Now that Christmas shopping is here, it’s appropriate to think about the problem of avian siblicide. The first murder in the Bible was a case of siblicide, where Cain killed his brother Abel for essentially the same reasons as in a nest of baby hawks, where the larger, more aggressive siblings kill the smaller, more compassionate ones in order to get all the attention and gifts from their parents. We were taught in a Catholic school that Jesus had no brothers or sisters. That made a lot of sense to me because I reasoned that no one with a brother or sister could possibly lead a perfect life because they would eventually get into arguments.
Chicks in nearly all siblicide bird species vary in size because the females begin incubating as soon as the first egg is laid. Since a mother Blue Jay does not begin incubating until her entire clutch of five eggs is laid, the young hatch almost simultaneously and equally spaced out. When a hawk’s younger sibling is weak and unable to defend itself, the larger sibling will sometimes not only beat up the weaker sibling but also devour it. Though it seems incomprehensible to us as humans, this makes perfect sense from an energetics perspective. Because of the problems in many sibling relationships, we may argue with our siblings, making Christmas tense and painful for some of us, but that’s usually the extent of it. A hawk knows it’s in serious trouble when it gives its younger sibling a Valentine’s Day card that reads, “Sugar is sweet, violets are blue, roses are red, and so are you.” A baby hawk uses the phrase “you are what you eat” literally. During the season most associated with brotherly love, brother and sister birds that have survived the winter together are safe from one another, living far apart and not even exchanging Christmas cards. When hawks hear those ominous words, “Big Brother is watching you,” their fear is entirely different. .
Apparently some species of birds have more babies than they can raise on purpose, as insurance. What’s the purpose of baby birds killing each other, and why don’t their parents stop them or at least yell at them or take away their allowance every now and then? Typically, double-crested cormorants lay four eggs, but very rarely do more than three of them hatch. When the first hatchling dries off, whooping cranes leave the nest permanently, leaving the second egg, which is typically viable, unhatched and unloved. However, the parents’ efforts would have been well worth it if one of the older baby cormorants suffered from an illness or accident, or if the first crane wasn’t viable.
Of course, some species of baby birds get along well with their siblings. I’ve raised a whole family of Blue Jays and observed the young ones in their nests; despite their competition for food, they were all quite courteous. They all yell, “Me first! Me first!” when their parents arrive with food, but they don’t undermine each other’s efforts after that. They also never argue or bicker about who has the best caterpillar after their parents depart. However, some families of birds treat one another horribly, even when the parents are looking on. Anyone who has ever watched chicks as babies understands how incredibly literal the phrase “pecking order” is. Whether or not there is an abundance of food, the largest chick in a heron or egret nest attacks and typically kills the smaller ones. The majority of hawks argue but do not become violent unless they are hungry. However, the most exquisitely beautiful hawk, the Swallow-tailed Kite, is obligate siblicidal at first, meaning that ninety percent of the kites we see gracefully gliding through a Florida sunrise have previously killed a younger sibling.
Another aspect of siblicide relates to food resources. Siblicidal species are typically those for which it is not always possible to guarantee a sufficient supply of food for young birds. This is caused by a circumstance, like a drought, in which parents are unable to find the steady, plentiful supply of food required to keep all of their children healthy and happy, not by parental neglect. This sets up a competitive relationship for the babies.
activities. This week, wrens built a nest in our garage, so we have to keep the doors open until the young depart. Getting to see the birds and their fledglings is well worth the effort.
Seasons with plenty of food allow for the successful feeding of multiple nestlings and the prevention of siblicide. Siblicide as a strategy to guarantee the survival of the fittest may seem harsh to humans. However, the phenomenon is well-known and evidently effective among birds.
If you see a baby bird fall from its nest this spring, it might not be an accident but rather the result of a sibling’s decisive action. But dont pass judgment on such behavior. Any animal species will typically behave in a way that increases the likelihood of its offspring inheriting its parents’ genes, even if that behavior appears cruel to us. Natures ways are exceedingly complex.
A characteristic of siblicidal behavior that has been found to be highly significant is the existence of some size difference between the nestmates. To ensure that one egg is larger than the other, the mother of a black eagle, for instance, hatches the two eggs three days apart. Then, if there is a shortage of food in a given year, the larger nestling kills the smaller one. The second nestling takes over if the first one is in any way unhealthy. In either case, the parents can expect to have at least one child who eats well.
FAQ
Do baby birds kill their siblings?
Will birds kill other birds babies?
Do baby birds peck each other?
What percentage of baby birds survive?