Mating

Birds have a couple ways of mating,but the most common and the one I will focus on is mating by singing to attract a mate. Most bird mate by singing and its noticeable most birds sing at dawn and sometimes at dusk. They sing in the morning because scientists looked at a bird's energy reserves throughout the day and found that since birds cannot predict exactly how much energy they will need to survive the night, they tend to over-eat before they go to sleep. Most nights are not that cold, so the bird still has reserves of energy at dawn. They use spare energy on a quick burst of song before their breakfast.
Another smaller peak in energy reserves happened at dusk, which is after their supper and their using some end of the day “extra energy” to sing before they go to bed.
So a bird‘s first priority is to make sure it has enough to eat. If it has any spare time and energy, it tries to attract a mate by singing a song.
One interesting note on patterns of breeding is that birds with bright colors attract mates easier and generally have more offspring, the draw-back of being brighter though is that they get caught by predators much more often then those birds of duller colors. Duller colored ones survive longer and easier but since they are more hard to find, they don’t find mates as easy, resulting in less off-spring.
During the breeding season a bird’s(more specifcly male’s) sexual organs may be several hundred times larger than they are during the rest of the year and can account for as much as a tenth of the male's body weight. The massive enlargement of the testes is triggered in temperate-zone birds by day length. As the days lengthen in the spring, increases in hormones produced by the brain initiate this. This stimulus occurs weeks in advance of the actual breeding season, so that the male arrives on the breeding grounds with the organs fully developed. A similar sequence results in the enlargement of the female reproductive organs, development of eggs in the ovaries and so on.
These hormones also cause the skin to brighten, skin or feathers change colors and stimulate singing and mating behavior.
When the birds conceive, the sperm remain for a while in storage at the lower end of the female “oviduct” and then swim to the upper end of that duct to fertilize the egg.
In most species, the birds mate on the ground, on a tree limb, or on some other perch. Some aquatic birds (ducks) mate primarily in the water. White-throated Swifts, however are interesting in how a group may come swooping down a canyon at high speed, shortly after dawn, with pairs tumbling together as they mate in midair.