Excessive Egg-laying in Birds
I see many pet birds that have been laying too many eggs and are beginning to fall ill. The species I most commonly see are canaries, Gouldian finches, zebra finches, budgies, cockatiels, green-cheeked and other small conures, and Moluccan and umbrella cockatoos, and hybrid macaws, although any species of bird may be affected. The clutch size varies depending not only on the species of bird, but in some cases on the breed. For some birds, it’s not unusual to double-clutch or triple-clutch in a year without harm, while in other birds it is extremely rare to produce more than a single clutch. This variation in egg output by species and breed makes it difficult to know when too many are being produced in too short a time; in general, you have to know the breeding particulars of a species in order to recognize excessive egg-laying.
Before I go any further, let me clear up some of the confusion about egg-laying. In most species of birds, a hen (female) does not need a mate in order to produce eggs. There are some species that require either the courtship calls or displays of the male or actual copulation in order to induce ovulation, but the majority of birds have reproductive cycles cued to the light cycle (also known as photoperiod). Spring layers are triggered by gradually increasing day length from winter to spring. Fall layers are triggered by gradually decreasing day length from summer to fall. A single bird, alone in the home except for its non-avian companions, is the most common patient I see with excessive egg-laying.
A bird doesn’t need a proper nest area in order to lay eggs. If the hormonal cycle is working, an egg will be produced whether or not there is an appropriate place to lay it. Many clients discover eggs on the bottom of cages, in food bowls, or even precariously balanced on stuffed toys attached to perches high up in cages. The right sort of nest area, or even one of the “sleeper tents” may stimulate egg-laying in birds that are already primed. It’s uncertain if there is any increased risk of egg-binding (dystocia) if a bird does not have an appropriate nest.
A bird doesn’t need extra calcium or a special diet to lay eggs. Many birds will produce eggs on startlingly poor diets, even when the birds are showing signs of malnutrition. These birds are at higher risk of becoming ill as the eggs withdraw vital nutrients from the females. Calcium, fat, vitamin A, and trace minerals are rapidly depleted in malnourished birds, and this can lead to life-threatening problems.
Finally, one misunderstanding is at a bit of a tangent. I’ve had clients puzzled how their “male” birds have just produced eggs. The sex of a bird isn’t confirmed by lack of eggs; in other words, a bird that has never laid eggs is not necessarily a male. Even DNA sexing via blood, feather, or egg residue is not 100% accurate. If a bird is not sexually dimorphic, the only way to be 100% sure of its sex is to find an egg or to have the bird surgically sexed via endoscopy. I’ve known many “male” birds that have laid eggs after being alone for several years.
Factors affecting clutch size
Analyses of clutch size represent a complex branch of ornithology and is beyond the scope of this article. It is clear that there are genetic and environmental factors that influence clutch size. Some ornithologists prefer to call them long-term considerations (e.g., longevity) and short-term contraints (e.g., food availability). Some general trends are known. For example, over half of the bird species studied has 2 to 3 eggs in a clutch while over 6,000 species produce 5 or fewer in a clutch. Tropical species tend to lay fewer eggs than temperate species, and longer-lived birds produce smaller clutches than shorter-lived birds. Thus a small tropical species of bird is more likely to lay 3 eggs than 5 eggs in a clutch.
For captive-bred birds, within a species the biggest determinants of clutch size appear to be the genetics (or bloodline) and the diet. Some breeders select for larger hens that produce large eggs so that the hatchlings are larger; these larger hatchling parrots may sell at a premium price. Others have selected for the number of eggs that the hen produces regardless of the size of the hen, and the hatchlings are often smaller; while these may sell for less than the larger babies, more are available for sale per clutch. I’ve noted this trend most commonly in African greys and budgies.
Birds that are fed a balanced diet tend to produce larger clutches than ones on suboptimal diets. It’s particularly important to provide sufficient protein, fat, vitamin A, calcium, and trace minerals to support egg production, and these must be balanced with other nutrients in order to be most effectively utilized. Be aware of the amount of calcium found in a supplement and avoid sources of calcium that also have high levels of heavy metals. For example, oyster shell flour has 38% calcium and 0.07% phosphorus but has enough lead so that it is not recommended by many human pediatricians as a source of calcium for children. It also has over 3000 ppm of iron. Iron has profound effects on the hematopoietic system and immunity as well as being likely to cause liver damage, particularly in birds like lories and toucans. An unhealthy hen will not produce healthy fertile eggs.
What is “excessive-egg laying”?
As mentioned, you need to know the breeding habits of your breed and species of bird in order to recognize “excessive egg-laying”. (See Table 1) The following general guidelines apply:
- A hen continues to produce eggs after reaching the upper end of reported clutch size
- A hen starts to lay more eggs several days after the first clutch is finished, and before the first clutch’s last egg would have hatched
- A hen that lays one or more eggs outside of the normal breeding season, particularly if the eggs are laid at irregular intervals
- A hen that is producing eggs with one or more of the following: thin shells, abnormal coloring, undersized, or misshapen
- A hen that is steadily losing condition with each egg or showing signs of illness (loss of appetite, labored breathing, change in stools, fluffed, lethargic, unsteady on feet, spending a lot of time sleeping on the nest rather than being watchful, or spending a lot of time on the bottom of the cage)
What do I need to do?
There is some debate about what is the best way to manage an excessive-egg layer. First, if the bird is seemingly ill or is producing eggs that look abnormal, get her to an experienced bird veterinarian. Your bird’s life is on the line. If the hen is seemingly healthy, you can try a couple of tricks to shut-down egg-laying but do not delay getting her to an experienced veterinarian if she shows any distress or signs of illness. You may end up at the veterinarian anyway if you are not seeing results within a few days of trying some of these suggestions.
Dummy eggs are often used when eggs are pulled for artificial incubation or as a form of birth control. As an egg is laid, it is replaced by a dummy egg that is the same size and shape as the real egg. Most hens shut down egg production after they have laid the typical clutch size. Sometimes putting in enough dummy eggs to reflect the upper end of the clutch size will cause even a prolific hen to stop laying.
Dried raspberry leaf supplement may work synergistically with light cycle manipulation (see below) but can also be used on its own. There’s not any hard-and-fast rule for supplementation, but typically ½ to 1 teaspoon per half-pound of food is sufficient. The exact method of raspberry’s action is undocumented but it seems to have some hormone-like action that stops hens from further ovulations, and may help ease passage of eggs already shelled and in the oviduct. It may also be brewed as a tea and used as a drinking source, but this has not been as dependable as consumption in food. If it does work, it may be administered as a prophylactic treatment in future years. The raspberry leaf should be started about 4 weeks before the date that the first egg was laid.
Manipulation of the light cycle is a simple but stressful way to interrupt egg-laying. Leaving the hen in a cage exposed to continuous light for 3 to 7 days in a row may upset the circadian and annual rhythms to “reset” the reproductive hormones to a resting state. Most birds will rest with 3 days of continuous bright light but some may need up to 7 days. The light needs to be bright at all times, about as bright as a room gets in the middle of the day. You may need to leave on 300 to 400 watts worth of bright white incandescent bulbs in the room with the cage, or about 4200 lumens worth of daylight compact fluorescent bulbs (i.e., 95 CRI, > 5500°K). You have to remove the nest box or anything that the bird could hide in or under to get away from the light. If the hen goes off food or starts to appear fluffed or otherwise stressed, the natural day-night cycle should be resumed. Light cycle manipulation can also be used as a preventive, with the treatment started about 3 to 4 weeks prior to the date that the first egg was laid. If the bird continues to lay after a light cycle treatment, more aggressive intervention may be needed.
Many hens do not respond to home treatments. An experience veterinarian will perform a thorough examination on the hen and may recommend a variety of diagnostic tests to better assess the bird’s condition. If there is a problem, that will need to be corrected. It’s not unusual for older hens to have a diseased ovary, either from infection or a tumor, that has sparked the unusual egg laying. In some cases, a veterinarian may recommend injections with leuprolide acetate or other hormones. Leuprolide is an expensive drug, and may need to be repeated three or more times. A cockatiel may require $75 worth of leuprolide which a large cockatoo may require $400 or more each injection. The veterinarian may recommend the raspberry leaf and light cycle too as adjunctive therapies for the raspberry leaf. There are many other possible treatments that may be offered depending on exactly what your veterinarian thinks is wrong with your bird.
In some bird surgery is needed. Removal of the ovary is difficult in many birds and requires expert avian surgeons comfortable with endoscopic surgery. Salpingectomy, removal of the oviduct, is a simpler procedure may prove practical for birds that are excessive egg-layers with seemingly healthy ovaries. This surgery leaves behind the ovary but removes the oviduct and thereby breaks an important part of the hormone feedback loop that governs egg-laying. This works very well but there is a slight risk that a hen may ovulate into its body cavity if the feedback loop continues to function.
Excessive-egg laying can be a life-threatening disease of many common pet birds, as well as the more uncommon species in captivity. While there are some steps you can take to stop this physiological process, often the hens are in need of the care of an experienced avian veterinarian. Don’t delay – if you are not certain that your hen is able to cope with the number of eggs she has laid, schedule an appointment!
Table 1. Commonly kept species and their expected clutch sizes.
|Species||Common Clutch Size||Normal Range|
|Blue & gold macaw||3||2-4|
Kevin Wright DVM DABVP (Reptiles & Amphibians)
Wright Bird & Exotic Pet House Calls
4902 S Val Vista Drive, Suite 108
Gilbert, AZ 85928
(480) 495 3420
FAX (480) 323 2947