This AHY male Common Yellowthroat got no farther than the main north entrance of the Noble Research Center today.
Well, here we go. Today marks the end of my 9th year conducting spring/summer monitoring for window-killed birds at the Noble Research Center. Tomorrow I begin year 10. Ten years of near daily monitoring of window-killed birds. Here’s a quick 9-year wrap-up:
- 40: average minimum casualties annually
- 360: total casualties (minimum)
- 64: species confirmed as fatalities
- 10: average number of days for birds to be removed/scavenged
Top ten (eleven) species most commonly encountered as casualties at this site:
- Lincoln’s Sparrow (45)
- Ruby-throated Hummingbird (29)
- Painted Bunting (24)
- Indigo Bunting (20) *tie* Grasshopper Sparrow (20)
- Mourning Dove (17)
- Clay-colored Sparrow (16)
- Nashville Warbler (14)
- Common Yellowthroat (11) *tie* Mourning Warbler (11) *tie* Song Sparrow (11)
Since Monday night, we seem to have received at least 5 inches of rain here in Stillwater. That’s great as I’ve been lamenting the lack of even clouds for a few weeks. The system that brought the rain might have kept birds bottled up to our north because once it cleared last night (Wed.) there was one heck of a flight.
Of course, attempts to correlate window collision mortality with big radar echoes of migrating birds are fraught with confirmation bias. There are plenty of big flights that result in no dead birds on my rounds, and I’m a lot more likely to check “last night’s radar” on a morning when I find multiple casualties. Today was one of those days.
I walked to the Noble Research Center on a route that took me past the long row of windows on the southern side of the Food and Agricultural Products Building, aka, FAPC. This is just across a parking lot from the NRC and I’ve made several incidental finds there. Today, these “bonus birds” numbered three: an Ovenbird, a Common Yellowthroat (collected) and, around the corner, a female Indigo Bunting that had been there for at least a few days. So before I even made it to the NRC, I encountered 3 window-killed birds.
The yellowthroat was an apparent AHY-male, with fat = 2 and weighing in at 12 g.
At the NRC was another surprise. Surprisingly, after all these years and considering how common these birds are as migrants and wintering residents, I found the project’s first Savannah Sparrow, in the northwest alcove.
There was also a trapped Common Yellowthroat at the main north entrance and another Savannah sparrow flitting around – through not trapped – just west of the southern portico entrance. The Savannah Sparrow was AHY-U, weighing 18g with a fat score = 2.
As I’m about to head out for a conference this week, spring and summer monitoring comes to a close. I’ll begin August 2017 the 9th consecutive year of (mostly) daily monitoring for window casualties at the Noble Research Center on the campus of Oklahoma State University in Stillwater, Oklahoma, USA.
It’s been a busy spring.
Beginning Mar 1st, here’s what has turned up at the Noble Research Center.
- Indigo Bunting – 5
- Painted Bunting – 5
- Ruby-throated Hummingbird – 3
- Lincoln’s Sparrow – 2
- Mourning Dove – 2
- Nashville Warbler – 2
- Orange-crowned Warbler – 2
- Baltimore Oriole – 1
- Chipping Sparrow – 1
- Eastern Meadowlark – 1
- House Wren – 1
- Northern Parula – 1
- Tennessee Warbler – 1
- Yellow-billed Cuckoo – 1
That’s 28 individuals of 14 species, and damn, that is disheartening.
On the plus side, my commitment to checking almost every day has put me in position to save a few birds by getting them safely away from the building and taking them someplace secure to rest and recuperate for a bit. I can’t guarantee that all 6 of these survived the ordeal, but they seemed to be in good shape when I last saw them:
- Northern Cardinal
- Common Yellowthroat
- Mourning Dove
- Song Sparrow
- Yellow Warbler
- Carolina Wren
I found this rather early fellow right in front of the doorway to the southeast alcove this morning. He’s a gorgeous, ASY male Common Yellowthroat with fat score = 1. He was dazed enough that I caught him but alert and feisty in the hand, and he perched well when I moved him to a safe spot. In addition to being one of history’s all-time great yellowthroats, he has the distinction of being the 100th “trapped” bird that I’ve been able to move or shoo away from the Noble Research Center. If even one of them recovered enough to fly on and live out its life then every one of these walks around the NRC has been worth it!
Unfortunately, something went screwy with my camera and this is the only surviving photo:
Flight calls abounded last night as I walked the dog at least thrice. Those calls – little tsips! and tseeps! sounded to me like sparrows flowing from the north after three straight days of strong winds blowing from the south. A quick check of Paul Hurtado’s Nexrad radar birds page confirmed a big push in Midwest and the Plains:
Sadly, with that push came two casualties at the Noble Research Center: a Lincoln’s Sparrow (AHY-U with fat = 2) at the southwest alcove and a Common Yellowthroat (AHY-M with fat = 2) at the northwest alcove. (Apologies for the shaky portrait on the Yellowthroat – it looked clear on my phone.)
Although casualties continue to pile up in the west alcoves where I’ve treated several windows with ABC Bird Tape, it has so far appeared to be the untreated panes in those alcoves that are claiming the casualties.
The night before last, we had our first real cold front of autumn push through, pushing overnight lows down to the 50s for the first time in months. I expected that yesterday would have been a big flight that would result in window collisions, but last night seems to have ushered in a bigger wave of migrants. I found two at the south face of the Noble Research Center this morning (providing additional evidence that the direction of the prevailing wind has little to do with where on the building birds will end up).
The first was this beautiful Clay-colored Sparrow (fat = 2):
Not far away was this Common Yellowthroat. She was very much alive, and I was happy to see her fly away strongly when I shooed her away from the building.
This bird was an ID challenge: She was very pale on the throat, breast, and belly, but her yellow undertail coverts were quite obvious. That pattern, and the fact that she was pumping her tail a bit, had me thinking she might have been a Palm Warbler. Her pale legs and the lack of white on the tail tips ruled out Palm Warbler, as did her lack of other plumage details that might have strengthened the link. Instead, she looks to me like a hatch year, female Common Yellowthroat, but from the “Interior West” according to Sibley: those are the yellowthroats that can lack yellow throats, unlike the eastern subspecies that should show a bright yellow throat in all plumages.
There looked to be a House Wren and two Lincoln’s Sparrows hanging around this morning, but I still can’t consider these birds “trapped” if I can’t get close enough to them to effectively herd them away from the building.
I did find a window-killed Lincoln’s Sparrow at a nearby building yesterday, and it seems to have hit the same window that an unfortunate Common Yellowthroat did a few days ago.
This building is the Food and Agricultural Products Center, located just west and across a parking lot from the Noble Research Center. This is a weird little corner of the building that every year claims several birds, even though it seems very protected.
I was worried being out of town yesterday morning that I would miss important data on a mid-September morning that had been foggy and rainy. This morning when I got to the NRC, it was clear that my worry was warranted. There had been a lot of activity at the north entrance since Friday morning. Here’s what was waiting for me today:
1) Live House Wren – very tame, allowing a close approach but apparently not injured.
2) Live Yellow-breasted Chat – this bird is a first for the project.
I was able to steer the chat away from the building so it should be okay. The wren – if it’s the same bird I found last week – might be in trouble, but so far it’s too energetic for me to steer anywhere, and it’s most interested in hiding out in the tiniest shrubs around.
In addition to these two live birds, I found the remains of 3 dead ones:
3) Sora (scavenged) – Identified from these feathers, I can only say that a Sora met it’s end at the building this weekend; I have no way to know if it’s the Sora from Friday that somehow got trapped again. My policy on found scavenged remains is to assume that the bird was scavenged in less than 24 hours, so it’s a day-0 event in this case.
4) Yellow-breasted Chat (scavenged) – These narrow, olive-edged rectices at 84 mm are just the right length, color, shape, and pattern to convince me that they came from a chat. I found them just a few meters away from the live chat. (Day-0 event, as well.)
5) Dickcissel (unscavenged) This Dickcissel has not been touched other than by ants and beetles that’ve started eating away at its back.
And finally . . .
6) Common Yellowthroat (live) – I found this bird in the northwest alcove. As I struggled to get a look at it before it made its way out of the area, I audibly asked “Are you a yellowthroat?” “Tchep!” was the answer.
For folks keeping track, this was one of the busiest days in the history of this project, with three trapped birds and three casualties. In addition, three species were new additions to the casualty list: Sora, Dickcissel, and Yellow-breasted Chat.
Here is just a quick summary of casualties at the Noble Research Center from July through December 2010:
I detected 25 individuals of at least 16 species among the casualties. The complete list:
grasshopper sparrow – 4
ruby-throated hummingbird – 2
mourning warbler – 2
song sparrow – 2
Lincoln’s sparrow – 2
unidentified passerine (1 warbler, 1 sparrow) – 2
black-and-white warbler – 1
Carolina wren – 1
mourning dove (juv) – 1
least flycatcher – 1
common yellowthroat – 1
black-throated green warbler – 1
brown thrasher – 1
house wren – 1
red-breasted nuthatch – 1
white-throated sparrow – 1
field sparrow – 1
Because I was able to get to the NRC earlier each day during autumn than practical in 2009, I encountered more individuals that were stunned and “trapped” by the building for some time period without obvious mortal injury. Most of these birds are presumed to have eventually moved on, but it is quite likely that the house wren and one of the Lincoln’s sparrows on the “stunned” list were unsuccessful in their respective bids to escape from the confusion of the NRC, and are listed above. The bat represents the first mammalian “capture” by the NRC:
Lincoln’s sparrow – 5 (4 in one flock)
house wren – 1
common yellowthroat – 1
Nashville warbler – 1
grasshopper sparrow – 1
dark-eyed junco – 1
It’s dark when migrants like this Lincoln’s sparrow drop out of the sky and try to find a good spot in which to rest for the day. I’m beginning to think that most collisions are occurring in that last hour before sunrise.
the House Wren is still hanging around and today there was a Common Yellowthroat trapped in a west alcove.
It looks like Sep. 1 is the only day I did not check for casualties this month. Here’s what I found on the days I did check:
2 Mourning Warblers
1 unidentified warbler
1 Least Flycatcher
1 Common Yellowthroat
1 Black-throated Green Warbler
1 Ruby-throated Hummingbird
1 Brown Thrasher
I found two unlucky young migrants this morning, a Common Yellowthroat and a Least Flycatcher. Both were hatch year birds with fat scores of 1. The yellowthroat was a male; the sex of the flycatcher is unknown.
While the yellowthroat was easy to identify, the still-warm Empidonax flycatcher presented a challenge. I used Sibley’s Guide to Birds and Kaufman’s Advanced Birding to nail it down.
The bird is small (total length ~ 132 mm or 5.33″) and it has a broad yellow-orange bill with a diffuse dusky tip. It has complete eyerings that do not flare behind the eye. The primary projection is relatively short (0.18 the length of the wing chord). The belly and undertail coverts are a creamy yellowish-white – this area is separated from the grayish-white throat by the olive-gray breast band. All of these features are congruous with Least Flycatcher. The buffy wing bars and tertial edges confirm it as an immature bird. Because this is a new species for the NRC monitoring program, here’s the range map from the Cornell Lab or Ornithology’s All About Birds:
On August 20th, I completed a full year of regular surveys for window-killed birds at the Noble Research Center. Here are some vital statistics for August 20 2009–August 20 2010:
I conducted (occasionally with help from assistants like Danielle Benson) 153 surveys over the full year of monitoring. This equates to an average of 2.39 days between surveys.
Coverage was irregular throughout the year. For example I did no monitoring in January 2010. For this reason, analysis of casualties by season must be viewed through the lens of dissimilarities in sampling effort among the seasons. I defined sampling effort as the number of surveys per days in a given season. I defined seasons as follows: Dec. 1–Mar. 20 (110 days) = “winter,” Mar. 21–May 20 (61 d) = “spring,” May 21–Aug. 19 (91 d) = “summer,” and Aug. 20–Nov. 30 (102 d) = “autumn.” The 11 winter surveys provided an effort of 0.10. This approximates 10 days on average between surveys. Effort indices were 0.87 for spring (53 surveys in 61 days), 0.44 for summer, and 0.48 for autumn. Thus effort was most consistent during spring with near daily surveys.
I recorded window strike mortality for 38 individuals of 22 different species over the year of monitoring. This rate of collision mortality places the NRC on par with other high-mortality buildings referenced in Klem 1990 and O’Connell 2001.
Of the 38 casualties, 5 were “local” (i.e., recently-fledged offspring of local breeders), 5 were “hatch year” birds (i.e., “immature”, or birds < 1 yr. old), and 28 were adults or of undetermined age.
Of the the 38 casualties, 8 were identifiable as male, 5 as female, and 25 were of undetermined sex.
As in O’Connell 2001, Neotropical migrants in passage comprised the greatest percentage of individuals among all casualties. The birds dying at the NRC are not local residents that commonly occur in the OSU campus. These are transient individuals traveling long distances that just happen to meet their end here. (Note that the number of resident individuals among the casualties is inflated by the fact that 5 of the 7 casualties were recently fledged mourning doves and northern cardinals.)
On at least four occasions, I encountered live birds that appeared to be trapped near a window but were not injured from a collision. These individuals are not included in the collision data, but they may have been had I not been there to flush them away from the windows and encourage them to move along:
9/22/09: Grasshopper Sparrow and suspected Swainson’s Thrush
10/19/09: Grasshopper Sparrow
11/2/09: Two Dark-eyed Juncos
6/21/10: Carolina Wren
The scavenging rate proved to be unpredictable over the year. For example, some carcasses left in place remained visible for several weeks and were untouched during that time. Others were identifiable only from feathers left behind of a carcass that, based on the timing of my most recent survey, had been scavenged just a few hours after the bird’s unfortunate collision. Further confounding the interpretation of scavenging rates, some carcasses were scavenged but readily identifiable feathers of the carcass were left behind and still in evidence long after scavenging. For example, the Yellow-billed Cuckoo that I found on 6 June 2010 was scavenged on 15 June. As of 3 September 2010, that bird’s primaries are still readily apparent at the location where I first found it on June 10th, approximately 86 days after the bird’s death.
I found evidence of 15 scavenged carcasses over the year. Thus, out of 38 total casualties, 39% were ultimately scavenged. (Of course, I collected the majority of the carcasses I found, most of which were fresh and in excellent condition and were photographed for entries in this blog. Presumably, a high percentage of these would ultimately have been scavenged.) Two carcasses were scavenged on day 0 and three were scavenged after just one day in situ. Four were in evidence for at least 30 days; the average number of days a carcass was apparent in place was 18.6 – nearly 8 times the length of time between consecutive surveys. Thus, the regular, frequent surveys provided ample opportunity to discover carcasses before they were removed or no longer visible. In addition, the most frequent condition of freshly scavenged carcasses of warbler-sized birds was a pile of remiges cleanly sheared off near the base of the feathers. Thus, even small birds were usually left in place after scavenging; this increased the probability that I would find the carcass even if it had been scavenged. Nonetheless, it is likely that at least some individuals were scavenged and removed from the site before I could document the casualty, so mortality rates calculated from my surveys must be viewed as underestimates of actual mortality.
The following table lists all the species found as window collision casualties at the Noble Research Center, 8/20 2009–8/20 2010:
Common Yellowthroat 5
Mourning Dove 5
Lincoln’s Sparrow 4
Black-and-White Warbler 3
Grasshopper Sparrow 3
Painted Bunting 2
Mourning Warbler 1
Gray Catbird 1
Wilson’s Warbler 1
Canada Warbler 1
Indigo Bunting 1
Orange-crowned Warbler 1
Song Sparrow 1
Nashville Warbler 1
Dark-eyed Junco 1
Sprague’s Pipit 1
Swainson’s Thrush 1
Orchard Oriole 1
Northern Cardinal 1
Yellow-billed Cuckoo 1
Ruby-throated Hummingbird 1
Carolina Wren 1
HY male; fat = 2.
I hadn’t planned to check the NRC this morning, but I received an email from a colleague with an office in the building that an unusual warbler had met its maker near one of the west entrances. The warbler was indeed unusual, and one I have yet to see in the Sooner State: Canada Warbler.
Photo via cameraphone by Jesse Burton. Looks to be an AHY female.
Unfortunately, in the roughly 10 minutes that elapsed between Jesse taking the photo and me getting to the location, someone had swept the area and removed the bird! I did some dumpster diving to try and find it, but to no avail. I am hopeful that whoever collected it did so because they recognized it, and the specimen will eventually make its way to our collections.
Although I missed the Canada Warbler, I did find another Common Yellowthroat. This one looked to be a HY female, fat = 2.
1 HY Common Yellowthroat, presumed female, but feathers on head not well preserved. Fat = 3.