The children simply live at "home" and the separated or divorced parents take turns living with them there, but never at the same time.
The core element of this arrangement is that each parent maintains a separate residence where they live when it is not their turn at the "bird's nest". When one parent arives for his/her designated time, the other vacates right away, so as to minimize or eliminate the presence of both at the same time.
At times, bird's nest access can be coupled with specified access with the other parent say, for example, for dinner one night a week.
Sometimes, this form of access or custody will end when the youngest child reaches the age of majority at which time, one parent either buys the other out of their interest, if any, in the former family residence, or it is sold and the proceeds divided pursuant to the matrimonial property regime or separation agreement.
The arrangement can be expensive as it generally requires that three separate residences be maintained, the "nest" and a separate residence for each parent.
The concept is somewhat novel and appears to have as its origin a Virginia case Lamont v Lamont.
In Canada, Greenough v Greenough was a ground-breaker case in that the Court implemented a bird's nest custody order even though it had not been asked for my either party. Justice Quinn, in Greenough stated:
"In Lamont ... the court made a bird’s nest custody arrangement in which the children (aged 3 and 5 years) remained in the home, with the mother staying in the home during the week and the father on the weekend. I think that the benefits of a bird’s nest order are best achieved where the children are able to stay in the matrimonial home, particularly if it has been the only residence that they have known....
"Time and time again I have seen cases (and this is one) where the children are being treated as Frisbees. In general, parents do not seem to appreciate the gross disruption to which children are subjected where one of the parents has frequent access. In this regard, I do not believe there must be evidence that the children are suffering before the court is free to act. To me, it is a matter of common sense. At the risk of falling prey to simplistic generalities, I am of the view that, given a choice, I do not see why anyone would select a living arrangement which involved so much movement from house to house."
Research and Further Reading: