Tuesday, October 29, 2013

Prairie Merlin: overlooked in Central America?

Sunday morning, I photographed this female or immature Prairie Merlin (Falco columbarius richardsonii) behind our house, on a dirt road that leads to the top of Cerro de Hula. In this plumage they are similar to Taiga Merlins (ssp columbarius), the expected ssp in Central America, but subtly differ in the following aspects: paler overall; rufousy thin breast streaks on a white breast; malar stripe nearly absent; paler mantle. The overcast weather made for a very dark photo. In the field, the bird looked pale.

Two years ago, there was an adult male on the campus of Zamorano University, about 27 km from Cerro de Hula. The weather was about the same that day, i.e. overcast and drizzly, but adult males are a little easier to identify. See this blog entry for a detailed description and photos of that observation, and for a discussion of the regional occurrence of the various Merlin subspecies.

There’s one other record on eBird for the region, from Belize two years ago. That bird was photographed only after it had flown further away from the observers. Although the photo apparently was too distant to be conclusive, the description is convincing. Interestingly, that observation was 5 days apart from ours in Zamorano. The Zamorano bird was not seen again that winter, despite regular coverage. I wonder if our Cerro de Hula bird will stick around.

Prairie Merlins are thought to winter no further south than northwest Mexico, but these reports indicate that small numbers may winter further south than previously thought.

Saturday, October 19, 2013

Cool yard bird: Black-billed Cuckoo

Lately, I have had cuckoos on my mind. There was a week or so last year when you couldn't bird just about anywhere in central Honduras without seeing at least one of the Coccyzus cuckoos – usually the more common Yellow-billed Cuckoo. But that was late September / early October, and after mid-October this year, I thought the window was closing on them, and I wasn't going to see one this year.

Then suddenly there was this hatch-year Black-billed Cuckoo in my own backyard this morning! Probably not a rarity in Honduras, where the entire North American population must pass through in migration twice a year, but all the same a species rarely reported, due to its secretive habits.

Now I need to find me a Yellow-billed Cuckoo.

27 October 2013 postscript:
Eight days later and 200 m further, Roselvy and I found an immature Black-billed Cuckoo today! According to eBird, nobody else is reporting this species in Central America this fall, and here we are with two immature Black-billed Cuckoos. Are they the same bird? It seems likely, yet I'm not 100% convinced that they are. Here are some photos of today's bird, seen along the dirt road that goes up to Cerro de Hula (Honduras). As I said, this is roughly 200 m from our backyard.

We're looking at the other side of the face, compared to last week's bird. But note the distribution of the darker color on the (lower) mandible. Here's a photo in which the bird turned its head:

Compare that to the bird at the top of this post, and tell me if it's the same bird or not.

I never did find that Yellow-billed Cuckoo...

Friday, October 11, 2013

Raptor migration in the Gulf of Fonseca

Swainson's Hawks migrating over San Lorenzo, Valle
Exactly one year ago, on 10 October 2012, I observed a large raptor flight in San Lorenzo, Valle. Thinking the same phenomenon would likely be visible at the same location a year later, Roselvy and I went down to the southern lowlands yesterday, where we visited the same site, and a few nearby birding spots.

Sure enough, when we got there, we found a sizable raptor flight in progress. Like last year, the flight consisted mostly of Turkey Vultures and Swainson's Hawks, with modest numbers of Broad-winged Hawks and a smattering of other species present. Unlike last year, most lines were far away from the salt ponds complex La Ostia, where we started our birding, so there we focused on the shorebirds present.

Wilson's Plovers
Those too were nearly the same species and number as last year! Last year I missed Stilt Sandpiper – yesterday two were present; and I missed (western) Willet – yesterday three were present. We missed Solitary Sandpiper yesterday, but apart from those differences, we observed the same species in more or less the same numbers as exactly one year ago.

Stilt Sandpipers
After an hour and forty-five minutes in oppressive midday heat, we bailed and looked for food, shade and a better view of the raptor flight at Restaurante Brisas del Golfo. There we observed a raptor line directly overhead, one further south crossing the Gulf, and one further inland over the hills. Although we didn't count, we estimated about 10,000 Turkey Vultures, 6,000 Swainson's Hawks and 500 Broad-winged Hawks to have been passing us during the one hour and forty-five minutes we spent there.

Swainson's Hawks
A final stop at nearby shrimp farm Culmavic added migrant Chimney Swift and American Kestrel to our list, as well as the locally common Clapper Rail.

Tuesday, September 17, 2013

More small hummingbirds

Bumblebee Hummingbird
Very similar to the Wine-throated Hummingbird of the previous entry is Bumblebee Hummingbird, which replaces it north of the Isthmus of Tehuantepec. I myself went north of the Isthmus of Tehuantepec last week, on a business trip quite similar to the one I undertook in March of this year. This time I visited the Veracruz River of Raptors project, a project I worked for in 2008, 2009 and 2011. I got one day of birding in the pine-oak forests of La Joya in, just west of Xalapa. Bumblebee Hummingbird is locally common there.

Unlike the male Wine-throated Hummingbird, which perches conspicuously and vocalizes constantly, flashing his brilliant gorget in all directions, the male Bumblebee Hummingbird is more low-key, and apparently perches inside the vegetation, where it was difficult to find. Every once in a while, a conspecific would fly by and mouse-like squeaks emanated from the vegetation, while the producer of those squeaks remained invisible. They were more easily seen when feeding, moving slowly but constantly like a bumblebee from flower to flower.

Sparkling-tailed Hummingbird
A similar feeding style is seen in Sparkling-tailed Hummingbird. This morning I photographed this female as it fed quietly in a flowerbed on the top of Cerro de Hula (Honduras).

Monday, September 2, 2013

Wine-throated Hummingbird

Many migratory birds that breed in the United States and Canada have finished breeding and have started to show up in Honduras recently. Many residents have also finished their breeding season, and juveniles of those species which retain a juvenal plumage for a while (like Rusty Sparrow, Eastern Bluebird and Bushy-crested Jay, to name a few) now seem to be everywhere.

For one group of residents – the nectarivores – the breeding season is just starting here in Honduras. Both hummingbirds and flowerpiercers are easily found these days, because many of them are quite vocal and active. Some species, like the Wine-throated Hummingbird pictured above, spend much of their time displaying at leks, and produce an endless series of chips when perched on a favorite branch, or a surprisingly musical song when hovering in front of a female. 

While chirping from an exposed perch, the male often puffs up his extravagant gorget, which glitters bright magenta from some angles, but shows a duller green or a dark wine-red from other angles.  

Posturing also forms part of the display of this species. Every once in a while, whenever a conspecific flew past (my feeling was males mostly, but I'm not 100% sure), the displaying perched male would spread his tail and raise his wings, but remain perched, apparently to impress another male, or perhaps to impress the watching female.

We observed these Wine-throated Hummingbirds in La Tigra National Park, near Tegucigalpa, last Saturday. While hummingbirds and flowerpiercers can be hard to find at times, their songs are now frequently heard, and watching their displays is fascinating. We also observed several male Green-breasted Mountain-gems dueling fiercely in mid-air.

Friday, August 9, 2013

Cerulean Warbler

Fall migration is truly underway here in Honduras also, not only with a good variety of shorebirds present (Roselvy and I had good shorebirds last Monday), but with the first warblers also showing up now.

This afternoon, on a brief outing on the slope of Cerro de Hula, right behind our house, we found a first fall male Cerulean Warbler feeding in a free-standing oak surrounded by farm land. Cerro de Hula has some notable residents, including Ocellated Quail and a sizable population of Sedge Wren, but things really get interesting in migration. Last year in spring migration I had a Cerulean on the same dirt road going up to the top of Cerro de Hula; that was my first in Honduras. Today, number two.

Cerulean Warbler is an early migrant, with the first individuals reaching the South American wintering ground in August. The eBird map shows birds just starting to arrive on the Gulf coast; our record is the first in Central America this fall.

Sunday, July 28, 2013

Fonseca Rails

I've written here a couple of times before about the Clapper Rails of the Gulf of Fonseca. I've even written a short note documenting breeding in Honduras for El Esmeralda, the bulletin of the Asociación Hondureña de Ornitología (ASHO).

Clapper Rail was first found and documented in the Honduran part of the Gulf of Fonseca in 2010, by Robert Gallardo and Mayron Mejía. In 2012, the species was first reported from the Nicaraguan side of the Gulf by Jens Olek Byskov, Salvadora Morales, Orlando Jarquín and Juan Carlos Alaniz, and in 2013, Oliver Komar, Roselvy Juárez and I found it on the Salvadoran part of the Gulf.

I corresponded about these birds with James Maley, a rail researcher from the University of Wyoming, who expressed an interest in sampling specimens from this population. Together, we wrote a research proposal which we submitted to ICF, the Honduran governmental organization in charge of research permits. James is here right now and we have just finished a week of field work, in which we collected a total of 8 specimens. This series will be used for a taxonomic description of this population.

This week, with the help of playback, we got a sense of how common this species really is in the Gulf of Fonseca. For example, one transect that was about 450 m long had an estimated 15 pairs and 3 single individuals – that's 33 individuals, on a relatively small stretch of mangrove. In some parts, densities seemed so high that we wondered if Clapper Rail was perhaps the second most common species there, after (Mangrove) Yellow Warbler! While few birders or biologists have seen this species in Honduras, most locals that we talked to in the salt ponds and shrimp farms of the area knew the bird well. One of them assisted us with field work, and he told us those birds have been common there for as long as he could remember – at least 40 years!

Remarkable then that this population, apparently never rare, went undiscovered for so long. Given available habitat and abundant food resources, there are probably thousands if not tens of thousands of these rails in the Gulf of Fonseca.

Monday, July 15, 2013

Two tropical birds: one expected, one not

Last Saturday, Roselvy and I set out to find Long-tailed Manakin and Blue-tailed Hummingbird in Choluteca, two species that we hadn't observed yet this year in Honduras. While we easily found those species in a community called La Fortuna, situated in humid middle elevation forest among coffee and mango plantations more or less in the middle of the department of Choluteca, I did not get any (reasonable) photos.

I did get photos of Tropical Pewee (top) and Tropical Gnatcatcher. While the former was expected and indeed quite common there, the latter wasn't really on our radar screen for that part of the country. 

When we heard a descending trill, we didn't immediately recognize it. Locating the singer was not difficult, and upon seeing a gnatcatcher producing that song, I instantly realized it had to be Tropical Gnatcatcher. It occurs in eastern and northern Honduras, and is no doubt common in many areas, but these are exactly the areas far from where we live, where we haven't done that much birding yet.

For us, this was a cool and unexpected find, well outside its known range.

Monday, July 8, 2013

Great Swallow-tailed Swift calls

Yesterday I recorded Great Swallow-tailed Swifts vocalizing near El Obraje, in the Honduran department of El Paraiso. I just uploaded these calls to Xeno Canto, and as far as I've been able to ascertain, these are the first public recordings of this species.

I went to El Paraiso yesterday morning with Roselvy Juárez, Oliver Komar and Ruth Bennett to bird another data-deficient eBird quadrant. It was a pleasant and productive morning of birding, as we found 92 species for the quadrant, including Little Tinamou, White-tailed Hawk, Rufous-tailed Hummingbird, Fork-tailed Flycatcher, Lesser Greenlet, Rufous-and-white Wren, Tropical Parula, and Giant Cowbird. 

Chantler and Driessens, in their 1995 book "Swifts: a Guide to the Swifts and Treeswifts of the World" cite Edwards' 1989 book "A Field Guide to the Birds of Mexico and Adjacent Areas", which describes the call of the Great Swallow-tailed Swift as "a plaintive tyee-ew". Yesterday, one of the individuals in a flock of five gave that call, illustrated in the following recording:

Howell & Webb (1995) give another description of a Great Swallow-tailed Swift vocalization, noting a "reedy, screechy chipping, including a distinctive, accelerating series, ending emphatically, may recall Pileated Flycatcher song: kree kri-kri-kri-kri kree-kreeh!" One of the birds yesterday also gave that call, illustrated in the following recording:

I recorded these calls from a single-species flock of five individuals, at an elevation of 1000 m, as they flew over us. The habitat there was montane semi-humid forest, with some shade coffee plantations, and steep rocky canyons.

Until now, neither Xeno Canto nor the Macaulay Library had any recordings of this species, which appears to be fairly common in the highlands of Honduras.

Cited literature:
Chantler, P. & G. Driessens. 1995. Swifts: a Guide to the Swifts and Treeswifts of the World. Pica Press, Sussex.
Edwards, E. P. 1989. A Field Guide to the Birds of Mexico and Adjacent Areas: Belize, Guatemala, and El Salvador, Third Edition. Corrie Herring Hooks Series.
Howell, S. N. G. & S. Webb. 1995. A Guide to the Birds of Mexico and Northern Central America. Oxford University Press, Oxford.

Thursday, July 4, 2013

eBirding southern Honduras

female Rose-throated Becard
Roselvy and I targeted another data-deficient eBird quadrant yesterday morning, trying to fill gaps in our knowledge of bird distribution in southern Honduras. We did seven complete checklists of about twenty minutes each (plus one incidental list) in a quadrant just north of Nacaome, in the department of Valle, where most of the habitat is Pacific dry forest interspersed with corn and bean subsistence cultivations, small mango orchards here and there, and small-scale cattle farming. Some of the birds we found are uncommonly reported from Honduras (such as White-bellied Chachalaca, or Thicket Tinamou), while others we found in higher than usual densities (like Striped Cuckoo). In total, we dug up 68 species for this quadrant. Not bad, considering all winter visitors aren't there right now. We'll come back for them later.

the 'empty quadrant' we visited yesterday

We stopped at three different river crossings, and thus likely biased our counts toward waterbirds. This explains three kingfisher species on our list (Ringed, Amazon and Green), and the high frequency of riparian birds like Rose-throated Becard (present on 70% of our checklists yesterday). Cuckoos appear to be genuinely common in this area, with Groove-billed Ani on 85%, Striped Cuckoo on 70%, and Squirrel Cuckoo and Lesser Ground-cuckoo each on 40% of our checklists. The only species present on all of our seven checklists yesterday was White-tipped Dove. Curiously absent was Black Phoebe, diligently looked for but not found, while Social Flycatcher only appeared on one out of seven checklists – normally a more common species in disturbed areas.

Sulphur-bellied Flycatcher

Our best birds yesterday included Collared Forest-Falcon, White-bellied Chachalaca, Thicket Tinamou, and Green-breasted Mango. Soon we'll try to hit the quadrant above it, to continue eliminating as many holes on the map as we can. The area around Tegucigalpa is starting to look pretty good!

Sunday, June 2, 2013

Great Swallow-tailed Swift

Great Swallow-tailed Swift
Although Chantler & Driessens in their Guide to the Swifts and Treeswifts of the World (1995) describe it as "one of the rarer species", Great Swallow-tailed Swift is regularly reported from Honduras. Monroe (1968) considered it a common resident in the interior mountains of Honduras, and around Cerro de Hula, half an hour south of Tegucigalpa, we see this species occasionally. Last fall, it was regular (daily) for a couple weeks at the very top of Cerro de Hula, with sometimes up to 8 individuals together. Another spot where we have been seeing this species every now and then is from a dirt road behind the community of El Tizatillo, about 15 minutes south of Tegucigalpa.

While most sightings of Great Swallow-tailed Swift are of birds flying high and fast, we had a pair flying rather low and slow this morning at El Tizatillo. Despite the poor lighting, I was able to get a few pictures of this cooperative pair. The apparent damage in this individual's right wing did not seem to hamper it in flight.

At some point, we saw one of them was carrying something in its bill, but we couldn't quite see what. Could it be nesting material? [Edit: I now think this is simply a throat bulging with food.]

Great Swallow-tailed Swift is found from southwestern Mexico through Guatemala, northern El Salvador and the central highlands of Honduras, to northwestern Nicaragua.

Cited literature:
Chantler, P. & G. Driessens. 1995. Swifts – A Guide to the Swifts and Treeswifts of the World. Pica Press, East Sussex.
Monroe, B. L. 1968. A Distributional Survey of the Birds of Honduras. Ornithological Monographs No. 7, American Ornithologists' Union.

Thursday, May 23, 2013

Baby boids!

recently fledged Plumbeous Vireo

Down here in Honduras, 'tis the season when young birds are everywhere. This is a recently fledged Plumbeous Vireo, one of the members of the Solitary Vireo complex that is resident here. Its parents look more like Cassin's Vireos than northern Plumbeous, but that is how they remain classified for now. With some genetics work, this Central American population may one day be elevated to species level.

On a short walk I encountered a couple of Plumbeous Vireo families, now more easily detected because of the constant begging calls that the fledglings produce. 

these feathers were all grown at once, and thus – although new – are of poor quality

I photographed this bird a couple of days ago in the pine-oak forest of San Buenaventura, a small village 30 minutes south of Tegucigalpa, close to where we live. Also present there were recently fledged Eastern Bluebirds.

recently fledged Eastern Bluebird

This bird's dad was singing from the top of a tall, nearly dead pine tree. I recorded his song and posted it on Xeno-Canto:

Sunday, May 19, 2013

Lesser Nighthawk breeding in Honduras

Incubating female Lesser Nighthawk
The Lesser Nighthawk is a common migrant and winter visitant in Honduras, occurring in the lowlands of both coasts and in the interior highlands to 1,200 meters. It prefers arid situations and is most abundant along the Pacific coast and in the arid interior valleys. It is also a regular migrant in the Bay Islands and the Cayos Cochinos. There is no direct evidence that the species breeds in Honduras, although several specimens have been secured in June (Eisenmann, 1963: 165).

Burt Monroe, 1968, A Distributional Survey of the Birds of Honduras

Twenty-seven years later, Howell & Webb (1995) did not know much more ("exact distribution poorly known"), and their map shows it (incorrectly) as a breeding resident in the interior of northern Central America, from Mexico through Guatemala to western Honduras. Juárez & Komar (2012) however described breeding of this species on the beaches of El Salvador and Guatemala, away from the interior. They noted that breeding of Lesser Nighthawk is still not reported for Honduras.

Yesterday, while in the company of one of these authors, I almost stepped on an incubating Lesser Nighthawk down at one of the salt ponds in the Honduran part of the Gulf of Fonseca. Although a brown bird against a green background should have been obvious, we just weren't prepared I guess. 

Nest of Lesser Nighthawk

As the female flew off, a little scrape on the ground revealed two eggs. We decided to quickly take photos and then leave, to let the female go back to her nest.

Can you find the nest?

When we passed again an hour later, we found her back on her nest brooding her eggs. This time I took some photos of the bird on the nest, but was careful not to flush her again.

Although near the coast, the habitat here is notably different from breeding habitat on the beaches of El Salvador and Guatemala, where the birds were found breeding on white sand close to the high water line (Juárez & Komar 2012). This Honduran nest was approximately 20 m from a shack used by the supervisor of the salt pond complex, and on short grass, about 7 km away from open water.

At times we have seen large numbers of Lesser Nighthawks at dusk in the lowlands of the Gulf of Fonseca. Are these birds perhaps breeding in the salt ponds here and there, and on the beaches of Choluteca, between Punta Ratón and Punta Condega?

Cited literature:
Howell, S. N. G. & S. Webb. 1995. A Field Guide to Birds of Mexico and Northern Central America. Oxford University Press.
Juárez-Jovel, R. C. & O. Komar. 2012. Nuevo sitios de anidación para el Chorlito Piquigrueso (Charadrius wilsonia) y el Chotacabras Menor (Chordeiles acutipennis) en El Salvador y Guatemala. Bóletin SAO, Vol. 21, 6 pp.
Monroe, B. L. 1968. A Distributional Survey of the Birds of Honduras. Ornithological Monographs No. 7, American Ornithologists' Union.

Friday, May 10, 2013

Spring shorebirding in Honduras

Buff-breasted Sandpiper

This second week of May, the shorebirding has been rewarding down here in Honduras. We were alerted to this by our friend Oliver, who found Baird's Sandpiper, Pectoral Sandpiper and Wilson's Phalarope on the Zamorano University campus last weekend. On Monday, we swung by and observed those birds with him.

Wilson's Phalarope Monday at Zamorano University campus

We figured, however, that the southern salt ponds in the Gulf of Fonseca should be productive as well, so Wednesday morning we set out to bird that area. In our haste to be in the field as early as possible, before the infernal heat of midday, I forgot my camera. I'm sure any photographer will back me up when I say that it is precisely at such times that great photo opportunities abundantly present themselves.

Pectoral Sandpipers with a Buff-breasted Sandpiper

A cattle pasture next to extensive salt pans had a large flock (150+) of Pectoral Sandpipers, with four Buff-breasted Sandpipers and four Baird's Sandpipers mixed in. In the salt pans themselves, we found scattered little flocks of Wilson's Phalaropes, one large peep flock that consisted of 93 Semipalmated Sandpipers and 8 Westerns, some scattered Leasts, as well as another Buff-breasted, some Pectorals, scattered Stilt Sandpipers, Semipalmated Plovers and various other shorebirds. The best bird there was a White-rumped Sandpiper, a first for me in Honduras. We had great looks at all these birds, but no way to document them other than with field notes.

The next morning, we went back there, this time armed with a camera. Upon arrival, shorebird numbers seemed to be a little lower than the day before, but in the end we managed to see – and photograph – every species we reported the day before, with the exception of Greater Yellowlegs. 

Baird's Sandpiper

Only one Baird's Sandpiper remained in the field where the day before we had observed four. This individual had a small bill deformity, and the bill color was a little off too, but otherwise structure and plumage were good for this species.

Wilson's Phalaropes

In the adjacent salinera, scattered groups of Wilson's Phalaropes were still present, and easy to find.

This White-rumped Sandpiper (right) is too tired to stand on its legs

We also found a White-rumped Sandpiper, but this individual was clearly much more rufous than the one from the day before. It was in the company of Western Sandpipers, but unlike them it just sat there looking utterly exhausted, probably having just arrived after a non-stop flight from Tierra del Fuego!

Sunday, May 5, 2013

Buff-breasted Flycatcher

Buff-breasted Flycatcher is a fairly common resident of pine-oak forests from the southwestern US through Mexico to Guatemala and Honduras; apparently rare in El Salvador. eBird does not have records for Nicaragua, although I observed this species in Honduras not far from the Nicaraguan border in 2007 and 2008 (as eBird reminds me), so it may occur there also. There's a historical record for El Salvador of four specimens collected in Chalatenango in 1927 (Dickey & Van Rossem 1938), and a slightly more recent record - 1976 - from Thurber et al. (1987). Evidently, the SalvaNATURA database (unpublished) has a few more recent records from northern El Salvador.

Yesterday we found a pair in Reserva Biológica Misoco (Honduras), on the border between the departments of Francisco Morazán and Olancho. This observation put a new dot on the eBird map for this species and a new bar (for the first week of May) in the Honduras eBird bar chart

Since the birds were vocalizing, I grabbed some audio and uploaded that to Xeno Canto. Although in the middle of the day there was no singing, they did vocalize briefly every time they changed position.

Dickey, D. R. & A. J. Van Rossem. 1938. The Birds of El Salvador. Field Mus. Nat. Hist. Zool. Ser. No. 23, 609 pp.
Thurber, W. A., J. F. Serrano, A. Sermeño & M. Benitez. 1987. Status of uncommon and previously unreported birds of El Salvador. Proceedings of the Western Foundation of Vertebrate Zoology, Vol. 3, No. 3, 294 pp.

Sunday, April 28, 2013

Raptor migration at Derby Hill

Broad-winged Hawk
Last week I visited New York, and part of my trip was an excursion to the Derby Hill hawk watch, where I was a raptor counter in 2006 and 2007. I consider those spring seasons at Derby Hill formative in some ways, for these were my first seasonal field gigs in North America, and the first of several hawk watch engagements I've been on. I've counted hawk migration in Michigan, Texas, Florida, New Jersey, Veracruz Mexico, and even in Honduras, where I now live, but it all began at Derby.

Golden Eagle

It was good to see familiar faces, meet new people also, and of course the birding wasn't bad either. Birding in Central America means that I don't get to see Golden Eagle, Rough-legged Hawk or Northern Goshawk on a regular basis anymore, so those were my target species for the trip to Derby. I was not disappointed. I was also lucky to catch a spectacular (500+ both days) Black-capped Chickadee flight along the bluff.

Northern Goshawk

Derby Hill, located in the southeastern corner of Lake Ontario, does best on southeast winds, and as luck would have it, the two days I was there the winds were from that most favorable direction. Such winds push the stream of migrant raptors to the lakeshore, which they then follow, trying to stay close to land where thermals form. Especially the second day started out beautifully with a parade of low-flying Broad-winged Hawks and other raptors. However, with plentiful sunshine and relatively light winds, the inevitable happened: the hawk flight got higher and higher, and birds were seen further and further out over the lake. This is a classic scenario that Derby regulars have observed many times. Gradually, the flight becomes a 'scope flight', in which observers scan just over the tree line in the direction of the lake, occasionally picking up distant kettles that shimmy in and out of vision, and sometimes are barely visible even in the scope. 

Whenever this happens, the locals speak of birds 'cutting the corner of the lake' or 'jumping off at Nine Mile (Point)' Nine Mile Point being the name of the nuclear power plant 13 km (8 miles) west of Derby Hill. If the thermals, which the SE wind gently blows out over the lake, take the hawks high enough, the distance to the east shore of lake Ontario doesn't seem so threatening anymore, and hawks can bypass Derby.

Back in 2006 and 2007, I remember looking at NEXRAD radar from weather sites and being fascinated to see a hawk flight out over the lake – on radar. We always wondered if this would be visible by an observer on the ground also.

To field test this, my travel companion and I went over to Selkirk Shores State Park on Tuesday afternoon. For about 35 minutes, we scanned the skies toward Nine Mile Point and observed small groups of raptors coming in off the lake. Between 3:00 and 3:35 PM, we observed 15 Turkey Vultures, 1 Osprey, 1 Golden Eagle, 9 Sharp-shinned Hawks, 2 Bald Eagles, 135 Broad-winged Hawks, and 14 Red-tailed Hawks making landfall at Selkirk Shores. Not bad for an afternoon half hour of hawk watching!

But if the observers at Derby Hill cannot see all the birds 'cutting the corner', we in turn probably didn't see the entire flight either.

Here are some radar images from today (28 April 2013), with a very similar weather situation (light SE winds):

 photo DerbyHill28APR2013_zps26835144.gif

The clusters of green dots are groups of raptors flying along the lake shore. We can see them fly over Oswego, but when they get to Nine Mile Point, where the lakeshore topography changes direction, they seem to simply continue in more or less the same direction, passing north of the corner where Derby Hill is located. The birds appear to make landfall between Selkirk Shores and Sandy Pond, after which the stream of green dots changes course and follows a more northerly route, parallel to Highway 81.

At Derby Hill, the official count got to 843 raptors today, and counter Steve Kolbe noted a high flight in blue skies. Here's some more radar imagery, from almost an hour later. From 1:22 EDT to 2:10 EDT, several flight lines are shown: one over the lake, one over Derby Hill, and even some flight south of Derby Hill. The change of direction west along Highway 81 remains visible.

 photo DerbyHill28APR20132_zps88b4a29f.gif

Isn't it incredible that hawk flights can be seen on radar this way? And what about other hawk watches? The NEXRAD radar network covers the entire United States, so in theory it ought to be possible to see these flights for other major hawk migration sites. The thing is: it all depends on how far the hawk watch location is from the nearest radar station.

Think about it: the earth is round, while the beam of the radar is straight. Thus, the radar samples relatively close to the ground in its immediate vicinity, but at higher air strata further away.

Here's a look at a slice of today's radar for Braddock Bay, like Derby Hill a Great Lakes raptor count site with a good spring hawk flight. At the time of writing, they hadn't posted their day totals yet. Around midday, there was only a modest flight visible on radar:

 photo BraddockBay28APR2013_zpsfc3ae35e.gif

Birds can be seen following the lakeshore east, but the gray and green blocks zip off the screen, presumably as the flocks gain altitude and fly above the radar.

What about Whitefish Point, Michigan? Sadly, that site is at the edge of the range of the nearest radar (in Marquette) and thus radar images for Whitefish show nothing. There may well have been a flight there today, but due to its location relative to the nearest NEXRAD radar, it will never be visible on that radar.