Great reed warbler females lay 3–6 eggs in an open cup-nest in reeds.
Some pairs of warblers are monogamous, but others are not, and unpaired, so-called "satellite" males still father some young.
Great reed warblers defend their nests using graded alarm calls, directed towards a wide range of enemies, although these alarm calls might reveal the whereabouts of the nest to brood parasites.

A long-term study of the factors that contribute to male fitness examined the characteristics of males and territories in relation to annual and lifetime breeding success.
It showed that the arrival order of the male was the most significant factor for predicting pairing success, fledgling success, and number of offspring that survive.
It also found that arrival order was closely correlated with territory attractiveness rank.
Females seem to prefer early arriving males that occupy more attractive territories.
These females also tend to gain direct benefits through the increased production of fledglings and offspring that become adults.
In addition, male song repertoire length is positively correlated to annual harem size and overall lifetime production of offspring that survive.
Song repertoire size alone is able to predict male lifetime number of surviving offspring.
Females tend to be attracted to males with longer song repertoires since they tend to sire offspring with improved viability.
In doing so, they gain indirect benefits for their own young.

Great reed warblers have a short, polygynous breeding cycle in which the male contributes little to parental care.
They defend large territories in reed beds where there is reduced visibility, which may allow males to practice deception by moving and attracting a second female.
This second female may not realize that the male has already mated.
Polygyny of the great reed warbler was assessed in another study that showed the importance of female choice.
The differences in territory characteristics seemed to be more important.
However, there is also a strong correlation between male and their territory characteristics.
Models based on the polygyny threshold and sexy son hypotheses predict that females should gain evolutionary advantage in either short-term or long-term in this mating system, yet the study did not support this.
The data showed that secondary females had greatly reduced breeding success.
Great reed warbler females lay 3–6 eggs in an open cup-nest in reeds. Some pairs of warblers are monogamous, but others are not, and unpaired, so-called "satellite" males still father some young. Great reed warblers defend their nests using graded alarm calls, directed towards a wide range of enemies, although these alarm calls might reveal the whereabouts of the nest to brood parasites.
A long-term study of the factors that contribute to male fitness examined the characteristics of males and territories in relation to annual and lifetime breeding success. It showed that the arrival order of the male was the most significant factor for predicting pairing success, fledgling success, and number of offspring that survive. It also found that arrival order was closely correlated with territory attractiveness rank. Females seem to prefer early arriving males that occupy more attractive territories. These females also tend to gain direct benefits through the increased production of fledglings and offspring that become adults. In addition, male song repertoire length is positively correlated to annual harem size and overall lifetime production of offspring that survive. Song repertoire size alone is able to predict male lifetime number of surviving offspring. Females tend to be attracted to males with longer song repertoires since they tend to sire offspring with improved viability. In doing so, they gain indirect benefits for their own young.
Great reed warblers have a short, polygynous breeding cycle in which the male contributes little to parental care. They defend large territories in reed beds where there is reduced visibility, which may allow males to practice deception by moving and attracting a second female. This second female may not realize that the male has already mated. Polygyny of the great reed warbler was assessed in another study that showed the importance of female choice. The differences in territory characteristics seemed to be more important. However, there is also a strong correlation between male and their territory characteristics. Models based on the polygyny threshold and sexy son hypotheses predict that females should gain evolutionary advantage in either short-term or long-term in this mating system, yet the study did not support this. The data showed that secondary females had greatly reduced breeding success.
Great reed warbler