Last year I wrote a blog post in which I concluded that late-hatching chicks returned at a rate no different from early-hatching chicks. I found the result surprising, as one would expect early hatchlings to have a head start in learning to feed themselves, honing their flight skills, and preparing for their first migratory journey. The photo and story I got from Linda Grenzer a few days ago has forced me to wonder if I need to collect more data on this question.
The breeding pair on Squaw Lake had an eventful year in 2018. Delayed, like all other pairs, by the late thaw, they initially nested along the shoreline near the boat landing. After a predator snatched both eggs off of the nest, they nested again not far away. This time they were more fortunate; the eggs hatched, but not until about July 22. When we captured the family on August 3rd, we found the chicks almost comically small — two little puffballs that did not approach the size of the many other juveniles we had encountered. Chicks are cute in their first few weeks, and we enjoyed observing them and handling them cautiously while giving the female a new set of bands.
Our delight at seeing the adorable chicks was tempered by the fear that chicks hatched so late would not mature in time to complete the southward migration. The fear is justified; parents must balance the energetic demands of their demanding offspring against their own need to maintain good body condition and prep for their autumn journey. Inevitably, adult loons spend progressively less time on their home lake in September as they forage intensively, molt into drab winter plumage, build up fat levels, and, in late October or early November, head south. This goes for parents and non-parents alike.
So it was not surprising to get a report from Linda that the Squaw adults had left their breeding lake, leaving their late-hatched chicks to fend for themselves. What was alarming was that one chick had chased someone’s jig, managed to hook itself above the base of the bill, and was no longer diving or foraging normally. Further evidence of its desperate condition was that it was not difficult to capture and weighed a mere 1750 grams — roughly 1 kg less than it should have at 9 weeks. Following an X-ray at Raptor Education Group, Inc. in Antigo, the chick was found to have swallowed a second hook from a separate encounter with an angler.
Since we have long since ceased our routine visits to study lakes, we can only speculate about the series of events that put the chick in this bind. Marge Gibson of REGI suspects that, without parents to help it satisfy its foraging needs, the chick was struggling to feed itself. In its desperation, the chick began to attack fishing lures until the hook in its cheek and weakness conspired to incapacitate it.
If Marge is right, and late-hatched chicks are sometimes left with too little feeding capacity to maintain themselves, then this pattern should show up in our data. Specifically, we should see fewer very-late-hatched chicks return as adults to the study area. This plausible scenario will fuel another round of data analysis…when I find time!
To end on a positive note, the angling victim is bouncing back at REGI and feeding voraciously. If you do not believe me, look at this video from the REGI website.
If it continues to thrive, the REGI folks will face another challenge: what to do with a healthy juvenile, but one whose stay in captivity and recovery made flight practice impossible.