During the spring the frog's pituitary gland is stimulated by changes in external factors, such as rainfall, day length and temperature, to produce hormones which, in turn, stimulate the production of sex cells - eggs in the females and sperm in the male.
The male's nuptial pad also swells and becomes more heavily pigmented.
 Common frogs breed in shallow, still, fresh water such as ponds, with spawning commencing sometime between March and late June, but generally in April over the main part of their range.

The adults congregate in the ponds, where the males compete for females.
The courtship ritual involves noisy vocalisations (croaking) by large "choirs" of males.
The females are attracted to the males that produce the loudest and longest calls and enter the water, where the males mill around and try to grasp them with their front legs — although they may grasp anything of a similar size, such as a piece of wood.
The successful male climbs on the back of the female and grasps her under the forelegs with his nuptial pads, in a position known as amplexus, and kicks away any other males that try to grasp her.
He then stays attached in this position until she lays her eggs, which he fertilises by spraying sperm over them as they are released from the female's cloaca.
The courtship rituals are performed throughout the day and night but spawning typically takes place at night.
The females lay between 1,000 and 2,000 eggs which float in large clusters near the surface of the water.
After mating the pairs separate, the females will leave the water and the males will try to find another mate.
Within three or four days all the females will have laid their eggs and left the water and the males disperse.
During the spring the frog's pituitary gland is stimulated by changes in external factors, such as rainfall, day length and temperature, to produce hormones which, in turn, stimulate the production of sex cells - eggs in the females and sperm in the male. The male's nuptial pad also swells and becomes more heavily pigmented.  Common frogs breed in shallow, still, fresh water such as ponds, with spawning commencing sometime between March and late June, but generally in April over the main part of their range. 
The adults congregate in the ponds, where the males compete for females. The courtship ritual involves noisy vocalisations (croaking) by large "choirs" of males. The females are attracted to the males that produce the loudest and longest calls and enter the water, where the males mill around and try to grasp them with their front legs — although they may grasp anything of a similar size, such as a piece of wood. The successful male climbs on the back of the female and grasps her under the forelegs with his nuptial pads, in a position known as amplexus, and kicks away any other males that try to grasp her. He then stays attached in this position until she lays her eggs, which he fertilises by spraying sperm over them as they are released from the female's cloaca. The courtship rituals are performed throughout the day and night but spawning typically takes place at night. The females lay between 1,000 and 2,000 eggs which float in large clusters near the surface of the water. After mating the pairs separate, the females will leave the water and the males will try to find another mate. Within three or four days all the females will have laid their eggs and left the water and the males disperse.
Common frog