The fall in fall migration

September 13, 2017 • 11:30 am

by Greg Mayer

For many bird watchers, the fall migration is the most exciting time of the year, as passage migrants, the arrival of winter visitors, and breeding birds in juvenile plumages, add to the diversity of forms, colors, and species that can be observed. For the birds, unfortunately, the fall migration is a time of high mortality, which is increased by the presence of human structures and lighting across the landscape. Many birds fly into buildings, cell towers, and other structures, and fall, dead or stunned, to the ground. Here’s a stunned bird I found with my vertebrate zoology class yesterday morning at 8 AM in front of a building. Note the closed eye and the drooping wing.

Fallen warbler, UW-Parkside, Kenosha, WI, 2017 09 12.

Fall warblers can be hard to identify, so much so that many bird field guides come with a section entitled “Confusing Fall Warblers“, or something similar. I will leave it to readers as an exercise, to identify this one. The following photo might help, as it shows more of the ventral coloration.

Fallen fall warbler.

I picked him up, and moved him away from the door to the top of a rock (elevated so as not to get stepped on, and perhaps slightly harder for a passing cat or other predator to find).

A fallen warbler on a rock.

After class was over, at 9:30 AM, I checked and he was gone. He may have recovered sufficiently to fly away. My understanding, though, is that birds that fly off have often sustained sufficient injury to their heads that they succumb a few days later.

34 thoughts on “The fall in fall migration”

  3. A Fox Sparrow flew into a window this morning with a loud ‘whap’. I ran out and picked up the stunned bird and is my custom put it on a towel and covered it with a hat. Sometimes I’ll leave it for several hours and occasionally overnight. This bird started fluttering around in 10 minutes or so and I released it. It flew to a perch and sat looking around for a few minutes. I may have seen some blood on it’s beak. It flew to a feeder and then away. We have netting over many of the windows here but not this one.

  4. A search on the web says your stunned bird looks like a mourning warbler or the willow warbler. If it’s immature it would be harder to name.

  5. I came across a bird that was small and greenish while walking with a co-worker a few years ago. It was not moving but breathing. She picked it up and it died in her hands. I carried it to an apple tree nearby and left it underneath. I wasn’t really sure what to do.

    The bird could also be a Nashville warbler.

    I like to watch the turkey vultures glide around. They are so beautiful. I’ve noticed they sometimes fly in mirrored patters. After I started noticing them a few years ago, I began to notice a lot of birds.

    1. I strongly recommend joining your local bird club. You will find out your local area has a great number of wildlife habitats you never dreamed were there.

        1. A small caution…I’m retired and I can take advantage of my club’s Wednesday morning bird hikes. For those still in the labor force occasional weekend trips do occur. Your mileage may differ – but do check into it, either way.

          1. I was going to say before that I had already checked this out a few months ago. I believe Cape May, NJ has a lot more going on but there are some things close to me too. The Great Swamp in NJ is amazing. I walk around there and find turtles. Actual turtles. It’s incredible. So those groups meet there in the morning and go watch birds. It’s BYOB (bring your own binoculars) – ha I just made that up but it’s true. You have to bring your own. I would love to meet people who watch the birds. It started with the Turkey Vultures but I also watch cardinals, blue jays, crows, seagulls, and pigeons when I’m in NYC. The last time I went to see a play on Broadway, I came off the train at MSG and was just staring at the pigeons on the busy sidewalk like there was nothing going on around me. I was just calmly observing. Sort of in awe that it was a “new” bird for me. I’ve seen them all my life but never had the appreciation I do now. The starlings – that is now on my bucket list. I’d like to see the starlings move together. I saw them first on a video and it was like instead of laughing at a funeral if you are unable to handle emotion such as grief, which I am good with now, I was laughing instead of being so overwhelmed with how beautiful it was. Not really laughing but just in awe. I also have interests in Seth Lloyd’s work with quantum biology and the magnetoreception of certain birds. I think the walks near the Great Swamp are around 3 miles or maybe 5. I don’t know yet for sure.

          2. Indeed, birding can become a very fascinating and sometimes obsessive preoccupation. The rewards are many. So much to see. So little time…

  6. My brain, full of mischief, immediately asks: Why would I want to confuse a Fall warbler? I have no idea how to even begin.

    1. Are you kidding? You ever see the look on a confused warbler’s face? That skrunched up beak alone is worth it.

  7. I’m pretty sure this is a Connecticut Warbler which is a chasable bird for us in the eastern states. This species has an unusual migration pattern as it migrates north using the Mississippi Flyway and circles down south using the Atlantic Flyway so we only see them in the Fall.

    This bird has a clearly defined, complete eye ring ruling out Mourning Warbler which has a less defined and incomplete eye ring. It is also apparently yellow throughout on the bottom (ventral?)side ruling out Nashville Warbler which has a whitish section there and, though Nashvilles do have a complete eye ring, they always show substantial gray on the head. Connecticut Warblers have a gray hood in spring but first year birds and fall females often lack this feature. Common Yellowthroat would be the likeliest alternative but they don’t ever have such a distinct eye ring (though photos can be misleading). Also, Connecticut Warblers walk on the ground so if Greg saw it walking that would confirm the ID, all the alternative birds would be hopping on the ground (though it sounds like this guy was out of it).

    Best practice is to put the bird in a box or paper bag to give it time to recuperate from the impact. They will start fluttering when they are ready to go and can be released.

    1. Noticed the white section on the Nashville Warbler. That’s so neat. It probably isn’t the grey-headed canary-flycatcher either although they look similar.

      1. Flycatcher beaks are totally different, wider for grabbing insects mid air. Warblers generally are gleaning leaves, branches and understory for insects so their beaks are “designed” for probing. Also the Gray-headed Canary Flycatcher lives in tropical Asia and I would book a flight to see one in the mid-west.

        1. It definitely looks like the warbler beaks are longer. That is interesting. I knew when I posted the grey-headed canary-flycatcher lives in Asia but thought it was neat they looked similar. A little bit when you look at all of the detail.

          2. This was amazing. The first one was lower pitched and the next one higher. The next one was higher too but with a gobble. Like Thanksgiving gobble. The last one sounded like a chirpy morning bird. Chirpy but loud and chirpy. Enough to wake you up. So beautiful.

          3. At least some can be, American Crows and Fish Crows live around here, look almost exactly the same but have different calls.

    2. I consider myself a good birder (I certainly have plenty of experience!) Full disclosure, though, I’m surprisingly bad at identifying birds from still photos (I guess in the field I use extra id clues, such as behaviour, habitat and calls more than I realize) and I have very little experience with Connecticut Warbler: just one sighting several years ago at Cape May, New Jersey. Nevertheless I’m going to agree with Robert that Connecticut Warbler (Oporornis agilis) is the correct identification. (By the way, many warblers are very inappropriately named and this is one of them; it breeds mostly in northern central Canada and is rare in Connecticut.)

      Connecticuts can be very difficult to tell apart from Mourning Warblers but I agree with Robert that the eyering is too prominent for the bird to be a Mourning. Connecticuts often have a curious slight gap in the eyering at the back of the eye and I feel one can see this in this bird in the second photo (like a very small shadow). This bird (which is presumably a first-year female in immature plumage) seems much too robust to be a Nashville Warbler. Also, Nashvilles have white on the underparts near the legs (surrounded by yellow), which would probably be visible in the second photo if the bird were a Nashville.

      Connecticuts are great skulkers (i.e, stay hidden low in the understorey) and are uncommon virtually throughout their range, so under different circumstances such a great view of an elusive species would be cause for celebration. I really hope it survived.

      Connecticut Warbler is by far the bird I most want to see in my home area (Ottawa, Canada). They’re rare here but do occur. My twitter handle is actually OporornisPaul(!) A friend of mine who is a far more active birder than I am has not managed to see one here in 45 years of birding, however, so I’m not holding my breath. Other local birders have had more luck, including one who’s seen no fewer than 7 here over the years. So hope springs eternal. Unfortunately, because of the different migration routes in spring and fall mentioned by Robert, this species is more numerous here in fall (when they’re not singing and close to impossible to detect) than in spring (when they might sing and thereby reveal their presence). This fall the window when they might occur here is rapidly closing (no sightings by me or anyone else). Maybe next year!

        1. Thanks! My seeing one may well require divine intervention. Oh wait a minute, we’re all atheists on this site.

  8. The other factor in declining bird numbers, as I have seen documented, is the large numbers killed by cats, both feral and domestic. I know everybody here loves cats, but they need to be controlled, especially the feral populations.

    1. I’m not going to disagree with you on the feral cat population problem, but there is a question of whether it is responsible for the perceived drop in migrating numbers. Have cat populations increased significantly over the relevant time period, or are there other issues which have more effect on the populations? Is there – in medicine terminology – a dose-response relationship?
      Another question is – who is responsible for the conditions that are supporting (alleged) increased feral cat populations? Are there more cat-owning households? Is municipal waste management becoming more lax, allowing more scavanging?

  9. I used to work with wildlife scientists picking up injured native birds. They had an interesting way to check for neurological and other damage – while holding the bird quite gently, they’d give it a quick (but again gentle) tip into a slightly head-down position. If OK, the bird would automatically flick its tail upwards to maintain “level flight”. Likewise. a quick tipping movement to one side would make the bird flick its wing out to counteract. The ones that couldn’t do that were judged unlikely to survive.

  12. To prevent migration into the US, Trump should build a ‘great net’ and make the birds pay for it (I seem to be channeling HuffPo).

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