Shorebird Migration and Sweden in 2 Days!

Went birding last Saturday morning, briefly before the oven was turned on to 35°C, but not too much was around. A significant increase in Wood Sandpipers and Common Snipe was notable, and there were several huge Lapwing flocks (one with as many as 150 birds), and one of which contained several Common Greenshanks dispersed throughout, discovered first by their distinctive, falling tew-tew-tew flight call, to me reminiscent of Greater Yellowlegs only usually slightly more relaxed (delivered not quite so rapidly). Four Black-necked Grebes (Eared Grebes) were a nice find at Stöhna, as was a distant soaring Honey Buzzard at the same location. Over the past few weeks, there has also been increasing numbers of small flocks and pairs of Cranes found at most locations around Leipzig at least, and a Marsh Sandpiper was reported a week prior at Windischleuba, but was not refound afterwards to my knowledge.

In two days I will be flying to central Sweden, and heading for a two-week volunteering stint at Kvismare Bird Observatory. I believe this will be a great chance for me to assess my potential at doing something I have dreamt of trying for a long time. I love details and the chance to examine birds in the hand would be a great privilege, and knowing that I am helping the birds indirectly by contributing to the mass of statistics collected over the years which lead to population trends for different species over the years can indicate whether attention must be given to certain ecological needs, in order to assure that bird populations can remain strong or if necessary increase back to a stable population. In addition, some the the birds banded/ringed in Sweden will be recaptured in other parts of Sweden, Europe, Turkey or Africa and thus contribute to the growing database of knowledge on migrations of specific species, which also helps us pinpoint where a problem could be occurring if a certain specie's population seems to be in decline.

To check out what is going on at Kvismare, check out their website: Kvismare Bird Observatory. Within the section "projects" one can peruse the plethora of conservation and ornithological related research, such as the monitoring of Marsh Harriers every summer. The statistical results, when available, are displayed here too, like the pretty steady increase in population of breeding Marsh Harriers between 1954(before the observatory existed!) and 2010! Banding (ringing) has been conducted with the same number of mist nets, in the same locations, and during the same time of year since 1961! Their collected statistics have been used in peer-reviewed journal publications and so I am quite reassured that these guys are quite professional, and so I would receive a good initial education from them hopefully. Well, let's see...should at least be fun, albeit tiring a bit, as I now will explain.

I believe I will be waking up quite early (3-4am) to band/ring mostly passerines until around noon when the weather is decent, and when the conditions are right at night, I might get to also try my hand at netting shorebirds (dark moonless nights are the best i suppose, when the mist nets are least visible). I'm excited but also a bit worried about the potential raptors might also get caught in the nets, as I have seen in the past they have had kestrels and sparrowhawks, though quite rarely. Time to be a man I suppose, and get torn up a bit (or just leave them for the professionals).

I plan to post updates daily (or at least every other day), along with some pics of course; I suspect this is one case where my dinky Canon Powershot will not be too disadvantageous at taking decent photos?

Well, have to go start packing or at least make the packing list.

Do Peacocks prefer shade to sun??

New (for me) Butterfly Observation:

The butterfly bushes (Buddleia) which have been nicely planted in several locations around the Fraunhoffer building next to my workplace on the TU Dresden campus, have just blossomed a few days ago in beautiful shades of violet and purple, and today I noticed butterflies on it for the first time, and there were quite a few! I checked them everyday on my way to work, and to my disappointment they have been completely void of any lepidopterans for several days, despite ideal weather! This morning (11:00am) on one well-lit bush there were:

4 Painted Ladies
3 Peacocks
4 Brimstones
1 Cabbage White
2 Small Heaths

During my afternoon coffee break, I checked the bush again, and there were still 3 Ladies, 2 Peacocks and 2 Brimstones (no Small Heaths, and lower numbers of all types), but then I decided to check this pair of bushes which this time of day (4:00pm) are completely in the shade (unlike the aforementioned bush, which was still fully bathed in radiation). To my surprise there were a total of 7 Peacocks between the 2 bushes...and no other species of butterfly! I think from the combination of facts: that there were more than 3 times as many Peacocks on the bushes in the shade (5 on a single bush even!) and that there were no other butterfly species, is quite strong evidence that (at least locally) the Peacock prefers shade or they are more opportunistic than other butterflies in the area. I will continue to check on this and see if some pattern can truly be seen over a longer survey.

OK, so back to BIRDS...

It has been hot and dry the past couple of weeks, although small numbers of waders have trickled in the few areas still holding some water/mud. (Funny thing is I hear they are having the opposite problem over in Cape May: too much water). So two weeks ago (Saturday, July 13) I met Michael in Leipzig, and we checked some flooded field south of Leipzig (Stöhna area) where we had only 3 Ruffs, and a flock of Lapwings (later may have been local breeders). But when we had heard a report of a Parasitic Jaeger/Skua near the border of Thüringia just a bit further south at "Windischleuba", we slowly made our way there all the while keeping eyes peeled for it sounded like it was on the move and would not likely stay at the same location for long. Sure enough, we never had the fortune to cross paths with the Jaeger, but we had a nice Smorgasbord of commoner wader species at Windischleuba, including: 1 Greenshank, several each of  Green, Wood, and Common Sandpipers, and about 10-15 Little Ringed Plovers and 30+ Northern Lapwings scattered all over.

I have been using this relatively quiet birding time to study for oral exams, thesis writing, and preparing for my 2-week stint volunteering at Kvismare Bird Observatory, Aug 9 - Aug 26. This will be my first time trying my hand at serious banding (ringing) of birds, in this case mostly passerines, but also some waders (night) and sometimes a hawk or 2 are caught in the mist nets. They have been banding birds at the same locations for over 50 years now, and so I feel pretty confident that these guys know what they are doing and are very professional. More on that to come in the near future!

Good birding,
SR

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]

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!

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

Review of Locustella Warbler Vocalizations

Late Spring heralds the return of River Warblers (Locustella fluviatilis) to their localized habitats of young deciduous growth along river and swamp edges, after the other two Locustella species, Common Grasshopper Warbler (L. naevia) and Savi's Warbler (L. luscinioides), have already been coming through since late April. Due to inclement weather this weekend, I did not get a chance to search for any in the field, but by casually browsing recordings on Xeno-Canto (http://www.xeno-canto.org) for River Warbler, I discovered they have a quite interesting repertoire of vocalizations, and thought I'd share some points here, along with a comparison with other Locustella Warblers.

Locustella species all have brownish plumage, pointed bills, flat foreheads, and really broad, rounded tails. They are major skulkers of low vegetation, making them often difficult to see; they're more likely to scamper away on the ground than fly out.  But fortunately, 4 of the 5 species reportedly found in Europe (those listed above, and Lanceolated Warbler, a rare vagrant to Europe, usually summering in the Siberian Taiga) give some unique variation on a monotonous, mechanical, insect-like call, which are usually heard at night and in the early morning.

Common Grasshopper Warbler
Of the three species under comparison, this is the most likely to be heard, as they are most widespread; not being as picky with habitat preference as the other two. At Xeno-canto, you'll find that most of the recordings posted have sonograms looking similar to this:

XC134381: (Common) Grasshopper Warbler (Norway by Ingar Bringsvor)

Here is a link to listen: http://www.xeno-canto.org/134381
They all have this monotonous, dry ringing or insect-like whirring. Maybe the pitch (along the vertical axis) varies a tiny bit among individual birds, but always higher than Savi's (see below).

Savi's Warbler
By comparison, Savi's Warblers have higher tempo (frequency) and lower pitched calls: more like a fine buzzing than a whirring. Here is a good example of a sonogram from a typical call:

XC129525: Savi's Warbler (Poland by Matthias Ritschard)

Here is a link to listen: http://www.xeno-canto.org/129525


River Warbler
Now comes the species of the group with (what I find) the greatest repertoire, though some of the calls indeed are probably rarely heard, but perhaps they could be different populations, too.
A typical sonogram looks like:

XC83760: River Warbler Typical/'Type-1' (Czech Rep. by Kamil Cihak)

Here is a link to listen: http://www.xeno-canto.org/83760

Pitch can vary a bit, but usually between Grasshopper (higher) and Savi's (lower). The main distinction of Rivers are the slower frequency which makes it sound like a powerful sewing machine. However, there are also some unusual variations on the modulations, such as this (let's say) "Type-B" sonogram:

XC129502: River Warbler 'Type-2' (Poland by Matthias Ritschard)

Here is a link to listen: http://www.xeno-canto.org/129502

Such saw-tooth modulations create in the ear an uncanny resemblance to an antique (low-powered) car engine! Such recordings have been submitted to xeno-canto from Poland and Sweden. Finally, I'll leave you with 2 more untypical songs I stumbled across just to illustrate the vast variety in this Warbler's repertoire:

XC101139: River Warbler Untypical (Poland by Tomek Tumiel)

Here is a link to listen: http://www.xeno-canto.org/101139

XC80979: River Warbler (Norway by Ingar Bringsvor)

Here is a link to listen: http://www.xeno-canto.org/80979

Lanceolated Warbler

Just for comparison I have decided to add this species at the end. It has a song that most similarly resembles Common Grasshopper Warblers, and according to Svensson, Mullarney and Zetterstrom (SMZ), some rare, aberrant Grasshoppers have vocalizations that are "very similar" to Lanceolated: so if you are in Europe and think you have heard a genuine Lanceolated, listen carefully (or better yet, get a visual and take a photograph to document it). They are regular (annual?) vagrants to the northeast, but extremely rare elsewhere.

That being said, Lanceolateds' song has slightly higher pitch and higher tempo than Grasshoppers'. Supposedly the verses are shorter as well, rarely lasting more than a minute each (sometimes Grasshoppers can continue a verse 5-10 minutes!) Well here is a prime example of a Lanceolated song:

XC83260: Lanceolated Warbler (Sweden by Lars Krogh)

Here is also the link to listen: http://www.xeno-canto.org/83260

As pointed out in SMZ, it has a quality closer to the shuttling River Warbler's than the uniform, dryer reeling of the Grasshopper Warbler.

If you ever have a weekend day with horrible weather, and no other pressing responsibilities, I recommend playing around with Xeno-canto's brilliant site.   ;)

Good birding and listening!

Steve

First Day of Home Visit to Cape May!

This is a belated report with pics from Friday, April 26.
The first full day home in Cape May, to rest and visit family and friends, was of course partially spent out in the field on my home turf where I started birding. I had an amazing reunion with some unexpected bonus birds. I headed to Cape May Point State Park. I fell in love all over again with Common Yellowthroats, Northern Cardinals, Carolina Wrens, and even Laughing Gulls. Nice surprises were 6 species of Swallows (missed the reported Cave though), a single early Blackpoll Warbler, nice close looks at a handsome Palm Warbler (foraging on the ground about 6 feet away!), a flyover Green Heron, a preening Wilson's Snipe hiding along the edge of Bunker Pond, and a Merlin flying high over the pond, along with many other raptors including 2 sub-adult Bald Eagles, and several Broad-winged Hawks. But the raptor of the day, actually, THE BIRD of the day, was an almost unbelievable Swallow-tailed Kite, cruising low over the parking lot of the State Park, heading towards the lighthouse...likely the same bird reported (and highly photographed due to excellent looks) two days earlier, hunting in the field off of Seagrove Avenue, in Cape May Point. Being that there were no other birders around, and I didn't have a working cell phone, I rushed to the Northwood Center (local CMBO store very close by), I found and informed Mike Crewe, and after ~15 minutes  from my initial sighting he sent a rare-bird alert out (KEEKEEKERR). I do not now if the bird was relocated thereafter.

Below I posted some decent photos I took; well, decent considering I only used a Canon Power Shot held up to a scope?...good birding to all!

Great Egret

Forster's Terns

Piping Plover

Piping Plover noticing me!

Snowy Egret

Tree Swallow