The Roller

European Roller (Vallée de Baux, France) by Tom Finch

European Roller (Vallée de Baux, France) by Tom Finch

The European Roller (Coracias garrulus) is arguably one of the most distinctive birds in Europe, breeding in warm, open landscapes across Europe and into Central Asia. Rollers are primarily insectivores, preying on beetles (Coleoptera) and grasshoppers (Orthoptera), but also other invertebrates and small vertebrates. They generally hunt from an exposed perch, flying down to take prey from the ground or ‘hawking’ insects in flight. Rollers are obligate secondary cavity nesters – this means they breed in cavities, but are unable to excavate their own, instead making use of existing holes in trees, cliffs, sandbanks, abandoned buildings and, increasingly, artificial nestboxes. They lay 3-6 eggs between mid-May and mid-July, with chicks hatching after 17-19 days of incubation. Chicks fledge at 25-30 days old, at which point they depend on their parents for food for a further 3 weeks. Despite their name, European Rollers spend the northern winter in the dry, open habitats of sub-Saharan Africa.

Map

Global distribution of the European Roller, with breeding range in Green and winter range in Blue. Data from BirdLife International.

 

Below is a Polish recording of a European Roller. The call is quite distinctive, and is often the easiest way of knowing that a Roller is nearby (despite their bright colours, they are surprisingly difficult to spot against green foliage).

 

A worrying decline.
Given their fairly specific requirements in terms of nesting and foraging habitat, it is perhaps unsurprising that, in common with many other farmland birds (see this paper), Rollers are declining, having already gone extinct in several central European countries. Rollers are classified as globally Near Threatened and Vulnerable in Europe. Whilst this is probably a result of the intensification of farmland ecosystems in Europe, (perhaps reducing the quality of foraging habitat and / or the availability of nest sites), the exact mechanisms behind their decline are still unclear, making it difficult to implement successful conservation strategies.

 

burfield

The Roller is declining in most European countries. Here, blue areas show declines, black arrows increases, black bars stable populations and black crosses extinct populations. The size of the symbol is proportional to the size of the population. (From Burfield & van Bommel (2004) Birds in Europe: Population Estimates, Trends and Conservation Status, BirdLife International)

Further complication arises from the fact that Rollers are migratory. This means that the Roller may also be being facing problems en route or overwinter in Africa, as well as in the local breeding areas. Indeed, long-distance migrants are another group of birds which are suffering declines across Europe (see this paper). Tackling this issue is difficult, as we often have a pretty poor understanding of what ‘our’ migrants get up to once they leave Europe. 

So, the Roller is a farmland bird (in general) and a long-distance migrant (always), and both of these groups of birds are, overall, declining in Europe. In order to identify the specific processes causing these declines (and hopefully to halt them) we need in depth ecological studies, linking environment, behaviour, demography and population dynamics.

Enter, me!