English abstracts of Bernard Joubert’s articles in the Alauda journal

Since 1996, the author has studied the breeding population of the Short-toed Eagle in part of the upper Allier valley (Haute-Loire, Massif Central). In the area concerned (130 km[2]), density – which varies from I pair per 12 km[2] to I pair per 4,3 km[2] and reaches locally 1 pair per 2,25 km[2] – is among the highest in Europe. The total population of the whole area of river gorges (635 km[2]) is estimated at 38 pairs and that of the Haute-Loire departement at 56-63 pairs, which represents 6 to 7% of the French breeding population. The author attempts to analyse the causes of this abundance. There are data on: habitat, laying dates and breeding success, As far as possible, these are compared to those available for Europe and the Near-East.

Three modes of behavior of the Short-toed Eagle, observed in Haute-Loire (F) during breeding season, are described and analysed. As for other raptors, the sky-dance display flight corresponds to an affirmation of territory – it appears on various occasions. The marking of the nest – sequence during which the male holds its wings pointed upwards and shows the white parts of its plumage – also has a territorial function; as well as being an act of communication towards the female. Before laying date, certain males show a curious behaviour of hollowing the nest, especially by using rotative trampling movements.

In Short-toed Eagle – as with many other birds of prey -, the building pair bonds is not easy. Before they can mate, each bird must first accept the presence of the other in its immediate surroundings, and then allow physical contact. This procedure of acceptation is long and complex for newly formed pairs. This paper describes one behavioural pattern observed when a new pair is formed. Hovering flight usually used for hunting may become behavioural way of gaining trust. Certain circumstances cause the birds to show the inner struggle they experience during the process of accepting the other. They are torn between two opposites – attraction and repulsion – and must act in a way that will free them of their own inhibition and that of their partner.

In relation the size of the Short-toed Eagle, its nest is of modest dimensions. This paper presents some behavioural information concerning the gathering of nest material. Twigs and branches are either picked off the ground, or directly broken from the tree. During incubation and rearing, the supply of nest material is more a ritual offer than proper nest building. The adaptive behaviour of the species is also analysed. The nest, part of the adaptive strategy, allows for a good breeding rate in spite of its size and conspicuousness. Data are provided on the frequency with which pairs change nest, in the upper valley of the river Allier (Haute-Loire. Massif Central; France). Nest fidelity varies considerably between pairs but the factors explaining this variation could be identified. (Trad. J. N. Brongers-Joubert).

Fifteen pairs of Short-toed Eagle have been monitored over the past nine years in the eastern central Massif Central (Upper Allier area, Haute-Loire département). Breeding success, over the 101 monitored rbreeding cycles, was of 0.61 slightly above the national average (0.58, n=922). This paper highlights the variability of breeding success between sites (0.33-0.87) and years (0.25-0.90). The high level of non breeding territorial pairs (16.8%) is noted. Causes of breeding failure are also analysed, highlighting ecological, geographical and ethological factors, with the latter seeming most important. In line with their K type adaptative strategy, the Short-toed Eagle demography is controlled, thus limiting the species pressure its scarce food supply.