This AHY male Common Yellowthroat got no farther than the main north entrance of the Noble Research Center today.
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.
Ahead of the official official ten-year anniversary of window collision monitoring at the Noble Research Center on August 20th, here’s a recap of my very first post from 7 September, 2009.
Those were heady days, indeed.
Here are some basic things I’ve observed and learned, August 2009–July 2019.
With some occasional help when I’ve been out of town, we surveyed the perimeter of the Noble Research Center for window-collided birds 2,141 times. I’ve generally run surveys every day (usually within about two hours of sunrise) during heavy migration periods in autumn and spring, scaling back to more like weekly surveys during the dead of winter.
Including 4 unidentified passerine remains, at least 414 individuals of 67 species died in window collisions at the Noble Research Center.
The most frequently encountered casualties were:
- Lincoln’s Sparrow 51
- Ruby-throated Hummingbird 36
- Painted Bunting 26
- Indigo Bunting 23
- Grasshopper Sparrow 20
- Clay-colored Sparrow 18
- Mourning Dove 17
- Nashville Warbler 16
- Mourning Warbler 15
Tenth is a four-way tie with 11 casualties each for Common Yellowthroat, Orange-crowned Warbler, Song Sparrow, and Yellow Warbler.
The spatial distribution of those casualties looks a bit like this:
Window treatments applied to selected panes in 2016 have, evidently, not contributed to a decline in collisions.
I plan to continue my monitoring at the NRC for as long as I can, and in the next 10 years hope to appreciably reduce the mortality here.
Although I consider July to be spring/summer, today’s casualty screams fall migrant. I was saddened this morning to find the pinnacle of avian evolution, Louisiana Waterthrush, at the far northwestern corner of the Noble Research Center.
This bird looked pretty good on the outside, but it was pretty rank. It’s Monday and the bird came in at some point between Friday afternoon and this morning. The relatively bob-tail has me thinking that it might be a HY bird, but I’m not sure.
After a bit of a slow start it did not take long to wrack up 20 casualties this spring. Today it was a “day 0” Yellow-billed Cuckoo at the main north entrance, meaning that it hit and was scavenged before I found it. Here again is a reminder of the difference between scavenging and removal: This bird was immediately scavenged, but it will likely be many weeks before all traces of its feathers are gone.
My walk to the Noble Research Center revealed two window-killed birds outside the Food and Agricultural Products building, a male Yellow Warbler and Ruby-throated Hummingbird.
I also found remains (wingtips) of the Summer Tanager and Indigo Bunting that were scavenged from the southwestern alcove.
New casualties this morning were a SY male Painted Bunting in the southwestern alcove and a male Tennessee Warbler (9.5g, fat = 1) in the northeastern alcove.
There were no new casualties on my survey from about 7:30 this morning, but then the sharp eyes of students Dalton Deshazer, Jake Rowland, and Corey Sage noticed this Yellow-billed Cuckoo in the southwestern alcove. (On my check the next day, the bird had been moved off the sidewalk and was much less conspicuous. It persisted until removal on May 5th.)
As a bonus, Corey Sage provided this photo of a trapped Cedar Waxwing, also at the southwestern entrance, later that afternoon.
I received a message last evening that there was a casualty at the southeastern alcove. Thanks to Thomas Hess for the heads-up and this photo from 3:37 pm on April 25:
I found it right where he said it was this morning: technically a 4/25 casualty but I’ll consider it 4/26 for my records as that is when I would’ve found it on my own. I moved the bird off to the side and it remains in place as of Monday morning, 4/29.
In a corner of the main north entrance to the Noble Research Center, I encountered this mystery today:
And I’m all like:
So let’s get to work on this.
First, this wasn’t here on Nov. 3 (Saturday), I did not check yesterday (Sunday), and when I found it today (Monday, the 5th) it had already been scavenged. I count examples like these as scavenging/removal on day 0.
Okay, so there’s a feather pile and a fruit pile. The fruit pile is on top of the feathers. The fruits show no signs of digestion, other than some of them having been opened and the pits are exposed. There is a single large pit inside a small fruit that is round and black with a highly glossy finish.
After much reading, comparing, consulting, etc., I’m pretty well convinced that these are chokecherries, Prunus virginiana.
My guess? I think our bird gorged itself on chokecherries before undertaking a migratory flight that, sadly, ended at a stupid window. The scavenger burst the bulging crop of this poor bird but had no interest in the fruits (in turn, feeding my opinion on the scavenger). So the remnants of this event are a pile of feathers and a pile of chokecherries.
Ah yes – the scavenger!
Well, we know that on campus we have skunks, foxes, opossums, raccoons, and feral cats as the most likely scavengers. The most likely of those to turn up its nose at a pile of chokecherries? I’d say cat. A cat scavenger would also be pretty well supported by the clean shearing of the flight feathers from the wings, visible here:
So what’s the bird? Well it’s clearly a meadowlark, but whether Eastern or Western takes some additional work. As with the fruits, I’ve spent a lot of time reading, consulting, and comparing. Perhaps the best resource for this task was a blog post from Kevin McGowan ca. 2000. (I also couldn’t get the USFWS Feather Atlas to load.)
Everyone knows that Western Meadowlark shows a yellow malar and in Eastern Meadowlark this is whitish. Without the bird’s head this character was of no use to me, however. In fact, there were just three feathers in the pile showing any yellow at all. Two other character differences are more relevant. First, both species have white outer tail feathers, but on Eastern the outer two are fully white and the third is mostly white. On Western the white is less extensive and even the outermost feather isn’t always fully white. In addition, Western looks paler overall than does Eastern, with the pattern on its tail and in the folded wings over the back appearing lighter brown/gray with blackish stripes. On Eastern, those same areas are darker brown with thicker blackish stripes often joined at the center of the feather creating a fern-like shape instead of distinct stripes. What do you think of these?
I’m leaning toward Western Meadowlark as the original owner of these feathers.
So I’m reporting today a pile of feathers that I think was Western Meadowlark, scavenged by a mammal I think was a cat, and that the cat showed no interest in what I think was a pile of chokecherries in what I think was the crop of the meadowlark.
Challenges, thoughts, etc? I welcome any and all!
This morning I found another White-throated Sparrow. In the last two days, the number of this species I’ve found since 2009 has doubled from two to four. We’ve also reached a yearly milestone with now 50 casualties for 2018.
For a bit of added sadness, I also happened upon this Song Sparrow at the Kerr-Drummond complex.
I found two Lincoln’s Sparrow victims today, both in somewhat odd places. At the Noble Research Center, one met its end at the door leading out to the eastern courtyard. This might be only the 2nd or 3rd victim in the courtyard since 2009.
I also occasionally check for window collision victims at the Food and Agricultural Products Center just to the west across the parking lot and Monroe St. This morning there was a Lincoln’s Sparrow in a tiny alcove where I’ve found birds in the past. This one I noticed by looking to my right as I drove down the street this morning.
Same window, different day, same result: a HY male Ruby-throated Hummingbird whose first trip to the Neotropics was cut short by a pane of glass in the southeastern alcove.
This was the 370th casualty and 34th Ruby-throated Hummingbird found at the Noble Research Center since August 2009. Today’s casualty puts 2018 at number 7 out of 10 worst years for casualties at the NRC, and there’re still 3 1/2 months of monitoring ahead.
This morning I found the fifth dead Mourning Warbler on campus in the past two weeks: Four (including this one on the northwest alcove) at the Noble Research Center and one incidental find just across a small parking lot from the NRC at the Food and Agricultural Products Center.
For a bit of perspective on how unusual this is, i.e., Mourning Warbler is a secretive, migratory transient in Central Oklahoma that is far more likely to be found dead at a window than live on an eBird checklist, this was the 15th Mourning Warbler casualty I’ve found at the NRC since I began surveys in August of 2009. In comparison, I’ve only found 17 casualties over the same time period of the far more abundant and year ’round resident Mourning Dove.
This one was a hatch-year bird – so just a month or two old – with fat = 1.
Both Mourning Warblers this week were left in place for removal trials. Tuesday’s bird was not visible on the 25th because it had been covered in fresh mulch. Thursday’s bird is still there as of Saturday morning.
This Ruby-throated Hummingbird at the main north entrance is the first official fall migration casualty of 2018, a dubious honor.
Note how the window is a triple threat for migrating birds: It reflects vegetation behind, provides a pass-through illusion to the other side, and it contains a naturalistic rock garden inside visible through the glass.
In other news, the Black-and-white Warbler from 31 July was scavenged overnight, with 2–3 primaries and a single downy tuft all that remains. It lasted 9 days.
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)
I found a pre-scavenged Mourning Dove at the main north entrance today. This is another great example of the difference between scavenging and removal.
The carcass was scavenged even before I found it. The whole point of working to determine scavenging rate is a matter of detectability, i.e., that our raw counts will always underestimate mortality because some carcasses are scavenged before they can be found. But scavenging isn’t the issue per se, removal is. If the carcass is scavenged but not completely removed, then it is still detectable. Therefore, the act of scavenging was irrelevant to my ability to detect the carcass, and thus the event.
We can do some field trials with known specimens and determine that our observers detect, for example, 95% of the carcasses in their search area. We can also do removal trials by setting out specimens and determining what proportion of them are removed in a set period of time. For example, let’s say 25%.
If we do some window-collision monitoring and find 10 dead birds at a building, we can modify our estimate according to our imperfect detection rate: 10.00/0.95 = 10.53. That’s the detection-adjusted estimate of mortality. The removal rate of 0.25 suggests that another 2.5 carcasses were removed before they could be detected (or at least before 95% of them could be detected). Removal rate bias then bumps our estimate from the raw count of 10 to an adjusted count of 12.5. Factoring in the detection rate on that estimate increases our adjusted mortality to 13.16 from the raw count of 10 carcasses we actually found.
This matters naught if our objective is to highlight the total number of casualties. It’s is not the case that public outcry to help solve the problem of window collision mortality with be louder for 13.16 casualties than it is for 10. For comparisons among studies, however, it is important to have this information presented and standardized. If, for example, two sites are compared according to their respective landscaping or lighting influence on mortality, that analysis would be corrupted if there was an unaccounted stark difference in removal rate between the two sites. So it is important to quantify rates of detection and removal in monitoring so that our efforts can be of greatest use.
In this long-term monitoring project, I have approached removal rate differently. I leave some carcasses in place to determine for how long they are detectable. Some are removed before I ever find them; some are immediately scavenged but not removed so I can detect them for weeks after the event. Some are never removed and their feathers and bones can still be detected months afterwards. On average, carcasses in my my study last about 10 days on the ground, and I conduct my surveys every 1–2 days. This means that, on average, I have 5–10 opportunities to detect a carcass before it is removed.
That’s pretty good.
Though they might have come in yesterday (when I didn’t check), there were two birds in the southwestern alcove today: a Tennessee Warbler (AHY-U, fat = 2) and a Painted Bunting (SY-U <probably female>, fat = 2).
There was also a bonus at the Food and Ag Products Center: a window-killed Yellow-billed Cuckoo and a trapped Black-and-white Warbler. The warbler flew off fine as I approached.
The Indigo Bunting has been removed – May 12 – but the Painted Bunting and Yellow Warbler remain.
The odd thing today was that I found a dead Swainson’s Thrush along the northern wall. This might be the first casualty on this side of the building since monitoring began in August 2009. I then found a second – and alive! – Swainson’s Thrush in the southwestern alcove. The bird was feisty in the hand and perched strongly when I placed it in a nearby shrub.
The first casualty of 2018 – and the 334th on the project – was an AHY (after hatch year, i.e., adult) male Northern Cardinal at the southeast alcove. He was probably an ASY (after second year, i.e., definitively hatched prior to 2017), but one cannot be entirely sure because cardinals occasionally undergo a complete molt in preparation for their first breeding season, and it’s not possible to age them any more specifically than AHY based on plumage characters (i.e., molt limits) alone.
One thing is pretty obvious for this cardinal: The trauma at the tip of its bill indicates a significant collision took place. Evidently, he was attempting to fly through the pass-through illusion to the southwestern alcove.
I left the bird in place (actually a few meters off to the side so it wouldn’t get stepped on by traffic through that entrance) and it was present on the 17th and 18th, but gone on the 19th.
Song Sparrow finally gone. It sat untouched for 20 days.
I’m mourning the loss of another one today – this AHY female I found at the northwest alcove. She was fat (=3) and healthy at 12.5g.
This was the unofficial 315th casualty on the project and, for a new sobering record, the 44th this year. The previous annual high was 41. We’ve surpassed that already in 2017 and, for us, migration is really just ramping up.