Just like humans, swans pair monogamously for a few years, then panic and break things off (only to be filled with immense regret). "Researchers also noted that only humans and swans enter a painful spiral of regret over their lost relationship and then compulsively mate with several partners in a futile effort to recapture what they once had."
If you think that's interesting, how about this research (from a slightly different -- and usually less entertaining -- type of publication) about fairy wrens?
"Fairy-wrens are notorious for their infidelity: despite living in seemingly harmonious monogamous pairs, females produce mostly illegitimate young, and males spend more time courting other females than their own partner. Among these promiscuous birds, researchers from the Max Planck Institute of Ornithology in Germany and the University of Freiburg, Germany have now found a uniquely faithful species, the purple-crowned fairy-wren. What's more, males of this species have lost all striking adaptations for extra-pair mating that characterise the other fairy-wrens, including presentation of flower petals during courtship displays."
In other words, the truly monogamous males are the only ones who don't bring flowers.
Many thanks to Shea Houlihan for sharing this insightful article!!
Revealing how closely the waterfowl’s social behavior resembles that of humans, a study released Thursday by the University of Georgia has found that swans are the only other members of the animal kingdom that mate for a few years, get scared, decide to end things, and are later filled with immense regret. “Although most animals either procreate freely or select a single partner with which to mate for life, we observed that swans, like humans, get freaked out about their relationship after an extended period of time together, abruptly call things off, and then come to realize they made a huge mistake,” avian biologist Michael Brooks told reporters.