Jays at attention
Magpies, crows and the like are considered the thinkers among the birdies: their tactics for acquiring, storing and finding food are almost unrivaled among birds. And they pay close attention to whether they're being watched.
The forester's best helper is the jay: the corvid tirelessly collects ripe acorns in autumn and buries them in various places in the forest so that it can always fall back on a well-stocked food depot during the winter. But he doesn't find all of the thousands of seeds he stores like this - they can germinate in the spring, and that's how the jay keeps the forest young.
Although part of their collection slips through the fingers of the birds, they still show a veritable mental effort. After all, they have to remember several hundred locations and take into account that their appearance changes significantly over the course of the year.
But the animals have even more to offer, as revealed by previous and recent research by Joanne Dally and her colleagues at the University of Cambridge. Her work focuses on the western bush jay (Aphelocoma californica) from North America, which, like so many of their relatives, also saves acorns, nuts or other delicacies for when the going gets tough.
The blue-grey-white jays are not content with simply hiding food: if they have the opportunity to plunder the depots of their fellow species, they show no mercy. On the other hand, these ravens naturally try to minimize precisely these misdeeds on their own property or to prevent them entirely: they relocate their prey if they think they are being watched, or defend their lairs if necessary if there are no alternatives.
But under what circumstances do the animals react and how? After all, it is known that they share their food with their partner, so that the presence of the partner should not really play a role according to the researchers. But what about strangers: When do you move and when do you fight?
Dally's team observed nine bush jays while the animals were allowed to hide mealworms either unobserved or under the eyes of partners, dominant competitors or sub alterns. They were provided with compartmentalized storage boxes, one of which was relatively close to the potential observers in the flight cage, while the other was placed further away - and thus obviously less easily visible to competitors. Three hours after the prey was placed, the nine jays were each allowed back into the cage containing the boxes and tending to their larders.
The animals generally hid their mealworms in the places closest to them when no other bird or possibly their partner was looking at them - the confirmation for the researchers that the jays really do not see any competition in their relationship.
However, they behaved completely differently when higher or lower-ranking conspecifics were present. From the beginning, the fed animals preferred to store their food in distant and therefore possibly safer hiding places. But that alone was no longer enough for them after the three-hour absence, because now they dragged their guarded supplies into a new hiding place - without renewed observation, but obviously with knowledge of the previous one: one that often had nothing at all to do with the given storage boxes had, but that was outside of it. If the birds were not able to bury their prey in an alternative hiding place, they would at least move it several times within the one box, which also makes subsequent theft less likely.
In a further experiment, the foraging jays were observed both during the first deposit attempt and during the subsequent hiding again - however, the observers were partly the same and partly different birds. The biologists wanted to find out whether the animals differentiate not only between third parties and partners, but also among strangers.
And indeed, the jays shifted a significant portion of their prey when observed by well-known competitors. On the other hand, under the eyes of birds that had not noticed the first attempts to hide, they mostly kept calm and left the food where they had originally hidden it. But even with the permanent observers, the bush jays made differences - depending on the status of the observer.
If it was a weaker competitor, they behaved less actively than with a dominant animal. It is easier to defend the depot against lower-ranking birds, while with stronger specimens the cost-benefit calculation speaks more for the relocation of the pantry than for a mostly hopeless fight. With partners, on the other hand, theft is tolerated, yes, the jays even go so far as to defend their acorn or mealworm stores, should it be necessary and possible. Love seems to go through their stomachs, too.