I know that budgies without a nesting box can usually still mate and not have eggs/babies... and that once you put a nesting box in, it can often encourage them to lay eggs and have babies.

 

Does anyone know actually how it works that they can mate and not lay eggs unless the environment supports it? I mean seems as though it's not like mammals, where mating either results in fertilisation or it doesn't, and if it does, you have to have a baby whether you have a "nest" or not.

 

Is it a bird specific thing or can other species do this too?

 

I can't figure out how to google this question to get a good website article about it lol

Many species will only produce young when conditions support the raising of babies. Kangaroos also are the same.

I think that's generally the case however, not always!

 

I currently have a hen who is laying eggs on the bottom of the holding cabinet and incubating them- I keep on removing them and fostering them out but it hasn't stopped her!

It sure is fascinating......

 

Does anyone know how it works though, like, scientifically? I just find it amazing that something external like the presence of a hole in a tree can actually trigger off a hormonal/physiological/behavioural response in an animal. Would love to learn more about it.

It is based on seasonal rainfall, the knowledge they have of food sources and how long they will have food and water to sustain babies.

But they don't consciously/mentally control it right? So it must be a hormonal/chemical related thing or something?

I think it is, I have a funny feeling I can remember reading or hearing somewhere that they see conditions as being okay to nest in and the females secreats a hormone that aids in egg production. It's not something that can turn on and off at a whim but something that the environment effects. A vet once told us that cronic egg layers do not have the ability to turn off the secreation so they just keep laying as the eggs form. Hmmm I know I have a reference somewhere will have to look it up!

Thanks AV aren't budgies amazing

It is really complicated, but I can tell you the gist of it, extrapolating from what I know of mammalian reproductive cycles. I know it must be similar, because we use the same hormone in birds as we do for the mammals to help them stop laying/coming into season.

 

It is initiated by a series of environmental inputs including plenty of food and water, temperature, the presence of a male, mating rituals, vocalisation, and the length of day. For example, in mammals a hormone called melotonin is excreted in the absence of light. Melotonin acts on the hypothalamus, an area in the brain which you might call Hormone Central. Melotonin affects different species differently. In sheep it is decreasing daylight that initiates the reproductive hormones, so they breed in autumn. In horses it is increasing daylight, so they breed in spring. I assume budgies must be increasing daylight breeders. I have also read that bird brains can directly tell how much light there is through their eyes and through their skull!

 

Many hormones interact at three basic levels: hypothalamus -> pituitary -> target organ. The way the three interact is intricately linked. In the case of reproductive hormones, the hypothalamus secretes GnRH (gonadotropin releasing hromone) to turn on the pituitary, which secrets LH (luteinising hormone) and FSH (follicle stimulating hormone) to target the gonads to produce testosterone (males), oestrogen or progesterone (for females. In mammals, these relate to being "in heat" and "being pregnant").

 

Oestrogen initiates a series of events including readiness for the ovaries to ovulate (release an unfertilised egg for fertilisation), and other preparations for the oviduct to prepare for egg laying/chick production. The presence of oestrogen also targets the hypothalamus, telling it to turn on and produce more oestrogen (if conditions are right and other hormones are increasing/decreasing) or turn off (again in the right conditions, the switching off of the original hormone by the last hormone is called "negative feedback"). I won't go into further detail, but it is a very delicate play between all these hormones. In males, testosterone enlarges the testes and induces them to manufacture sperm.

 

So a budgie may breed but its reproductive tract will not be ready, and this readiness depends on external and internal factors turning hormones on and off. It affects both males and females.

 

In birds and other mammals, there is an implant we can use that mimics GnRH, which initiates the cascade and then turns itself off (negative feedback). This is used in some chronic egg laying birds to stop that hormone cascade and to tell their bodies that it is not the right season.

 

Contrary to your original statement, in mammals that aren't primates, the environment can play a huge role. If you mate them in the wrong season they will be completely infertile, and if you mate them when conditions aren't quite right you will get poor results. As I've mentioned, sheep and horses depend on daylight. In the horse breeding industry where there is pressure to produce a foal each year, some studs will leave the lights on until 11pm to make the horses' brains think that the day length is long and therefore shorten the period where they aren't ready to mate. There are things like the ram or stallion factor, where the mere presence of the male can make a female go into heat (we call it "teasing" where a vasectomised male is put in with the females, he still produces testosterone but is unable to impregnate the females).

 

I hope that helped a little, it is based more on mammals, but I think it is very similar. If you would like me to clarify something, I will try my best. http://people.eku.edu/ritchisong/avianreproduction.html has a nice diagram regarding the three levels of hormones I was talking about.

Edited June 22, 200916 yr by Chrysocome

Wow thanks Chrysocome! That certainly does answer all my questions haha -- that is so interesting, and I really appreciate you taking the time to explain all that so well!