Bird "hybrids" are rare enough, but how come there are also hermaphroditic birds?

Many readers know that many caged hibiscus bird lovers often breed some hibiscus bird hybrids, among which they often use male siskins or red-fronted goldwings to mate with female hibiscus birds. If the father is a siskin, the offspring will be dull grass green; if the father is a red-fronted goldwing, the offspring's feathers are often mottled, and the obvious red spots are the red of the red-fronted goldwings. On the yellow background of the hibiscus bird, the previous colored spots are not obvious, probably because the female hibiscus bird is not a wild gray-green type, but is likely to be a pure yellow. The hybrids of these birds are rarely female, and most of them will not have mature sexual organs. But if the hibiscus bird is crossed with the similar canary, fertile offspring can be obtained.

Generally, there is a rule that only hybrids of birds that are closely related can produce hybrids whose sexual organs can mature and who are capable of reproduction. However, the offspring of birds whose parents are more distantly related cannot mature sexually and cannot reproduce.

People have also done similar hybridization experiments with pheasants. For example, when the Mongolian subspecies and the Chinese subspecies of the ring-necked pheasant are hybridized, the differences between them are not big, and the hybrid offspring can reproduce. The same is true for the offspring of the two golden pheasants, the red-bellied pheasant and the white-bellied pheasant, and various pheasants, such as the famous white pheasant and black pheasant. If people mate the duck genus with the black duck genus, the offspring can mature sexually. The offspring of the mallard and the pintail duck, and the offspring of the mallard and the spot-billed duck, can also mature sexually. Surprisingly, the spoonbill and the egret are obviously very different in classification status, but the hybrid offspring can mature sexually. If this offspring is backcrossed with the original parents, it can form a spoonbill with 3/4 bloodline that looks very much like an egret.

By mating a male golden pheasant with a common pheasant, you can also get a golden pheasant-pheasant hybrid (when naming a hybrid, the male bird is written first), but their hybrids have all proven to be sexually immature. Crossing a male peacock or a male domestic chicken with a female guinea fowl, or doing the opposite sexual cross, has also been successful. But as we all know, these offspring will not be sexually mature either, because they do not have well-developed gonads, and the feathers of these animals are not bright. People hope to cultivate such a hybrid, that is, to pass on the characteristics of the parents to the hybrid, such as the gorgeous feathers of peacocks and the beautiful spots of guinea fowls; similarly, by crossing a male mallard with bright feathers with a painted duck, or vice versa, you can get the base color of the beautiful male duck and the brilliant colors of both, as well as the shiny chocolate feathers. Of course, these offspring will not be sexually mature, because the classification and blood relationship of mallards and painted ducks are quite different.

Many birds will develop a love relationship if they live together in cages for a long time, such as the colorful mountain parrots in Australia and the blue waterfowl of the rails, which can mate after a long time. In this example, the blue color in the feathers may have played a stimulating role. Another example is that a steamboat duck in South America and a knob duck in Africa fell in love, and they are inseparable, which makes it difficult to explain. Obviously, the eggs produced by this combination cannot continue to develop and cannot produce the next generation. There have been many examples of hybridization of different species of birds in the Shanghai Zoo in my country, but unfortunately some were unsuccessful, and some offspring were only one, and it was never known whether they were sexually mature. Interspecies marriage is even more common.

In the taxonomic relationship, the hybrids formed by the hybridization of species that are very different are mainly males. It may be that male fertilized eggs are easy to develop, while female fertilized eggs are very easy to die. Or it may be because only eggs that can hatch males are produced. The examples mentioned above were all observed in zoos or by bird breeders, but these facts just prove that birds are easier to achieve the purpose of hybridization than mammals. The mating of the latter is probably due to the great role of smell; for those birds that are particularly in love and have a long-term pairing, the acquaintance between individuals is more important than that of most mammals. Male mammals do not have the task and responsibility of raising young.

It can be said that birds that are easy to mate with each other and whose hybrid offspring can reach sexual maturity are closely related species in the classification system. They have common ancestors and may have differentiated and evolved into different species only due to geographical isolation. On the contrary, if distantly related birds are raised in cages and interspecies hybridization is carried out, even if they can mate and lay eggs, the hybrid birds hatched will not reach sexual maturity. However, there are some exceptions, such as the spoonbills and egrets mentioned above, which can mate and reproduce.

In nature, the hybrids of slender-billed grouse and black grouse can be seen, and the offspring are also infertile. A bird lover in Sweden once hybridized a male grouse with a female grouse to obtain a hybrid rooster. This hybrid rooster was mated with a three-year-old female black grouse to obtain four eggs. Later, four chicks were hatched from these four eggs, two of which died immediately after hatching, and the other pair died of poisoning from intestinal anthelmintics at 55 days old. The female mandarin ducks in the Far East are very similar to the female painted ducks in North America. They both nest in tree holes and have similar development. The males of both also have gorgeous feather colors. We can regard them as the same species due to geographical isolation, and they are truly distantly related to other birds of the Anatidae family. People put mandarin ducks and painted ducks in a large cage at the same time and let them live together for a long time. In this way, you can often see the pairing of painted ducks and mandarin ducks or mandarin ducks and painted ducks. They are very affectionate to each other. After mating, they look for a nesting place together, and the female lays enough eggs in the tree hole. Judging from their behavior, people do not need to keep them together. Painted ducks and mandarin ducks can keep friendly relationships. Unfortunately, the hybridized painted duck eggs or mandarin duck eggs cannot develop, which has been confirmed in many experiments. People mate painted ducks of either sex with distantly related red-necked ducks, mallards, Bahamian ducks, and red-headed pochards. The eggs obtained can hatch ducklings, but their sexuality is always immature. Mandarin ducks are different. People can easily mate them with small domestic ducks and other ducks, but it is not easy to get offspring. In other words, although mandarin ducks can mate repeatedly with various ducks, only male mandarin ducks and female domestic ducks can mate to produce eggs. As a result, a new artificial duck breed is obtained, but this duck cannot mature sexually. The reason why the offspring obtained from the hybridization of mandarin ducks and other ducks cannot mature sexually is because the number of chromosomes and the pairing of the genetic material of the hybrid are abnormal. The various species of ducks and wild chickens are very similar to each other, and they can easily form hybrid chickens or hybrid ducks.

Among birds and insects, there are also animals that are half-hermaphroditic, that is, they have both male and female reproductive glands. Songbirds or woodpeckers, which originally have different appearances for each sex, also have individuals with half of their bodies in male color and half in female color. This feature is sometimes very obvious. An ornithologist once examined a hermaphroditic individual of a yellow siskin and found that this little bird was sometimes male and sometimes female. When it jumped back and forth in a cage, it could be seen that one side of its chest was red and the other side was light green with brown flashes. It is amazing that this hermaphroditic bird with half of its left and half of its feathers, that is, half of the color of the male bird and the other half of the female bird, is also rare in other birds. Only one person with this feature can be found in about one million wild ducks, pheasants or chickens. It has been observed that hermaphroditic birds often have female colors on their left side, and it is indeed found that the left ovary of this bird is still retained. If the left ovary or right testicle is removed, the individual may also have the opposite situation, that is, the left side is covered with male feathers, and the right side is covered with dull female feathers.

(Xu Xinjie, Vice President of Henan Zoological Society, Senior Engineer)