The European Roller in the Vallée des Baux, Provence

European Roller (Coracias garrulus)

The populations of the European Roller (Coracias garrulus) were reclassified by BirdLife in April 2005 as Near Threatened. Studies conducted over a number of years by A Rocha France in Provence’s Vallée des Baux have shown that in this area there are currently 50 breeding pairs on 1300 ha, amongst the highest densities in Europe. In addition to background studies on such matters as arrival and departure times, territories and the incidence of second broods, two major A Rocha studies have been completed on Roller hunting and diet. This is important because success in hunting is potentially linked with the survival of nestlings and adults.

A Rocha has been studying the relationship between habitat and perch type and hunting success. Rollers mostly eat large insects and characteristically hunt for their prey from suitably commanding lookout posts such as dead branches, electric wires and trees. Hunting behaviour patterns and success were observed over the summer breeding season in the Vallée des Baux during peak hunting periods. The height of the perch and its type were noted, as was the distance flown to the prey and whether or not the attempt was successful.

These studies show that as perch height decreases there is corresponding increase in hunting success. They also indicate that as perch height increases the range hunted increases. The implications of this for conservation are considerable: increasing the number of low perches (under 3 m) in known hunting areas at around 10 to 15 m intervals should allow Rollers to hunt with a higher level of success.

The nature and nutritional value of the Roller prey in the Vallée des Baux was also investigated. From a conservation point of view this is important as the key to increasing Roller breeding success may be to ensure an abundant food supply. Normally Rollers nest in tree cavities, often using holes made by the European Green Woodpecker (Picus viridis), but they have adapted to using nest boxes, provided by A Rocha. Because the nestlings produce pellets of indigestible material and these are left behind in the nest box, pellet examination gives valuable evidence of the diet. Previous studies have found the Roller to have a very varied diet, eating a wide variety of invertebrates, and occasionally vertebrates or even fruit. Arthropods usually dominate the diet, particularly Coleoptera (beetles) and Orthoptera (grasshoppers and crickets).

The contents of five nest boxes all occupied by successfully breeding Roller pairs were examined after the young had flown in 2004 and 2005. The minimum number of insect individuals the Roller successfully brings back to the nest has been estimated to be 400-500. The body parts in the pellets and boxes were separated and identified as accurately as possible.

The results confirmed the diversity and breadth of Roller diet. A total of 32 species were identified, with many remains left unidentifiable to a species level. The real number of species eaten is likely to be a good deal higher as many soft-bodied prey will leave no remains and be unaccounted for. Orthoptera is the main source of prey, making up 85-90% by number of the Roller’s observed diet.

Variation between the four sites was marked, suggesting a non-specific diet and an adaptation to local abundance. Despite the difference in diet, all five nest boxes successfully fledged five to six young – a remarkably high rate.

Farmland in the Vallee des Baux, Provence

On this basis, general conservation recommendations would be the encouragement of the already abundant beetle and grasshopper populations in the Vallée des Baux. This might include making local land owners and farmers sensitive to the presence of the Roller and its needs. Specific recommendations include tree planting for long-term availability of nest sites, creating more perches, and encouraging uncultivated strips along fields, reduction of pesticide use and development of grazed meadows.

Future plans for Roller research include long-term monitoring of the breeding population and breeding success, detailed diet survey (both with photographic and visual methods for different periods), habitat use and their relationship with management forms, selection of nest sites both for the cavity excavator and for the Roller. We hope to be able to highlight the conditions that help Rollers nest in high densities, especially in semi-colonies.

Conservation measures include public campaigns and monitoring networks across France. This species is an excellent flagship species for Mediterranean conservation as the bird is widely known and popular, and needs both healthy riparian ecosystems and mixed, non-intensive farmland.

***

Project leader: François Tron. For further information please contact france@arocha.org