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Friday, June 21, 2013

June 15-16 Report: Black Stork, Bee-eaters, & a strange Phylloscopus

There was too much birding activity this past weekend, so I will just give a selection of the sightings this time...

Time: Saturday, June 15
Location: Ratzener Teiche (Ratzen Lakes), near Lohsa (within the Oberlausitz Biosphere Reserve)
Weather: sunny early, with partial cloudiness increasing from 10:00 to cloudy around 12:00. Warm, ~25°C.

Great Bittern: 2-3 (2 heard in different locations, and later 1 flew overhead in a circle and then took off to another distant pond)
Garganey: 3
Common Tern - 6+ (at least 3 pairs)
Coot: 15
Great Crested Grebe: 10-15
Crane: 2
Grey Heron: 1
Osprey: 1
Black Kite: 1
Red Kite: 2
Common Buzzard: 5
Marsh Harrier: 8
Eurasian Kestrel: 2
Long-tailed Tit: 13 (single flock in Lohsa)
Yellow Wagtail: 1
White Wagtail: x
Skylark: x
Reed Bunting: 2
Yellowhammer: x
Cuckoo: 2
Red-backed Shrike: 2 (a pair)
Penduline Tit: 4 (found one nest)
Chiffchaff, Blackcap, and Willow, Eurasian Reed, and Great Reed Warblers: many

In the evening, after returning to Dresden (and taking a short break), Ashwin and I headed to Dresden Neustadt, on the north shore of the Elbe. A fellow American birder, living and working in Dresden for the moment, who found my blog and contacted me after arriving in Dresden, let me in on the location of a Tawny Owl roost in a hole of a large tree on the grounds of the "Japanese Palace". Thanks to the map he sent us, we had no problem locating the gorgeous, red-phase Tawny just before dusk, two days prior, and even enjoyed watching it take of for an evening buffet!
On this evening around 8:30pm, about an hour before getting dark, we found the owl perched in the same spot, but this time Ashwin had brought his scope and camera. Our friend and colleague at the lab, Ahmad Omar, joined us to enjoy the owl and practice photography. One minute we were not keeping an eye on the owl, chatting, and then the next minute we go to check, and it wasn't there...and like before, it probably went right over our heads!
Unfortunately I don't have any picks at the moment, but keep checking in the near future for some nice photos of Tawny (the ingenious name we decided for the bird).

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Time: Sunday, June 16
Location: area around Werbelin Lake, north of Leipzig
Weather: cloudy and cooler than previous day, ~15-20°C.

Black Stork: 1 soaring bird, an overdo LIFER!
Red-necked Grebe: 4 (2 adults+2 juveniles)
Lesser Black-backed Gulls: 5
Mediterranean Gull: 20+ pairs!
Little Ringed Plover: 2
White-tailed Eagle: 1
European Bee-eater: 6 gorgeous birds, plu-pluing overhead at a Sand Martin colony by an old coke mine.
Nightingale: 1 heard
Red-backed Shrike: 4
Grasshopper Warbler: 2 dueling (duetting?) at same location.
Linnet: 2
Corn Bunting: 3, FOYs

Also interesting was a bird which gave a song, delivered several times, that began like a Chiffchaff and ended with a downward, spiraling Willow Warbler song! Upon further investigation, Ashwin found this site, which is a nice review of Phylloscopus warblers which can switch songs in various ways (4 examples given, with further links). I think the bird we heard very well fits the description of "Examples 2 & 3: Willow Warbler's song incorporating rapidly delivered Chiffchaff-like notes". Here is a link to an example of a similar mixed song uploaded on Xeno-canto.org, from Germany also. Unfortunately we did not find the bird, as it was quite far off and did not stick around or long. But it seems likely it was a Willow warbler singing with Chiffchaff-like notes.
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And now for a few bird pics from Saturday:


Penduline Tit nest...aint it adorable?! [photo by Ashwin Mohan]
Ashwin enjoying his new scope, id-ing a distant tern.

the Great Bittern that circled directly over our heads (like it was checking us out), and then made a bee line to a another distant lake/pond. [photo by Ashwin Mohan]


Thursday, June 13, 2013

Odyssey to the Ortolans

This past weekend presented the first decent weekend-weather since I returned to Germany from my US vacation, and so my bins were definitely calling me to grab them and head out to the field asap...
Unfortunately due to the worst flooding in central Europe since 2002, pretty much all the birding areas near Leipzig  (with lakes) became temporarily impenetrable. So Ashwin Mohan and I agreed that this would be a perfect time to attempt an adventure: we had read in the German book of birding locations in East Germany that there were 2 locations in eastern Saxony (near Görlitz and the Polish border) where Ortolan Buntings (reliably) breed, and this bird (rare in the rest of Saxony) would be a lifer for both of us. One location was so vast, that without a car it would have been futile to search for Ortolans. Fortunately the other location, known in the book as "Talsperre Quitzdorf", is a huge lake with surrounding mixed woods and wild, overgrown fields.

After a 2 hour journey on 2 trains and a bus, we arrived around 8am in the nearby town called Niesky (yes, we were still in Germany, just about 23 km northwest of Görlitz), and continued to hike downhill out of town about 1 km (less than a mile anyway) and we found a dirt path starting from a busy road and going through woods on the left side of the path (a mixture of evergreens and deciduous trees, including birches) and a narrow clearing  (full of tall grass and shrubs) with woods continuing beyond it to the right. We heard the usual morning chorus including several Chiffchaffs, 2 Blackcaps, and a laughing Green Woodpecker. After about 10 minutes walking we came to the edge of the woods, which bordered some nice wild fields to the right of the trail and plowed fields on the left. Soon we started hearing the rising trill-like call of a Yellowhammer; not the bunting species we were after, but a vibrant yellow-headed male perched on a nearby dilapidated wooden blind in the middle of the field was a nice start.

The book mentioned that Ospreys nest here, and sure enough, they were right; on top of a power line tower, in the middle of the plowed field to our left, was a huge, organized pile of sticks and 2 dark figures. One of the pair of adults was standing inside the nest, and appeared (as we hoped) to be feed recently-hatched chicks (we couldn't be 100% sure however as the nest was too high off the ground to see small chick heads), and the other was preening its feathers from a perch on the edge of the tower, a few meters left of the nest. The first interesting observation was that the nest was built inside some sort of "bowl", constructed from metal railing; I suppose Ospreys (probably the same pair even) have been nesting here so long that locals erected such a container in hopes to entice the birds to return in subsequent years to nest? It was also a revelation to me to see one of them, a little while later, gliding low over the field and pouncing on mice in the field, having grown up at the seashore, where all the Ospreys I've seen over the years nested in marshes and only caught fish from bodies of water, such as lakes or just off-shore, near the surf. I've read that this has been observed before by birds with no other choice, i.e., when no fish is available. Okay, but the strange thing was that, in fact, there were several small ponds and one big lake very close by...?
Even the German name for this bird, Fischadler, means "fish eagle", so it was interesting to watch such atypical behavior.

I should also mention that we had the chance to get nice looks at the Ospreys with Ashwin's new scope! There is a (relatively) new company we heard about from Michael Schulz (our Saxon birding mentor) called DD Optics (after the acronym for Dresden seen on license plates!) where they were selling some decent optics at very affordable prices, and Ashwin purchased the Pirschler HDX 15-45x60 S (angled eyepiece) along with a tripod: I must say that, for the price, it has very clear resolution and zoom. I imagine he must be very happy with his new toy!

Anyway, so back to the trail through tree-lined fields, which looked like prime habitat for Ortolan buntings, from what I read in SMZ: "Breeds at lower levels in agricultural country with patches of trees and deciduous copses, in open wooded pasture and in clearings..." According to the Saxon birding book, they bred along the same path, just west of the Osprey nest (in the direction we were heading). Sure enough, it wasn't long before we heard a deeper, slower and less-accelerating ringing trill, with a distinctly lower final note than that of Yellowhammers...Ashwin and I turned towards each other, wide-eyed in the realization that this could be the bird we had hoped to find, but surely not guaranteed. You see, we had spent a good part of the long train ride from Dresden listening the songs and calls of this bird from my mp3 player. It turned out to be one of those rare, perfect opportunities to do a comparative study of birdsong (one of my biggest fascinations, as you would have no doubt guessed already if you read my last two posts!), as both the Ortolan and a Yellowhammer were duetting from opposite directions! It was like the auditory equivalent of finding a Short-billed and Long-billed Dowitchers probing together in the same mud flat. Or for the European birder reading: finding habitat where both Willow Warblers and Chiffchaffs coexist, so you could directly compare those primary projections?

Then, suddenly 2 bunting-shaped birds flew out of a tree along the trail ahead of us, and dropped into the field, disappearing from sight in the meter-high grass. We waited, not hearing any song or call notes, for several minutes (seemed much longer at the time), and finally one flew out and disappeared back into the tree. By the song he heard coming from this direction, and by elimating other possible species which we could recognize more readily, I was quite confident that the bird was an Ortolan. An additional reason was the behavior of the bird: flying from trees to field, heading straight for the ground (they forage mainly on the ground according to SMZ), and acted quite wary of us (SMZ says "rather shy and wary, quick to take cover"). Just when it was starting to become frustrating, the other bird sprang up and perched on a blade of tall grass. It indeed was an Ortolan bunting with that cream-colored Fu Manchu moustache (stripe) and throat on an otherwise greenish-grey head, light eye-rings, contrasting orange-brown belly, buffish-pink bill and legs. It was a shame neither of us had our cameras (I could have attempted some amateurish digiscoping at least). But all too soon (about 15-20 seconds in fact) this bird flew the coup as well, disappearing into one of the leafed-out oaks skirting the path, leaving us thirsty for more. Latter on we only saw a replay of the same scene, only without either bird perching anywhere (clearly) visible. Oh well, I think we should come earlier next time on not such a hot day.

Here is a map showing where we were with respect to Görlitz:


Other birds of interest we came across on this leg of the journey included at least 2 Common Whitethroats (one was singing its heart out from halfway up one of those power-line towers; quite atypically high!), 3 Black Kites, 2 Red Kites, a Common Buzzard, and a distant flow of 5-10 Northern Lapwings.

We turned around and headed back to the woods, where he took a different trail that headed towards the lake. Here we heard a Raven call, and most interestingly the first (of eventually three) juvenile Greater Spotted Woodpeckers calling from its nest in a nearby birch tree. We ventured off the path a short way, and we eventually converged onto the location of the crying young woodpecker; it wasn't that easy due to the oscillation in volume of the bird's calling from both inside the cavity, and when protruding its head outside. The bright red forehead was visual evidence that this bird was indeed a juvenile, waiting for lunch to be delivered. Now it really felt like June.

When we reached the edge of the lake we did not have much time; if we had brought bikes (and surely we will next time), it would have been much more practical to attempt the whole 16km circumference of the lake. However, the little stretch of lakeside path we did take was significantly fruitful and I will just finish with a list of highlighted finds:

Black Woodpecker - one heard calling, and later another (probably different individual) was drumming.
Golden Orioles - everywhere in there typical deciduous, riparian habitat
Icterine Warblers - 2, first-of-the-year (FOY) for both of us, we had nice views of both, though their loud mimicry accented with their unique raspy, shrill notes were the first indications of their presence.
Spotted Flycatcher - 1, also a FOY, and nice surprise.
Garden Warbler - 1, yet another FOY.
Hobby - 1, cruising for dragonflies overhead, and our 4th FOY (including the Ortolan lifer!)
Hawfinch - 1

All in all, we had a great dry and mostly sunny day (a thunderstorm started to roll in as we commenced the return trip to Dresden), with many excellent birds, including many FOYs and 1 lifer even (and a beautiful one at that)! There still is much potential and much to learn about the birds in Saxony, Germany. It deserves better credit; the reason not more rarities are reported is mostly due to the lack of active birders here looking around!

The upcoming weekend weather report looks promising; hope the water level will have dropped enough to head back to Leipzig one day and look for some Locustella warblers and terns.

I bid you all good weather and good birding!









Sunday, June 2, 2013

Influence of Habitat and Morphology Variation on Birdsong Evolution (from WCSP to Locustella)

Well, the rain has not ceased at all (it seems) in the past week; and I believe it is not a far stretch to label this Germany's new monsoon season!
Not being able to go wander the fields for the second weekend in a row during the tail end of spring migration has got me kinda bogged down. But being stuck indoors (especially since I'm still recovering from some spring allergy-related cold-thingy I first caught 3 weeks ago at home in Cape May, and mainly due to the weather, not been able to shake fully yet), I have spent some time thinking about my last post, and I started to wonder: how did the different species of Locustella warbler evolved their different trill songs?

The first idea I had, which seemed logical, was that the environment in which a bird lives (its surrounding habitat), must play a significant role in shaping the quality of its song(s) and calls.

My curiosity led me to a google-search frenzy, upon which I stumbled across one intriguing paper, whose pdf copy is publicly available here:
Ecology Shapes Birdsong Evolution: Variation in Morphology and Habitat Explains Variation in White-Crowned Sparrow Song (Derryberry 2009)

It was refreshing to read a technical paper that was actually both interesting AND comprehensible!
Anyway, this paper presented the first evidence of variation of song with variation of morphology and habitat within a single species (White Crowned Sparrow (Zonotrichia leucophrys) in this case).

The main findings of the paper include that both trill rate and minimum frequency decreased over time in populations in which vegetation density increased. This makes sense to a condensed matter physicist, if one allows a ridiculous oversimplified generalization of the situation: habitats with dense vegetation are like "lattices with many scattering sites", where sound waves (or any waves, generally speaking) can be reverberated and attenuated in an amount proportional to the frequency. Therefore one expects that birds with slowly repeated notes and lower frequencies (least attenuation) will transmit their songs better in those territories, thus their genes will remain in the gene pool, and so on...at least that is one theory that seems logically sound to me, and maybe even true in many cases. ;)

Besides habitat, though, she also discussed how morphology can shape a bird's song. For instance there is a limit to how fast a bird can open and close its bill depending on the size of the bill, so longer and/or deeper bills have a maximum frequency due to mechanical constraints of the bill, and so the evolution of bill size may influence the evolution of birdsong. Birds with larger bills are also predicted to produce slower trills with narrower bandwidths of frequency (i.e., "lower performance" songs)

Now back to my initial quandary. On the one hand when one considers the habitats that (Common) Grasshopper, Savi's, and River Warblers generally occupy, one sees a relation between trill frequency and vegetation density; namely, frequency is inversely proportional to density. For instance, Savi's has the lowest frequency trill and is also usually the skulkiest, singing from deep in the reeds...whereas on the other end of the spectrum (literally in this case) you have the Grasshopper's variable-but-usually-highest frequency trill, and he usually sings from exposed perches, like from a branch of a short tree on the edge of a reed bed. River warbler falls in between both in trill frequency and in density of habitat vegetation, I believe.

On the other hand, Savi's has the fastest tempo of individual notes, so that the trill is morphed into a fine buzz (to our ears at least, which cannot pick up the individual modulations), which would logically seem unfavorable in dense vegetation. River Warbler, on the other hand does have relatively slow tempo, so that one can hear the frequency modulations well. So it seems that, for Savi's at least, there must be other factors that have evolutionarily shaped its song.

So then I wonder about bill sizes. I have not seen bill size differences emphasized (or even mentioned) in any field guide as a character for differentiating these species, but just looking at the drawings in SMZ. It seems that the bill length, in relation to overall body length, is almost identical for Savi's and River Warblers, but slightly smaller for Grasshopper. Especially considering that Grasshoppers are the smallest of the three (L 12.5-13.5cm according to SMZ), this seems to indicate that they have the shortest bills, meaning they should be able (mechanically) to produce the highest frequency, by being able to open their mouth the widest...and that is what we do indeed hear! On the other hand, Savi's is next largest (L 13.5-15cm) and Rivers are usually the largest (L 14.5-16cm). This means, if bill-length-to-body-length ratio is the same, Savi's should have a shorter bill and thus be able to produce higher frequency than River...but then why don't they? Maybe for Savi's, unlike some other species, the females prefer to select males with lower trill frequencies?

When one thinks of bill evolution, the example that first comes to mind is Darwin's Galapagos Finches, right? Here, due to isolated populations with different food sources available, evolution led to the proliferation of various bill sizes, and thus splitting of species into subspecies (and later on, after more genetic divergence, splitting into completely different species). With some birds though, it seems another mechanism is behind the diversification of bill sizes/shapes...sexual selection. Because of this, males which need their courtship songs to be transmitted over as long a distance as possible, may need to vary the tempo and frequency of their song due to vegetation density constraints, as mentioned above. This, then in turn, favors certain bill mutations, and thus over many generations favors shorter or larger bills.

I would love to hear from anyone, such as a bander/ringer, who has done bill length, width, and/or depth measurements on these three species, and whether my hypothesis is correct. To the best of my knowledge (really to the best of my google-searching ability), there are no reported findings, similar to the above-linked paper, for Locustella warblers, so I think it would be interesting for recreational birders to look into, and even a nice topic for a budding PhD student of ecology/evolutionary biology! :) 

Good (dry) birding everyone!
Steve