The Eurasian hoopoe is a medium-sized bird, 25–32 cm (9.8–12.6 in) long, with a 44–48 cm (17–19 in) wingspan. It weighs 46–89 g (1.6–3.1 oz). The species is highly distinctive, with a long, thin tapering bill that is black with a fawn base.
The diet of the Eurasian hoopoe is mostly composed of insects, although small reptiles, frogs and plant matter such as seeds and berries are sometimes taken as well. It is a solitary forager which typically feeds on the ground. More rarely they will feed in the air, where their strong and rounded wings make them fast and manoeuvrable, in pursuit of numerous swarming insects. More commonly their foraging style is to stride over relatively open ground and periodically pause to probe the ground with the full length of their bill. Insect larvae, pupae and mole crickets are detected by the bill and either extracted or dug out with the strong feet. Hoopoes will also feed on insects on the surface, probe into piles of leaves, and even use the bill to lever large stones and flake off bark.
Hoopoes are monogamous, although the pair bond apparently only lasts for a single season. They are also territorial. The male calls frequently to advertise his ownership of the territory. Chases and fights between rival males (and sometimes females) are common and can be brutal. Birds will try to stab rivals with their bills, and individuals are occasionally blinded in fights. The nest is in a hole in a tree or wall, and has a narrow entrance. It may be unlined, or various scraps may be collected. The female alone is responsible for incubating the eggs. Clutch size varies with location: Northern Hemisphere birds lay more eggs than those in the Southern Hemisphere, and birds at higher latitudes have larger clutches than those closer to the equator. In central and northern Europe and Asia the clutch size is around 12, whereas it is around four in the tropics and seven in the subtropics.
Hoopoes have well-developed anti-predator defences in the nest. The uropygial gland of the incubating and brooding female is quickly modified to produce a foul-smelling liquid, and the glands of nestlings do so as well. These secretions are rubbed into the plumage. The secretion, which smells like rotting meat, is thought to help deter predators, as well as deter parasites and possibly act as an antibacterial agent. The secretions stop soon before the young leave the nest. From the age of six days, nestlings can also direct streams of faeces at intruders, and will hiss at them in a snake-like fashion. The young also strike with their bill or with one wing.
The incubation period for the species is between 15 and 18 days, during which time the male feeds the female. Incubation begins as soon as the first egg is laid, so the chicks are born asynchronously. The chicks hatch with a covering of downy feathers. By around day three to five, feather quills emerge which will become the adult feathers. The chicks are brooded by the female for between 9 and 14 days. The female later joins the male in the task of bringing food. The young fledge in 26 to 29 days and remain with the parents for about a week more