Answer:
1)
Advantages:
Cowbird: this kind of relationship means that they can afford to lay a large amount of eggs scattered across various nests, ensuring more offspring that usual.
Oriole: this relationship increases the odds of their offspring surviving in the case where the nest is attacked. since their is a larger number of nestling, this increases the probability of each nestling surviving an attack on the nest.
Disadvantage
Cowbird: if not properly timed, the cowbird's eggs might not hatch in synch with the orioles bird eggs which may reduce the survivability of the cowbird's chicks. And sometimes, the host bird might reject the cowbird's egg or the chick after it hatches.
Orioles: this relationship puts extra load on the host parent bird by increasing the number of mouth it feeds.
2) if the oriole bird's population should reduce, it might translate to a reduction in the cowbird population if there are no other host bird species around since the cowbird relies on a large number of host bird. In the case where there are no other host birds, the cowbird's population will reduce since the orioles is important to their reproduction.
3) This is a brood parasitic symbiosis.
