White-Tailed Kite Behavior Question

I've been doing some preliminary filming for a bird-centric documentary at the Arcata Marsh and Wildlife Sanctuary sporadically over the past few months, and have been enjoying watching this year's fledgling kites grow up. They've been exploring outside the nest for about two months now, and no longer need their parents help hunting. About two weeks ago, the adults started attacking the children during their evening hunting sessions; there are two breeding pairs and their children hunting in the same field now, but from their preferred hunting patches and favorite perches, I'm fairly certain the adults are attacking their own offspring. It's not as rough as when males fight over territory during mating season (there's no locking talons and spiraling toward the ground), but they are diving with claws out and occasionally making contact.

http://www.moonpotato.com/pictures/kitewar3.jpg

Are the parents teaching their children how to fight, or are they trying to drive them away to different hunting territory now that they're self-sufficient? The Sibley Guide to Bird Life and Behavior and Pete Dunne's Field Guide Companion didn't have anything about this behavior, but I'm very curious about it.

Thanks in advance for any insight you can provide.

Welcome to BPN Alan...glad you're using this awesome sub-forum as your first post! Super behaviour you observed, must have been fascinating. My guess, and it really is just a guess, is that the parents are trying to make the young ones move on their own territory. Hope others with more experience with raptor behaviour chime in! :-)

Thanks, Daniel.

It looks like they were probably trying to drive their children off. After a few days of persistent clouds, rain and fog, we had some suitable weather for filming again today, and I only spotted two adults and one juvenile in the field (as opposed to 7-8 individuals on my last couple outings). The reason I was wondering if the adults were teaching their children how to fight is that the juveniles were being bullied by the local harrier after some of their first successful hunts <a href="http://www.youtube.com/watch?v=Xdq64DhhMF4" target="_blank">as seen here</a>. For a few days after that incident, the juveniles stopped exploring and hunting, and went back to perching near the nest and screeching for food. While the adult kites have no trouble fending off the relatively slow harriers, the juveniles really seemed to have their hands full and clearly needed to learn how to protect themselves.

Hi Alan- Welcome to BPN as well.

Young birds do learn a variety of things from their parents. Usually this relates to finding food.

I think the idea that the parent kites were trying to sever the bond with their chicks is a good one. But why would they want to do this from an evolutionary standpoint? Shouldn't it always be advantageous to provide care to offspring? After all they are closely related kin. The answer comes from a important topic in evolutionary biology called parent-offspring conflict. This is not the conflict that might be generated by teenager Johnny not tidying his room! It is a conflict about what is adaptive and optimal in an evolutionary sense. I'll try to be brief. During the course of chick development up to fledging, there may be little or no conflict between parents and offspring about what is evolutionarily optimal- parents are in the business of feeding and protecting their offspring, and offspring gladly accept this care. Both go in the same evolutionary direction- towards producing the healthiest offspring that eventually go on to breed themselves. This peace and tranquility does not last though, and evolutionary conflict often develops once the chicks become independent. The source of the conflict is as follows. Parents need to reduce their costs of raising the current batch of grown offspring in preparation for the next batch in the following season because breeding takes its toll and the investment in the current brood takes away from their ability to invest in future broods. Therefore at some stage the parents "turn-off" investment in the current brood. On the other hand, it is evolutionarily advantageous for the grown chicks to continue to extract as much investment out of their parents as they can, because they have their future breeding success to "think" about, not that of their parents. Therein lies the conflict. Parent-offspring conflict can take many forms but what you witnessed would be an excellent example, and you probably guessed, parents usually win!