Although aviculturists want their birds to lay eggs, pet bird owners face a dilemma that is the exact opposite – they want to stop, or at least limit, the number of eggs their bird lays. Left unchecked, some birds, especially cockatiels, will lay one egg after another until they are completely exhausted. This is a common problem in pet birds, who live in conditions very different from wild or aviary birds.
This article discusses why some pet parrots will start to lay large numbers of eggs, what effect this has on their health, and what we have to do to stop it.
Why do birds lay eggs?
Most wild parrots are seasonal breeders, laying 1 or 2 clutches of eggs at a time when it is most likely that their offspring will survive and flourish. The number of eggs laid varies between species: cockatiels and budgies usually lay 4-5 eggs; galahs 3-5; black cockatoos 1-2. For most birds, this egg laying occurs in early spring when food resources are usually abundant. Birds living in arid zones (e.g., budgies, cockatiels and some cockatoos) are more opportunistic in their breeding, laying eggs after heavy rain likely to result in a flush of new vegetation growth.
So, what controls this seasonality?
The first factor is the increasing daylength seen in early spring. This has an effect on the bird’s pituitary gland, stimulating the release of sex hormones that prime the reproductive tract. This initial stimulus is then reinforced by things such as rainfall and increased availability of high energy foods. This whole surge in reproductive activity is then fine-tuned by the presence of a suitable mate, the beginning of courtship behaviours, and a nesting site that seems to be safe and secure.
The result is a clutch of eggs, the number (as mentioned earlier) dependent on the species and age of the birds, with the hen brooding this clutch (i.e., sitting on the eggs to keep them warm till they hatch). Brooding behaviour stops reproductive behaviour until the chicks have hatched, fledged, and weaned; after that, if the season is still good, another clutch may be laid.
These ideal breeding conditions are often replicated in a pet bird’s household, usually without their owner’s awareness. Increasing daylength is duplicated by the effect of artificial lighting. Many owners interact with their birds when they get home from work, usually after sunset. They feed their birds a high energy diet (seed) and often mist them with water (or even shower with them). These activities prime the bird’s reproductive tract, ready for egg laying. Fine tuning occurs with the petting and grooming some owners give their birds, and behaviours such as allowing the bird to eat out of the owner’s mouth, kissing the bird, and even allowing the bird to sit on their shoulder. If the bird is given a secure nesting site in the form of a cage, it should not be surprising that some birds start to lay eggs.
This is then aggravated by the owner who, on finding these eggs, removes them from the ‘nest’. This means that, instead of laying eggs until the number reaches a genetically programmed clutch size, the bird continues to lay eggs to replace those considered to have been lost.
The result of all these interactions and behaviours is a pet bird laying 20-30 eggs in a month, contrasted to a wild bird that may lay 5-10 eggs in a year.
What happens when a bird lays too many eggs?
Developing and then laying an egg is a physically draining event for the female bird (hen). It requires body reserves of calcium, protein and energy, physical fitness and strength, and stamina. Unfortunately, many pet birds are deficient in most – if not all – of these requirements even before egg laying. The calcium, protein and energy requirements are met by the diet, but seed is deficient in all of these except perhaps energy. The physical fitness, strength and stamina come from exercise – flying many kilometres each day looking for food. Most pet birds are lucky to fly a few metres each day, let alone kilometres.
The result of these deficiencies is a drain on what body reserves the bird does have and, when these reserves are depleted, the bird gets into trouble. Just some of the problems that can result include:
- Egg binding: The combination of calcium deficiency, obesity, and the lack of fitness and strength results in the bird been unable to lay her egg. This leads to exhaustion, compression of the air sacs and lungs, circulatory changes and finally death.
- Yolk peritonitis: After a lot of egg laying the bird’s oviduct becomes bruised and swollen. Eggs can no longer pass down it and yolks, coming off the ovary, fall into the abdomen. The bird’s immune system then mounts an inflammatory response to try and remove this material. The result is a sterile peritonitis and the bird’s body distended with fluid.
- Bone fractures: When there is not enough calcium in the bird’s diet, the calcium for the egg shell comes from the bird’s bones. This weakens them and makes fractures more likely, even from something as simple as landing heavily or awkwardly.
There are other possible complications – yolk embolism (‘yolk stroke’), retained eggs, infected oviducts, etc. – bit the ones listed above are the most common.
On top of the physical problems, there are often behavioural issues associated with reproductive activity – aggression in defence of a nest site or mate, constant courtship behaviour, screaming, etc. These behaviours can become so pronounced that some owners choose to surrender their birds to a rescue group rather than continue having deal with it these behaviours. Obviously, this can be as bad for a closely-bonded bird as the medical problems described above.
What can we do?
As with everything with birds, prevention is better than cure. Managing your bird so that this behaviour is not inadvertently encouraged or allowed to develop will prevent a lot of headaches and heartache later.
Firstly, manage your bird’s diurnal cycle. This means no late nights! Simply covering a cage is insufficient – the cover often lets in light and cuts down on ventilation. n Some birds also eat threads off the cover and run into gastrointestinal problems. It is often better to move your bird into a quiet dark room at about 6pm and leave them there until 6 am. Although the bird’s cage can be moved into this room, the use of a night cage – a separate cage from that the bird spends most of its day – serves the dual purpose of giving the bird a shorter daylength while reducing their territorial instincts. In whatever works for you, try and ensure your bird gets at least 12-14 hours of dark each day.
Secondly, manage the bird’s environment to minimise their territorial attachment to a potential nest site. This can be done by: moving the cage to a new location every few days; re-arranging the furniture in the cage regularly; and avoiding placing things in the cage that could be utilised as a nest box. Changing from a day cage to a night cage, as mentioned earlier, can also help to reduce this attachment. Training your bird to come out of the cage voluntarily will also help.
Thirdly, control your bird’s diet. Fat and sugar are two high energy nutrients to be minimised or removed from your bird’s diet. This means avoiding predominantly seed diets, or lots of fruit. As previously mentioned in other articles, a diet based on a well formulated balanced diet and lots of vegetables is not only healthier but helps to reduce your bird’s libido. This is not to say that your bird can’t eat seed, but it should be regarded as a treat or a training reward to be given in moderation, rather than a dietary staple.
Fourthly, maintain a normal human-bird relationship between you and your bird. This is not a master-servant relationship, but nor is it an intense bond that the bird perceives as a bonded pair relationship. Rather, it is a shared relationship as two members of the same flock. Utilise basic reward-based training to maintain a relationship, while avoiding excessive petting, grooming, or kissing. While a pet bird can sit on your shoulder, a closely bonded bird should not be allowed to do this.
But what if your bird is already laying large numbers of unwanted eggs?
All of the environmental, dietary, and social modifications described above have to be implemented. If this is not done, nothing your vet can do will help. Strict lighting control, dietary changes, environmental modification, and breaking down of one-person bonding are all key elements in stopping the egg laying. Eggs should not be removed, or they should be replaced with appropriately sized and coloured marbles.
Once these changes are in place, your avian veterinarian can help with hormonal manipulation. This involves the use of hormones that switch off the production of the sex hormones from your bird’s pituitary gland. These medications can be either injections or a long-acting implant. These are expensive drugs, but do not work in isolation. The length of time they work for varies between individuals and is dependent on how strict the dietary, environmental, and behavioural modifications are made and continued.
If all else fails, your avian vet may discuss surgery to remove the bird’s oviduct with you. However, there are significant risks with this approach. The ovary cannot be removed due to the intricate nature of its blood supply, and some birds may continue to ovulate after surgery, resulting in yolk peritonitis. When combined with the risks of surgery in such a small patient, this procedure is a last resort treatment and should not be considered an elective procedure.
An unwanted spinoff of keeping birds indoors as pets has been a rise in their reproductive activity. When looked at critically, this activity is the result of the mixed signals the bird is getting – long day lengths, secure nest sites, high energy diets, and an apparently suitable mate – all telling the bird that reproductive success is likely.
Sadly, this activity often leads to health and behavioural problems that can result in the death or re-homing of the bird. Excessive egg laying is therefore a common problem that many avian vets deal with regularly.
By recognising the triggers that lead to this behaviour and avoiding them, the bird’s reproductive activity can often be controlled. For those birds who do not respond to simple changes, veterinary treatment can be used.
Prevention is better than cure. Managing your bird’s environment and diet, as well as your own behaviour, can stop egg laying before it gets started. Remember, this is a problem of captivity and it is up to us to manage and prevent it.
Doneley B (2018) Avian Medicine and Surgery in Practice: Companion and Aviary Birds, 2nd ed. CRC Press