This article covers the following areas:
· Causes of Infertility
· Gender and Behavioural Problems
· Environmental Problems
· Medical Problems
Infertility is the failure of a pair of birds to produce eggs with a viable embryo. It differs from low hatchability where eggs are laid fertile but subsequently fail to hatch.
You can differentiate between poor fertility and poor hatchability by doing egg post-mortems and by egg candling. These are both simple to perform and I encourage you all to try them and use these techniques regularly. The only place where candling is not applicable is with pigmented eggs.
CAUSES OF INFERTILITY
· Gender and Behavioural Problems
· Homosexual pairs in sexually monomorphic species – suggest surgical sexing or DNA sexing of all infertile monomorphic pairs.
· Birds can go through all the actions of a heterosexual pair and can be very strongly bonded even if homosexual.
· Incompatibility - mate selection is best left to the bird unless desperate for a particular pair to mate. A system of a central cage with a number of potential mates in adjacent cages has proven effective in Amazons or colony selection.
· Check birds are not bonding with adjacent birds- if they are, separate them - they must be away from sight and sound of their old partners.
· Mate presence or absence - may stimulate fertility by removing partner in non-breeding season and returning at same time as nestbox placement.
· Both visual and auditory signals between mates may be necessary to initiate breeding.
Lack of pair bonding - signs of good bonding includes mutual preening and feeding,
If available, setting up a video camera to watch a pairs’ interactions when left alone can be very informative about the state of the pair bond.
Immaturity - be aware that each bird is not going to reach sexual maturity right on the breed average. Some birds are late developers. Younger birds also need more stimuli to breed. Older experienced birds will commence breeding much more readily. Inexperience contributes to infertility. Mistakes are made in courtship, mating and nesting. Style improves with age.
· Senescence- failure to breed due to advanced age is uncommon in aviaries even if it is common in aviculturalists. This may change as husbandry methods improve and the bird population ages.
· Imprinted birds - hand raised birds may be bonded to human hands, toys, mirrors etc.
· Fostered birds may become imprinted on the wrong species.
· Improper behaviour.
· Hand raised birds may be ignorant of the correct social signals to send or be unresponsive to courtship signals
· Neurotic and psychotic birds certainly exist, especially among Cockatoos. These birds are best removed from a breeding program.
· Aggression - more common in certain species, e.g. Major Mitchells. May be due to one mate becoming sexually active before the other. Can occur in pairs that have been together for years and bred successfully. Harsh lighting or excessively long daylight hours in indoor enclosures can contribute to aggression. Strategies to overcome aggression include:
1. wing clipping the aggressive partner.
2. providing escape routes/safe areas for the victim by isolating a perch with unclimbable sheet metal.
3. placing escape hatches at bottom of nest boxes.
4. keeping mates separate till breeding season.
5. keeping potential mates in colony situation till mature.
6. re-pairing when necessary.
· Length of daylight (photoperiod) is less important for tropical species but in birds from temperate areas increasing daylight hours can stimulate the production of reproductive hormones and breeding behaviour.
· If long daylight hours are maintained for long periods (months) the birds’ response will diminish over time.
· Temperature - extremes will cause temporary infertility.
In some species climate changes are the stimulus for breeding, especially tropical and desert species. Some of these birds can be stimulated into breeding by using misters during the breeding season.
· Season - the more domesticated the species the less important this becomes. Most species will nest more than once if all other conditions are suitable.
· Other birds- presence of other breeding birds is a necessary stimulus in social and colony birds.
· Proximity of other pairs can reinforce the pair bond by stimulating territorial defence. However, excess time spent in defence can result in lowered fertility.
· Human and other animal interaction - if birds are stressed by human presence then this will limit fertility. Either condition the birds with regular interaction or isolate them.
· Limit visitors and disturbances during breeding season.
· Noisy, ill trained dogs are more hindrance than help.
· Predators such as cats, hawks, rodents and snakes must be kept out.
· An important point is that the birds’ proper response to invasion should be aggression not fear. Fear may be an indicator of inadequate pair bonding.
· Nests - the appearance of the nestbox and nesting materials can be a powerful stimulant to reproduction if placed at the commencement of the breeding season. Placing a nestbox with a smaller than required hole will sometimes encourage pair bonding through the nest hole widening process. The placement of the box, its design and materials can also be important.
· The relationship of the exterior perch to the nest box is important. All perches should be firmly fixed to enhance feelings of security at the nestbox and also for mating.
· Enclosure design - size should ideally match the birds natural territory, too small will cause insecurity, if too large, excessive time will be spent on territory defence. The enclosure should enhance feelings of security especially with regard to perches, nestboxes, screens, walkways and feeding platforms.
· Inadequate dietary calcium, sodium and energy can interfere directly with egg laying and fertility.
· Excesses - over supplementation of zinc can cause infertility.
· Obesity - causes problems with egg passage, mating and decreases ovulation especially in Galahs, Budgies, Amazons and Macaws. Best solution is to withhold protein supplements in non-breeding season and allow flighted exercise.
· Variability - increasing the variety of foods fed can stimulate fertility.
· Flushing - this is the practice of increasing the energy content of the food fed as the breeding season approaches. It aims to mimic the natural abundance of food that is a trigger to reproduction in most species. Can increase the number of eggs ovulated.
· Feed quality - aflatoxins (fungal by-products) in seed can lower fertility.
· Inbreeding - with increased levels of inbreeding the greater chance there is that gene defects will be expressed. It can cause lowered semen quality, abnormal mating behaviour, more physical defects, and more behavioural defects. To illustrate the point, 20 lines of inbred mice were monitored over several generations. Only one family survived to ten generations, the other nineteen died out.
· Conformation - some species have been breed so far from the wild type they have become physically unable to breed eg turkeys, budgies
· Hybrid eggs - have a low hatchability.
· Medical Problems
· Poor condition for whatever reason.
· Overuse of medications - Doxycycline lists amongst its side effects a lowering of male fertility.
· Use of sex steroids always lowers fertility (for example body builders on testosterone have the nickname of "sultana nuts").
· Reproductive disorders
· Physical impairments
Talk to your avian vet - there are many factors which contribute to infertility. Its not always the birds’ fault, so take a good look at your management practices and try a few things before writing a pair off. May we all look forward to a good breeding year.
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