As early as the 1930s, it was shown that reproduction in nature is influenced by day length and the amount of light. Light, which penetrates the skull, promotes the growth of genitals. As the days grow longer, the birds begin to look for a territory to initiate reproduction. Captive birds are exposed to artificial light almost day and night to keep egg production going.
Territory
Finding a breeding ground
The first thing birds do when extending the days is to choose a territory. There must be breeding facilities, a sufficient supply of food and it must be safe. The territory is demarcated and it must be ensured that no intruders come to disturb the area. The territory is defended by singing: I’m here, don’t disturb me. Threats can also take place and sometimes even physical violence is involved.
Food offer in the spring
Lots to eat
The weather conditions improve in the spring and the days get longer. This is more the case in the southern hemisphere than in the northern hemisphere. In the south, breeding starts earlier and there will be more clutches per season. In the spring, birds have access to numerous food sources. The females need more food than normal during lay and the newborn fry also need food. For example, birds that eat insect larvae start reproduction earlier than those that eat adult insects. They usually wait until June.
Exception
Tawny owls start breeding in the winter months. In the winter months, the trees and shrubs are still bare and it will be difficult for the prey to hide from the owl.
Balts and pairing
Balts
In birds, the males seduce the females. They do that through courtship. The courtship comes in many forms. Singing a male can entice a female. Similarly, a bird’s throat can swell, the warts or wattles will turn brightly. In the air, birds show the most acrobatic flying acts or are engaged in offering food to a future mate. A mating dance is also a form of courtship. Likewise, a male’s plumage can take on the most beautiful colors. The goal is to stand out.
Pairing
Females select their males by age, song, stature and courtship behavior.
Some couples stay together for life, others split up after mating. Couples also stay together until the young fledge.
Nest construction
Generally, the females build the nest. Sometimes helped by the males. Nests vary greatly in size and shape. One nest is neatly woven and the other is built meager with a few twigs. Nests can be high in the trees, between dense shrubs, in the reeds along the water or just in the middle of a lawn. The purpose of a nest is protection from the elements and protection from nest robbers or other intruders.
Mating
When the nests are ready, the actual reproduction begins: mating. The size of genital organs is increasing in enormous amount. A female’s ovary (ovary) can grow as large as 1500 times. The male’s testicles grow to about 300 times the size. When mating, birds put their cloaca against each other. The cloaca is the opening where feces, urine and eggs come out in birds, reptiles and amphibians. The seeds can reach the fallopian tube of the female from the seminal tube through the cloaca. Females mate with one or more partners.
Laying and brooding eggs
Number of eggs
The number of eggs a bird lays depends on the species. Some birds lay one egg per year, others lay twelve and also have several clutches. This depends on the species or size of the birds. It also depends on the environment, lifestyle and food supply. Usually the female broods, that is incubation mentioned. After laying all the eggs, she starts with that. In some birds, the female and male take turns brooding.
Breeding spot
Parent birds that are engaged in breeding lose down on their bellies just before breeding. There the skin is bare and has a lot of blood. This place will breeding ground or brood spot mentioned. The eggs are against this spot. The bird sometimes turns the eggs so that all sides remain warm. Depending on the species, the eggs hatch after 12 (sparrow, starling) days or only after 34 (stork) days.
And then the education to fly, eat, sing and care begins.