And You Thought Your Family Had Issues

Have you ever thought your parent(s) favor you brother/ sister over you? It may surprise many to find out that human families are not the only families with issues. Just like humans, birds fight over parental duties and even favor certain offspring over others. A study done by Tudor Draganoi, a post doctoral researcher at Leiden University in the Netherlands, shows some bird pairs split up and even divide offspring between the mother and father.

This study observed black redstarts, Phoenicurus ochruros, in the small mountain village of La Valla sur Rochefort, France. The study found that these birds would sometimes split up because of conflicts; many times one of the birds would abandon some of the young. The divorced birds would split up, and take with them the favorable offspring.

The study also concluded that parents responded more to the calls of the babies which they doted on. The parents prefer certain offspring over others. The factors are not known as to why the parents prefer certain young over others. Size and sex do not seem to be a factor.

The division of the two parents may result from conflicts over parental investment. Draganoi believes each parent may try to do the least amount of work and push the other parent to work harder. This will maximize current reproductive success, and also save energy for future reproduction. This theory makes sense because it would maximize reproductive success, but more studies need to be done to confirm it. The splitting up of offspring between parents also occurs in a number of other species including: blackbirds, robins, bluethroats, dunnocks, prairie warblers, song sparrows, white-throated sparrows, great crested grebe, and the coot.

Posted by Brian Salem (6)