![]() ![]() Chicks of assigned couples were a bit neglected by the fathers, which may have caused the higher chick mortality. This likely explains why assigned females laid more infertile eggs. Females of chosen pairs were more faithful to their partner while females of assigned pairs often were not very interested in mating with their partners. They measured behaviors, including how often they were close to each other and if their activities were coordinated.Ĭhosen couples were more ‘lovey-dovey’ but scientists did not notice more coordination of activities. So what makes a couple more behaviorally compatible? To answer this question, scientists watched each couple behind one-way glass. These results imply that, when choosing a partner, zebra finches choose behaviorally compatible mates. In other words, birds were not as good at raising young when they had to breed with a partner they did not choose. Mortality rates of embryos and offspring in chosen and assigned pairs. However, chick mortality was 60% higher if chicks were raised by an assigned couple. This means the partner of choice did not lead to better genetic compatibility. Overall, the same number of chicks died before hatching in chosen and assigned pairs. Bird parents must work hard constantly to feed their chicks, and chick mortality can be surprisingly high. ![]() Chick survival therefore depends on behavioral compatibility between the parents raising the chick. At that point, survival does not necessarily depend on the biological parents. ![]() To the contrary, after a chick hatches, its survival is only determined by the behavior of the parents that raise the chick. Embryo mortality is a sign of genetic incompatibility between the two biological parents. In zebra finches, a developing chick, also called an embryo, can die while it still is in the egg. This shows that getting a partner someone else wanted does not work as well as getting the partner you wanted. Overall, parents from the chosen couples raised 37% more chicks than parents from assigned couples. Scientists also followed the growth of each chick until they were all out of their nests and independent from their parents. They removed eggs that did not hatch and any chicks that died. Scientists monitored the fate of every single egg laid by inspecting each nest every day. This graph shows the fitness of males and females from chosen and assigned pairs. Birds could freely choose a mate in a situation somewhat similar to a speed-dating event. Scientists formed groups of 20 females and 20 potential male partners. And, if this was the case, they wanted to know what caused these differences. In this experiment scientists wanted to find out if zebra finches that were allowed to mate with the partner of their choice would raise more young (i.e., reach higher fitness) than those that had to settle with a partner they did not choose. We will refer to the ways two parents interact directly as ‘behavioral compatibility’. What about direct compatibility benefits? For instance, coordinating and sharing tasks could be easier with one male than with another. Therefore, one possibility is that the genes of a female work better with the genes of one male than with those of another - an indirect benefit. This means the father’s and the mother’s genes have to work well with each other. The genes of a father and a mother mix in their offspring. There are four different benefits an animal can get from choosing a mate. How can one male be more compatible with a female than another? This suggests that females may choose males that match them best, because they are most compatible. Yet, in some species, females do not share their preferences. Overall, females prefer higher quality partners. A wisely chosen partner can pass on good genes that allow offspring to survive better. But benefits of mate choice can also be indirect. For instance, if a chosen male brings a lot of food to the nest, this makes the work easier for his female partner. A specific partner can give direct benefits. Picking the right partner can be important in many ways. They choose their partners in a way that is specific to each individual, meaning different birds do not agree on which bird is most attractive. The zebra finch is similar to humans in some of their relationships. These birds bond with one partner for life and share the duty of caring for their offspring. But some birds aren't as different as you might think. Click for more information.īirds have beaks and wings they use to fly, which makes them seem very different from humans. The female is on the left and the male is on the right. ![]()
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