Tuesday, September 27, 2016

A very unexpected first state record - Yellow-Green Vireo

Little Bear

Normally the daily post for Captain Sam’s comes before the one for Little Bear. It’s the longer-running, more-established station, and it has more nets and often more crew members. Today, however, the Little Bear post is leading the entry because of what we captured out there this morning.

The photo below is the first South Carolina record of Yellow-Green Vireo (if accepted by the South Carolina Bird Record Committee).

Yellow-green Vireo (hatch-year, unknown sex)


In addition to being a wholly unexpected vagrant, this bird has a story behind it too.

First, I have been banding birds for 8 years now, and in those 8 years I have been fortunate enough to spend about one-third of my time working on projects in Central and South America. Yellow-green Vireo is not an unfamiliar species to me, and in fact I have gotten very annoyed with them for being so abundant when they pass through northwest Costa Rica in early March because 10 or 20 of them singing all at once drowns out the sounds of other species. I have captured and banded them in both Costa Rica and on their wintering grounds in eastern Peru.

Back on Thursday, about midway through the morning, Ryan Donnelly and I were checking the nets together. At net 2 we came across a very brightly colored vireo. Once we had brought the bird back to the banding station and started processing it, I started wondering if it was too bright to be a Red-eyed Vireo. It seemed absolutely absurd that a Yellow-green Vireo might be in coastal South Carolina, but the bird was very, very yellow.

I asked Ryan to hand the bird to me and I started taking additional measurements. Yellow-green Vireo has a longer bill than Red-eyed Vireo, most evident in the measurement known as “exposed culmen”. This bird’s exposed culmen was 15.2 millimeters—about a millimeter and a half longer than the maximum for Red-eyed Vireos. Although this may not seem like much, a millimeter difference in a bill measurement is enough to separate several species of Empidonax flycatchers in hand.

At this point I started getting excited and measured the difference in length between the bird’s 9th primary and 5th primary. There is very little overlap in this measurement between the two species—Red-eyed Vireo has a range of 4-8 millimeters and Yellow-green Vireo has a range of 1-5 millimeters. The measurement I got for this bird was 7mm.

Disappointed, we chalked up the coloration and the odd bill measurement to the bird being a hatch-year bird that might have eaten something that affected its pigmentation, much like how Cedar Waxwings and other frugivores with yellow plumage can eat certain berries that change their yellow areas to orange or red. We put the bird down on the data sheet as a Red-eyed Vireo and released it without taking any photos.

About three minutes later I realized that, unlike most other vireos, Red-eyed and Yellow-green Vireos have only 9 primary feathers instead of 10. I had measured the wrong feathers!

Roughly an hour after that, while checking the nets again, I saw the potential Yellow-green Vireo perched on a branch directly over net 1, preening. Despite my best efforts, I was not able to flush it into the net. It flew back into the brush somewhere, scolding me the entire time.

Several agonizing days followed. I was haunted by knowing that I had potentially had a first state record in my hand, dismissed it as something ordinary (despite being very familiar with the species) because of how unexpected it seemed to be, and then let it go. We held out some hope that the bird wasn’t going to leave for a few days—the winds were unfavorable for migrants to take off and the bird had had very little in the way of fat deposits—but with each passing day our hopes for recapturing it diminished.

This morning changed all of that.

While checking the nets at 10:25, I rounded the corner next to net 16 and saw an extremely bright yellow vireo in the middle of the net. It was already banded. The band had the number that was burned into my brain from 5 days earlier!

This time I did all the measurements correctly. Exposed culmen of 15.2mm, p9-p5 of 2mm. A definite Yellow-green Vireo!

We took many photos of the bird and of when I measured the bird. In addition to photos of only the Yellow-green Vireo, we took photos of it alongside a Red-eyed Vireo of the same age that we captured at the same time.

Yellow-green Vireo (hatch-year, unknown sex) and Red-eyed Vireo (hatch-year, unknown sex)
Outshined by all of this are all the other birds we caught today at Little Bear. We had 40 new birds and 22 recaptures representing 21 different species. Other highlights include a Nashville Warbler and our second Warbling Vireo of the season.

Warbling Vireo (hatch-year, unknown sex). Note how the outermost primary feather extends beyond the primary covert feathers. This feather is either absent or shorter than the primary coverts in the similar Philadelphia Vireo. This bird also has a slight bill deformity.


--Blaine
 


Captain Sam's 

The excitement level at Little Bear was unfortunately not carried over to Captain Sam's this morning. Due to early morning showers the station was not able to get the nets open until around 8 AM. Despite catching a Red-eyed Vireo before we were finished getting the nets open, the morning was quite slow. We banded 12 new birds and had 7 recaps. Fortunately for us the slow numbers day gave us a chance to get some of the holes in the nets repaired before this weekend. We're hoping for some bigger numbers as a front pushes through over the weekend.


-Collette

SpeciesCaptain Sam's Little Bear
New Recaps New Recaps
Downy Woodpecker
-
-
1
-
Common Ground-Dove
-
-
-
1
"Traill's" Flycatcher
-
-
-
1
White-eyed Vireo
1
1
1
4
Warbling Vireo
-
-
1
-
Red-eyed Vireo
1
-
4
-
Yellow-green Vireo
-
-
-
1
Carolina Chickadee
-
-
-
1
House Wren
1
-
1
-
Carolina Wren
-
-
-
1
Blue-gray Gnatcatcher
-
-
1
-
Gray Catbird
7
-
8
6
Northern Mockingbird
-
-
-
1
Northern Waterthrush
-
1
5
2
Nashville Warbler
-
-
1
-
Common Yellowthroat
2
-
10
1
American Redstart
-
-
2
-
Yellow Warbler
-
-
3
-
Prairie Warbler
-
-
1
-
Northern Cardinal
-
2
1
-
Painted Bunting
-
2
-
2




 Banding Stats Captain Sam's Little Bear TOTAL
# Birds Banded
12
40
52
# of Recaptures
7
21
28
# of Species
8
21
21
Effort (net-hours)
109.2
80.0
189.2
Capture Rate (birds/100 net-hours)
17.4
76.3
42.3
# of Nets
26
20
46

Banding Staff
Aaron Given (CS)
Blaine Carnes (LB)
Alison Nevins (LB)
Col Lauzau (CS)
Michael Gamble (LB)
Michael Rodgers (CS)
Ryan Donnelly (CS)

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