As storms rolled through overnight, I assumed I might find a casualty this morning. There were two: a completely rain-soaked female Indigo Bunting in the southwestern alcove and a completely dry and fluffy Mourning Warbler at the south entrance under the rain protection provided by the portico’s overhanging roof. The latter was an AHY male with fat = 3.
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 was out of town from 21–30 June and no surveys were run during that time. On June 30th, however, I heard from Dawn Brown and Corey Riding that there were three casualties at the southwestern alcove of the Noble Research Center: a badly decayed Northern Parula (adult male), a female Ruby-throated Hummingbird, and a female (with brood patch!) Indigo Bunting. It’s possible that the bunting came in on the 30th, but the others were clearly killed prior to that date. (Photos by Dawn Brown.) This is officially the first Northern Parula found on the project.
With special guest stars James O’Connell and David Mallen, today’s survey turned up a male Indigo Bunting and a trapped Yellow Warbler at the main north entrance. (No photo of the warbler; it was a male.)
Let’s take a closer look at that Indigo Bunting:
The multiple obvious molt limits on this bird illustrate two generations of feathers on the same individual, some of which grew in last summer and some which have come in quite recently. This confirms the age of the bird as second year (SY).
Sad to think that this spectacular specimen of an ASY male (fat = 2) Indigo Bunting safely crossed the Gulf of Mexico a few days ago but could not safely navigate the Noble Research Center.
Indigo Buntings, of course, have no blue pigment. Blue is produced by birds through light reflectance – it’s structural color, not pigment.
You might think, then, that Indigo Buntings would look really cool in UV light. They don’t, unless you think charcoal looks cool!
The photos illustrate how obvious it is to find many of the carcasses at the Noble Research Center. Today it was an Indigo Bunting in the southeast alcove.
This was a hatch-year bird and probably a male owing to the faint bluish tinge in the wings and tail. Were those blushes of color resigned to the upper tail coverts, female would be a bit more likely. Fat = 0 on this bird.
Today I found a Red-eyed Vireo in the southwestern alcove and an Indigo Bunting at the main north entrance.
The Indigo Bunting was a second-year male with zero fat and an impressive contrast of old and new feathers. I left him in place for a removal trial. The Red-eyed Vireo, an ASY female with a brood patch and no fat, is the first vireo I’ve ever recovered as a window-kill from the NRC.
I found an SY female Indigo Bunting this morning on the north side of the NRC. She allowed me to pick her up, squawking about that a bit, but I’m not optimistic about her recovery. Generally, if a wild bird with no other obvious external injury allows me to pick it up, I assume it’s got things wrong on the inside that are irreparable.
I moved her to a secluded spot in dense vegetation by Cordell Hall with a clear sightline to the north, but I will count her as a mortality given her condition.
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
Female, found in courtyard on east side of the NRC. This is the first time I’ve found anything in this space.