18 August 2014 – Ruby-throated Hummingbird (another one)

Another day, another window-killed hummingbird.  This one was heading north when it met its end. This is the 10th hummingbird fatality, and the 180th overall.

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Regular readers will note a very similar post from yesterday, and a superficially very similar-looking bird. 

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This one was more obviously a Ruby-throated Hummingbird.  The following photo illustrates that the tailtip extends well beyond the wingtips.

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Next, I examined the bill to look for corrugations indicative of a hatch-year bird.  I can’t see any.  This looks like an after hatch-year bird; plumage-wise, she’s female.

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So I’ve got an AHY, female, Ruby-throated Hummingbird.  I checked one last thing to clinch that identification – the shape of the 6th primary.  Sure enough, it’s a perfect match for the shape indicated as “AHY/ASY” female Ruby-throated Hummingbird in Peter Pyle’s Identification Guide to North American Birds.

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17 August 2014 – Ruby-throated Hummingbird (I think)

Today marked the inauspicious observance of the first window-killed bird at the Noble Research Center for fall, 2014.  It was a hatch year Archilochus hummingbird at the southwest alcove that I have somewhat tentatively identified as a Ruby-throated. To nail down the identification as best as I could, I consulted David Sibley’s the Sibley Guide to Birds (2000) and Peter Pyle’s Identification Guide to North American Birds (1997).

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Step 1 for identification of these hummingbirds is to confirm the age.  As hatch-year hummers develop, their bills lose characteristic striations or corrugations over time. A hummingbird with these markings extending for > 10% the length of the bill can be reliably considered HY/SY (i.e., less than 1 year old).   Here’s this morning’s bird (with bonus photo of hummingbird tongue tip):

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The markings are evident over probably 90% of the bill length. This is a hatch-year bird.

The problem with the bird is that it presents some characters (admittedly subjective in some cases) that suggest Black-chinned more strongly than Ruby-throated.  For example, there is low contrast between the auriculars and the throat, and that throat is spotted.  Both of these are Black-chinned characters as rendered by Sibley. The flanks are dirty gray with just a hint of cinnamon – also suggesting Black-chinned.  More pronounced is the relative length of folded wing and tail:  If anything, the wingtips extend beyond the tail tip as opposed to obviously shorter than the tail as typical for Ruby-throated. 

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So it was going to take some measurements to help solve this puzzle.  The wing chord came in at 46.5mm:  that’s too big for a male of either species.  So with that information, I knew I now had a HY, female hummingbird.

The length of the tail (24.9), culmen (18.8), and tail fork (0.10) – and the width of the outermost tail feather (r5, 5.2) offered no help in determining which HY female Archilochus I had.  However, the shape of the outer primary (p10) and primary #6 (p6) were both in line with expectations for Ruby-throated.  The photos aren’t great, but p6 is featured in the next two photos:

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So, based on my analysis of the characters this bird presented, I’m calling her a Ruby-throated Hummingbird.  The possibility of hybrids is very real for this species and Black-chinned, however, so I will be sharing this information with some more experienced folks to get some other opinions.  Stay tuned!

11 August 2014 – no casualties

The 6/10/14 Mourning Dove is still in evidence, but I’m calling today it’s last day of observation. This is arbitrary I know, but at 62 days visible, the point is made that evidence of collision can be collected long after the event itself, and that remains often remain even after a bird has been scavenged.

Spatial summary: Aug. 2012–Jul. 2014

I have just completed two years of carefully tracking the specific locations at the Noble Research Center where I have found dead or trapped birds. To analyze those data statistically, I digitized the perimeter of the NRC in Google Earth and measured the apparent length of each segment (defining a segment as a straight line at least 2m in length). I identified 59 such segments for the NRC from a total apparent perimeter length of 847m. That’s right, the perimeter of that building is nearly 1 km long.

Next, I characterized segments according to whether or not they formed the terminus of one of the “alcoves”, which I defined as a recessed facade bordered by two segments of at least 4m oriented at right angles to the facade. So the question was, were more birds likely to be trapped and killed in alcoves than at random segments?

Predictably, that answer was “yes”: Birds were 49 times more likely to show up dead or trapped at alcove segments than at other segments along the 847m perimeter of the NRC.

The question now is “What’s the best way to represent these data graphically?” I like the idea of a map showing exactly where birds ended up – if you visit here regularly, you see those little red or blue dots overlain on a map of the building every time I find a bird there and report it here. Are those red and blue dots the best way to go for a two-year summary or does a numeric representation convey the information better? Please check out these images and use the comments feature to let me know which one you find to be more effective. Thanks!

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7 August 2014 – trapped Grasshopper Sparrow and local Mourning Dove

Screen shot 2014-08-07 at 10.37.11 AMI’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.”
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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.
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1 August 2014 – no casualties

As August dawns I begin what I consider to be the official start of fall and winter collision monitoring at the Noble Research Center, and the 10 or so Barn Swallows streaming past as I conducted this morning’s survey reinforced that migration is well under way. On the 19th of this month, I will mark the official 5-year anniversary of near daily monitoring at the NRC. Right now, I am scrambling to get some ABC Bird Tape up on a critical alcove surface for an in-the-field test of that window treatment’s efficacy in reducing collisions.

The spring/summer monitoring just concluded spanned the 153 days of Mar.–Jul. 2014. With some assistance from Scott Loss, we conducted surveys on 122 (80%) of those days or one survey every 1.25 days. I left 6 carcasses in place to estimate removal rates during this period, and the first 5 lasted 1, 5, 6, 3, and 4 days, respectively, before removal (mean = 3.8 days). Thus, my survey rate was well within the bounds of the removal rate and it is unlikely that I missed many fatal collision events. In other words, the total 18 dead birds I found is close to the total number of birds that died at the NRC during this period. This is excluding the outlier Mourning Dove estimated to have died on June 10 that has now been easily discernible and identifiable for 52 days this summer.

One positive note for this period is that (also with Scott’s help while I was away), 5 “trapped” birds were discovered and steered away from the building before they too became casualties.

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