Aggressiveness between Short-toed Eagles
I am writing to tell a strange incident happened yesterday: a lady calls the CRAS Pignola (PZ, Italy) /map/ saying she had found two «hawks» in trouble and asks if she can deliver. After an hour she arrived with a pair of Short-toed Eagle! The huge female is in good condition and will probably be released in a couple of days.
The male instead had deep lacerations to the chest and throat, so as to show the crop.
Basically the skin in some places no more, and also the pectoral muscle is damaged.
The crop was full ….. and a tail sticking out from the bill….. we pulled out a snake of 1.20 m ….. probably had it in the throat the day before, when the lady found them and brought home with him.
The strange thing is that the lady has told of seeing them sticking up in the air to fall on the ground. At that point they roll in a pond for irrigation, where she intervened.
According to the reconstruction the healthy one (the female) has repeatedly attacked the other’s throat causing him serious injuries.
A reconstruction does not convince me at all, has anyone had such experiences? That is, if by chance you know so much aggressive behavior between Short-toed Eagles?
Consider that the male will almost certainly not survive due to septicemia in very advanced stage.
Categories: En-Misc, Province of Potenza, Questions.
In october, we will have a meeting of Snake-Eagle specialists in the south of France (everybody can come) in the Cevenne National Park.
My intention is to present a power point on the conflict behaviour (Gestion des conflits chez le circaète).
The STE gives us an excellent exemple for SAM (sequential assessment model).
The aggressiveness varies greatly : in some pairs, the female is aggressive – in some others, it’s the male. And it seems that the aggressiveness varies greatly too with time.
Francesco is right : violent contacts are unusual.
In my study area in Central Italy, although the Short-toed Eagles tolerated the close presence of other raptors nearby, they proudly defended large home-ranges and nesting areas against the intrusion of conspecifics.
The establishment, expansion and daily maintenance of a territory would be impossible without effective behavioural patterns related to threat and appeasement , to offensive and defensive actions . In other words , the rights of privacy and exclusive territorial space must be gained and confirmed. I recorded 280 examples of aggression involving at least two individuals belonging to different pairs. I considered only the agonistic sequences in which I was able to witness the beginning and the end of the sequence. 59.1 % of them refer to two birds, 13.6% to three individuals (both partners of monitored territory and one intruder), 18.2% to three birds (one from monitored pair and two intruders) and 9.1% to four individuals (both partners of monitored pair against two intruders). Interactions ranged from 20 seconds to 55 minutes.
Most sequences consisted of mutual soaring, with the rivals trying to gain height and keep an advantage over the other. Fast pursuits, beating with wings, and a wide use of the threat display were recorded each time. In some cases resident eagles were seen taking off from their perch suddenly, moving in direct flight against the intruder up to 2 km away from the nest. The Short-toed Eagles behaved very aggressively and the interactions usually ended only when the intruding birds left the area. In one instance, an intruding eagle perched only 300 m away from the nest of one pair where the female was incubating, incurring a sudden attack of the male. Of 17 interactions involving the partners of one pair, 12 (70.6%) were performed by the male, 1 by the female (5.9%) and 4 (23.5%) by both partners. Difference is statistically significant (X2 test, P<0.01).
Short-toed Eagle threat flight posture, with a distinctive call, is well recognised in the field. The tail is slightly raised above the back, the head and neck are held up and stretched out, the wings held well forward and up while the legs are dangling.
This is generally an aggressive display flight and there is no physical contact, the birds flying alongside each other until the intruder leaves or the two rival couples each go back to their own territories, anyway I recorded seven instances when one bird struck at another with its talons. It was a physical, violent contact.
According to my observations during more than 20 years hard conflicts are rare for the Circaetus gallicus population in northern Ukraine. Probably this could be explained by relatively low density of it. Usually only special ritual air demonstrations are observed here. The real hard conflict, when 2 birds grabbed each other, fell down and disappeared behind trees, was observed only once. The incident happened at a distance of more than 2 km from the observation point, so it is not known how it ended. I think Bernard agrees with the idea that overwhelming majority of such conflicts are based on territorial claims.
In 2010, 2 dead Snake-Eagles were found in Ardèche (France). They were grabbed together. (source : JP CERET)
In 16 saisons, I have seen 151 conflicts, more often in march-april-may (n = 121). Two times, it was very hard : the birds grabbed together and fell on the ground. When it was possible to know the sexe of the birds, the females were more agressive than the males : 45% they were attackers (alone) and 27.5% were attackers of a third bird, both with the male.
With other birds, Snake-Eagles are few aggressive : 5.2% (n = 9), they attack (just enactment) – 60.3% (n = 105), they are attacked – 34.5% (n = 60), it was neutral relations.