Molt, Social Aggression
Their Impact on Wild and Captive Gouldian Finches
By Rob Marshall
This article is adapted from a paper entitled "A Relationship between the Moult and Airsac Mite Infection in the Gouldian Finch", which the author presented to the 2009 Annual Conference of the Australian Chapter of Association of Avian Veterinarians.
Historical & Research Review
Scientific research of the Gouldian finch begun in 1989 after the Northern Territory Government recognised that the wild population had rapidly declined over the previous two decades. The Gouldian finch was listed as an endangered species at this time.
Research initially focused on breeding biology, population trends, disease factors, and the impact of fire on seed resources. This work revealed that the Gouldian finch relied upon a restricted seed diet and that the key wet season grasses were patchily distributed and fire, grazing and rainfall significantly affected seed production of these grasses. More recent research examined the foraging behaviour of Gouldians (photo 1) and the consequences of assortative breeding (i.e. a preference of Gouldian finches to select similar head coloured mates).
Twenty years of scientific research have now passed revealing significant findings but our understanding of the Gouldian finch remains limited.
Researchers have presented several possible causes for the rapid decline of the wild populations. These include commercial trapping for aviculture, habitat destruction associated with land clearance by fire and destruction of some important perennial grasses by grazing cattle, feral pigs and wild buffalo. Behavioural and genetic differences between the red and black-headed Gouldian finches are now being considered as an important cause of the decline. Death from airsac mite infection is believed to be involved with declining numbers but the exact reasons for an increased susceptibility to this infection have not been investigated.
- Trapping for Aviculture
Trapping was vigorous for almost three decades from 1960-1988 and provided many thousands of Gouldian finches for aviculture. Although trapping had a significant effect on Gouldian numbers and populations during this time, numbers should have rebounded over the ensuing twenty-year period because of their prolific breeding ability. This has not occurred and at the present time numbers in remaining populations are stable but remain low. An estimated 2500 birds remain in the wild.
- Habitat Destruction
Altered fire regimes have had a serious effect on the seeding grasses and nest holes available to Gouldian finches (photo 2) and is believed to be the single most important reason why Gouldian finch numbers have not rebounded since trapping became illegal in 1988.
The loss of traditional fire burning practices over the past forty years appears to be responsible for the destruction of essential understorey grasslands that provide wild populations with a reliable food resource. The loss of traditional knowledge occurred when cattle stations no longer employed aborigines following legislation in 1966 that gave them the right to receive equal pay as white Australian station hands. Before this time, aborigines worked for food and lodgings, and imparted their traditional knowledge of burning practices to the landowners. Traditional fire burning practice maintains the habitat of the Gouldian finch by patch burning that uses low heat fires lit in the morning during the late wet season or early dry season.
Traditional fire methods have a positive effect on the environment and help regenerate several of the perennial wet season grasses (e.g. Cockatoo grass, Curly Spinifex) favoured by Gouldian finches.
Non-traditional fire practices produce large hot wildfires intended to clear the land of undergrowth and native grasses, thereby allowing introduced drought resistant grasses (e.g. Buffel grass) favoured by cattle to establish themselves more readily. These uncontrolled fires destroy important perennial grass tussocks and nesting habitats. However, excluding fire completely would not be beneficial, as traditional fire practices have a positive influence on the quantity of seed produced by Cockatoo and Curly Spinifex.
Grazing and destruction of perennial grass plants (Cockatoo grass and Ribbon grass) by feral pigs and buffalo have also reduced the amount of food available to Gouldian finches during the wet season, which has a negative effect on breeding outcomes.
Although reduced availability of critical wet season grass seed resources due to changes in land use and consequent changes in grazing and fire regimes, combined with natural fluctuations in seasonal rainfall is thought to be involved with the decline of the Gouldian Finch in its natural environment, as yet there is no clear links between resource scarcity and its endangered status (Dostine and Franklin 2002; Fraser 2000; Crowley and Garnett 1994). In other words, starvation due to lack of food supply is not believed to be the cause of the decline in Gouldian numbers. There must therefore be other reasons for the decline in numbers.
- Behavioural and Genetic Issues
Recent research by Pryke and Griffith has discovered behavioural differences between the red and black-headed Gouldian finches (Pryke & Griffith, 2009) that may account for the greater number of black-headed birds in Nature, although the red head colour is genetically dominant over black heads. It has been suggested that in the distant past the red and black headed populations were separated geographically and existed as two distinct sub-species before coming back into contact again to co-exist together as a single population. The geographic separation may also explain the distinct behavioural differences displayed by the different head colour.
Both male and female red headed birds are more aggressive than the black-headed birds. The more competitive nature of red headed birds may be explained by a limited availability of nest sites, water and food resources in the region they inhabited during their geographic separation. The passive nature of black-headed birds may reflect habitation in a plentiful and less competitive environment.
Previous research has shown that there is a higher mortality of daughters compared to sons when interbreeding between different species, subspecies or races occurs. Pryke and Griffith found that fewer Gouldian offspring survived when red headed and black-headed birds were paired together compared to when pairs of the same head colour were allowed to breed.
There are three possible head colors for wild-type Gouldian finches - red, yellow and black (Figure 1). Black headed birds comprise approximately 70 percent of the wild population although red head colour is a genetically dominant feature. High levels of male sex hormones in red headed birds suppresses immunity and predisposes them to high mortality which in the end results in greater numbers of black-headed birds even when the aggression created by testosterone gives the red heads a huge dominance advantage (i.e. allowing them to occupy the best nesting hole, be first to drink at water holes etc.) over black heads.
||Black head is a sex-linked recessive trait, so cocks can be double factor or single factor whilst hens can only ever be single factor. For this reason hens can never be split for black head. In Nature black-headed birds outnumber red-headed birds by three to one.
|Red colour is also a sex-linked trait and dominant to black head colour. Although red is dominant to black these are more black head wild birds because there is a genetic and behavioural bias towards breeding black headed birds. Although black headed pairs produce 100% black headed offspring, red-headed pairs may produce black headed offspring. Mixed pairs where mother is black headed or father is a single factor red will also produce a proportion of black headed offspring.
|Yellow head color is an autosomal recessive trait, but is expressed only when the bird also has the red gene. In the absence of the red gene, birds that have yellow trait will have black heads and yellow-tipped beaks instead of the typical red-tipped beak. The yellow-headed birds are very rare in the wild consisting of less than one individual per thousand. These birds avoid all aggressive interactions with both red and black heads, and tend to experience great difficulty in retaining possession of suitable nesting hollows.
|As a result of this complex genetic color-coding system breeding expectations favour the production of black-headed birds but not to the extent of three to one as found in the wild population. Behavioural differences are responsible for increasing the ratio of black headed birds in the wild.
Figure 1 Genetic and Behavioural Differences of red, black and yellow headed Gouldian Finches.
Photo 4 Red headed male Gouldian finches are seen here dominating the fresh Newcastle grass seed spray.
Head colour is also very important when Gouldians are selecting their mates. Female Gouldian finches choose their mates based on several head features including head plumage color. They prefer a mate with the same head colour. This preference has been found to be highly significant for the survival of offspring. Pryke and Griffith confirmed that genetically incompatible pairs experience a 40.2% greater mortality of sons and an 83.8% greater mortality of daughters than in broods produced from genetically compatible matched pairs (i.e. same head colours). Additionally daughters produced from mixed matings - where parents differ in head color - suffer from genetic incompatibilities between their parents that cause about 84 per cent to die young. It was also found that female Gouldian finches paired with mismatched males produced significantly more male chicks (82.1 percent), whereas females in matched pairs produced nearly equal numbers of both sexes (45.9 percent males).
This series of studies revealed that female birds choose the sex of their offspring independent of genetic forces.
This new body of work reveals a behavioural and genetic incompatibility between black and red headed birds, which may provide the answer behind the failure of Gouldian populations to recover after Gouldian numbers were dramatically reduced by trapping. At this time it is likely that a greater proportion of females mated unwillingly with incompatible mates (i.e. red and black headed pairings) because of a lack of mate choice. Higher numbers of these incompatible pairs would have a negative impact on the ability of the local population to increase, due to a decreased likelihood of offspring survival and an increased number of males amongst surviving offspring (Pryke & Griffith, 2009). The end results are a decrease in females passing into the next and future generations (Pryke & Griffith, 2009).
- Airsac Mite Infection
Airsac mite infections have also been thought to play a role in the decline of the Gouldian finch (Tidemann & Woinarski 1994). It has been speculated that the impact of S. tracheacolum might be exacerbated during periods of physiological stress associated with the moult and food shortages at the onset of the wet season (Lane & Goodfellow 1989 cited in O'Malley 2006a; O'Malley 2006).
Infection with airsac mite S. tracheacolum has a rapid effect on the health and survivability of captive Gouldian finches. Airsac mite infections, which often appear during the moult and breeding period in captive populations, are likely to be involved with the decline of the wild Gouldian Finch population. However, because a symbiotic relationship between Gouldian finches and airsac mites exists, any devastating effect on the wild population would require a set of circumstances that dramatically affect immunity.
In captive Gouldian finches, airsac mite infection is likely to occur when immunity is compromised during periods of overlapping stress, which are most likely to occur during the natural stress periods of moult, breeding and adolescence. For example, airsac mite infection is likely when a compressed moult is abruptly interrupted and when breeding birds and their offspring experience food shortages. Importantly, red headed birds are more likely to succumb to airsac mite infection.
Special Features of the Gouldian Moult
The time taken for the Gouldian finch to complete the moult is rapid compared to co-occurring masked and long-tail finches (Franklin et al. 1998), and thought to reflect the more mobile and dispersive nature of the Gouldian finch (Tidemann and Woinarski 1994).
Gouldian finches have adapted to an environment under control of a tropical weather system that divides the year into two seasons - a wet and dry season (figure 2) - where they breed and moult at different times than other finches. A rapid moult appears to be an evolutionary adaptation to an unpredictable climate and tropical woodland breeding environment where the wing moult needs to be completed before the end of the dry season when seed shortages are frequent and prior to arrival of the wet season when torrential rains reduce foraging activity and curtail their ability to fly long distances in search of alternative food supplies.
- A Rapid Moult
The rapid nature of the Gouldian moult has been noted by scientific researchers (Franklin et al. 1998) and is its most notable feature. Conflicting scientific reports regarding the moult in wild Gouldian finches reflect a variable rate of progress rather than any observation failing. Milton Lewis (2001) has noted both adults and juveniles moult during September, October & November with most of the wing flight feathers being replaced during October and the entire moult being completed by mid December. The moult for Australian captive Gouldians is completed most rapidly when they are housed in temperate climatic regions of Australia, have finished breeding activities by June and are provided with a perfect diet. Under these conditions the wing moult is completed late in October and the head moult by the last week in November. Under less than ideal conditions the moult period may continue until the end of December.
From Milton Lewis' research the early completion of the wing moult appears to be a significant event that guarantees strong flight by the onset of the wet season when heavy rains make foraging activities more demanding. Tidemann & Woinarski (1994) record that the wing moult period finishes November. This finding compares favourable to the time when the wing moult is completed for Gouldian finches housed in Australian aviaries. These two researchers also mention that seed shortage can occur near this time, a finding that supports a need for Gouldian finches to complete their wing moult as rapidly as possible.
For wild Gouldian finches, breeding behaviour starts as they seek out hollows late in the wet season (March and April) when a drop in humidity stimulates the germination of Sorghum grasses and the release of sex hormones that initiate breeding condition (figure 3).
The total rainfall and extent of the wet season varies from one year to another, so that Gouldian finches are both seasonal and opportunistic breeders. During drought periods the extent of the wet season is truncated whereas during good seasons the amount of rainfall and extent of the season may be prolonged resulting in up to three clutches of eggs to be produced during a breeding season.
The amount and timing of rainfall during the wet season influences not only breeding success (Dostine et al. 2001) but also has a direct impact on the ability of Gouldian finches to complete their moult as quickly as possible. The start and extent of their breeding activity coincides with a period of peak resource availability within their habitat.
[Click to Enlarge Figure]
Following good wet seasons, plentiful supplies of native sorghum and other fallen seeds (Dostine & Franklin 2002; Dostine et al. 2001; Goodfellow 2005; Tidemann 1993b, 1996; Tidemann et al. 1993) provide nestlings and fledglings with a reliable food resource that remains into the moult period.
Figure 3 details the availability of several of the different grasses favoured by Gouldian finches during the breeding and moult periods.
Woinarski and Tidemann (1992) noted that the Gouldian finch is more vulnerable to drought during a moult than other co-occurring finch species because it is moulting at a time when seed shortages may occur (figure 3). The moult is a time during which birds may experience physiological stress, as it is a highly energetic process.
The rapid moult of Gouldian finches renders them more vulnerable to the effects of stress, because there is a greater energetic cost involved with a rapid moult than a normal moult (Guillemette 2007).
Although Gouldian Finches have a more restricted diet compared to other co-occurring granivorous birds (Dostine and Franklin 2002; Fraser 2000; Crowley and Garnett 1994), the seeds of the annual grasses (e.g. Sorghum spp., Sarga spp., Vacoparis spp. Fire grass etc.) they seek and available to them for most of the moult period provide a higher quality of nutrient resource than early wet season perennial grasses such as Cockatoo grass and curly Spinifex grass.
It is thought that the critical period for physiological stress for wild Gouldian finches occurs at the end of the dry season and onset of the wet season when food supply may be very low during drought. This is a time when the flight feathers are also being replaced. The length of time food supply is scarce may vary according to the pattern of rainfall in the wet season and the dry season fire regime.
A potential to slow down or accelerate the growth of new feathers is a notable feature of the Gouldian moult that has been observed in captive but not recorded in wild birds. This adaptive feature - that is also likely to occur in Nature - allows the rate of progress of moult to increase or decrease according to the availability of nutritional resources and changing climatic conditions.
Providing additional nutrition via a soft food mix helps to accelerate the progress of the moult in captive Gouldians. The moult may also be delayed (slow down) when nutrient resources are lacking, during excessively cold or hot weather, when breeding activities extend into the moult period or by disease. In Nature, with an uncertain food supply, physiological stress in the Gouldian is avoided by its ability to accelerate or slow down the moult.
In captive birds, a compressed moult is the visible sign of an accelerating moult, whereas a delayed moult refers to a moult that is progressing slowly. The concepts of a compressed and delayed moult have not been discussed in Gouldian finches before. This paper details my understanding of a delayed and compressed moult in Gouldian finches, their relationship to each other and disease with possible links to the decline of wild populations.
The Moult in Captive Gouldian Finches
The moult of captive Gouldian finches is an annual seasonal event with a starting time that may vary slightly depending upon local climatic conditions. In Australia captive Gouldian finches may start to moult as early as July. Across the Northern Hemisphere the moult should start in January (figure 4). A loss of the first (most proximal) primary flight feather heralds the start of the moult period; an occasion that often goes unnoticed because no other feathers are moulted and very few feathers are noticed on the aviary floor. The moult progresses slowly at this stage with a single primary flight feather of each wing being replaced gradually over a period of several weeks until after the fourth primary flight feather is dropped. At this time the secondary flight feathers start to moult (photo 5).
[Click to Enlarge Figure]
Captive Gouldian finches carry between nine and ten primary flight feathers. They follow the same moult sequence as for wild populations with the first four primary flight feathers of each wing being replaced one at a time and in sequence (photo 5). The main wing moult period begins in August following the re-growth of the fourth primary flight feather on each wing and ends late October. Normally, during this time each primary and a corresponding secondary flight feather of each wing are replaced in sequence and one at a time. The body moult is less critical for survival than the wing moult and is heaviest during September and October. The head feathers are the last to be replaced. These are moulted during the last weeks of November and first week of December. Sometimes pinfeathers appear on the head (photo 6).
Photo 5 Four new primary flights feathers
are seen in this wing. No secondary
flights have been moulted yet.
Photo 6 Pin feathers on the head
may occur in some birds towards the
end of the moult period. This may be
a healthy or unhealthy finding.
The speed of the moult may accelerate or slow down at any stage in captive Gouldian finches. It is the primary flight feathers that best reveal a change in pace of the moult.
The start time of the moult in captive flocks exposed to natural sunlight conditions may vary slightly according to geographical location and local weather conditions. However under ideal conditions, captive Gouldian finches in Australia start to moult their primary flight feathers in July. February is the equivalent month in the Northern Hemisphere.
This initial stage of the moult often goes unnoticed as the four proximal primary flight feathers are replaced one at a time (figure 5). The replacement of these four feathers is gradual and takes over a month to complete. Consequently there is no undue energetic or nutritional burden on the bird and physiological stress is minimised. However, the early progress of the moult may be retarded by poor nutrition, disease, breeding activity or cold winter weather conditions that often persist throughout July and August in temperate parts of Australia and in New Zealand.
In order to avoid a delay in the progress of the starting phase of the moult, captive Gouldian finches should not be allowed to breed beyond June in the Southern Hemisphere. In the Northern Hemisphere all breeding activity should cease by January.
Most Australian Gouldian breeders and scientific researchers view September as the beginning time of the moult period. However, this is incorrect as the moult begins at least a month beforehand. Instead September is the time when the peak phase of the moult begins, being obvious to fanciers as many feathers appear on the floor of the aviary. At this time, both primary and secondary flights start being replaced and new feathers on the body of juveniles appear. This is a time of increasing physiological stress and vulnerability for the Gouldian finch, as there is a sudden increase in energetic and nutrient requirements.
[Click to Enlarge Figure]
When the moult is progressing as rapidly as possible, the wing moult is complete by mid October (see figure 5). As with wild birds, there is variation with some individuals taking longer to complete their moult (Milton Lewis, 2001).
Individuals born at the beginning of the breeding season start to replace their primary flight feathers within a month of fledging. This occasion also goes unnoticed by breeders, as the wing moult progresses very slowly and juvenile body colour remains unchanged until August/September.
Under ideal conditions the moult of adult birds begins as early as July. By the first week of August three or four primary flight feathers have been replaced in both adult and juvenile birds. Juveniles bred early in the breeding season start the body moult (i.e. replace their body contour feathers) by the second week of August. Adult birds start to drop body contour feathers during the second half of August.
Under normal conditions, each primary flight feather is replaced one at a time in an orderly sequence starting from the innermost (proximal) and ending with the outermost (most distal) primary flight feather. The body feathers and secondary flight feathers start to moult when the fourth primary flight has been replaced.
This marks the beginning of the peak period for the wing moult that continues throughout September and into October. Sometimes two or more adjacent new primary flight feathers may be seen growing simultaneously during the peak period of the moult. All wing flight feathers are replaced by mid October. The head feathers start to be replaced towards the end of the wing moult. The moult is concluded during the first weeks of December (photo 7).
Photo 7 This photo taken on December 5th in Australia shows the head moult is almost complete in this healthy orange headed cock.
Photo 8 A prolonged head moult with evidence of baldness is an indication of an abnormal moult, the cause of which should be investigated.
Variable Moult Speed
The progress of the Gouldian moult may be accelerated, delayed or completely halted. Moult abnormalities are most noticeable in captive birds towards the end of the moult when head feather abnormalities (photo 8) appear. These feather problems indicate a delayed moult, which may be created by poor nutrition, disease, poor housing conditions during the period of the moult. Stress induced Airsac Mite infection and other diseases will also delay the moult. The presence of a compressed moult indicates an accelerating moult. Baldness is the most obvious sign of a cessation of the moult.
From my observations, captive Gouldian finches are capable of growing multiple primary flight feathers simultaneously. The goldfinch (Carduelis tristis) shares this ability (Middleton 1977). This moult pattern is known as a compressed moult (Storer & Jehl 1985). A compressed moult is the visible evidence of an accelerating moult (photo 9).
Photo 9 Photo 9 A compressed moult is identified when multiple flight feathers are seen growing simultaneously.
This is a healthy sign.
Theoretically a compressed moult in captive Gouldian finches may occur at any stage of the moult but mostly involves the 4th to 10th primary flight feathers. Sometimes it is seen at the end of the moult period when many pin-feathers appear together on the head. It is necessary to examine the flight feathers in order to differentiate a delayed moult from a compressed head moult (figures 6 & 10).
There are a number of reasons why a compressed moult may occur. A compressed moult occurs most frequently during the peak period of the moult (September - October in Australia and March - April in USA). A compressed moult is more likely to occur when there has been a delay at some stage of the moult period. As well, healthy strong individual birds may have compressed moult, which in Australia may allow them to complete their wing moult by mid October.
A compressed intense moult of some seabirds is believed to be an adaptation for exploiting an abundant food source (Storer & Jehl 1985). In Gouldian finches a compressed moult occurs only when plentiful food resources are available as there is a great energetic cost for flight feather growth (Guillemette 2007, Murphy M.E. 1996) with daily energy expenditure increasing up to 20% during the peak period of the moult (Jenni & Winkler 1994). Protein requirements are also increased during the moult as feather mass comprises 20% of total body protein (Murphy, King et al. 1988).
Consequently a compressed moult will not occur when food resources are low or of poor nutritional quality. A compressed moult should be considered a natural and healthy event for Gouldian finches and occurs in Nature as a compensatory mechanism to ensure that the wing moult is completed as rapidly as possible.
Theoretically, conditions for a compressed moult in wild Gouldians (figure 7) occur when premature rains falling in September break a drought and quickly provide a bountiful supply of the annual and nutrient rich Fire Grass, the seeds of which are highly nutritious and favoured by the Gouldian. A compressed moult may also appear following a drought period when heavy rains fall in early October and initiate rapid tussock growth of Cockatoo Grass that produces a very large nutritious seed also relished by Gouldian finches.
Delayed or Interrupted Moult
Prolonged cold winter temperatures or exposure to cold spells at the beginning the moult period coupled with an inadequate diet is the most common causes of a delay in the start of the moult in captive birds. Hot or fluctuating temperatures during the peak moult period may also interrupt the progress of a moult. A compressed moult often follows a few weeks later as the stress from the hot period wanes. Food supply must be plentiful during September or early October if a compressed wing moult is to occur in wild birds.
Theoretically, physiological stress associated with the growth of the flight feathers in wild Gouldian may start as early as August and continue until late October at the close of the wing moult (Milton Lewis, 2001). During this time seed resources are declining and by late September and early October may be at their lowest level. Often when there is drought, food supply may abruptly decline (Crowley and Garnett 1994) around this time and delay the progress of the moult.
For captive finches, a moult may be delayed by an extremely poor level of nutrition or by overlapping stress factors that may stop the moult completely. If this is to occur it will be seen after the first four primary flights have been replaced. Baldness is a sign that the moult has ceased completely (figure 7).
Baldness is a sign of a moult that has stopped completely and often for a prolonged period of time. Nutritional supplementation is the first step to curing baldness.
Often secondary infections (cnemidocoptes mite, bacterial and yeast contamination) accompany baldness. There is a limited likelihood of recovery from long standing and age related baldness.
Examination & interpretation of the wing flight feathers.
The flight feathers have stopped growing midway through the moult.
The tail feathers are not being replaced.
Figure 8 Baldness as a Sign of Moult Cessation
Moult, Immunity and Disease
In my experience, Airsac Mite and Streptococcus infections are the most common stress induced diseases of captive Gouldian Finches. In wild birds, they become life threatening when there are overlapping stress factors. This circumstance exists during drought when food resources are restricted during their moult. By delaying (slowing down) the moult wild birds may reduce the level of stress and limit disease likelihood. Under these circumstances infection is unlikely to cause catastrophic losses because a sudden increase in airsac mite numbers is unlikely to occur. However, catastrophic losses are possible when there is a sudden interruption of a compressed moult. Red headed birds are more susceptible to catastrophic losses from airsac Mite or Streptococcus infection as immunity has already been compromised by high testosterone levels as well as the moult process itself.
In Nature, a compressed moult is likely to occur when rain follows a dry period that has delayed the onset of the main wing moult (i.e. the simultaneous growth of the primary and secondary flight feathers) that starts in August. The sudden availability of a rich food resource following rain promotes a compressed moult but the Gouldian finch will experience a sudden and high level of physiological stress if this food supply abruptly stops. Food supply may abruptly decline during a compressed moult when no further rain follows early September (producing fire grass) or October downpours (germinating Cockatoo grass). A compressed moult is interrupted at this time because the life cycle of these grasses is very short-lived and seed availability abruptly declines (figure 6 & figure 7).
[Click to Enlarge Figure]
Moult, Immunity and Airsac Mite Infections
Sparrow studies reveal an increased energetic cost and a reduced immune response during a moult (Martin L.B., A. Scheuerlein, and M. Wikelski. 2003). Lowered immune responses were seen in sparrows during the heaviest part of their moult and greatest loss of immune function occurred immediately at the conclusion of the moult (Martin L.B., A. Scheuerlein, and M. Wikelski. 2003).
A critical reduction in immunity is to be expected when a sudden decline in food availability occurs during the height or at the conclusion of the moult (Franklin et al. 1998). This statement is even more relevant when there is a sudden decline of food during a compressed moult. In wild populations of Gouldian finches, it is during these instances of extreme physiological stress that immunity against airsac mites and Streptococcal infections may be overcome (Lane & Goodfellow 1989 cited in O'Malley 2006a; O'Malley 2006).
Airsac mite and Streptococcus infections are common in captive Gouldian finches during the peak period of the moult (September-October in Australia and April –May in USA) and at the conclusion of the moult (November-December in Australia and June–July in USA). Airsac mite infections during these months are often due to poor nutrition or fluctuating weather conditions. Fortified nutrition and repeat Airsac Mite treatments will prevent infections at these vulnerable times and help complete a timely moult.
Airsac mites are found naturally in the Gouldian finch (E. gouldiae) and 6 co-occurring species (long-tailed finches (Poephila acuticauda), masked finches (P. personata), pictorella manikins (Heteromunia pectoralis), zebra finches (Taeniopygia guttata), double-barred finches (T. bichenovii) and budgerigars (Melopsittacus undulatus) (P.J.Bell 1996). The prevalence and intensity of infection in Gouldian finches is significantly higher than in other species except Pictorella manikins (P.J.Bell 1996).
In the face of continuous threats from parasites, hosts have evolved an elaborate series of preventative and controlling measures - the immune system - in order to reduce the fitness costs of parasitism (Sheldon B.C. and S. Verhulst 1996). However, these measures do have associated costs (Sheldon B.C. and S. Verhulst 1996). In Gouldian finches, infections are capable of causing respiratory problems that can lead to death (Bell 1996; Tidemann et al. 1992c, 1993).
A symbiotic relationship between Gouldian finches and the Air-sac Mite (Sternostoma tracheacolum) is likely to exist, as this endoparasite is present in a high proportion of the wild population (Tidemann et al. 1992c, 1993).
In captive Gouldian finches, Airsac mite infection is a common cause of illness and death. Infections cause illness in captive birds that then interrupt their moult. Signs of infection may not be obvious in many birds other than the effect it has on the progress of the moult. Infection delays the moult the signs of which - mostly baldness - do not become apparent until the end of the moult when immunity is at its lowest ebb.
Acute infections often result in death as Airsac mite numbers can rapidly increase within a short time. Persistent infection often results in death from secondary infections (photo 8). Death from Airsac mite infection is a rare event when adequate nutrition is provided during a normal moult i.e. when flight feathers are being replaced one at a time. However, diets fed to captive Gouldian Finches during the moult are often inadequate, which predisposes them to subclinical Airsac mite infection, the signs of which are non-specific (i.e. fluffed up look, inactivity, ill-thrift and a delayed moult).
Acute illness and death associated with Airsac mite infections are most common when a delayed or compressed moult is interrupted by adverse weather conditions.
Immuno-protection during part of the life cycle of Sternostoma tracheacolum helps explain the symbiotic relationship. Transmission of infection between Gouldian finches is by non-gravid non-gorged females that mainly inhabit the upper respiratory tract, buccal and nasal cavity. These females may also move to the posterior abdominal airsac, where they are protected from the host's immune response (P.J.Bell 1996).
Disease caused by a sudden increase in gravid female numbers is controlled by conditions that maintain a healthy immune system. Non-gravid non-engorged female mites residing in the posterior airsacs being protected from any immune response remain a potential source of rapid re-infestation should immunosuppression occur.
When immunity is compromised – by social aggression or when a compressed moult is suddenly interrupted - a rapid increase in gravid females may occur because unfertilised eggs in the lungs are capable of arrhenotokous parthogenesis (i.e. unfertilised eggs capable of developing into haploid males) and proportionally more male mites persist in the lungs with small infra-populations (Experimental and Applied Acarology 1996).
Gravid females tend to occupy the airsacs, syrinx and trachea and move to the lungs to lay their eggs. This form of the mite is most responsible for the sudden onset of severe respiratory symptoms that will end in death. The eggs quickly hatch with the nymphs and sub-adults feeding off the blood rich pulmonary tissue. This stage of infection causes asthmatic type symptoms leading to an inability to fly and disinterest in foraging. Adult males remain mostly in the lungs. The life cycle may be completed within 6 days (P.J.Bell 1996) so that many birds can become infected and die over a very short period of time.
The consequence of Airsac mite infections is rapid and severe because infra-populations may dramatically increase in size within a very short period of time. Infections decrease appetite and mobility and become rapidly life threatening because finches must eat and drink each day. This ability of Airsac mites to complete their life cycle rapidly under certain conditions and produce many mites that renders Gouldian finches extremely vulnerable during times of acute stress.
Gouldian finches, especially juveniles are thought to become vulnerable at the closing stages of the moult when the nutritional resources needed to support the moult are lacking. In Nature, Gouldian finches are most vulnerable at the end of the moult period when food resources are low or abruptly decline at this time. The high prevalence of Airsac mite infection seen in captive Gouldian finches at this time supports the view that airsac mite infections are a result of a depressed immune response.
Catastrophic losses are possible as a result of infection because Airsac mite numbers can rapidly explode when the immune response is severely compromised. Losses are likely to occur as a result of Airsac mite infection at the conclusion of the moult in November and when a compressed moult is interrupted by a sudden decline in available food resources during October.
Acute physiological stress during the moult period is most likely to occur when a compressed moult is interrupted, when a delayed moult is compromised by cold weather or poor nutrition towards the end of the moult period. Acute airsac mite infection of red-headed individuals is also possible when they exhibit social aggression at the beginning of the breeding season.
Management of Wild Populations
The Gouldian finch is now considered rare in Western Australia and endangered in both Queensland and the Northern Territory (Tidemann et al., 1999; O'Malley, 2006). In 2000, wild population numbers were predicted at 2500 breeding birds, with a downward trend evident (Gelis, 2003).
To conserve the wild Gouldian Finch populations and save the species from endangerment, management strategies must be implemented and recovery programs realised.
The most significant action taken to improve the current status of the Gouldian finch has been the development of a National Recovery Plan (O'Malley, 2006). This was initiated in 1994 in collaboration with the National Gouldian Finch Recovery Team, as a guide into research of the diet, reproductive biology, population dynamics and potential threats of the finch (O'Malley, 2005). The plan outlines actions such as land management, taking into account the impact of fire and grazing on the finch, restoration of habitat and reintroduction into the wild (O'Malley, 2005; Soucek, 2008).
Land management has important conservational implications with regards to the Gouldian Finch (O'Malley, 2006). Although precise habitat requirements are still unclear, persistence of populations of the Gouldian Finch at certain sites enables recognition of critical elements contributing to the success of such populations (Dostine et al., 2001). A number of landscape components appear to be important for the survival of Gouldian Finches. Large areas of rocky hills with a dense understorey of sorghum grasses characterise the finches' breeding habitat during the dry season (O'Malley, 2006; Soucek, 2008). The topography of these sites, in addition to natural barriers such as rivers and creeks, restricts the spread of fire, reducing its impact on seed availability (Dostine et al., 2001). Presence of large numbers of gum trees in these areas, favourably salmon gums or northern white gums, is also important in providing nesting
hollows for the finches (Dostine et al., 2001). Gouldians need to drink every day, hence reliable water sources are essential, preferably in the form of shallow waterholes protected from predators (O'Malley, 2006). Patches of grassy woodlands within 10 kilometers of the Gouldian Finch breeding grounds in the lowlands provide a food source in times of seed shortage, such as throughout the wet season (Dostine et al., 2001). In habitat management, preservation of these areas of woodland is critical to ensure the finches have access to alternate feeding sources at times of food shortages that may occur towards the end of the dry season (Dostine et al., 2001; O'Malley, 2006).
Identification and preservation of key habitat areas is critical to conservation of the species (Dostine et al., 2001). It has facilitated monitoring of population trends and analysis of health in different finch populations, which is an essential in assessing the success of any management regime (Dostine et al., 2001; O'Malley, 2006). Knowledge of the landscape is also important in developing appropriate fire and grazing management strategies in major Gouldian habitat sites (Dostine et al., 2001; O'Malley, 2005). Finally, realising aspects of the habitat that contribute to the persistence of Gouldian Finch populations in these areas could also assist in strategising the reintroduction of additional populations into carefully managed habitats (O'Malley 2005).
As described earlier, fire and grazing processes are significant threats to the long-term survival of the Gouldian. Current management regimes regarding these two issues are being implemented at sites where significant Gouldian Finch populations have been identified in an effort to preserve the crucial habitat required by the finch for survival (O'Malley, 2006). Manipulating the distribution and timing of fire has also been described as a way of encouraging seed growth of the key wet season grasses, but also protecting nest trees and feeding areas from the detrimental effects of large, hot fires (Dostine et al., 2001; O'Malley, 2005). Fire management is based on forming mosaic patterns of burnt and unburnt patches of land, with the intervals between each burning varying (O'Malley, 2005). This mimics traditional practices carried out by Aboriginal people, prior to European settlement (O'Malley, 2006).
In terms of grazing management, fencing off important wet season grasses from production animals and feral pigs has been suggested to preserve feeding habitat (O'Malley, 2006). However, this could affect livestock productivity, thus cooperation with pastoral land managers may be difficult. Feral herbivore control is the current grazing management practice. These management regimes are still not ideal, so further progress needs to be made with regards to current knowledge on habitat, diet and foraging behaviour of the Gouldian Finch, and the precise impact of inappropriate fire and grazing practices on the survival of the species (Dostine et al., 2001; O'Malley, 2006).
The availability of cockatoo grass during the wet season is thought to have a positive impact on breeding outcomes for wild populations. Landowners in regions inhabited by Gouldians could benefit financially by replacing grazing land for a commercial plot of Cockatoo grass and at the same time provide Gouldians with a reliable food supply during the wet season. Commercial production of Cockatoo grass is underway in northern Territory, the seeds of which are favoured by Gouldian finches during the wet season.
Recently, the reintroduction of aviary-reared birds into protected habitats has been trialled as a conservation tool (O'Malley, 2005) in Mareeba, Queensland. Its success relies strongly on habitat enhancement, threat abatement in release areas, and continual monitoring of the reintroduced birds (O'Malley, 2006). Predation has hindered reintroduction efforts (Wildlife Conservancy of Tropical Queensland, 2009), and O'Malley (2005) describes plans for future trials where finches spend less time in captivity, in the notion that they will have retained predator avoidance behaviour by the time of their release.
One final management strategy to be considered is community involvement and increasing public awareness. Members of the community can facilitate the monitoring of Gouldian populations by reporting sightings or participating in annual waterhole counts (O'Malley, 2005). Additionally, encouraging pastoralists and Aboriginal landowners to test fire management regimes on their properties would be of significant benefit to the Gouldian recovery effort (O'Malley, 2006). Although this would involve some economic cost to the landholders, productivity losses would be reduced due to improved fire practices thus limiting large, hot wildfires that destroy property and pasture resources (O'Malley, 2006). The Jawoyn Aboriginal Corporation is actively involved in the recovery effort, participating in fire management and feral herbivore control on Jawoyn lands with significant Gouldian Finch populations. It is in the interest of the recovery team to increase the involvement
of the Aboriginal community, as the finch distribution covers much of their land (O'Malley, 2006).
There have been 3 successive recovery plans for this species (O'Malley, 2006). The current program runs from 2007 to 2011, with an estimated cost of $970, 000. This is being met by State and Territory governments, numerous organisations, including Aboriginal, pastoral and conservational groups, and the general public. However, it is likely that costs will continue past the length of the plan, as the recovery process of the finch is anticipated to exceed 5 years (O'Malley, 2006).
For the conservational status of the Gouldian to be changed, populations will need to show a sustained increase in numbers over several seasons (O'Malley, 2006). By adopting the management practices described above, such a goal may be achieved.
Management in Captive Birds
Good management of captive flocks during the moult should be a priority for all Gouldian breeders because a rapid moult is a sign that breeding outcomes will be good.
Above all, a balanced diet fortified with protein and energy is required by Gouldian finches to rapidly complete their moult. The soft food recipe and water supplements outlined for the Moult period (August-December) provides all the additional nutrients required for a rapid moult. In addition repeat treatments against Airsac mites will ensure a rapid moult.
Preparations for a good breeding season must begin early (the beginning of August for the Southern Hemisphere and 1st February for the Northern Hemisphere) to ensure the moult is completed as rapidly as possible.
Every effort must be taken to support a rapid moult, because there is a strong relationship between the completion of a rapid moult, good health and a successful breeding season.
When receiving the best care, the moult of Gouldian Finches will be completed in November (the Southern Hemisphere) and May (Northern Hemisphere). Breeding may then commence by Christmas (the Southern Hemisphere) and 25th June (Northern Hemisphere).
The accompanying Moult and Breeding Programmes will give your birds the opportunity to enjoy a rapid moult and two highly successful breeding rounds before June (the Southern Hemisphere) and December (Northern Hemisphere).
Airsac mite infections are inherent to wild Gouldian finch populations and it should be assumed Airsac mites are present in all captive Gouldians. Infection exists in a dormant state when ideal conditions create good health Any stressful episode will activate infection. In captivity, stresssful conditions occur during the moult, breeding and in juvenile birds.
Cold spells at the start of the moult may delay the moult and create a compressed moult. During a compressed moult multiple flight feathers grow simultaneously. Ivermectin treatments administered for 2 consecutive days each three weeks must be given during a compressed moult because Gouldian finches become vulnerable to airsac mite infections at this time even when they receive good nutrition.
Airsac mite treatments must be given regularly during the moult and breeding seasons in order to prevent infection during these naturally stressful periods. Gouldians are particularly vulnerable to infection at the end of the moult and at the beginning of breeding when their immunity is at its lowest ebb.
Poor breeding results are likely when treatments are not regularly administered as Gouldians infected with Airsac mites succumb to Chlamydia (Ornithosis) and Streptococcus infections. Airsac mites become a problem when Gouldians experience stress, and especially when additional stress factors such as changing weather conditions (e.g. warm weather followed by sudden cold and wet spells) occur during the moult. The immediate effect of Airsac mites is to retard the moult, so that often birds with baldness are suffering from Airsac mites and respond quickly when treated with ivermectin or moxidectin each week for 3 weeks. Airsac mite infection starts a vicious cycle that interrupts and delays the normal moult cycle. The end result is a prolonged moult, weakened bird, infertility, parental neglect, rejection of the babies, parental deaths and poor breeding outcomes.
[Click to Enlarge Figure]
Figure 9 Complete Health Programme for Captive Gouldian Finches
This programme ensures that a rapid moult precedes breeding activity and protect the flock from illness (especially airsac mite related illnesses) when their immunity is low (i.e. during and at end of the moult).
An austere period following the moult period is not advised for captive birds, but instead a diet that protects immunity but prevents obesity is recommended at this time.
Repeat airsac mite treatments are recommended as airsac mite infection occurs whenever there is physiological stress. Airsac mite infections affect health and vitality and predispose to other infections (e.g. Chlamydial and Streptococcal infections) that affect breeding success. Any physiological stresses are controlled by providing soft foods, supplements and regular airsc mite treatments.
Environmental diseases (e.g. worms, Coccidiosis, Thrush and E.coli) more prevalent in juvenile birds are controlled by regular treatments. Prevention of disease associated with changing weather conditions is achieved by acidifying the drinking water.
The Gouldian moult may be normal, compressed or delayed. Normal and compressed moults occur in well-managed aviaries.
A delayed moult (eg head baldness, pin feathers on head (photo ) indicates a failure to provide good nutrition, airsac mite prevention or a protected aviary environment.
Pin feathers on the head of a red headed female Gouldian were observed on December 8th.
Examination of the wing flight feathers is required to identify the significance of this finding.
Pin feathers on the head may occur in a healthy bird experiencing a compressed moult of the head feathers.
More often, this finding is the result of a delayed moult of which there are many causes, including stress induced diseases such as streptococcal or airsac mite infections of disease(s) related to an interruption of a compressed moult.
Examination & interpretation of the wing flight feathers.
The first four flight feathers have moulted successfully and are in very good condition. This indicated the normal moult cycle has started well. The 10th (outermost) primary flight feather is half grown. This indicates the moult cycle is delayed, because the growth of the feather should have been completed by early November. There are also stress marks on the tips of both 5th and 6th primary flight feathers. This indicates a short stress period has interrupted a compressed moult involving these feathers and possibly the 7th and 8th flight feathers as these are broken off towards their base.
From these finding the presence of the head pin feathers indicates
an interrupted compressed moult of the 5-8th flights occurring during September. As a result, this bird developed disease identified as streptococcus and Aspergillosis. The moult was concluded within 3 weeks following their treatment together with fortification of the diet. A 6 week recovery period before she was allowed to breed was needed to prevent soft shelled eggs, egg binding and breeding failure.
Figure 10 The Interpretation of Pin feathers on the Head of Gouldian Finches
It is during the peak moult period (October) and immediately following the conclusion of the moult (late November or early December) that most moult-related health problems appear. Bird deaths and catastrophic outbreaks of airsac mite infections are likely during these times especially when a cold spell interrupts a compressed moult. The information below will prevent these problems. I hope you enjoy a successful breeding season.
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