There is something almost magical about Short-eared Owls, a sense of otherworldliness that comes from their nomadic nature. For many birdwatchers it is the winter months that provide the best opportunities to catch up with this species. Wintering ‘shorties’ make use of lowland grazing marshes, areas of early-stage plantation and rough grassland - habitats that in previous decades might once have supported breeding pairs.
Better up north
The three Breeding Bird Atlases show how the breeding range of the Short-eared Owl has contracted northwards within Britain. The species is becoming increasingly restricted to our northern uplands, the Hebrides and Orkney. Short-eared Owls are nomads, turning up to breed wherever their favoured small mammal prey are abundant. Historically, large numbers turned up to exploit the plagues of Field Voles that once occurred in parts of Scotland and northern England, their populations changing dramatically from one year to the next. The northwards retreat has virtually seen the disappearance of the population that once bred around the East Anglian coast, south to the north shore of Kent, and the loss of the species from the brecklands of the Norfolk/Suffolk borderlands. It is thought that our breeding population now stands at between 750 and 3,500 pairs but, like many things about the species, there is uncertainty around these figures because of our wider lack of knowledge about them.
Small mammal specialist
The Short-eared Owl is a specialist predator of small mammals, predominantly voles and the Field Vole forms c.90% of the prey taken. Short-eared Owls can be seen quartering an area of suitable habitat, hunting on the wing and listening and looking for signs of prey in the grass below. Quartering flight involves a mixture of flapping and gliding, the bird sometimes hovering before dropping down onto an unsuspecting small mammal or bird.
Bird prey can be important at some sites and at some times of the year, with pipits, small waders and other species taken more often during the winter months. It is not unusual to see several Short-eared Owls hunting over the same area, sometimes hunting alongside Barn Owls and even Kestrels. These hunting ‘shorties’ will often roost on the ground using taller cover, typically close to the sites where they have spent time hunting.
On the wing
While many Short-eared Owl populations are nomadic, some live a more settled existence. Information from Short-eared Owls ringed as young at the nest, reveals that our birds undertake long-distance movements, dispersing away from the area in which they were born. A wider examination of movements, looking across Europe, reveals that the average distance moved after ringing has declined since the 1970s. This may reflect the pattern of less pronounced vole cycles and the amelioration of the climate, both of which may see these birds remaining further north than they did just a few decades ago. This would also explain the contraction that we have seen in the UK breeding range. As with a number of other species, there is good evidence that northerly populations are more migratory than southern ones.
The business of breeding
Short-eared Owls are early breeders and many pairs will be back on their breeding territories by late March. Strongly territorial, the birds may be seen advertising ownership of their breeding territory or chasing away intruders. Individuals utilise a number of different display postures and rely more on these than on vocalisations, something that reflects their association with open rather than wooded habitats. These birds have a reputation for defending their nest and young, attacking predators, dogs and human observers with some ferocity.
Increasing our understanding
Researchers based at BTO Scotland have been carrying out work to improve our understanding of this charismatic species. Some of this work has been directed to improving fieldwork methods for detecting and censusing this species, while other work has looked at ranging behaviour and longer distance movements. Knowledge of where Short-eared Owls occur during the winter months comes from periodic atlas surveys and, importantly, from the records of birdwatchers collected through BirdTrack, meaning that anyone can contribute to our knowledge of this enigmatic species.