Chronic Egg-Laying in Birds

Chronic egg laying occurs when a female bird lays more eggs in one clutch than the usual number or lays repeated clutches of eggs. A clutch is defined as the total number of eggs laid in one nesting attempt. Chronic egg laying is more common among pet birds that live without mates and that therefore lay infertile eggs.

Chronic egg laying may lead to malnutrition due to the chronic depletion of calcium to produce eggshells. In time, calcium depletion may result in egg binding (see handout "Egg Binding in Birds"). Chronic egg laying may also lead to infection or inflammation of the oviduct, which in turn may cause problems with egg laying that often lead to egg binding.

Do certain bird species tend to be chronic layers?

Single female cockatiels, lovebirds, eclectus parrots, and budgerigars (parakeets) often become chronic egg-laying birds and, to a lesser extent, amazon parrots and macaws. However, any species of bird can lay eggs chronically. Hand-raised birds that see their owners as mate substitutes generally develop the problem more frequently than wild-caught birds.

What causes chronic egg laying?

The cause of chronic egg laying is not fully known. However, something stimulates these birds to lay more eggs than normal, or more frequently than normal.

• Some individual birds may have a genetic defect that allows the ovary to be overproductive.
• Ovarian cancer may contribute to excessive egg laying.
• Environmental stimulation has a dramatic effect on the stimulation of the ovary to start egg production.

The following factors may contribute to hormonal stimulation that can lead to chronic egg laying: 

• Access to nesting areas in the house or the cage
• Constantly stoking the bird on its back or pelvis
• Having a male bird of the same species in the same room but not the same cage

A lack of hormonal feedback to a bird’s brain, telling the bird to stop laying eggs, likely occurs in chronic egg-laying birds. Removing eggs that are already laid may induce birds to lay even more eggs, depending on the birds’ species.

Some birds, such as budgies, are determinate layers, which means that they will only lay a set number of eggs per clutch, no matter what. Others, such as cockatiels, may lay one egg after another, continuously, particularly if they are not sitting on recently laid eggs or eggs are removed from their nest. These birds are called indeterminate layers. The number of eggs laid has to do with the bird’s brood patch — the bare skin on a bird’s abdomen that transfers body warmth to the eggs during incubation. The tactile sensation in this area lets the layer know she has reached the appropriate number of eggs.

Are there any health problems associated with chronic egg laying?

Egg laying uses up a great deal of the bird’s stores of calcium not only to make eggshells, but also to help contract muscles and stimulate nerve conduction to push eggs down the bird’s reproductive tract. For birds on healthy diets, this is not a problem, as calcium from the bird’s diet can replace depleted body stores. However, birds eating all-seed, calcium-deficient diets may not be able to replace these depleted stores quickly enough, and they may suffer from an overall lack of body calcium (hypocalcemia).

Hypocalcemia can lead to egg binding, seizures, and even death. After months or years of chronic egg laying, the oviduct may become diseased, and produce abnormal or soft eggs. Egg shell material may also build up in the oviduct, which may eventually lead to a blockage of the entire reproductive tract. This condition requires a salpingohysterectomy — surgery to remove the reproductive tract.

Are there any other problems associated with chronic egg laying?

Birds that lay eggs chronically are often less friendly when they are under the powerful influence of reproductive hormones. They may act more aggressively and become more vocal, as they protect their clutch. They may also become more cage protective and territorial. As mentioned, chronic egg layers may develop hypocalcemia, which can make the bird weak and lethargic.

What can I do if my bird is a chronic egg layer?

There are some things you can do to help deter chronic egg laying:

• Decrease the number of hours the bird is exposed to daylight or room light to 8 hours per day, which may decrease the stimulus to lay eggs.
• Move the bird's cage to a different location in the house to decrease her feelings of comfort and security, making her less likely to lay eggs.
• Minimize handling of your bird, especially stroking or petting her on the body, as these actions often send a sexual message to the bird to continue laying. It is also possible that decreasing the amount of time spent with your bird may help deter further egg laying.
• Do not remove eggs from the cage after they have been laid, so that they have contact with the bird’s brood patch. Leaving the bird to sit on her eggs for a complete incubation period (generally 21–28 days, depending on the species) may signal her body to stop laying and may allow her to rest and replenish body calcium stores. At the end of this period, the eggs may be removed, one every 1–2 days. However, some birds may start to lay again after the eggs are removed.
• If there is a male bird of the same species in the same room, move him to a separate room.

If these steps do not work, are there any medical treatments for chronic egg laying?

Medical therapy may be needed for chronic egg layers that have been laying so long that they are debilitated, or for egg-laying birds that have developed problems such as egg binding. Birds in these situations should be examined by an avian veterinarian as soon as possible.

Your veterinarian may want to administer leuprolide acetate hormone injections to try to stop egg laying temporarily. These injections are very safe and generally do not have significant side effects. However, birds typically stop egg laying for only 3–4 weeks, and injections need to be repeated to have continued effectiveness. For some egg-layers, this is enough time for them to recover and replenish depleted body stores of calcium. Calcium supplementation may be necessary in some cases to treat or prevent hypocalcemia.

For other birds in which egg laying needs to be halted for longer periods, your veterinarian may perform a simple surgical procedure, in which an implant is placed under the bird’s skin, over its back. The implant contains deslorelin, a hormone that is slowly released over a period of weeks to months to inhibit further egg laying. The duration of this inhibition varies depending on the bird’s species and her specific hormonal patterns, but in general it lasts an average of 3–6 months or longer.

As a last resort, if deslorelin fails to stop egg laying, veterinarians can permanently prevent egg laying by performing a salpingohysterectomy (removal of the oviduct). This surgery should only be performed by an experienced avian veterinarian, as it entails significant risk (including death). Owners of chronic egg-laying birds that require treatment to stop egg laying should speak to their avian veterinarian to determine the best course of treatment for their bird.