The darkness of these photos illustrates how rainy and gloomy we were when this poor Orange-crowned Warbler met its end at the northeastern alcove. This bird was removed/scavenged on 7 May.
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’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.
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
Yesterday (Friday 4/21/17) dawned stormy after an equally stormy night. We picked up nearly 2 inches of rain (+ some hail!) and enjoyed several hours of lightning and thunder. It was dicey enough – and I busy enough – that I skipped Friday’s morning survey.
Saturday, Earth Day (!) was misty, windy, and cool but mostly dry. After a morning field trip, I checked the Noble Research Center and found the fifth Orange-crowned Warbler of the survey. (Recall, that Thursday, 4/20, produced the fourth.) It is tantalizing – and sad! – to think of two birds traveling together and dying together, especially considering that the collision took place at the same spot on the building. I don’t think, however, that this ASY, fat = 0, probable female had been in place since Thursday. She was much too dry to have lain out in the open during Friday’s deluge. So I think she really did come in overnight and if not traveling with Thursday’s male, evidently following a similar route.
Surprisingly, the 277th casualty on this project was just the 4th Orange-crowned Warbler, which is a common migrant here in central OK. This one was an ASY male with fat = 1. I first spotted him from about 80m away.
Check out this guy’s truncated rectrices, blunt-tipped primary coverts, and his pointed primaries:
The most exciting thing about him, though, is that this old guy actually had an orange crown. I’ve never seen one so orange, which makes me wonder if this fellow was closer to 10 years old than merely “ASY”. It is so sad to see such a vibrant, mature, elder statesman of a warbler cut down by something so stupid as a window. He deserved better.
It felt like a big flight overnight, with migrant flight calls every time I walked outside. At least one of those migrants was this unfortunate little Orange-crowned Warbler:
This was an AHY-U bird with fat = 2. As evident from the photo, this bird in the southwestern alcove appears not to have been saved by ABC Bird Tape.
On a cloudy morning after a nighttime football game that shone bright lights on low clouds, there were birds left behind at the Noble Research Center. The first I found was this hatch-year Clay-colored Sparrow (fat = 2):
Then there were 3-4 birds trapped around the north entrance, including a House Wren. Is this the same little guy hanging around for weeks?
There was an obviously stunned Orange-crowned Warbler as well. The bird was sitting low and unresponsive, but it perked up when I picked it up.
The bird looks okay above. Had it remained this way I would’ve counted it as merely “trapped”. When I set it down, however, the bird did not fly away and it actually had trouble standing. For cases like this – in which a trapped bird has trouble standing – my policy is to consider the bird as a casualty. I’ll be interested in checking tomorrow to see if my suspicions are correct.
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
The bird was limp and seemed fresh, but the ants had already gotten to the head, and I didn’t collect the specimen. Follow this link to learn more about the Orange-crowned Warbler. I couldn’t determine sex of the bird, but it was full of fat – fat score = 3.
Range map below:
In addition to the Orange-crowned, I found a very much alive Grasshopper Sparrow in one of the western alcoves of the NRC this morning. I herded it out to safety.