Question

the male african long - tailed widowbird, euplectes progne, has tail feathers about half a meter long. the males are territorial, each defending a territory of about the same size. the females build their nest in the territory of their mate and provide food and care for the young.
a researcher treated the tails of four groups of e. progne males by either clipping their tail feathers, gluing more feathers to their tail, or both. each group contained nine e. progne males. the birds were then released and their territories observed for active nests. the graph shows a summary of the results.
why are longer tails a selective advantage for male e. progne?

Explanation:

The graph shows that males with longer tails (after treatment of gluing feathers to lengthen tail) have a higher mean number of new active nests per territory compared to those with shorter tails (tail - clipped). This implies that longer tails make male E. progne more attractive to females. Females are likely to choose males with longer tails as they may be perceived as healthier or more genetically fit. A higher number of nests in a male's territory suggests more female interest, which is a key aspect of sexual selection.

Answer:

Longer tails in male E. progne are a selective advantage because they attract more females. As shown in the graph, males with lengthened tails (by gluing feathers) have a higher mean number of new active nests per territory. This indicates that females prefer males with longer tails, likely due to perceptions of better health or genetic quality, which is a form of sexual selection.