This morning dawned bright and sunny, but there was a Northern Cardinal in the northwestern corridor and a Yellow-billed Cuckoo on the northeast corner to dampen my mood.
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.
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
Today was a first for me, and I’ve been doing this almost daily for 6 years . . .
I rounded the corner to enter the northwest alcove and was greeted by the sound of a very angry cardinal. This one, in fact:
She was chipping nonstop – her mate was there too but hanging back a bit – at another lady cardinal who looked like she’d been having a bad day.
The corner was strewed with her feathers; she was mostly bald on the back of her head.
Here’s what seems to have taken place. The disheveled female smacked the window and got stunned and then, as a “trapped” bird, couldn’t figure out how to turn around and escape. Then, like taking a wrong turn down an alley and getting trapped by local street thugs, the pair of birds didn’t take kindly to this interloper and they tried to drive her off their territory. The poor stunned bird just sat there and endured quite a pummeling by the female of the pair.
Window collision leads to intraspecific aggression in Northern Cardinal. This note practically writes itself.
Despite her rough morning, however, the female weathered the abuse pretty well, and I even had a bit of difficulty in catching her. Here’s where the story takes on a more heartwarming aspect.
One delightful feature of life in Stillwater, OK is that we play host to the Special Olympics each May. Thousands of athletes with their families and support crews in the planet’s brightest T-shirts were on campus today, and heading over to the football stadium for Opening Ceremonies. One such group approached me just after I had caught the cardinal and inquired if they could cut through the building on their way to the stadium. I checked the door, determined that it was unlocked, and invited them to pass through the alcove, much like so many birds think they can do but, sadly, cannot.
Of course, when some Special Olympians and their squad are approaching you whilst you’re holding a disheveled lady cardinal in your hand, you make sure they get a chance to see her up close, and I did!
It’s always fun for people to see birds up close, but there’s something about the times when I’ve worked with differently-abled folks that I’ve noticed that their sense of wonder and appreciation for such things is on a whole other level. Their excitement did not disappoint! They were really gentle, though, and very careful to ask first if they could touch the bird. (I told them “no” just because I wasn’t sure they’d have a chance to quickly wash their hands after doing so, and that’s always the first thing I do after handling a wild bird.)
Then came the questions, and the first one knocked me for a loop: “What’s her name?” The first thing this little girl wanted to know was not the strange set of circumstances that led to some guy walking around with a cardinal in his hand, she first wanted to personalize the cardinal. It was a startlingly beautiful reaction to the situation!
I was a bit proud of myself for maintaining my composure rather than simply crying and hugging this little girl, so I responded,”I don’t know. What do you think we should name her?”
Without missing a beat: “Layla. Her name is Layla.”
“Layla it is, then!”
For the next few minutes, I explained to them that Layla hit the window and got confused and that the local cardinals were angry with her. On cue, the male started singing robustly. “See? That’s the male up there on the roof.” I told them that I was taking Layla to the row of trees nearby where she could rest a bit and then get on with her day. She was going to be just fine. In the span of a few minutes, they learned a lesson in window collisions for birds, territoriality, and intraspecific aggression. They didn’t need a lesson in empathy or compassion – they already knew that stuff.
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
Nothing at the NRC today, but there was a juvenile Northern Cardinal that met its end at a window of the Food and Agricultural Products Center a mere stone’s throw from where I’m sitting right now in Ag Hall.
One of the primary messages I try to communicate with the window collision issue is that our common, abundant, year-round residents are rarely among the dead beneath our windows. It is the long-distance migrants that make up the lion’s share of casualties. Today’s baby cardinal and the 2 or 3 juvenile Mourning Doves I’ve found this spring illustrate that our residents do occasionally fall victim to windows as well. But it tends not to be the adults in their prime, but the weak, uncoordinated, and inexperienced youngsters who fall victim.