An introduction to cooperative breeding and why helpers help:
Part 1: What is a cooperative breeder, and what does a helping bird do?
Apostlebirds have many common names, Lousy Jacks, Grey Jumpers, and Happy Families. They indeed look like happy families with all their preening, chatting and cuddling up together on a branch. But, why all this cooperation?
In an earlier post, I told you about the drama I witnessed during the winter/ off breeding season and all the fighting, screeching and foot biting. Also, all the chasing of other groups, the scramble for bread and monopolization of access to the food lady- all this conflict! But despite all the fighting, year after year, since at least 2004 when this study was started (not by me, but by my adviser) these hardy birds breed cooperatively.
What is cooperative breeding, you ask? Well, it is when adult birds help to raise offspring that are not their own. And help they do, with everything from the diligent building of cup shaped mud nests, to the hours and upon hours of protecting the eggs from the cold of the outback nights and the arid heat of the Australian sun, to the feeding of the every begging and hungry young. And then they help some more, as the growing birds in the nest need care beyond filling their gaping mouths. They need preening to clean the chalky sheaths of their newly emerging feathers, and parasites need to be picked away from their delicate baby skin and they even need their poo to be carried away ( and some cases eaten away!) so that they do not sit in an ever growing mound of partially digested food.
All these baby care task, and more, the helpers do. Helpers will even remain vigilant for predators that they will mob and chase away, if necessary. But why? Why all this effort in a land that can be so unforgiving, that can go from tolerable to hot and dry with nary food (insects and seeds) in a blink of the eye? And to raise offspring that are not your own? Why not settle down and wait until you can have your own children?
Well, first thing that comes to most people’s mind is that, well maybe you can’t have children on your own. Maybe waiting for a good season is too long, longer than your breeding life. Alright, so you need help? Who will help you? Maybe they themselves want to breed? That sounds like one big bird fight waiting to happen- and maybe it does, and maybe that is what all this conflict during the winter is about. Fight it out, beak to beak, who gets to bred. Well, somebirdy comes out a winner and somebirdy has to help. But what keeps a bird from being a sore loser and birdy-ing off. That would be system collapse wouldn’t it? Maybe the helpers get something then for helping.
Think of it this way. Maybe you are an older child, or maybe you have younger cousins. Remember being made to babysit when you were a teen? Your parents may have paid you for it, but chances are it was “your responsibility” to help. Society expectation, maybe, but also as a “rent payment” . This is especially the case, if you are an adult and later visit with parents, aunts, friends with children, etc....
Some other adult keeps a roof over your heads the fridge stocked, shampoo in the bathroom, etc… and those are all resources in their territory and their house. So, maybe cooperative breeders, like the Apostlebirds, pay rent (Pay to stay- see the papers below for more info). Apostlebird juveniles (younger than 1 year) stay at their parents place and continue to beg at adults for food, although they also look for food and feed themselves. When they get older, they will feed younger siblings and by the time they are an adult (~2 years) they start to help at the nest. Younger adult birds will tend to stay at home and help mom and dad raise their younger siblings, until at some point, mainly the daughters leave home, while their brother stick around the territory where they were born, sometimes even after mom and dad are long gone. Maybe a male will inherit breeding status and take over the home stead himself, in a few seemingly rare cases, he may leave himself, or maybe he just continues to help as an adult. We don’t conclusively know what apostlebird males do yet, as the current study is only 6 years old, not long enough to follow enough birds from egg to breeding (yet another story waiting to be told).
Next time, Part 2: When are you going to have kids? Why an adult bird may still be helping rather than having their own children.
1-A few interesting papers on "Pay to Stay" here:
http://www.anu.edu.au/BoZo/kokko/Publ/Rent.pdf
http://www.ericlwalters.org/koenig_walters2011.pdf
http://people.bu.edu/msoren/McDonald.pdf
http://www.life.umd.edu/faculty/wilkinson/BIOL608W/Sachs&Rubenstein07_BP.pdf
