31 July 2018: end of season wrap-up

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)

 

30 October 2016 – 2 Grasshopper Sparrows

I found a trapped Grasshopper Sparrow at the main North entrance to the NRC today, and then a second dead bird at the southeastern alcove.  The trapped bird took quite a bit of effort to eventually guide away from the building, but the time was worth it if I was able to keep it from ending up like its comrade.

 

 

7 August 2014 – trapped Grasshopper Sparrow and local Mourning Dove

I’m quite conservative when it comes to Mourning Doves around the Noble Research Center. This is one locally breeding species that can sometimes be found just hanging out near the building but not really trapped by it as our migrants often are. Our recent fledglings (“local” birds in bird-banding parlance) seem sometimes to seek out these protected places until they become stronger fliers and when i find them thus I almost never document them as “trapped.”

Almost never. Today, I found one of these local Mourning Doves that flew up and away from the north entrance and right into a window in the southeast alcove. Then it flew back toward the north entrance and banged into the windows there again. In all, I watched hit windows (low-speed crashes, but still) three times before it headed off a bit further from the building and out of what I considered immediate danger. Given its behavior, I’m counting it as trapped. There was a second local bird as well, but at no point did it fly into a window or seem in any way impeded by the structure of the building so I did not count that one as a trapped bird.

A more obvious trapped migrant was the Grasshopper Sparrow I found at the north entrance. It took a bit to get that one out of harm’s way too, but ultimately I watched it take off and fly strongly to a spot about 300m north of the NRC from where I hope it can get its bearings and be on its merry way.

13 October 2013 – 2 Clay-colored Sparrows and a trapped Grasshopper Sparrow

It was another big night for migrants here in the Southern Plains.  I found dead Clay-colored Sparrows at the northeastern and southwestern alcoves, and a trapped Grasshopper Sparrow at the northwestern alcove.

Clay-colored Sparrow #1 was heavy with fat (=3) and looks to be a HY bird.

 

Clay-colored #2 had a fat score of 2, and some tiny red ants had colonized it by the time I found it.  I left that one in place to check the removal rate.

 

The Grasshopper Sparrow was trying desperately to fly east from the northwestern to the northeastern alcove.  It was really wearing itself out.  Thankfully, it was easy to point in the right direction, and it flew well away from the building.

23 April 2012 – Grasshopper Sparrow and bonus Gray Catbird

I found an ASY Grasshopper Sparrow in a west alcove at the NRC this morning.  While processing the bird at my desk, a colleague stepped in with a frozen Gray Catbird that struck a window in his Stillwater home last night.

4 November 2011 – Grasshopper Sparrow and no net loss of Lincoln’s Sparrow

I found this AHY Grasshopper Sparrow (fat = 3) in one of the west alcoves this morning, after a night when temperatures in Stillwater dipped to 23 F.

As for the cryptic headline about Lincoln’s Sparrow, the individual I left in place on Oct. 27th was scavenged overnight.  Here’s what’s left:

So that bird lasted in situ for 9 days.

The “no net loss” comes from discovery of a new Lincoln’s this morning, and this is one I’ve missed for a few days.  How could I miss a dead bird in place for several days when I’m searching an area of lawn and sidewalk?  In this case, it comes down to the where the bird ended up.  It’s so close to the edge of the sidewalk that it’s only visible if approached from the south or east.  My normal walking route approaches this spot from the north, but occasionally I switch things around for exactly this reason.  Even something as simple as the direction of the route you take around a building can affect your ability to detect a bird carcass there.  (I’ll now leave this bird in place and see how long it lasts.)

27 October 2011 – four sparrows hit the end of the road

The four sparrows I found this morning might mark the deadliest evening I’ve seen in three years of searches at the Noble Research Center.  I found birds on three sides of the building after a cool and rainy night.  The first was a bedraggled Lincoln’s Sparrow (fat = 2) that I left in place for a check on scavenging rate.  Elsewhere, I collected these three Grasshopper Sparrows.  The two dry ones on the left were a few feet from each other on the south side of the building, the wet one on the right was in one of the west alcoves.

I aged all three as AHY and all were fat: 3, 3, and 2 from left to right.  Interesting to see the variability in dimensions of these birds, however.  Numbered 1, 2, and 3 from left to right, check it out:

1: 20.5 g, bill 10.6, wing 60, tarsus 23.2

2: 16.5 g, bill 9.2, wing 58, tarsus 21.5

3: 18.0 g, bill 10.4, wing 64, tarsus 22.8

14 October 2011 – 1 trapped Lincoln’s Sparrow

This one was on the north side and seemed to be pretty active.

The Grasshopper Sparrow has been removed.

13 October 2011 – Clay-colored Sparrow and trapped Lincoln’s Sparrows

It was a busy morning at the NRC after a crisp and clear, moonlit night that must have supported a big local flight.

I first checked on the Grasshopper Sparrow carcass – still there.

Next, I noticed a trapped Lincoln’s Sparrow on the north side of the building. This bird was flying well and should be OK.  In the west alcoves, however, were three more Lincoln’s Sparrows.  One was moving fine, one I was able to herd away from the building, and one was stunned enough that I was able to catch it.  I carried that bird around for awhile and it seemed quite perky in the hand.  I released it in the dense cover on the south side of Ag Hall, and the bird flew strongly away from me.  I will assume that it will be OK, so the tally will be 4 trapped Lincoln’s Sparrows with no casualties among them.

A fifth sparrow was not so lucky: this Clay-colored Sparrow I found on the east side of the NRC.

11 October 2011 – Grasshopper Sparrow

1 Grasshopper Sparrow on the south side of the NRC this morning.  I left it in place to assess removal rate.

29 September 2011 – 2 (and a half) Grasshopper Sparrows

As I rounded the corner to check the south side of the Noble Research Center this morning, I immediately noticed this guy (Grasshopper Sparrow 1 a.k.a. “GS1”) sitting stunned or tired at the base of the building:

Some distance behind him was unfortunate GS2, who must’ve hit a window within the last hour or so:

As I set down my camera and prepared to capture GS1 or flush it away from the building, it was evident that there was still a lot of life left in that little bird.  GS1 flew strongly away from me (west) and started to veer south away from the building.  Just before clearing the corner though, it turned back toward the building and flew up into the external rafters of the south overhang.  These rafters are perches and nest sites for starlings; I had never witnessed a “trapped” bird in them before this morning, but that’s just what happened to GS1.  It fluttered against the windows up to the very top of the rafters and repeatedly flew back and forth the length of the building, apparently unable to figure out how to fly down to find an escape route. GS1 was in the rafters when I left the scene several minutes later.

Hopefully, GS1 will eventually figure it out and fly away none the worse for wear.  That wasn’t the fate of poor GS3.  Apparently, when I arrived there this morning and noticed GS1 and GS2, I did not notice a third Grasshopper Sparrow already up in the rafters and unable to find its way out.  When GS1 flew up to the rafters, GS3 looks to have been spooked and flown into one of the upper windows.  I watched it drop from the rafters and land lifeless on the brick walkway below.

So again, it looks like the unique, angular shape of the Noble Research Center has “trapped” some migrants before collision with the building’s windows led to their death.  Below, GS2 and GS3 await processing on my desk:

Both birds appeared to be adults and in good health (fat scores both = 2).  Today’s survey illustrated some interesting things in addition to the problems birds can have with a building’s architecture.  This is probably the third time I’ve found Grasshopper Sparrows at the south side of the building during fall migration.  What gives?  I think they must have missed a memo.  Also, the tragic scene I came upon illustrates that this species likely travels in small groups.  Actually, for all I know these three could have been part of a larger, loosely organized flock or they could’ve been flying independently but simply ended up in the same place.  Anecdotally, however, it looks like they were flying more or less together.

Six-month summary: July–December 2010

Here is just a quick summary of casualties at the Noble Research Center from July through December 2010:

Very fat Mourning Warbler that never made it to the wintering grounds.

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.

16 November 2010 – revisiting a false ID

One of the reasons I keep and/or photograph window-killed birds is that the record gives me the chance to double-check identifications some time after I made the initial determination. Such was the case yesterday (Nov. 15 2010) when I was working on a specimen I collected a year ago to the day (Nov. 15 2009). The specimen was in a bag labeled as a LeConte’s Sparrow, but the bird that came out of that bag was clearly and obviously a Grasshopper Sparrow.

Why did I think it was a LeConte’s Sparrow in my hand a year ago? I have no idea. The bird was fairly buffy about the head and breast, and it had a well defined nape patch, but it was otherwise not at all a good match for LeConte’s. It seems to have simply been a brain malfunction on my part – and one that I never would have been able to correct without the specimen or photo in-hand.

2 November 2010 – Field and Grasshopper sparrows

NOTE: I did check on Nov. 1, but neglected to make an entry: no casualties.

I heard several flight calls while walking home from a basketball game around 9:45 last night, so I thought there might be a bird or two around the NRC this morning. There was.

First, I flushed a Grasshopper Sparrow from the hedges on the north side. Eventually, I herded this bird away from the building but he bumped into windows several times while trying to get his bearings. There was also a plump male Dark-eyed Junco similarly trapped by the building this morning, and I tried to herd him away as well. Time will tell if I was successful.

Another Grasshopper Sparrow was not so lucky. I found that bird in good condition but for some ant damage on the face, so I imagine that it came in some time yesterday. Either I missed it on yesterday’s search or it came in during the day. I left the sparrow in place to get some more scavenging rate data.

The second victim was this Field Sparrow, the first of this species I’ve found in window collision monitoring:
(AHY, Fat = 1)

October 2010 Summary

I checked for casualties on 25/31 days in October, and encountered the following:

1 unknown songbird
1 House Wren
2 Lincoln’s Sparrow
2 Grasshopper Sparrow
1 Red-breasted Nuthatch
1 White-throated Sparrow
1 Song Sparrow

26 October 2010 – Grasshopper Sparrow and Red-breated Nuthatch

The nuthatch (female, apparent AHY) had already been hit by ants about the head, so I left her in place to check on scavenging rate. This is the 2nd nuthatch I’ve found in the past week or so (but the first I’ve recorded at the Noble Research Center), and it might portend a big influx this winter. Check out the winter range of this species:

The sparrow (AHY-U, fat = 3) was another beautiful, fat, healthy victim of its own sensory perception being unable to detect a barrier of glass.

25 October 2010 – Grasshopper Sparrow

AHY
Fat = 3

A fresh Grasshopper Sparrow met its untimely end at the NRC overnight. There was another trapped at the north facing windows when I got there in the pre-dawn light this morning. I flushed the live bird out and it appeared to fly off and to safety.

19 October 2010 – unknown passerine

I think it was a Lincoln’s Sparrow, but the feathers I found were too nondescript for me to tell for sure.

The Grasshopper Sparrow has been scavenged.

So that was one bird scavenged on day zero and one on day two . . .

18 October 2010 – Grasshopper Sparrow

Given my schedule over the weekend hosting the Oklahoma Ornithological Society annual meeting, I was unable to check the NRC on the 16th and 17th. (I did, however, find remains of Lincoln’s Sparrow and Wilson’s Warbler at the Kerr Residence Hall).

This morning I found a single Grasshopper Sparrow at the NRC. This was the first time I’ve found a carcass at the bottom of the stairway on the east side of the building. Beetles have gotten to the carcass; I’ll leave it there to see how long it lasts. (The cuckoo from June is still visible btw, although only when I know to look for it. It has reached a stage of decomposition at which it is easy to overlook when just casually walking by.)

This last photo was taken without the flash, to provide a sense of how dark it was at about 7:25 when I did this morning’s survey.

A Year in the Death – Aug. 2009–Aug. 2010

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:

Effort.
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.

Data.
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.

I encountered more casualties during spring and fall migration periods than in winter or summer (though effort may have played a role in this result):

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.)

Non-lethal collisions.
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

Scavenging rate.
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.

Scavenged Swainson’s Thrush.

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.

Total data.
The following table lists all the species found as window collision casualties at the Noble Research Center, 8/20 2009–8/20 2010:

species number
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

O’Connell2001

28 April 2010 – Grasshopper Sparrow

Fat = 1
AHY
Lovely little bird.

22 September 2009 – no casualties, but . . . .

Two stunned birds by the windows this morning.

We had a powerful cold front go through yesterday, such that it was only 60 degrees (F) this morning, with clouds, sprinkles, and a northwest wind. It’s been months since we’ve seen weather like this.

So, dark and dreary as it was this morning, I didn’t notice the first bird until it flew. All I can say is that it was a songbird, about 6″ long, with an olive-brown back and pale yellowish breast. The bird flew in front of me, hit a window at slow speed, turned around, almost hit another window, and finally made its way out of the canyon of windows on the west side of the NRC.

The second bird, a Grasshopper Sparrow, looked a lot more alert and was flying normally. It was clear that this one had also hit a window, however. When I first found it, it was on the ground in the open and pointed at a window about 6″ away. As I drew to within about 20 feet, it flew back away from the window and into a little bench area with some ornamental trees and shrubs. There is perched beneath a shrub, and eventually let me get to within about 15 feet. It otherwise looked bright and alert, so I left it there.

These two birds illustrate very well how a non-lethal window collision can make birds vulnerable to predation.

12 September 2009

I was a way for a couple of days, and unable to check the NRC until Sep. 12th. Casualties were:

1 Gray Catbird – badly decomposed
1 Grasshopper Sparrow – ditto
1 Wilson’s Warbler