Yet another Mourning Warbler today. This one was in the southwestern alcove. I don’t know if it had been chasing this grasshopper and they both died at the window, but it sure did look unusual to find these two together.
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.
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.
Every day there is a casualty discovered is cause for a twinge of sadness. Some are worse than others, however, especially when our personal biases are affected. My internal monologue on noticing any dead bird is a classic Midwestern ope, but today it escalated to motherf****r! as I got close enough to see what it was lying in front of a glass entry on the northwestern corner of the Noble Research Center. Yep, it was the pinnacle of avian evolution, a Louisiana Waterthrush.
I would be remiss not to mention the unusually rainy, cool spring we’ve enjoyed here in the Southern Plains, and this week flooding has turned deadly. Here in Stillwater, we topped 7″ of rain on Tuesday, with roads and schools closed. But our saturated soils didn’t result from one super storm. Check out these 30-days totals:
In fact, we’re a solid 20″ above average for the year:
This is a pattern of rainfall that often washes out waterthrush nests, built along the banks of streams. Having returned at the end of March, it could easily be the case that our local waterthrushes have attempted to nest, and been flooded out, at least three times. Perhaps a scenario like that might explain how a second-year (check out the feather wear) female (she at least attempted nesting – check out the brood patch) Louisiana Waterthrush ends up outside its territory in unfamiliar habitat to die at a window on the 23rd/24th of May? Is this a local movement to find a new territory less prone to flooding and give it another go? Is this a bird that has given up for 2019 and was on her way to molt and prepare for southbound migration while other birds are still streaming north? These intimate details of birds’ lives provide endless fascination for me and, of course, can lead to new and interesting directions for research that can help these birds better survive their forays into human-dominated landscapes.
Besides the feather wear and brood patch, there were a couple of other interesting things about this bird. It had fat in the furcular hollow! Floods don’t keep waterthrushes from foraging well, despite their threat to nests. Still, actually accumulating fat is hormonally influenced, and it strikes me as odd for a bird to accumulate fat outside of migration. This bird also showed obvious trauma to the tip of the bill, indicating a window strike at full speed. I can’t quite tell if the mark on the right pectoralis major is a contusion from collision or the beginning of the progression of brood patch loss. Many questions . . .
There’s a small alcove on a northeast corner of the Food and Agricultural Products Center across a parking lot from the Noble Research Center that often lures birds to their death. Today, it was this second year Summer Tanager.
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.
It was a bitter milestone this morning as I encountered the 400th casualty on this project since I began regular monitoring in August of 2009.
Again, the long-term idiosyncrasies of this long-term monitoring have revealed something new. In this case, there have been 4 total Summer Tanagers I’ve recorded as window-kills since 2009. The first was on May 3rd 2013. That’s 6 years ago, and it was 4 years into the project. The last three were May 4th, May 6th, and May 11th of this year. So in one week in the tenth year of a project we’ve turned on its head what we thought we knew about Summer Tanager collision risk here.
This morning was a bit odd in that it’s rare to find window killed Summer Tanagers at the NRC, and that someone had moved yesterday’s Yellow Warbler. Now the warbler and tanager lie together at the main north entrance, and I can only assume that the tanager died very close by. (The Summer Tanager was a second-year male.)
To me, these window kills are saddest when the victim is an older individual in its prime. Case in point, consider this outstanding male Yellow Warbler from this morning that senselessly met its end at the main north entrance. Note, too how conspicuous these casualties can sometimes be. As soon as I got a glimpse of the north entrance I could tell there was a casualty there.
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.
It’s wonderful when spring finally springs, but that also means a return to dead birds. Today I found this wonderful male Ruby-crowned Kinglet at the southeast alcove, its life cut short en route to its breeding territory. This is the first casualty I’ve recorded at the Noble Research Center since last November. Even more significant, this is the first Ruby-crowned Kinglet I’ve recorded as a window-kill at the Noble Research Center, the 67th species casualty, and the 390th victim overall.
I haven’t analyzed this, but there have been many occasions that some unusual casualty will show up and another will appear on its heels – or on the same day. These events make me wonder about pairs migrating together or, at the very least, individuals from the same regions departing at about the same time and following similar routes. How else would we explain the 9th and 10th Orange-crowned Warblers hitting the same building less than 24 hours apart?
We had a serious cold front move through on November 11–12, dropping temperatures and a decent inch or so of snow. This was unusual in that we’ve pretty much had snowless winters for the past couple of years (a couple of ice storms and no more) and that it happened so early in the season. We were probably a week or so ahead of peak autumn color here; now all of those leaves are stuck to the trees and browning. Although brief, it was a hard freeze. Birds were caught a bit unawares too, as the results of today’s survey suggest.
First, there was a Lincoln’s Sparrow in an odd spot, along the northern exterior wall. This bird looks like it had been there for a bit, like maybe it had been buried under the snow and I had missed it.
Next was an Orange-crowned Warbler (AHY-male) in the northwest alcove.
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.
It was a bit foggy overnight so perhaps that contributed to the casualties I found today: An AHY male Nashville Warbler in the southwestern alcove (fat = 3) and a Clay-colored Sparrow in the south portico (fat = 2).
The one bright spot was the second Nashville Warbler. It was stunned but alive. On my approach it perked up and flew off strongly.
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 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.
I’ve been behind with stacks of papers to grade, and they’ve kept me from keeping up as often as I’d prefer. During the period from October 7–18, I conducted 8 surveys, skipping Oct. 8, 14, and 15. The data from these last 11 days look a bit like this:
- Oct. 7: HOWR
- Oct. 9: no casualties
- Oct. 10: no casualties
- Oct. 11: LISP
- Oct. 12: TUTI
- Oct. 13: no casualties
- Oct. 16: OCWA, SOSP, LISP, and NAWA
- Oct. 17: no casualties
- Oct. 18: no casualties
Just past mid-October, and we are crushing the annual mortality count right now with 55 dead birds.
Oct. 7 – I found just the third House Wren on the project. This one ended up on a warm air outflow grate from the air conditioning unit and was quickly desiccated.
Oct. 11 – I collected this Lincoln’s Sparrow from the south portico.
Oct. 12 – This Tufted Titmouse was a surprise in the southwestern alcove.
Oct. 16 – This was not a good day for migrants. I found an Orange-crowned Warbler at the northeast alcove, a Song Sparrow at the south portico, and a Lincoln’s Sparrow at the southwestern alcove. Shortly after completing my survey, a Nashville Warbler was turned in from a collision in the southwestern alcove.
Hummingbirds have been takin’ it in the shorts of late . . .
But what’s with the fractional hummingbird reference above? Well, “scavenging” and “removal” are not necessarily the same thing. Often I find the remains of a bird that has been scavenged, but there’s enough left behind that I am able to detect that a casualty has occurred. Those remnants – let’s say a pile of flight feathers left behind by a scavenging cat – can last in place for many weeks. Each time I survey for casualties I’m greeted at that spot with the information that a bird died there (or at least somewhere nearby) even though all the edible bits are long gone. We should be clear that scavenging isn’t the important rate to help us better estimate detection of window-killed birds, removal is. It’s only when every piece of that carcass is gone that I’m unable to detect the evidence of a casualty.
We see this played out all the time with hummingbirds. For some reason, the ants seem to get to the hummingbirds more quickly than they get to other birds. (I have some hypotheses about this, e.g., that hummingbirds are more often flying in daylight and might have lain in place longer than the night-flying warbler and sparrow migrants.) The result is that hummingbird carcasses are rarely in pristine shape when I find them, but they are still there.
Check out hummingbird #1 this morning from the southeast alcove. First, look how obvious it is to detect the carcass even from ~20m away. Up close, note that a good bit of her face has already been carted away, one ant-mandible-sized piece at a time.
This next one (or 0.33 of one) from the southwest alcove will put your observational skills to the test:
See it yet?
Oh, that explains it!
In this case, there’s a pre-scavenged hummingbird (likely also AHY-F Ruby-throated) that is represented by its tail only. But it’s still detectable and largely identifiable.
(UPDATE 10 AUGUST 2017: Today I found a head and wing near where I found the tail on Aug. 9. First, this looks much more likely as a HY-M than an AHY-F. Also, literal scavenging seems less likely. I suspect more that the carcass was chopped up by a lawnmower.)