Sibling rivalry is a fascinating but intellectually thorny behavior pattern. Why would a young animal hurt its own flesh and blood? To put it scientifically, why would an animal harm its full sibling when that sibling shares half of its genes and when the ultimate goal of animal behavior is to increase the abundance of one’s genes in the next generation?
But normal rules do not apply when food is limited early in life. If the food supply is inadequate to keep all members of a sibling group alive, then the only sound evolutionary strategy for each sibling is to battle mercilessly and become a survivor.
Such is often the case in loon families, especially those living on small lakes. Even with only two chicks to care for, loon parents are all out to keep them alive. This scenario creates the haves — chicks that hatch two days before their siblings and use their size advantage to pummel them and gain a greater share of the limited food that parents can find — and have-nots.
What of the have-nots? To avoid beatings from an aggressive older sib, a typical younger sib lags behind its family and, as a result, receives fewer feedings. It becomes weaker over time, is less able to defend itself, suffers more beatings, and begins to avoid its family altogether. Unable to escape this downward spiral, most beta chicks perish from starvation. Some undoubtedly fall prey to eagles.
But not all starving beta chicks die quietly on their home lakes. Sometimes a chick in such dire straits abandons its home and kin and strikes out over land in hopes of finding a new family of loons that will feed and protect it. If it sounds preposterous that a weakened, helpless loon chick would trek through the woods in hopes of being welcomed by a foreign loon family, it is. Only the prospect of certain death at home could induce a chick to make such a reckless, fanciful journey. And yet such “chick odysseys” happen commonly at this time every year.*
We are four weeks into the chick-rearing period in both Minnesota and Wisconsin study areas. So this is the time when a small cohort of starving second-hatched chicks from small lakes across the Upper Midwest are abandoning their abusive older siblings to seek a better life elsewhere.
A two-week-old chick in north-central Minnesota took this desperate approach. A good samaritan stumbled upon the brown puffball on a roadside and carried it a rehabber. But the rehabber had no future to offer the chick. Only loons can raise loons. In fact, only adult loons who currently have chicks of their own are (sometimes) willing to accept these waifs.
It is a chancy business to match a parentless chick with a foster family already rearing a chick. The chief danger is lack of acceptance by the biological chick. If the natural chick attacks the chick you are trying to add to the family, you are back to square one. Folks who attempt fostering of this kind report a success rate of about 35%.
The loon pair of Island Lake on the Whitefish Chain had a single two-week-old chick — very close to the size of the chick found on the roadside. As shown in the video below, the homeless chick quickly joined and bonded with the Island family. After an initial tussle with its new sibling ended in a draw, the biological chick seemed to resign itself to the new addition. Both chicks remained peacefully together this afternoon, three days after the introduction.**
We have no idea what the future holds for the adopted chick. Starvation, predation, a boat strike, or fishing entanglement might end its life before it reaches fledging age. Yet a chick that was a longshot to survive two days ago is suddenly ensconced with a protective new family. And this former have-not now stands a decent chance of reaching adulthood. It is hard not to feel good about that.
* Though these journeys are the most desperate of long-shots, they do not always fail. In fact, we had one case where a chick that fled across land reached a new lake, gained two new siblings, and lived happily ever after.
** The top photo shows the Island Lake pair and their two chicks as of June 28th at 1pm. Evrett Fiddian-Green, who took this photo, reports that both chicks are being fed by the parents. Most important, the chicks are not fighting.