Birds are without exception hatched from eggs, and most of them provide care for their offspring. Both of parents take care of the offspring (male and female might take turns while incubating (sitting on the eggs) or not). Sometimes, with the hen for example, only female will incubate, and in some cases, only the male (with phalarope for example). However, there are birds that after hatching eggs do not care for their offspring. Such is the case with the common cuckoo, laying its eggs in the nests of other birds, primarily in the nests of the whitethroat, garden warblers, robins and hedge accentor. The young cuckoo, which usually hatches before the young of the host, throws out the offspring of the host (eggs and young) from the nest, because otherwise it would have to share food between each other, and the cuckoo would get too little food and die soon after.
Birds build nests of various materials, most often they coat them with hair or feathers that they find around nests or with feathers plucked from their own bodies (ducks for example). Falcons and owls are known for not building nests, because they laid their eggs on the bare ground of rocky ledges, in hollows or in the attics of buildings. Some birds settle in abandoned nests of other birds. Owl nests are usually covered with the remains of prey.
In relation to the position, we distinguish several types of nests:
a) nests on the ground – located on the land, forest litter, sand, ... sometimes hidden in the vegetation, between stones, sometimes in the open, without shelter. They can be in the form of shallow depressions on the ground (for example, ringed plover) or built in the shape of a cone (mute swan);
b) floating nests – built of water plants on the water surface, anchored between the reeds and shrubbery, attached to underwater vegetation or the bottom (little grebe);
c) nests in trees – located usually in a crotch, close to the trunk (tree) and the top branches; they can be of different shapes, from flat (common wood pigeon) to the bowl-shaped (goldfinch); there are also the globular nests, which are either free hanging (Eurasian Penduline-Tit) or wedged between the branches (long-tailed tit). This group can also include nests located in the bushes and nests that hang between herbaceous plants (warbler);
d) nests in cavities – located in holes of trees. Birds that nest in this way are the so-called "cavity nesters" and we divide them into two groups: 1 - primary cavity nesters, those that excavate their own holes in the tree (woodpeckers) and 2 - secondary cavity nesters, those that settle in holes constructed by primary cavity nesters or in holes that naturally occur in dying and decaying heartwood; those often nest in birdhouses (tawny owl);
e) nests in holes - tunnels – dug in clay or sandy shores and rocks. They can be different in length, and the chamber with eggs is in the end of the tunnel (kingfisher);
f) nests on the rocks – birds usually nest on rocky shelves (peregrine falcon), in rock crevices (common northern wheatear) or the nest is attached to the cliff or rock shelter (common house martin).
According to the time hatchlings remain in the nest, birds can be divided into two groups:
Squatting, recently fledged (nidicolous hatchlings) – after hatching of eggs, little birds are naked, helpless, and often blind and therefore require more foster care; they will remain in the nest for a long time after hatching and leave it only when they learn to fly.
Downy (nidifugous species) – when they are hatched, they are covered with down feathering; they leave the nest soon after hatching and they are capable, under the supervision and help of adults, to look for food for themselves.
Migration of birds is the flight of birds from breeding to wintering areas and back, happening every year. Bird species that migrate only in parts are called partial migratory. Those that do not move are called resident. The most important environmental reason for the migration of birds is the availability of food and temperature. The migration of birds is always very exhausting and many individuals do not survive.
Montenegro is located in the Adriatic migratory corridor, one of the most important routes of migration in Europe, and few million birds fly over this route each year.
The most beautiful example of migration is the Arctic tern (Stern paradisaea), which annually travels more than 80,000 kilometers from pole to pole, passing each climatic region.
Watch the video at the following link: