One of the most common questions we’re getting right now is something along the lines of ‘Why don’t Mom and DM2 DO something about all of those beak-bonking battles?‘ We recognize that eagle parents are bonded to their children, so why don’t they stop potentially harmful behavior? It’s umwelt time, so let’s put our eagle heads on and think through the question!
Competition is an important part of eagle ‘society’, but eagles also need to surrender food to hungry mates and gaping little mouths. I don’t speak Eagle-ish myself, but mated eagles clearly have a verbal and physical language to communicate desires, needs, and intentions. When female eagles want food, they often wheedle or plea, move in quickly, and erect their feathers, making themselves look bigger and asserting their control. Male eagles who intend to share usually move away from their food gift. They often dip their heads or bow slightly, and they don’t mantle or vocalize back. The message is quite clear even to us human-types: “Here you go dear! Take it – I brought it for you!’.
But sometimes male eagles don’t want to give up their food. In that case, their body language looks a lot different. Males erect their feathers, spread their tails, and mantle over their food as females approach, sometimes vocalizing quietly but insistently back at their mates. Again, the message is clear: “This is mine and I’m not sharing!”. Female eagles may respond by taking the food or by backing down, depending in no small part on their own hunger and how insistently their eaglets are begging for food. Either way, it is a completely different interaction in terms of tone and body language.
If you think through these interactions, you’ll realize that something quite similar happens with young eaglets. If one eaglet is especially hungry or sees another eaglet as a food-threat, a bonking battle begins! The winning eaglet can’t erect its downy feathers, but it can sit up tall and loom over the losing eaglet, who usually signals its submission by collapsing to the bottom of the egg cup for a little bit. It is also pretty clear when an eaglet doesn’t care to compete. It might stretch out its beak and beg for food, but it doesn’t rise up and peck at its siblings.
Food intiates a lot of beak-bonking battles, but it isn’t the only reason eaglets compete. Their beaky beatdowns establish a pecking order and lay the foundation for similar patterns of behavior later in life. Sibling practice might refine an eaglet’s ability to alternately compete for and give up food, but the behavior is rooted in instinct and we see it at every nest we watch. Eagle parents simply aren’t concerned by eaglets acting like, well, eaglets and the dynamics of nest behavior aren’t entirely unknown in human families…even if we discourage knock-down-drag-out fights over who gets to eat first! Beak-bonking also helps eaglets develop muscles and improve coordination, since it takes strength and skill to tussle with a sibling.
What do mean when we say ‘Eagle Society’? Common American myth holds that eagles are noble loners, but the Flyway Cam shows us that eagles are quite social off their territories. They gather in large mixed age groups, perching, hunting, and squabbling over everything from who gets what perch to all out fish-flying fights!
On their territories? They aren’t usually social, but that can change with the presence or absence of eggs and young, the invader’s proximity to the nest, and the age and attitude of the invader.
Given what we know about Bald eagles, is it fair to say they form a fission-fushion society: a society in which the size and composition of the social group changes as time passes and animals move throughout their environments? Maybe. A lot of birds experience seasonal changes in sociality and bald eagles don’t meet some of the criteria for a true fission-fushion society. Nevertheless, it would have interesting consequences for the interactions we’ve seen in Decorah and on the Flyway, and we’ll be exploring it more in the weeks to come!
The Raptor Resource Project