I like reading scientific papers answering interesting questions. But what I really love are unanswered questions. This is why I have found so exciting the paper I want to highlight you today.
This is about a mysterious behaviour of a honey buzzard (Pernis apivorus) reported from central Spain by Carlos Camacho, Marta Guntiñas and Jaime Potti, and just published in Raptor Research journal. This is how they explain the behaviour:
"For 13 consecutive days (4-16 July 2012), we monitored behavioral displays by an adult Honey Buzzard of undetermined sex inhabiting an old oak (Quercus pyrenaica) forest in Central Spain (41º 04’ N; 3º 27’ E). We daily recorded the bird's behavior between 8:00 and 14:00 h for 2-hour sessions by alternating the time and additionally conducted four evening sessions from 18:00 to 20:00 h every 2-3 days in order to collect data throughout the entire daylight period. [...]
The ritual started shortly after dawn. The Honey Buzzard cut off similarly shaped fresh, leafed twigs ranging from 12 to 25 cm in length [...] from a single maple tree (Acer monspessulanum), whereas oak twigs were rarely selected (n = 3) despite their much higher availability. Twigs were arranged parallel to one another at a set distance of 1-1.5 m along a bare sandy road (Fig. 1a). Immediately afterwards, the Honey Buzzard stretched full-length on the ground (Fig. 1b) and remained motionless next to the newly placed twig for a long time (20-40 min), thus becoming almost undetectable to observers. Fresh plant materials were added at regular time intervals of ca. 35 min (0.5-1 h), although adding or replacing rates could reduce up to 2-3 twigs/hour during the hot midday period. The bird continued bringing new twigs for three days until the road held more than 40 items. Hereafter, old withered twigs were replaced with recently picked ones and the initial distance between adjacent twigs was gradually reduced as new fresh materials were added by the bird.
The Honey Buzzard's behavior was not incidental but repeated during the entire observation period. Similar-sized green materials were used throughout and the distance and position of the twig’s placement showed apparent consistency. [...] The high time investment required to perform such display contrasts with the inactive routine shown by the bird, as it spent a long time just laying on the ground close to the greenery work."
The authors give some tentative explanations, while recognizing that any of them can even remotely grasp the meaning of this behaviour "ritual" (it was so mysterious that they gave it the name of ritual! :). Luckily, I work next door to the senior author of this study, and I was fortunate to listen their story when he came back from the field. I love when researchers tell me about any unexplainable phenomenon; in their faces there is always a mix of excitement, frustration and hope for finding the solution; maybe someday, somewhere they will imagine the solution (maybe some morning while singing in the shower). I love these stories demanding an end; these are major motors of science.
Interestingly, if these stories are mysterious, it means that we may have not all the elements to understand them. It may be simply that we need further field observation (maybe more field observation would show, for instance, that this raptor was "simply" waiting for a prey). Or it may (excitingly) mean that there is some fundamental element that we not know from this species (or from birds in general!).
Thus, hopefully, understanding this "anecdotic" behaviour will unfold a new mystery. In this case of the honey buzzard ritual, studying it further may (why not) uncover a sophisticated sense (e.g. of vision, or smell), or it could be related with parasite control?, or it may be a "mere" manifestation of play (yes, this sounds weird...), or it may be exploiting some sense of insects, diverting the trajectory of bees and wasps when returning to their colonies (and follow them to feed on their larvae)?...or it may reveal an unexpected extraordinary intelligence... or a rich mathematical or aesthetic mind... or... or...who knows. This is why science is so exciting.
If you have any idea to explain this honey buzzard behaviour, or if you have a similar story (about a mysterious bird behaviour) please leave a comment below.
Pictures by Octavio Jiménez