Single-Parenting on Arrowhead

Raising of a child by one parent alone is common enough in humans that we have words to describe the phenomenon. Since humans are highly social, rearing of a child by a single parent — and a support network of friends and relatives — can be effective. Not so in loons. The loon breeding system could be called “obligate biparental care”, because both male and female are usually required to fledge even a single chick. When one parent is lost during chick-rearing, the typical result is rapid death of the chick or chicks, either because the loon that replaces the dead parent actively attacks them or because they receive much less food and protection from a single parent and perish from other causes. In fact, sustained single-parent loon families only occur when one parent dies or is evicted and the remaining parent somehow manages to sequester the chick from the new adult that fills the breeding vacancy. The occurrence is rare enough that I remember all of the cases in our study area. 

When the Washburn female was injured in 2000, she deserted her family and turned her attention to her own survival. Though it seemed heartless at the time, this decision made sense. Even though helping to rear the chick she left in the male’s care would have increased her reproductive fitness, she was right not to risk her life for the chick. An adult that sacrifices itself for a chick is throwing away many future years of breeding success. After the female left the family, the male spent his time at the northern end of the lake, feeding the chick vigorously when he could. Somehow he managed to fledge it. 

In 2006, the Garth male vanished just after the chick hatched, leaving the female alone to raise it. A single loon mother is in a bind; she lacks the size to intimidate and drive off other loons and ability to give the territorial yodel that could prevent many intruders from landing on her lake in the first place. Instead, single females must tolerate visits by many intruders and hope to keep them away from the chick. A new male soon took over Garth and paired with the female. The female and her new mate seemed to reach some sort of uneasy agreement; she spent time with him, while he neither fed nor attacked his step-chick. The chick, which we banded late in the year and affectionately call “Stripe Hell” because his bands are blue-stripe over taupe-stripe, red-stripe over silver, ultimately survived to adulthood. In fact, as an adult, this male claimed the breeding territory on Lee Lake in 2012 and produced chicks there in 2016 and 2017. Following his eviction from Lee in 2018, this product of a one-parent family settled on South Blue in 2019 and then resettled on Miller Lake this year, where he is now raising a chick with his mate. Apparently having been raised in a single-parent home does not prevent a loon from leading a successful adult life. 

Things do not always go smoothly for step-chicks. When the male succumbed to some unknown ailment on Flannery in 2015, he left his mate alone to fend for their 2-week-old chicks. In this case, the female led the chicks down to Velvet Lake, which attaches to Flannery at its southern end. When a neighboring male took over, he found the chicks and pecked them viciously, killing one and forcing the survivor to hide underneath docks in Velvet to escape his marauding stepfather. This chick never received as much food as a chick normally would; we are not certain if it survived the ordeal.  

Among the several single-parent families we have recorded in 28 years, Squash-Northwest is perhaps the most memorable. The Squash-Northwest male in 2012 hatched a chick with his mate but was injured and died when the chick was two weeks old. Left alone with a small chick, his mate not only protected and raised it to adulthood, she also found a new mate. She was able somehow to balance the demands of her ravenous youngster and the male that she paired with — while keeping them physically separated so that the replacement male did not harm his step-chick. On one visit, we would find her staying close to the chick, feeding it and fending off eagles at the northwestern end; on the next visit, the female would forage and rest with her new mate on southern side of the lake, while the chick hid near shore a kilometer away. While we marveled at the ability of the female to lead this double life and thus to keep the chick alive, we were on pins and needles during the entire chick-rearing period. It seemed inconceivable that the female could sustain her balancing act for the many weeks it would take until the chick was old enough to fend for itself. On each visit to the territory, we expected to find that the chick was dead or severely injured following an attack by its stepfather. Yet the fatherless chick, pictured above and dubbed “Miracle Chick”, not only survived but grew by leaps and bounds.

This year we have a new — and increasingly dark — variation on the single-mother theme playing out on Arrowhead Lake. About a month ago, the right wing of the 12-year-old breeding male became injured. (It is a soft tissue injury, we think, as we did not find a break when we inspected the wing after capture a week ago.) The injured male has engaged less and less with his mate and two chicks over the past month. Instead he spends his time resting and foraging alone on the southern end of the lake. His mate, a seasoned breeder who has produced at least seven sets of chicks with at least three different males on Madeline Lake and Arrowhead, appeared to step up her chick feedings and attendance to compensate for her mate’s absence. Her efforts seemed to pay off; the chick we caught a week ago had achieved a healthy weight, and its sibling (which we did not catch) was of roughly equal size. But the situation has degenerated in the past week. The male, though still alert and feeding himself, shows no signs of recovery from his wing injury and continues to avoid the family. In the past few days, the six-week-old chick that we did not capture was lost (to an eagle, according to lake residents). Today, Lyn reported that intruders landing on the lake roamed about it at will, because neither male nor female showed any semblance of territory defense. It seems only a matter of time before a new breeding pair takes over Arrowhead, and that will likely lead to the demise of the surviving chick. 

Let’s try to be optimistic. If the male recovers and begins to defend the territory again, the chick is in great shape. At six weeks, it has already survived the most difficult early phase of chick-rearing. The veteran female is an attentive mother; perhaps her care can keep the chick healthy in the meantime. And in the sad event that the male does not recover, the female’s efforts might be enough to keep the chick alive and growing even in the presence of a new male. After all, it has been done before. 

In any event, I think I have made my point. Biparental care is almost mandatory in common loons. While a human dad or mom can usually call upon a support network of friends and relatives to help feed and protect their child, a male or female loon that loses its mate during chick-rearing is very much alone.