It was an average day at Captain Sam’s today with 46 new
birds comprised of 10 species and 1 recapture.
As you may have guessed, Common Yellowthroats were the most common
species banded today with 34. It seems
we will continue with a similar bird activity pattern for the next few days
with things possibly picking up midweek.
Mixed among the Common Yellowthroats today were our two
most common species of vireos, Red-eyed Vireo and White-eyed Vireo. Most of the birds we band at KIBS are aged
based on a molt limit found in the wing but when it comes to these two vireos
species, the first thing we look at is eye color. Interestingly enough, when these species are
first hatched out they do not have the eye color that they are named for. Red-eyed Vireos start off with a dark brown
iris and over a period of a couple months will attain the bright red iris that
the species is known for. White-eyed
Vireos begin life with a gray brown iris that progressively gets whiter over a
period of several months. The full adult
eye color is usually reached during their first winter or late fall, making
aging based on eye color only useful during fall migration. When using eye color to age, as with any
other aging technique, it is usually a good idea to look at other
characteristics such as skull ossification and molt limits to age with
certainty. This was certainly the case today when we captured a White-eyed Vireo with a white eye. After studying the bird's plumage, we noticed a couple of things that pointed away from an adult bird. The outer tails feathers were narrow and tapered, and the primary coverts were faded. So we checked the bird's skull to see if it was completely ossified, and sure enough, it was not, meaning that this individual was a hatch-year bird (see last photo).
-Mattie
-Mattie
 | |||
| Red-eyed Vireo (top: hatch-year, bottom: after hatch-year) |
 |
| White-eyed Vireo (top: hatch-year, bottom: after hatch-year) |
 |
| Hatch-year with white eye similar to an adult. This bird was probably hatched early in the summer which gave it plenty of time to acquire a white eye by mid-September. |
Little Bear
We had another slow day at Little Bear today, although better than yesterday. We captured 22 new bands and 6 recaptures, of 11 species. About half of our new birds were Common Yellowthroats, but we also had a few other warbler species around today and Little Bear got its first-of-season Gray Catbird! There will be many more to come.
-Casey
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| Gray Catbird (Hatch-year, sex unknown) Photo by Casey Weissburg |
| Species | Captain Sam's | Little Bear | ||
|---|---|---|---|---|
| New | Recaps | New | Recaps | |
| White-eyed Vireo | 1 | - | - | 1 |
| Red-eyed Vireo | 1 | 1 | - | 1 |
| Gray Catbird | - | - | 1 | - |
| Ovenbird | 1 | - | 1 | - |
| Northern Waterthrush | 1 | - | - | - |
| Common Yellowthroat | 34 | - | 12 | - |
| American Redstart | 1 | - | - | 1 |
| Yellow Warbler | 3 | - | 1 | - |
| Palm Warbler (western) | 1 | - | 1 | - |
| Prairie Warbler | 1 | - | 1 | - |
| Northern Cardinal | - | - | - | 2 |
| Painted Bunting | 2 | - | 4 | 1 |
| Banding Stats | Captain Sam's | Little Bear | TOTAL |
|---|---|---|---|
| # Birds Banded | 46 | 21 | 67 |
| # of Recaptures | 1 | 6 | 7 |
| # of Species | 10 | 11 | 12 |
| Effort (net-hours) | 127.5 | 50 | 177.5 |
| Capture Rate (birds/100 net-hours) | 36.9 | 42.0 | 41.7 |
| Nets | 25 | 10 | 35 |
