Ornithology Lab, September 16

This is the third installment in a series of weekly posts for my ornithology class at Ohio University. We go out in the field every Wednesday (weather permitting) to do some birding and/or bird banding. One of our assignments is to write a blog post about each of these field trips, which is what this series will be about.

First Post: September 2
Second Post: September 9

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Lake Hope State Park

Beginning late last week, Southern Ohio has been experiencing more Fall-like weather (finally!), with cool mornings in the high 40's to low 50's before climbing up into the 60's and 70's. The morning of Wednesday, Sept. 16, was no different. We left Athens at 7:00 AM, just as the sun was climbing above the horizon and the thermometer was climbing out of the high 40's. Our two vans went off down State Route 56 toward one of my favorite areas in Vinton County. About twenty minutes later we arrived at our first stop of the day, a section of Zaleski State Forest. We were on top of Irish Ridge, a long ridge that's 1000 feet above sea level. The class set off along a trail that led us along a finger of the ridge. 

Now, state forests in Ohio are subject to selective logging. The specific part of Irish Ridge we were walking along was one such area. It had been selectively logged only a few years ago; a few trees of "normal" height dotted the area, but the majority of the vegetation was dense shrubs and young sapling trees. With great cover and ample food, this place turned out to be a bird paradise. The winds had also helped, and I'll show why.

Map courtesy of The Cornell Lab of Ornithology.

This weekend had brought one of the first big Fall migration movements to Ohio. Southerly winds, as I discussed in last week's post, had been keeping many migrants out of Ohio. Those dominant southerly winds changed to northerly winds over the weekend as a cold front moved through. As most birders know, cold fronts equal really good birding (generally). This is due to a multitude of reasons depending on what type of cold front and where it came from, but in this case the cold front brought northerly winds. Trailing behind the cold front on these northerly winds were thousands of migratory songbirds. These birds then began pouring into Ohio.

Map courtesy of The Cornell Lab of Ornithology.

Then something really interesting happened. By late Tuesday night, the winds in Ohio changed from favorable northerly winds to unfavorable southerly winds, as the map above shows. As I mentioned last week, most songbirds migrate during the night. Most of the thousands of individuals that had been migrating into Ohio over the weekend into Monday night were suddenly confronted with winds heading in the opposite direction they were trying to go. Instead of wasting tons of energy trying to fly against a headwind, the majority of these birds just stayed put over Tuesday evening. When we arrived on Irish Ridge Wednesday morning, all these migrants were still there, and they were very actively foraging to take advantage of the unfavorable weather. The goal this morning for your average migrant was to find as much food as possible, replenish the fat reserves they had just spent coming to Vinton County the previous night, and wait until the winds changed. 

This made for one of the most spectacular displays of migration I had ever seen in Southeast Ohio. Often during a good migration day, warblers are pretty easy to find. Today, they were everywhere one looked. These migratory birds easily outnumbered the permanent birds of Ohio, and it was wonderful.

A female American Redstart. This was one of the warbler species we saw on the trip. This photo was taken at Magee Marsh during May, 2015.

Let me give you a quick snapshot of a moment from Irish Ridge this morning. A nomadic flock of Cedar Waxwings cried in their high pitch calls overhead in one of the remaining older trees. Several White-Eyed Vireos sung "Peanut butter and jelly, CHECK!" on either side of our group. Eastern Towhees "towHEE'd" from the dense vegetation. A Prairie Warbler sung his buzzy song from the side of the hill. Eastern Wood-Pewees lived up to their flycatching name. A female Scarlet Tanager foraged quietly in one tree while a male sang loudly in another. Two juvenile Rose-Breasted Grosbeaks chased each other from tree to tree. A Tennessee Warbler lazily sung as it moved throughout the canopy of a tree. A group of Magnolia Warblers flew from bush to bush looking for insects. A young American Redstart flitted about a clump of leaves. Songs were sung while call notes rang from every bush and tree. I could go on and on and on. It was a sensory overload.

And then something else happened. Someone yelled "Hawk!" It only flew through the area for a split second, not even enough time for anyone else to see it. An Accipiter the person said, probably a Cooper's Hawk, a bird-eating hawk. And with that, silence. 

The entire area went from a sensory overload to being depraved of any noise or movement. There was literally not a single bird that anyone could see or hear. We had entered what Jon Young calls the Zone of Silence. Some of you might recognize the name; Jon Young is the author of the absolutely amazing book What the Robin Knows, a very well-known book that teaches the observant naturalist how to interpret bird vocalizations and behavior in order to gain an understanding of what is currently happening in that immediate area. This is a wonderful book that I highly recommend to anyone interested in birds; it will take your nature-knowledge and skills to a whole new level. 

Back to the hawk. As I said before, we were standing in the Zone of Silence. What exactly is that? Well, it's a type of response to a hawk. Accipiters are a genus of hawks (such as the Cooper's and Sharp-Shinned) that feed primarily on birds, and as a result are very dangerous to a small songbird. Songbirds are constantly watching for these hawks, and when one is sighted a fast chain of reactions are set in motion. Let's say a Carolina Chickadee on watch duty sees a Cooper's Hawk flying into the area, but it's still a somewhat decent way off. That chickadee will sound an alarm call that specifically designates an Accipiter hawk (yes, chickadees have specific alarms for specific threats). All the birds in the immediate area will hear that alarm call, and then those birds themselves will sound their own alarm call. Imagine this Zone of Alarm is like a giant bubble around the hawk. These birds can afford to sound the alarm because even though they are within danger, they are still away from immediate danger. Now imagine there's a smaller bubble that nestled within the large Zone of Alarm. This smaller bubble is the Zone of Silence. When a songbird is within this bubble, it is in immediate danger of being killed by the hawk; as a result, any bird in the Zone of Silence will attempt to hide, be as still as possible, and make no noise. It basically wants to disappear so the hawk won't notice it. 

If you've been in nature a lot, you know that the forest isn't really "silent" like people say. It's a noisy place. When it is silent, you know that something is up. It's disruptions, like true silence, from the baseline activity (as Jon Young calls it) that should always grab your attention. And trust me, if you're paying attention when birding, you will notice if everything that was just around you goes dead silent and disappears. It is important to note that this won't happen every time; sometimes the hawk will enter too quickly or too silently giving the birds no chance to react.

Of course, not all hawks elicit this response. The hawks of Ohio can essentially be broken into two main groups. I've already mentioned one, the genus Accipiter. The other group is a genus named Buteo. The Accipiters are "birds hawks," while the Buteos are "mammal hawks." As you might guess, a bird-eating Accipiter poses a huge threat to a bird, but a Buteo will generally avoid eating birds. As a result, a Buteo will still elicit an alarm, but a different type of alarm. Jumping ahead in the trip a bit, I want to talk about an encounter we had with a Red-Tailed Hawk. The Red-Tailed Hawk is the most common Buteo in Ohio. They, like other Buteos, eat mainly mice, voles, shrews, etc., and avoid birds. Songbirds still don't like Red-Tails, but they know that one doesn't mean an immediate threat. We saw one juvenile Red-Tailed Hawk at Lake Hope. We weren't the only ones to notice him though; several chickadees, a Magnolia Warbler, and a few other birds had found him and were actively mobbing him. They wanted to let the Red-Tail know that he wasn't welcomed there, and the songbirds didn't stop attacking him until he flew away. In this case, the Red-Tailed Hawk didn't cause a Zone of Silence, but simply caused different species to come together to get rid of him.

An Osprey from Old Woman Creek earlier in the Spring. I captured this photo while the Osprey flew over the beach at OWC.

After Irish Ridge, we moved down to Lake Hope State Park, which was right next door. We moved through a scruffy marsh region that transitioned into deciduous forest which bordered the lake proper. This was where we found the juvenile Red-Tailed Hawk I just mentioned, but we also had two other birds of prey. We accidentally flushed an Osprey, a raptor that specializes in eating fish. Later on we heard a Red-Shouldered Hawk calling from the forest. It was a good raptor morning!

Here's the total list (with both locations combined) of species for the morning:

1. Wood Duck
2. Turkey Vulture
3. Osprey
4. Red-Shouldered Hawk*
5. Red-Tailed Hawk
6. Mourning Dove
7. Eastern Screech-Owl*
8. Chimney Swift
9. Belted Kingfisher
10. Red-Bellied Woodpecker
11. Downy Woodpecker*
12. Pileated Woodpecker
13. Eastern Wood-Pewee
14. Eastern Phoebe
15. White-Eyed Vireo
16. Yellow-Throated Vireo*
17. Blue Jay
18. American Crow
19. Carolina Chickadee
20. Tufted Titmouse
21. White-Breasted Nuthatch*
22. Blue-Gray Gnatcatcher*
23. Gray Catbird
24. Cedar Waxwing
25. Tennessee Warbler*
26. Hooded Warbler
27. American Redstart
28. Magnolia Warbler
29. Bay-Breasted Warbler
30. Chestnut-Sided Warbler
31. Pine Warbler
32. Prairie Warbler*
33. Eastern Towhee
34. Scarlet Tanager
35. Northern Cardinal
36. Rose-Breasted Grosbeak
37. Indigo Bunting
38. American Goldfinch*

(Note, * denotes "Heard Only")

Overall it was a great morning, with 38 species I personally observed, including 8 species of warblers! This Thursday I head to South Carolina with the class for an extended 4-day field trip, so stay tuned for a post about that!