28 April 2017 – Indigo Bunting

Sad to think that this spectacular specimen of an ASY male (fat = 2) Indigo Bunting safely crossed the Gulf of Mexico a few days ago but could not safely navigate the Noble Research Center.

 

 

Indigo Buntings, of course, have no blue pigment.  Blue is produced by birds through light reflectance – it’s structural color, not pigment.

You might think, then, that Indigo Buntings would look really cool in UV light.  They don’t, unless you think charcoal looks cool!

Screen Shot 2017-04-28 at 9.34.19 AM

25 April 2017 – Lincoln’s Sparrow

The main north entrance claimed a Lincoln’s Sparrow today – ASY-U and bulging with fat = 3.  (Apologies for the lousy photos.)

Screen Shot 2017-04-25 at 11.53.21 AM

22 April 2017 – Orange-crowned Warbler (yep, another one)

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.

20 April 2017 – Orange-crowned Warbler

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.

19 April 2017 – Nashville Warbler

This one was twofold odd – the bird was found in an odd spot and I’ve clearly overlooked it for a few days given the state of decomposition.  The beetles, slugs, etc. were all over it.

 

Screen Shot 2017-04-19 at 5.11.38 PM

16 April 2017 – Mourning Dove scavenged

No new casualties today, but I noticed immediately that the Mourning Dove carcass had been removed.  Closer inspection revealed it to have been scavenged from its original location with remains scattered near the base of the building about 5 m away.

 

So what is scavenging rate all about, anyway?

The idea is that our detection of dead birds (or anything else) is imperfect.  We can collect data and report that, for example, 50 birds died at a building.  That estimate can only be a minimum, however.  Our raw counts underestimate the true number of casualties because our detection cannot be > 100% but it can be far lower than 100%.  Birds can collide but manage to flutter away and die outside of our search area.  Some might be difficult to see against the substrate on which they land.  Most important, some will be removed before we get there to find them. Cats, rats, opossums, raccoons, crows, etc. tend to be abundant in urban/suburban areas where most window collision research takes place and they can often remove a carcass before the investigator arrives onsite to conduct a survey.

For example, assume that the removal rate (whether by scavengers, human maintenance crews, etc.) is 25%. This means that, at best, the investigator is only predicted to encounter 75% of the casualties. That raw count of 50 dead birds? The detection-corrected number is actually closer to 50/0.75 = 67 dead birds.

Does that matter, though?  I struggle to attach relevance to what the removal rate is for any given study. Is there some magic number of casualties that is a threshold for conservation action?  Are there people for whom 50 dead birds wouldn’t register as important but 67 would? For comparing mortality rates among sites where removal rate might vary we assume that it is important to determine a separate removal rate for each site, but is it? Imagine 50 dead birds at our site with high removal of 25% compared to 50 dead birds at a site with low removal rate of 5%.  That’d be 67 compared to 50/0.95 = 53.  So?  Would we really be concerned about 67 dead birds at one building but not 53 at another?

My final concern is the false sense of security that we’ve determined “the” removal rate.  These rates are widely variable across space and time.  We’re kidding ourselves to think that we’re improving our estimates of collision mortality by adjusting raw counts with a detection probability that is itself a moving target.

In my study, I’ve conducted approximately 86 removal trials over the past several years. On average, a carcass lasts about 10.5 days on the ground before it is removed.  On average, I conduct a survey every 1.5 days.  That gives me 10.5/1.5 = 7.0 opportunities to find a dead bird before it is removed.  Ergo, removal rate is hardly noticeable in my study.  Whatsmore, scavenging and removal are not the same thing.  It is often the case – as with today’s Mourning Dove – that the carcass is scavenged but evidence remains.  The Mourning Dove died on April 5th and was scavenged on the 15th.  That’s 10 days.  The remaining bones and feathers, however, might still be here weeks from now.  On multiple occasions, I have found evidence of scavenging in the 24 hrs since my previous survey. For example, I check one morning and find feathers that weren’t there the day before.  I refer to these as “day 0” removals, but the feathers are still there to provide evidence of the casualty for days and weeks after the event. The longest I have had feathers or other remains in evidence is > 90 days.

So I see scavenging and removal rates – and detection rates in general – as red herrings in our monitoring of collision mortality. Unless part of a well-controlled design to compare, for example, mortality from two facades of the same building, there’s not much to gain from collecting data to estimate such rates.  There are, however, potential costs.  Many avocational birders and conservationists collect data on collisions opportunistically, and their presumed lack of rigor in methods limits the use of their data for serious analysis.  I maintain that those data are perhaps far more useful than we might presume because of an ill-defined obsession with calculation of detection as a study’s ticket to the club of legitimacy.

13 April 2017 – Lincoln’s Sparrow

The Mourning Dove was still there this morning, but it has been disturbed a bit and is now on its back.

Screen Shot 2017-04-13 at 12.00.30 PM

New this morning was an unfortunate Lincoln’s Sparrow at the main north entrance to the NRC. As is so often puzzling, this was a bird that had to have been traveling south to hit the glass there even though the net movement of Lincoln’s Sparrows in April in Oklahoma is north.

This bird had 0 fat, was of indeterminate sex, and looks to be a SY.  Note trauma to the bill tip indicating the point of collision.

5 April 2017 – Mourning Dove

This poor waterlogged Mourning Dove is the 13th MODO casualty and, unofficially, the 274th victim of collision at the Noble Research Center.  I left it in place for the first scavenging trial of 2017.

Screen Shot 2017-04-05 at 1.42.23 PM

4 April 2017 – trapped Song Sparrow

No casualties yet, but I’m up to the 3rd trapped bird of the new year: a Song Sparrow in the northwest alcove.  This one was stunned – or exhausted – but before I could get any closer than about 3m it flew away strongly – good sign!

 

This bird was likely riding a wave of migration that really lit up the radar last night (as linked from Paul Hurtado’s birding page). Check out the big blue blobs in Oklahoma from a little after 11 pm last night:

Screen Shot 2017-04-04 at 12.55.40 PM

Keep your eye on that slug of rain and storms (the green, yellow, and red) in the OK Panhandle, though.

Now check out the line of rain and storms that moved in overnight and set up shop on the Kansas border.  This is from a bit before 6:00 am, and nobody moving north through our state kept on moving through that!  This is a classic setup for a “fallout” of birds.  More storms today followed by strong north winds tomorrow will likely keep some staging migrants around for a few more days.

Screen Shot 2017-04-04 at 12.56.22 PM

 

3 April 2017 – trapped Common Yellowthroat

I found this rather early fellow right in front of the doorway to the southeast alcove this morning. He’s a gorgeous, ASY male Common Yellowthroat with fat score = 1. He was dazed enough that I caught him but alert and feisty in the hand, and he perched well when I moved him to a safe spot.  In addition to being one of history’s all-time great yellowthroats, he has the distinction of being the 100th “trapped” bird that I’ve been able to move or shoo away from the Noble Research Center.  If even one of them recovered enough to fly on and live out its life then every one of these walks around the NRC has been worth it!

Screen Shot 2017-04-04 at 12.08.15 PM

 

Unfortunately, something went screwy with my camera and this is the only surviving photo:

Screen Shot 2017-04-04 at 12.48.24 PM.png

20 March 2017 – trapped Northern Cardinal

Spring kicked off today with the first collision victim of 2017: a trapped Northern Cardinal at the northeast alcove.

 

He was a bit stunned, but alert in the hand and he perched strongly in the dense cover where I moved him away from the building.  Beautiful ASY male; I hope he makes a full recovery!