Text by Graham Bull, photos by Graham Bull and Simon Degenhard.
One can hardly wax lyrical on the spectacular visual brilliance of our subject when the species has the dubious honour of being the least colourful of all the Australian native finches. Despite this unavoidable fact, the Yellow-rumped Munia remains a highly desirable aviary subject. Personally, I regard a mixed finch collection as an overall more attractive spectacle when the more colourful species are mixed with some of the less spectacular earthy-coloured species. Having said this, I do regard its bright straw-yellow rump and upper-tail area starkly contrasting with its dark brown wings, under-tail and vent as a particularly attractive feature. When viewed in its ideal preferred habitat of dense tall grass plantings, I regard the sight of adult Yellow-rumps feeding on the growing grass seed heads as attractive a sight in a finch aviary as any other species. On an aviary tour during the 2011 QFS Finch Convention those present visited some very impressive collections containing many beautiful exotic finch species. Despite the veritable smorgasbord of rare and attractive finches seen on this day, the highlight of the aviary tour for me was the sight of a family of Yellow-rumps climbing through and feeding on the green seed heads of a large clump of palm grass growing in an attractive planted aviary.
The physiology of the Yellow-rump indicates a strong affiliation with dense seeding grasses as the key element of both habitat and diet. Disproportionately large feet and legs equip them well for adeptly climbing among grass stems, in which their equally oversized bills are the perfect tool for picking the seeds from seeding heads of the grasses.
The Yellow-rumped Munia is the least common Australian member of the Lonchura genus (Munias and Mannikins). It is very closely related to the Chestnut-breasted Munia Lonchura castaneothorax, it’s more common and widespread relative. Where the natural range of the two species intersects, the two species often form mixed species feeding, socialising and breeding flocks. Within these wild mixed flocks, hybrids have been frequently observed. The Yellow-rump will venture further inland compared to the Chestnut-breasted, which indicates a slightly better adaptation to drier habitat. In all of its range, the distinct preference is for areas dominated by dense stands of tall grasses, which are especially prevalent where the grassy habitat adjoins watercourses or swamps. They have also adapted well to the irrigated areas of the Ord River irrigation area especially where rice and other crops are cultivated. They also have population strongholds in the Daly and upper Roper River areas. Their natural range covers quite a large area from the west Kimberley through to western Arnhem Land in NT and the size of this range gives the impression that they must have a vast wild population, but this is not the case as they are seasonally nomadic within this area and rarely common outside of the few key habitat areas.
During the period in which legal trapping of wild finches was permitted in the Kimberley region of WA, hundreds of thousands of wild finches were trapped and sold into the Australian avicultural market. Despite legal trapping of other finch species being permitted until 1986, the Yellow-rumped Munia was excluded from legal trapping in 1976 by the WA government when it was found that the species was unable to withstand this exploitation of its wild population. I have seen a breakdown of numbers of wild-caught finches from the Kimberley region between 1974 and 1985 and Yellow-rump numbers trapped were just over one hundred birds compared to tens of thousands for most other trapped finch species for this period. Much trapping took place for a long time before this period as well, for which the numbers caught are not available as the trade was previously unregulated, but the total number of birds taken from the wild would definitely be considerable.
The captive status of the Yellow-rump in Australian aviaries has never been common. It is an uncommon species in captivity in most other countries as well. My very first recollections of them were in the aviaries of one of my uncle’s in the early 1970s from whom my Dad obtained a “pair”. The virtual impossibility of visually sexing uncoloured young of such a sexually monomorphic species resulted in the general rule of the time, “two’s a pair”. Dad’s two birds did breed once they eventually matured so he did fluke a pair. Indeed, the difficulty of visually identifying the sexes and the relatively long time young birds take to attain adult plumage have both contributed to diminishing the species’ popularity among finch breeders. The recent advent of DNA feather sexing technology has taken much of the guesswork out of sexing Yellow-rumps (and other monomorphic species) in a relatively non-intrusive and cost-effective way. I still prefer to let my young birds mature in holding aviaries, and then back my ability to observe physical and behavioural differences between individual birds to determine the pairs I keep for myself. This way I can also identify pairs that show obvious signs of pair bonding, as I regard compatibility as a crucially important but often overlooked component of very productive breeding pairs in any species.
Physical features that I compare when determining the sex of fully coloured, sexually mature Yellow-rumps are the head colour, bill shape, bill size and the width of the head. These physical differences are not significant, so an eye for detail is required as is the need to look for a combination of more than one of these slight differences to be confident in your sexing decisions or educated guesses. I find it essential to closely examine each bird which can only be done confidently when the bird is held in the hand. Male head colour is generally paler especially closer to the bill and around the eyes. Hens tend to be darker on the head, which is especially noticeable along the top of the head when viewed from above. Whilst viewing the bird(s) from above the head, males will have a wider head (especially noticed when comparing the distance from eye to eye) and a wider bill where it joins the skull. When viewed side on, male’s bills are deeper (higher from top to bottom), this is especially noticeable on the lower mandible at its base, and have a slightly more exaggerated convex curve over the top of the upper mandible. When viewed from under the bill, the width of the bill should again be apparent with males tending toward a rounded curve where the throat feathers adjoin the lower mandible, whereas females tend to have a narrower “v” shape here. If when comparing two birds with one in each hand, you can identify differences in all these areas, you can be confident of having a pair. Observing behaviour in a cage or aviary containing a group of birds with different coloured leg rings will reveal the males if they crow in your presence. Crowing males look like they are simultaneously choking, receiving an electric shock, and dancing. They stand upright with belly and crown feathers erect, bill wide open and let out a strange assortment of clucking and creaking noises, which is their excuse for song. If another bird shows any interest in the song, they may also dance (just bob up and down really).
As with other plain coloured species, especially those in the Lonchura genus, the Yellow-rump’s captive status experiences pronounced cycles varying from critically low numbers to enhanced interest by more finch breeders, but generally only as they realise their conspicuous absence from finch collections. The “Lonchura cycle”, as I call it, is a consequence of the at times fickle whim of bird breeders, which results in this predictable cycle in the market for less vibrantly plumaged finch species. These cycles of popularity pose an enormous threat to the future existence of viable captive breeding populations of all species so affected and have already been the vehicle for the captive extinctions from Australian aviculture of the Bronze-winged Mannikin Lonchura fringilloides and the Indian Silverbill Lonchura malacca. The Rufous-backed Mannikin Lonchura bicolor nigriceps is currently showing the daunting signs of acute genetic stress as a result of its tenuous ride through its most recent thin end of the Lonchura cycle. At the bottom end of each cycle, total bird numbers can become extremely low. The risk is that in these troughs the total population numbers and genetic variability can fall below the critical level required for the species to be sufficiently genetically viable to be bred up again if (and only if) breeders recognise their low numbers in time to undertake remedial breeding efforts again. Yellow-rumps are by far the most vulnerable of our native finch species to these cyclical fads of aviculturists. What the species requires to secure its ongoing future in aviculture is at least a handful of capable finch breeders to stick with them through the thick and thin fluctuations in market demand over time. I encourage all finch breeders with reasonable sized collections to breed at least one native and one exotic Munia or Mannikin species.
In recent times, a number of finch clubs have nominated some species of concern, which their members have undertaken to concentrate efforts to breed up in an attempt to maintain their captive status into the future. The challenge with these efforts is to maintain active and ongoing interest well beyond the initial “that’s a good idea” stage. Of these efforts, the Queensland Finch Society has developed a very effective and proven model for rehabilitating numbers of their chosen species for conservation breeding and they are to be congratulated for this. This scheme involves direct ownership of the program by the society where they buy the birds and distribute two pairs each of the target species to volunteer breeders who agree to pass back to the program the first six young bred each year. Each species has a co-ordinator who liaises with volunteer breeders and co-ordinates young birds bred for further volunteers, and so the breeder base for the target species grows. They have achieved resounding success with the African Silverbill Lonchura cantans thanks primarily to the outstanding coordination efforts of the species coordinator, Gary Fitt, and the network of volunteer breeders who have allocated space in their breeding aviaries for just a couple of pairs each of Silverbills. In a relatively short period this network of breeders has bred up hundreds of African Silverbills and the number of volunteer breeders continues to grow. Inspired by this success, I put my hand up to be a volunteer breeder for the QFS scheme for the Javan Munia Lonchura leucogastroides. The relevance of these programs to the aviculture of the Yellow-rumped Munia in Australia is to me very clear, as they are by far the most vulnerable of our native finch species to the toxic effect of the Lonchura cycle. You simply could not get a more prime example of a native finch species requiring the ongoing attention of a finch society or club for committed conservation breeding. The probable reason they fail to get a Jersey in the conservation concern shortlists of most clubs is the exact same reason they are vulnerable – their lack of vibrant colour resulting in members preferring to concentrate their conservation breeding efforts on more “worthy” (and coincidently more colourful) species.
The physiological features of Yellow-rumps and their wild habitat preferences already indicated, point to the ideal captive environment for the species. A well vegetated aviary with a definite bias toward dense stands of perennial seeding grasses is sheer paradise for any captive Yellow-rumps. Whilst not at all essential for good health or breeding success, such a grassy planted aviary provides the perfect environmental enrichment for this bird. If the grasses are few and the bird numbers high in your Yellow-rump aviary, they will soon strip it bare. Dense planting of well-established grasses is recommended before releasing your Yellow-rumped pair(s) into the enclosure. A single pair per aviary with independent young removed to a holding aviary or other unplanted enclosure is ideal for prolonged breeding if aviary plants are to be preserved. If colony breeding is to be attempted, I recommend keeping breeding pair numbers to a minimum and initially housing them all together in a holding aviary. Build up your birds’ eagerness with an abundance of green food for a period until the grasses in the proposed breeding aviary are absolutely peaking with vigour and seed heads. Then introduce your colony to the planted aviary for a flurry of breeding for just two rounds and then catch up all the birds, young and old, to allow the grasses to recover and the birds to have a couple of months rest from breeding, then let them loose for another two rounds, etc. Most Yellow-rump colonies will eventually get on top of and eventually denude even the largest and most densely grassed of planted aviaries if housed in there permanently, such is their propensity to chomp on anything green.
Large perennial grass plants provide a much preferred nest site for Yellow-rump pairs. When they nest in grasses, they skilfully incorporate the growing grass into the outer shell of the enclosed nest structure. They will also readily nest in dense brush whenever suitable grasses are not available.
The Yellow-rump’s dietary requirements, not surprisingly, feature prominently half-ripe grass seed heads as a key breeding stimulant and rearing food. A regular offering of seed heads of any grasses will always be eagerly devoured by Yellow-rumps. Sprouted seed is an excellent standby for times when a consistent grass seed supply becomes hard to obtain. Any fresh leafy green vegetables such as bok choy, cos lettuce, kale, endive or chicory will also be keenly stripped away to nothing whenever offered. Yellow-rumps are avid green food hogs. Edible green weeds such as chickweed, dandelion leaves, amaranthus and fat hen are all excellent fresh green offerings that are generally more obtainable in winter months when fresh grass seed heads are much scarcer in most regions.
The usual dry seed mixes of the various millets and plain canary seed provides the majority of the basic staple diet. A very useful and thoroughly appreciated addition to the dry seed component of the Yellow-rump diet is a dry green grass seed mix such as those marketed as “greens’n’grains” seed mixes. These mixes comprise a high proportion of barnyard grass seed, which has been harvested at the half-ripe stage whilst still green. A small dish offered daily is a perfect supplement.
If the green seed and other green foods are provided in a consistently dependable regular supply, Yellow-rumps will breed fairly consistently without the need for added live insect food. However, I have found that the number of young birds bred per pair is slightly better where some regular live food is also available to breeding pairs whilst they are rearing young. They will readily utilise live termites, mealworms or bush-fly maggots for their insect protein fix.
Fine shell grit and other mineral foods such as cuttlebone and baked eggshells are important mineral supplements which should be always available to any breeding pairs.
As the wild experience with their Chestnut-breasted relatives indicates, they are a strong hybrid risk with any other Lonchura species. Therefore, keeping just one species of Munia or Mannikin per breeding aviary is the only safe housing option to avoid the risk of producing unwanted hybrid progeny.
In the Yellow-rumped Munia, we have an easy to cater for finch species with a placid temperament and uncomplicated captive requirements to achieve regular breeding success. This gives us no excuse for allowing their captive population to periodically dwindle to dangerously low numbers. All Australian finch breeders with an interest in a range of species should feel obligated to make some effort to help ensure that our vulnerable Lonchura species do not slip away from us. The Yellow-rumped Munia is the most obvious Australian native representative of this group of vulnerable species.
Adult Yellow-rumped Munia.
A typically located Yellow-rumped Munia nest - the nest is in the middle of this large clump of grass.
The colouration of the Yellow-rumped Munia may be subtle, however they are nonetheless a very attractive species.
A typical Yellow-rump nest built in a large clump of tall, dense grass. - close up of the nest shown in the previous photo.
Hen Yellow-rumped Munia peeking out of her nest.
Yellow-rumped Munias are particularly suited to well planted aviaries that feature prominent stands of tall, dense grasses.