Birds do it, bees do it
Even educated fleas do it
Let’s do it, let’s fall in love
Like these Rosy-faced Lovebirds (native to southwestern Africa but released and thriving in North America and Europe), some birds form close pair-bonds that last for years. Other species that mate for life include Black Vultures, Bald Eagles, and Mute Swans. While it might seem like a love-match, forming a lifelong pair-bond probably has more to do with saving energy and producing more surviving offspring.
Ornithologists have found that long-term monogamy can be particularly advantageous when birds live in cooperative groups or in unpredictable environments. A study of wild Jackdaws found that the strength of pair-bonds varied across the population, but was consistent within pairs over time.