Love of their life? Not really

Love of their life? Not really
Well, most everyone survived Valentine’s Day. A few of you are temporarily in the doghouse. Many of you are good for another year, sort of. This holiday is usually a time for romance, love and kissy-faced obligations.
Fidelity in a relationship is a universal value of humans (some cultures are more liberal with their definition of fidelity than others). Back in 1990, the U.S. divorce rate was only 13 percent but nowadays it is over 50 percent. Whether it’s in the movie “The Postman Always Rings Twice”, the novel “Anna Karenina” or the TV show “Mad Men,” cheating on your spouse is frowned upon. The message being that no good can befall a mate that fancies another.
On the other hand, 90 percent of birds are monogamous at least for a year!
Some might say that when you’re a bird with a very short life span (songbirds average three years) it is easier to be faithful versus humans living an average of 70 years. But, to be fair, a bird's definition of monogamy is also surprisingly liberal.
Yet, there are a few species of birds that meet, court and form pair-bonds that result in many offspring, year after year, until one of the pair dies. These large birds are considered as mating for life. Among them are: mute swans, Canada geese, bald eagles and great horned owls.
Why birds mate for life is not as romantic as one may think. When you consider the possible time needed to migrate, to establish territories, sit on eggs and raise the young, you'll realize that the extra time and energy needed to attract a mate would minimize reproductive time.
The bald eagle, for example, spends just over a month incubating the eggs and almost three months raising their young in the nest. Establishing lifelong bonds works to their advantage.
The question of whether a bird mates for life comes from pondering what happens should one bird die. Many believe that birds mourn the loss of their mate, never to mate again. There is a lot of conjecture whether birds experience loss at some level or if we sometimes interpret confusion as mourning. I do know our wild birds will always attempt to find new mates.
Scientists have amassed enough data to debunk the romantic notion that most birds pair up faithfully for life. Lots of monogamous bird species “cheat” and some “divorce” but at rates much lower than humans. Male birds with a high proportion of daily female exposure are less likely to “divorce” their partner between breeding seasons. Interestingly, the absolute number of female interactions isn't important — just the ratio of females to males in the social group. This behavior was discovered by Dr. Antica Culina of Oxford University’s Zoology Department when they studied British chickadees.
But monogamy isn’t the same as mating for life. A pair-bond may last for just one nesting (two nests per season on average), such as with house wrens, or one breeding season, common with most songbird species, like chickadees and goldfinches.
Northern harriers and ruby-throated hummingbirds do not form pair-bonds; but instead consort only briefly — from minutes to hours. The male's investment in offspring is limited to sperm, and the female raises the young alone. Such mating systems, in which no pair-bond is formed, are termed promiscuous.
The most promiscuous birds in the world are our very own migrant saltmarsh sparrows that arrive in the middle of May and stay until October. Researchers found that 95 percent of females mated with more than one male each breeding season. "The chance that any two chicks in the same nest have the same father is only 23 percent," says Professor Christopher Elphick of the University of Connecticut.
There seem to be a lot of philosophical discussions around Valentine's Day regarding faithfulness and commitment, but birds shouldn’t be thought of as exhibit A for fidelity. There is more than meets the eye regarding divorce, monogamy, marriage rates, cheating, pair-bonding or promiscuity and other options than marriage in both humans and birds.
— Phil Kyle writes about birding every week for the Cape Cod Times. He is a past president of The Cape Cod Bird Club, and in his semiretirement, works summers as head naturalist for Barnstable Harbor Ecotours. He can be reached by email at archeopt@gmail.com.