The English (En) version of that article with links to more pictures:
• Konstantin PISMENNYI, 2018 – Le circaète dans le nord de l’Ukraine : état et avenir des populations, observations sur quelques couples et individus [The Short-toed Snake Eagle in Northern Ukraine, the population state and outlook, observations of certain pairs and individuals] // La Plume du Circaète n° 16-17: pp. 11-15.
The following paper by Bernard Joubert on Short-toed Snake Eagle communication abilities was recently published:
• Bernard JOUBERT, 2017 – Circaète Jean-le-Blanc : des "mots" pour le dire [Short-toed Eagle: "words" to tell] // Rapaces de France, n° 19: pp. 54-55. – 
(Fr) {rough translation}.
The summary
Short-toed Snake Eagles have the rich social language, various tools which help them to express their intentions and relation to behaviour of other representatives of their species. The main problem of studying their behavioural language is defined by difficulties of correct interpretations. Besides various vocal signals, these eagles reveal a rich body language vocabulary, thanks to the extraordinary plasticity of their plumage, which is used for hovering in different airflows while hunting. Simplistically, 3 types of signals are identified: those related to movements, postures and holding of plumage.
› Examples of the gestural communication are: aggressive demonstratively slow and strong wing-beats, so-called «vulture» flights, territorial «festoon» display flights.
› Communicating through postures includes: an aggressive «albatross» posture, a posture of «angel» which is used for marking a chosen nest for the partner.
› Communicating through appearance changes at close contacts comprises states of occipital feathers and pupil size, which can express both tension and relaxation of birds.
This brief review is nothing more than an invitation to observe and puzzle out those various and subtle means of ST Eagles’ communication.
A new article on Short-toed Eagles’ demonstrative and hunting behaviour is presented here by kind consent of the author – Viktor Belik. The article is planed to be published in next issue of the Strepet ornithological journal. This is a generalized result of 40 years’ field observations.
• Виктор Белик, 2009 – Особенности демонстративного и охотничьего поведения змееяда [Demonstrative and hunting behaviour of Short-toed Eagle] // Стрепет. Т.7 − Вып. 1-2 − С. 50–61 (Ru).