09/26/2026
While is crowning a champion grizzly, we can also celebrate the other members of the animal kingdom packing on the pounds (or grams) as winter approaches. It’s fitting for the end of ASI’s fall banding season in Alaska to appreciate our feathered friends as they bulk up for migration with a spotlight!
Sufficient fat stores are vital for fueling long-distance migration flights in songbirds. When banding, by blowing on and parting birds’ feathers, we can assess how much fat they have—songbirds usually deposit fat below their neck and on their abdomen and flanks. At CFMS, we score fat levels anywhere from ‘0’ (none) to ‘7’ (essentially bulging out everywhere!) Most of the time, birds are scoring 0 up to 2 for fat levels, but that can quickly change when they’re getting ready to take off to migrate. Towards the end of our season, we start seeing higher fat scores in our birds as their departure nears.
Over the last week, we caught a few especially full-bodied birds that deserve heavyweight recognition:
1. This young male Rusty Blackbird may be the uncontested title holder this year. Not only did he receive the highest fat score of any bird at CFMS this fall, but weighing in at nearly 80 grams makes him the heaviest Rusty Blackbird we’ve ever caught at the station!
2. American Tree Sparrows not afraid of feeling chunky. As one of our latest season migrants, they tend to consistently have some of higher fat scores in the fall. This big youngster was no exception.
3. A glimpse of the previous sparrow’s fat. Birds will store much of their fat in their furcular cavity below the neck, and it appears as an opaque yellow substance through the translucent skin. Look at those lovely mounds!
4. Though Ruby-crowned Kinglets are one of the smallest songbirds we catch, their diminutive stature doesn’t keep them from fattening up. At 7.2 grams, it may be scarcely more than a nickel, but it’s impressive heft for the species!
Which of these beefy birds do you think are most deserving of the honors?
