The Full Moon Call of the Tawny Owl

By Jose Luis Gallego, environmental communicator (@ecogallego)

On autumn nights, when the fields are bathed in moonlight and shadows envelop the hills, we might hear one of the most distinctive sounds of the forests: the call of the tawny owl. As it flies around its home range, the owl repeatedly emits a low, deep, and powerful hoot.

Elusive and very wary, the tawny owl is usually heard not seen. In fact, even if one was sitting in the tree directly in front of us, we might not see it, despite its large size, because the tawny owl has among the most mimetic plumage of any European bird.  Although generally grey-brown in colour, the feathers of the tawny owl (Strix aluco) can also take on shades of brown, toast, or clay, either mottled or striped, the perfect camouflage to blend with the patterns of tree bark.  

The tawny owl has a compact, rounded build, with a bulky head that is almost as large as the rest of its body. It lacks the characteristic ear tufts sported by another nocturnal bird of prey commonly found in our forests: the lesser horned owl. 

A tawny owl 

Owls have eyes with a nictitating membrane, which keeps them perfectly lubricated, and widely dilating pupils, up to a hundred times more light sensitive than ours, so that these birds can see very well, even in complete darkness. Then add the fact that owls can turn their heads almost full circle (270 degrees), and their capacity of sight becomes simply extraordinary. 

The tawny owl has two large round black eyes, which seem even larger, because of the facial disk around them. Up to 45 cm in height, tawny owls can weigh more than half a kilo and reach a wingspan, the distance from wing tip to wing tip, of a metre.  

During the day, tawny owls hide away in their roosts: a dark corner of the forest or wooded area from which they don’t emerge until well after nightfall. In contrast to other nocturnal birds of prey like the little owl, tawny owls only fly when it is completely dark. This is when they head out to hunt, preying on small nocturnal rodents that are their main food source.

Given their ability to adapt to all forest ecosystems, even settling in urban environments, tawny owls are among the most common and widely distributed nocturnal birds of prey on the Iberian peninsula.  Tawny owls live in all kinds of forests and wooded areas: from coastal ranges to high mountains; from pinewoods and beechwoods, to groves of oaks, poplars, and olive trees, even meadows.  

But they are also frequently found in urban parks and gardens, where we can hear their unmistakable vocalization near dawn, when the street noise dies down, especially on full moon nights in autumn. Rather than inspiring fear, their enigmatic, mysterious call connects us, instantly and viscerally, to nature.   

Since tawny owls are very attached to the tree where they roost, we can follow their call to its source. The next clue to help us spot one is to look for their pellets, usually scattered on the ground below the tree. Pellets are clumps of hair and bone which birds of prey and certain other birds regurgitate after swallowing their prey. In the case of tawny owls, these tend to accumulate directly below their roost.

A tawny owl in a tree trunk 

Nocturnal birds of prey play a crucial role in nature, because they control rodent populations, which would otherwise reach excessive numbers and turn into plagues. Although tawny owls can also eat other birds, reptiles, or insects, and even catch larger prey like rabbits, their diet essentially consists of small mammals and rodents: shrews, voles, rats, mice, and similar prey.  The tawny owl therefore does more than provide a soundtrack to rural nights: like all owls, it gives farmers an invaluable service. 

The breeding season of tawny owls begins in late autumn and extends well into the winter. They usually build nests in the cavities of large tree trunks. The female lays a clutch of three to five eggs, which hatch after about a month. The owlets start flying around the vicinity of the nest in early spring and become fully independent by summer.