Jeffrey Boone Miller
Figure 1. Dark-eyed Juncos dubbed Heart (left), Lefty (center), and Popsicle (right) based on their distinctive patterns of white feathering. Photographed by the author on January 20, 2018.
I find it immensely cheering that Dark-eyed Juncos (Junco hyemalis) choose to spend the winter with us in Massachusetts. Knowing that these birds feel at home in our long, cold, icy winters improves my own outlook. During the winter of 2017–2018, the flocks of juncos that visited our feeder were of more than the usual interest, because I was able to identify and repeatedly observe three individuals.
By mid-December of 2017, I had noticed three juncos that were identifiable as individuals among the otherwise indistinguishable juncos at our sunflower seed feeder in suburban Belmont, Massachusetts. Each of these three had a distinctive pattern of white feathering (Figure 1). One bird was a male with a symmetrical white spot on his breast that earned him the name "Heart." The second bird, dubbed "Lefty," was a male with a single white feather on his left wing. The third bird appeared to be a female and had a white outer tail feather on her left side that remained visible even when the tail was folded. This feather reminded me of a popsicle stick, hence she became "Popsicle."
Figure 2. Return of the juncos? Left: Junco with a white breast spot, perhaps Heart, seen on November 16, 2018. Center: Junco confidently identified as Lefty based on the single distinctive white feather on its left wing, also on November 16, 2018. Right: Junco likely to be Popsicle on November 28, 2018. Photographed by the author.
The birds had different styles of feeding. Heart and Lefty, the two males, usually took seeds directly from the feeder perch, but Popsicle only fed on seeds that had fallen or been scattered on the ground under the feeder. During the winter season, juncos develop dominance hierarchies that can affect access of smaller, less dominant birds to food sources (Nolan et al., 2002). At the feeder's perches, juncos regularly faced off with other juncos and tangled with sparrows, finches, and even cardinals and jays. Perhaps Popsicle fed on the ground because it was a less competitive feeding site.
By following an individual, I could estimate how much a bird was eating. For example, I once saw Lefty select, shell, and consume seven sunflower seeds in 20 minutes. Raw sunflower seeds provide about six calories per gram (U.S. Department of Agriculture 2018) and each gram consists of 14 or 15 shelled seeds (Statcrunch 2018). So, in those 20 minutes, Lefty ate about half a gram of seeds with three calories. In one study of juncos kept in a laboratory, each 18-gram bird consumed about 15 calories per day (Parrish and Martin 1977). At the feeding rate I observed, Lefty could eat 15 calories—2.5 grams—worth of sunflower seeds in less than two hours. However, free-ranging birds in cold temperatures no doubt require much more food than the laboratory birds did and so would need to spend additional time foraging. It would be interesting to know if "my" juncos also visited the other feeders in my neighborhood as part of their daily foraging.
By observing the comings and goings of the three individuals, I could also estimate the number of different flocks and total number of juncos that used the feeder. I sometimes saw lone juncos at the feeder, but the usual pattern was for four to eight birds to arrive at the same time. For Heart, Lefty, and Popsicle, usually just one of the three was present, less often two, and seldom all three—a pattern that suggests they were members of three distinct flocks. At least one additional flock, which did not include one of the identifiable birds, also visited. In total, therefore, the feeder attracted perhaps 25 or 30 different juncos that were members of at least four flocks. I was happy that all three identifiable birds survived the winter. Though this number is too small to estimate mortality rates with any confidence, at least none of these three were taken by the Cooper's Hawk that sometimes frequented our yard.
As it turned out, the departure of the juncos for the summer did not represent the end to my observations of these birds.
On November 16, 2018, not long after I started writing this essay and ten days after I first filled our feeder for the new season, I was astonished to see two juncos that looked like they might be Heart and Lefty (Figure 2, left and center). Then, to complete the scene, a bird arrived on November 28, 2018, that was almost certainly Popsicle, as it had Popsicle's distinctive white tail feather and habit of feeding only on the ground (Figure 2, right panel).
Because the birds were not permanently banded, I cannot be absolutely certain that the same individuals returned to our feeder. However, such a return would not be surprising, because juncos often use the same wintering site year after year (Ketterson and Nolan 1982). In addition, it appears that the birds retained their distinctive feather patterns through the annual molt cycle (Nolan et al., 2002). I would have expected that particularly the asymmetric marks of Lefty and Popsicle might have been due to injuries and so might have been repaired during molting.
It looks as if the winter of 2018–19 will provide new opportunities for getting to know individual juncos. I still have questions.
References
- Lasiewski, R. C. and W. R. Dawson. 1967. A re-examination of the relation between standard metabolic rate and body weight in birds. Condor 69: 13–23.
- Ketterson, E. D. and V. Nolan, Jr. 1982. The role of migration and winter mortality in the life history of a temperate-zone migrant, the Dark-eyed Junco, as determined from demographic analyses of winter populations. Auk 99: 243-259.
- Nolan Jr., V., E. D. Ketterson, D. A. Cristol, C. M. Rogers, E. D. Clotfelter, R. C. Titus, S. J. Schoech, and E. Snajdr. 2002. Dark-eyed Junco (Junco hyemalis). Version 2.0 in The Birds of North America Online (A. F. Poole and F. B. Gill, Eds.). Ithaca: Cornell Lab of Ornithology: https://doi.org/10.2173/bna.716.
- Parrish Jr., J. W. and E. W. Martin. 1977. The effect of dietary lysine level on the energy and nitrogen balance of the Dark-eyed Junco. The Condor 79: 24–30.
- Statcrunch. 2018. How much does a sunflower seed weigh? Accessed November 16, 2018 at: https://www.statcrunch.com/5.0/viewreport.php?reportid=41018.
- U.S. Department of Agriculture. 2018. Nutrient composition of raw sunflower seeds. Accessed November 16, 2018 at: https://tinyurl.com/rawsunflowerseeds
