Eurasian jays are monogamous and breed once a year in the spring. At the beginning of spring, usually in March and April, unpaired birds spontaneously form gatherings where they choose their mates. In these gatherings, birds pair up and display to each other. They use a wide range of vocalizations, one of which is named the “flight appeal” and is an invitation to fly. Males display more than females and they also chase them. Mating gatherings appear random and may be started by already paired birds chasing and displaying to each other, which excites nearby unpaired birds and encourages them to join in. The gatherings may be as small as three or four birds, but are often as large as thirty or more. These gatherings also sometimes happen later in the season, like in June, though those gatherings are most likely the result of a paired bird losing its mate or nest rather than new birds finding their first mates.
Males offer their mates food as part of courtship. He crushes or tears portions off a food source and offers it to her. If she acts too nervous to accept, he may try approaching her from below, as this is a less threatening way to approach a jay. The birds may call affectionately to each other and engage in a tug-of-war during the ritual. If the female brings the food to her mate, they may pass the food back and forth until one or the other eats it. The ritual appears to strengthen their bond. Later, when the female is busy with the nest, the male will continue to supply her with food.
Mating System: monogamous
Both parents build and line the nest. Their nests are cup shaped and built in bushes or trees. They are constructed of sticks, freshly broken off of branches, and lined with fine roots, hairs, and the birds’ own feathers. Egg-laying commences around the end of March, and usually only one brood is raised per season, 4 to 5 eggs are laid, each weighing about 8.5 grams, 6% of which is the shell’s weight. Both parents incubate. The young hatch in 18 days and are naked and blind. They fledge and first leave the nest when they are 20 to 23 days old, but they remain dependent on their parents. The parents begin to wean them when they are around 40 days old, and they are independent around two months of age, though they continue to rob food from their parents for a few days. Eurasian jays reach breeding age at 2 years.
Breeding interval: Eurasian jays breed once a year.
Breeding season: Eurasian jays breed from March through June.
Range eggs per season: 4 to 5.
Average time to hatching: 18 days.
Range fledging age: 20 to 23 days.
Average time to independence: 2 months.
Average age at sexual or reproductive maturity (female): 2 years.
Average age at sexual or reproductive maturity (male): 2 years.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)
Sometimes only the females incubates, though in many pairs it is both parents. Incubating females clean the nest of parasites by eating them. This behavior seems to be caused by a need to eat anything she finds in the nest that isn’t an egg, lining, or young. Sometimes her need to clean the nest can be exaggerated if she is stressed by the presence of a predator or other stimulus, and she may eat her eggs or young.
When a predator approaches, the incubating bird will react according to the situation. If the intruder is far away and may not have noticed the bird, the parent will simply sneak away from the nest or fly off altogether, sometimes making alarm cries as he or she leaves. If the predator approaches, the parent will crouch lower in the nest, facing the threat, with her bill open. An even closer predator will warrant a defensive threat posture, which involves spreading the wings and crouching down. If the parent decides the only course of action is to attack, she will fly at the predator, attacking it with her claws and beak and crying out using any number of alarm calls, either her own jay calls, the predator’s own calls, or the alarm calls of an entirely different animal.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Male, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)