack of "love mates".
In 1982 our experts picked a pair of black cranes which do not mate in captivity. Well, this couple hit it off, and in a few months the she-crane laid an egg which we decided to leave with the parents-we were not sure about our incubation regime yet. But the mother happened to be rather awkward: trying to move the egg elsewhere, she broke it.
In 1981 to 1985 one black crane couple hatched a brood of seven; and we reared all of the seven fledgelings. In the same period of time we raised three Canadian and two Japanese cranes, that is twelve birds in all.
All of the seven crane species living in Russia have produced progeny in our sanctuary. We've unlocked some of the mysteries of these royal fowls of the air.
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