After repeated attacks, the Lanner Falcons had successfully driven off North African Buzzards from their occupied nest. The usurpers went on to occupy the nest and lay their own eggs.
North African Buzzard (= Atlas Long-legged Buzzard) and Lanner Falcon are widely distributed throughout Morocco [read: North African Buzzard is not a Long-legged but a Common Buzzard]. Both species nest on cliffs as well as on trees. In the desert areas where available nesting sites are lacking, the North African Buzzard nests also on electric pylons.
Both species are known to re-use other species’ nests (mainly those of Common and Brown-necked Ravens), although the Buzzards also build their own nests.
Fierce competition for nesting sites
In desert areas, where there is generally plenty of prey but nesting sites are limited, life can be tough as we will see below.
On 20 December 2018, a pair of North African Buzzard occupied an old nest located about ten kilometers northeast of Boukra in Western Sahara. The nest, which is very accessible, was on an Acacia tree of moderate height. On 26 January 2019, the reconstruction of the nest was almost complete.
On 10 February 2019, two eggs were already laid on the nest. Four days later, on 14 February, when the North African Buzzard was incubating the eggs, a Lanner Falcon was observed harrying the nest occupant (the first part of the video and photo below).
By 27 February, when members of Anafis Association (Kharraj et al. 2019) re-visited the site, the battle was already over by some time. In fact, at this date, the aggressive Lanner Falcons had already occupied the nest and were incubating their four eggs (see photo below and watch the second part of the video starting at 17th second, we can see four Lanner’s eggs and one of the Buzzard’s eggs).
Lanner Falcon’s interaction with large raptors
A wide range of interactions between Lanner Falcons and large raptors (including falcons of similar size) have been described in the literature. These include competition for nesting sites, aggressive behaviour, piracy and predation. Giovanni Leonardi’s monograph “The Lanner falcon” published in 2015 compiled several examples of these interactions from throughout the species range. After checking all the cited interactions, we couldn’t find any case of Lanner Falcon evicting a large raptor actively occupying its nest and incubating the eggs. The closest case we found is its interaction with the Bateleur (Terathopius ecaudatus) in Zimbabwe (Steyn 1980 cited in Leonardi 2015). However, this interaction is more or less “peaceful” as it involved the occupation of the Bateleur’s nest after its breeding has finished (the egg has disappeared in one case, and the Bateleur chick has successfully fledged in another).
Despite its boldness and aggressiveness, the Lanner Falcon is not always the winner in these interspecific interactions. As an example, the decline of the Lanner in mainland Italy has long been attributed in part to its displacement by the dominant Peregrine Falcon. The latter species is usurping the Lanner’s nesting sites and forcing it to occupy less optimal ones (De Rosa et al. 2019, Leonardi 2015).
You can lose or win a single battle, but the most important is to win the war. It seems that the Lanner Falcon, at least in the Mediterranean region, is losing the war especially against illegal trade (for falconry) and habitat loss (Corso 2018). [read: Huge number of wild-caught Lanner Falcons held in captivity (video)].
Corso, A. 2018. Updated status of European Lanner Falcon, Falco biarmicus feldeggii (Schlegel, 1843) (Aves Falconiformes): a taxon on the verge of extinction, with brief comments on the North African Lanner, F. biarmicus erlangeri (Kleinschimdt, 1901). Biodiversity Journal 9: 23-44
De Rosa, D., Di Febbraro, M., De Lisio, L., De Sanctis, A. & Loy, A. 2019. The decline of the lanner falcon in Mediterranean landscapes: Competition displacement or habitat loss? Animal Conservation 22: 24–34. doi:10.1111/acv.12430
Kharraj, S., Hane, M.S., Kara, M., Laaroussi, M.A.S. & Qninba, A. 2019. Installation d’un Faucon lanier sur une aire de Buse féroce occupée (Bou Kra, région de Laâyoune-Saquiat Al Hamra – Sahara Atlantique Marocain). Go-South Bulletin 16: 46-49.
Leonardi, G. 2015. The Lanner falcon. Giovanni Leonardi, Catania.