FINCHES

Relationships between the Moult, Social Aggression and Disease:
Their Impact on Wild and Captive Gouldian Finches

 

Continued from The Moult: Part One

 

 

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 5) 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.

 

Photo 5       A prolonged head moult with evidence of baldness is an indication of an abnormal moult, the cause of which

should be investigated.

Compressed 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 6).

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 (Photo 6).

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.

Photo 6     

A compressed moult is identified when multiple flight feathers are seen growing. Theoretically, conditions for a compressed moult in wild Gouldians (Figure 5) 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 6).

 

 

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 5 & Figure 7).

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. 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 2012, 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.

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 indicates a failure to provide good nutrition, airsac mite prevention or a protected aviary environment.

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.

Important information on airsac mite infection, treatment and prevention in Gouldians.

Causes, treatment and prevention of baldness in Gouldian finches.

The moult and breeding success.

Alan Simpson's soft food recipe uses hard boiled eggs, breeding crumbles, and Dr Rob Marshall's health supplements to produce excellent breeding outcomes.

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