Abstract
Chestnut-Breasted Manni.kins (Lonchura castaneothorax) are a rare Australian finch whose numbers in this country must be increased if they are to remain available to American avicultu rists. In Finches and Soft-billed Birds, Bates and Busenbark call the species "one of the most beautiful of all mannikins."
Amelia "Micky" Mohr and I bought two "pair" from an import station in the early fall of 1976, and to our disappointment received three males and one hen. We decided to cross the two extra males to society hens. Perhaps, we reasoned, the hybrid offspring could be bred back to the pure stock to produce, after several generations of line breeding, birds identical to the pure male parents and useful in increasing our stock of this rare and expensive finch.
We expected the birds to cross readily. In Australian Finches, Klaus Immelmann lists nine different species that had hybridized with Chestnut-Breasteds, including not only Society Finches but Silverbills, Shaftails, and even Zebra Finches. With rarer Australian finches the hens often seem to be the main impediment to nesting activities, and as we had expected, the more domesticated Society hens produced young when paired with the Chestnut-Breasted cocks before our pair of pure birds had shown any inclination to nest.
We did not know whether the hybrid offspring would be fertile and therefore useful in further breeding experiments. Officers of the National Bengalese Fanciers Association, in the United Kingdom, could not predict whether or not the hybrids would be fertile, and asked that we inform them of our findings. A March, 1969 article in Australian A viculture praised the beauty of the offspring of such a cross but reported that only he males would be fertile.
We had paired the pure cocks with nearly self fawn Society hens. The hybrids emerged from nests looking much like chocolate self societies, with the exception that the chest was cream colored and the brown slightly Lighter than chocolate. After their first moult the hybrid young looked much like the pure parents, with several important exceptions: the barrings on the flanks were broken and thus less distinct than in the pure birds: likewise, the bold dark chest band of the Chestnut-breasted cocks was less distinct in the hybrids. Finally, the dark brown-black on the face of pure birds never appeared, the heads of the hybrids being uniformly middlebrown, and the gold on the pure birds' rumps never appeared on the hybrids.
Our first generation crosses are now only about five months old, however, and according to one written account, mannikin hybrids may continue to change in coloration somewhat during their first year.
When the first generation hybrids were about three months old we paired male hybrids to nearly self fawn Society hens and hybrid hens to their pure ChestnutBreasted parents. For the most part, offspring of the former pairing resemble fawn societies. Some were selfs, others had varying degrees of white on the head and body. These second-generation crosses to Societies are now in their first moult and are replacing some of the fawn feathers on the upper chest with the richer brown of the pure grandparent. But it is obvious they will not approach the dramatic pattern of the Chestnut-Breasted lineage. Still, we had verified that the cock hybrids are fertile.
The hybrid hens were more reluctant to breed, though this is not surprising considering their youthfulness. To date, one hen - paired to a pure cock has laid, and the eggs were fertile. We have therefore demonstrated fertility in the hybrid hens, as well, and added some small bit to the published avicultural data we were able to locate.
Unfortunately, the young from the hybrid hen X Chestnut-Breasted cock pairing died in the nest at about two weeks of age. Circumstances had forced rearragemen t of the aviary housing the pair in question and this disrupted further nesting activities, so at this point we do not know how closely the second-generation hybrids paired to pure mates will resemble the pure birds. Our experiment continues.
Our hope is that the young from a cross between a hybrid and a pure bird would be identical to the pure stock, and that after one more generation of crossing those offspring to pure stock the results could be considered suitably "pure" for inclusion in our breeding stock of Chestnut-Breasted Mannikins. If so, they will play an important part in making this seldom available Australian finch established in our aviaries.
Above all, our experiment has been for the sake of knowledge, and we do not yet profess to have answered all our questions. Will the Chestnut-Breasted hybridize with Societies? It is no surprise that the answer is yes. Will the hybrids be fertile? It is new information that the hybrids of both sexes are demonstrably fertile.
Can the hybrids be used to enlarge the breeding stock of pure birds?
This remains unanswered. We would appreciate information from anyone who has pursued this hybrid, or who has an understanding of genetics which would permit them to project how much breeding-back to pure stock is necessary before offspring could be added to our established and "pure" breeding stock.
The pure pair nested in a small aviary, seven by three feet by six feet high. The pure cocks and first generation hybrid cocks nested with societies in small breeding cages. The hybrid hens did not lay in cages but began to lay when placed in the aviary.